ENVIRONMENTALLY AND SOCIALLY SUSTAINABLE DEVELOPPMENT LJ"U) R/t/)t! Iff)c/9/R'/Dopmeit Work in progress 23764 for public discussion March 1999 Source Water Quality for Aquaculture A Guidlefor Assessment - HO '- - 1 ~~~-~A -o .._ 4 r - - _ [. 3 -R i D. Z - ~ ~ ~ ~ U -t ,,! _ - - I - - - V - Joh)//// 1). l1forlto/ A,I.I,/ Al Steawart ENVIRONMENTALLY AND SOCIALLY SUSTAINABLE DEVELOPMENT Rural Development Source Water Quality for Aquaculture A Guidefor Assessment RonaldD. Zweig John D. Morton Maol M. Stewart Thk World Bnmk WahiMngton, D.C. Copyright 0 1999 The International Bank for Reconstruction and Development/THE WORLD BANK 1818 H Street, N.W. Washington, D.C. 20433, U.S.A. All rights reserved Manufactured in the United States of America First printing March 1999 This report has been prepared by the staff of the World Bank. The judgments expressed do not necessarily reflect the views of the Board of Executive Directors or of the governments they represent. The material in this publication is copyrighted. The World Bank encourages dissemination of its work and will normally grant permission promptly. Permission to photocopy items for internal or personal use, for the internal or personal use of specific clients, or for educational classroom use, is granted by the World Bank, provided that the appropriate fee is paid directly to Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, U.S.A., telephone 978-750-8400, fax 978-750-4470. Please contact the Copyright Clearance Center before photocopying items. For permission to reprint individual articles or chapters, please fax your request with complete infornation to the Republication Department, Copyright Clearance Center, fax 978-750-4470. All other queries on rights and licenses should be addressed to the World Bank at the address above or faxed to 202-522-2422. Photographs by Ronald Zweig. Clockwise from top right: (1) Marine fish culture in floating cages sur- rounded by shellfish and seaweed culture (suspended from buoys in background), which feeds on released fish wastes. Sea cucumbers stocked beneath the cages feed on the settled fish wastes. Weihai Municipality, Shandong Province, China. (2) Pump house brings water from Bay of Bengal to Banapada Shrimp Farm, Orissa, India. (3) Day-old carp hatchlings are released to a nursery cage in a fish hatchery pond prior to sale to stock fish production farms. Yixing, Jiangsu Province, China. Ronald D. Zweig is senior aquaculturist in the East Asia and the Pacific Rural Development and Natural Resources Sector Unit of the World Bank. John D. Morton is a Ph.D. candidate in environmental and water resource engineering at the University of Michigan. Macol M. Stewart is an international development analyst in the Office of Global Programs in the US. National Oceanic and Atmospheric Administration. library of Congress Cataloging-in-Publication Data Zweig, Ronald D., 1947- Source water quality for aquaculture: a guide for assessment / Ronald D. Zweig, John D. Morton, Macol M. Stewart. p. cm. - (Environmentally and socially sustainable development. Rural development) Includes bibliographical references (p. ) and index. ISBN 0-8213-4319-X 1. Fishes-Effect of water quality on. 2. Shellfish-Effect of water quality on. 3. Water quality-Measurement. I. Morton, John D., 1968- . II. Stewart, Macol M., 1968- . III. Title. IV. Series: Environmentally and socially sustainable development series. Rural development. IN PROCESS 1998 639.3-dc2l 9841429 CIP I The text and the cover are printed on recycled paper, with a flood aqueous coating on the cover. Contents Foreword v Abstract vii Acknowledgments viii Abbreviations and Acronyms ix Glossary x Chapter 1 Assessing Source Water Quality 1 Choice of Source Water 1 Source Water Quality Issues 1 Guidelines for Evaluating Source Water Quality 3 Chapter 2 Phase I: Physio-chemical Water Quality Parameters 6 Basic Factors 6 Other Critical Factors 18 Chapter 3 Phase II: Anthropogenic and Biological Water Quality Parameters 22 Metals 22 Metalloids 31 Organic Compounds 33 Pathogens and Biological Contaminants 39 Chapter 4 Phase III: Field Study 42 Study Design 42 Criteria for Fish Growth and Health 42 Criteria for Contaminant Residues 43 Appendix Tables 44 Notes 53 Bibliography and Related Sources 55 Species Index 61 iv Source Water Quality for Aquaculture: A Guide for Assessment Boxes 1.1 Bioaccumulation 5 3.1 Protecting aquaculture ponds from pesticides 37 Figure 1.1 Analytical process for evaluating source water quality for aquaculture 4 Tables 1.1 Advantages and disadvantages of common water sources 2 2.1 General temperature guidelines 6 2.2 Optimal rearing temperatures for selected species 7 2.3 Turbidity tolerance levels for aquaculture 8 2.4 Optimal salinities for selected species and general guidelines 9 2.5 Alkalinity tolerance levels for aquaculture 10 2.6 pH tolerance levels and effect for aquaculture 11 2.7 Hardness tolerance levels for aquaculture 11 2.8 Optimal ranges for total hardness 12 2.9 Recommended levels of dissolved oxygen for aquaculture 13 2.10 Carbon dioxide tolerance levels for aquaculture 15 2.11 Factors affecting the toxicity of ammonia to fish 16 2.12 Ammonia tolerances for aquaculture 17 2.13 Optimal nitrite concentrations for aquaculture 18 2.14 Optimal nitrate concentrations for aquaculture 18 2.15 Optimal mud characteristics for aquaculture 20 3.1 Maximum cadmium concentrations for aquaculture 26 3.2 Maximum lead concentrations for aquaculture 27 3.3 Maximum copper concentrations for production of salmonid fish 28 3.4 Maximum chromium concentrations for aquaculture 29 3.5 Maximum zinc concentrations for aquaculture recommended by the European Union 31 3.6 Persistence of pesticides 35 3.7 Toxicity to aquatic life of selected chlorinated hydrocarbon insecticides 35 3.8 Pesticide solubility & experimentally derived bioaccumulation factors in fish 36 Appendix Tables 1 Effect of biological processes on alkalinity 44 2 Relative abundance categories of soil chemical variables in brackish water ponds 45 3 Relative abundance categories of soil chemical variables in freshwater ponds 46 4 Selected biomarkers proposed in study of environmental and/or toxicological responses in fish 47 5 Provisional tolerable weekly intake for selected elements 48 6 Import standards for contaminant residues in fish and shellfish 49 7 Import bacteriological standards for fish and shellfish 51 Foreword T he United Nations Food and Agriculture velopment and growth of fish and shellfish. It Organization (FAO) reports that most may also degrade the quality of the product species subject to capture fishing are by tainting the flavor or by causing accumu- overexploited and that the potential for in- lation of high enough concentrations of toxic creasing yields in the long term is extremely substances to endanger human health. The limited. Aquaculture is an attractive alterna- importance of water quality along with the tive to capture fisheries due to its potential for growth of the World Bank's involvement in production expansion, effective use of process- aquaculture projects has created a need of a ing facilities, and adaptability of production- guide for determining the suitability of to-market requirements. Facing the leveling of source waters proposed for use in these pro- production of capture fisheries, aquaculture, jects. It is the goal of this report to provide has grown in production at an average annual information useful to this end. rate of over 11 percent during 1990-94 accord- This report reviews the quality standards ing to FAO-reported trends. With this growth for water and fish product, looks at the pa- the World Bank has become increasingly in- rameters of greatest importance to aquacul- volved in assisting and financing aquaculture ture, and discusses the scientific basis for these project requests from member governments. standards. It can provide government offi- This report is thus meant to help private and cials, field technicians, and task managers with public sectors and lending institutions deter- necessary information to make informed judg- mine whether the water quality at a proposed ments. The report also contains practical, step- aquaculture development site is acceptable. by-step guidelines for use by task managers in The need for such a guide has become impor- determining whether the quality of the pro- tant and necessary with the continued degra- posed source water will present a significant tion of water resources from increases in risk to the success of a project. The prescribed industrial and municipal wasterwater dis- procedures would be of importance to site charges and agro-chemical use. selection for any considered aquaculture en- Water is the most important input for terprise and would also be of use to govern- aquaculture and thus a key element in the ments involved in formulating inland and success of these projects. Source water should coastal zone development/management plans be selected based on its suitability for efficient that would include assessment of appropri- production of high-quality aquaculture prod- ate areas for the establishment of aquaculture uct(s). Poor water quality may impair the de- facilities. v vi Source Water Quality for Aquaculture: A Guide for Assessment The information provided here is limited to There are plans to revise this report about that currently available in the literature and every two years to keep it current with the new from government standards and thus is not information being generated on the topic and exhaustive with regard to all species cultured also to make it available electronically on the and all aquacultural production systems in use. World Bank's website (www.worldbank.org). Alexander McCalla Director Rural Development Abstract !T'lhe report provides guidance on how to organisms (mostly finfish and crustaceans) and assess the suitability of source water for upon the consumer due to the presence and/or aquaculture. Aquaculture development bioaccumulation of toxins and pathogens that worldwide is growing rapidly due to increasing can be present in water. The current state of demands for its products and limited production knowledge on the acceptable limits of hazard- potential from inland and marine capture fisher- ous chemicals and pathogens in water used for ies. The report reviews the different sources of fisheries and aquaculture and the acceptable water that are or can be used for aquaculture and concentrations accumulated in the tissue of provides the current standards on acceptable aquaculture products are also furnished. These physio-chemical, anthropogenic pollutant, and standards vary somewhat among countries. biological factors that affect the quality of source The report also suggests a step-by-step proc- water. It provides the available knowledge from ess for evaluating source water quality for a literature review on these factors and the po- aquaculture that minimizes cost to the degree tential impact on the health of various cultured possible. vii Acknowledgments he authors want to express their sincere to Eileen McVey from the Aquaculture Collec- appreciation to Claude Boyd, Netty tion,tNationaleAgriculture Library; toBGertVan Buras, Hakon Kryvi, Carl Gustav Lundin, Santen as co-leader of the World Bank Fisheries Khalil H. Mancy, Roger Pullin, and Heinrich and Aquaculture Thematic Group for his sup- Unger, who provided technical and editorial port and endorsement of the document's con- comments on the text; to the World Bank Ru- cept and importance; to Maria Gabitan and ral Sector Board and Summer Intern Program Sunita Vanjani for their administrative assis- and to Maritta Koch-Weser and Geoffrey Fox tance in managing the report's preparation; to for their support of the report's preparation; EmilyFeltforprovidingimportstandards;and to the staff of the World Bank Sectoral Li- to Sheldon Lippman, Virginia Hitchcock, and brary for the provision of reference materials; Alicia Hetzner, whose editorial contributions to Ken Adson, Uwe Barg, Gaboury Benoit, much improved the presentation and clarity of Meryl Broussard, and James McVey for ref- thetext.GaudencioDizondesktoppedthisvol- erences and guidance in the text preparation; ume. viii Abbreviations and Acronyms Ag Silver HOCI Hypochlorous acid Al Aluminum KMnO4 Potassium permanganate As Arsenic LCSO Lethal count level (50 years) ASP Amnesiac shellfish poisoning mg 1-' Milligrams per liter BCF Bioconcentration factors Mn Manganese BOD Biological oxygen demand MPN Most probable number CaCO3 Calcium carbonate N2 Nitrogen gas Cd Cadmium Ni Nickel CFU Colony forming units NSP Neurotoxic shellfish poisoning Cl Chlorine Pb Lead CN Cyanide PCB Polychlorinated biphenyls COD Chemical oxygen demand ppb Parts per billion CO2 Carbon dioxide PSP Paralytic shellfish poisoning Cr Chromium PTWI Provisional tolerable weekly intake Cu Copper Se Selenium DO Dissolved oxygen Sn Tin DSP Diarrhetic shellfish poisoning TAN Total amnmonia nitrogen DDT Dichloro-diphenyl-trichloro-ethane TBT Tributyl tin EU European Union TCDD Tetrachloro dioxin FAO United Nations Food and TGP Total gas pressure Agriculture Organization USEPA United States Environmental Fe Iron Protection Agency HCN Hydrogen cyanide WHO World Health Organization H2S Hydrogen sulfide Zn Zinc Hg Mercury %. Parts per thousand ix Glossary Actinomycetes: Any of an order (Actinomy- Detritus: loose material (as rock fragments or or- cetales) of filamentous or rod-shaped bacteria, ganic particles) that results directly from disin- including the actinomyces (soil-inhabiting sap- tegration. rophytes and disease-producing parasites) and Divalent: Having a valence (combining power at streptomyces. atomic level) of two [e.g., Calcium (Ca +)]. Anthropogenic pollutants: Pollutants which Hypoxia: Acute oxygen deficiency to tissues. come from human sources such as emissions Ligands: A group, ion, or molecule coordinated to from an industrial plant or pesticide emissions a central atom or molecule at a complex. from agriculture. These pollutants are referred Most probable number A measure of bacterial to as anthropogenic because they typically are numbers in which the bacteria are serially di- associated with human activity. However, it is luted and grown. By identifying the dilution possible for some of them to come from natural samples in which the bacteria grow, the number sources. of bacteria in the original samples can be deter- Benthos: organisms that live on or in the bottom mined. of bodies of water. Necrosis: Localized death of living tissue. Bioaccumulation factor (BCF): A measure of the Osmoregulation: The biological process of main- extent to which a compound bioaccumulates in taining the proper salt concentration in body an aquatic species. It is calculated as (concentra- tissues to support life. tion of the compound in the body tissue) di- Parenchymatous: related to the essential and dis- vided by (concentration of the compound in the tinctive tissue of an organ or an abnormal water). growth as distinguished from it supportive Biological oxygen demand (BOD): The amount framework. of dissolved oxygen used up by microorgan- Physio-chemical properties of water The basic isms in the biochemical oxidation of organic physical and chemical properties of water indud- matter. Five-day BOD (BOD5) is the amount of ing salinity, pH etc. Note this does not include dissolved oxygen consumed by microorgan- concentrations of anthropogenic pollutants. isms in the biochemical oxidation of organic Redox: Of or relating to oxidation- reduction. matter over a 5-day period at 200C. Tainting or Off-flavor When certain pollutants Cations: The ion in an electrolyzed solution that such as petroleum hydrocarbons accumulate in migrates to the cathode: a positively charged ion. fish or shellfish to a level at which the flavor is Chelating Agents: A compound that combines affected. This makes the product undesirable with a metal. for human consumption. Chloracne: An eruption/inflammation of the skin Zeolites: Any of various hydrous silicates that are resulting from exposure to chlorine. analogous in composition to the feldspars, oc- Colony forming units: A measure of bacterial cur as secondary minerals in cavities of lavas, numbers which is determined by growing the and can act as ion exchangers used fro water bacteria and counting the resulting colonies. softening and as absorbents, and catalysts. x CHAPTER 1 Assessing Source Water Quality W ater is the most important element has become common in industrialized nations, for aquaculture. Selection of source a trend threatening the industrializing coun- water should be based on its suit- tries of Asia. ability for efficient production of a high quality For aquaculture in salt or brackish water, aquaculture product. Poor water quality may preference is for source water that is away from affect fish and shellfish health through impair- any generator of pollution, such as industries, ment of development and growth or may de- tainted river mouths, or agricultural areas. This grade the quality of the product by tainting its water is less susceptible to fluctuations in sa- flavor or by causing accumulation of high con- linity and other chemical properties and is less centrations of toxic substances which could en- likely to be contaminated by coastal discharges danger human health. The importance of water (Lawson 1995, 52). The most common advan- quality has created a need for guidelines for tages and disadvantages of each type of source determining the suitability of source waters are shown in table 1.1. proposed for use in these projects. Source Water Quality Issues Choice of Source Water Once potential source waters are identified, it The first step is identification of the most prom- is imperative to insure the water quality is suit- ising source water by carefully considering the able for aquaculture. Poor water quality may advantages and disadvantages of different cause project failure by producing a product types of water sources. Water sources fall into either in insufficient quantity or unmarketable roughly nine categories: marine/coastal, estu- size or quality. Water quality can cause death, aries, rivers/streams, lakes, surface runoff, disease, or poor growth in fish and shellfish. springs, wells, wastewater, and municipal In addition, poor water quality can contami- water. nate the product with compounds dangerous In general, for fresh water aquaculture, to human health. groundwater sources (springs and wells) are preferred. They maintain a constant tempera- Fish and Shellfish Health ture, are free of biological nuisances such as fish eggs, parasites and larvae of predatory in- Fish and shellfish health is very sensitive to sects and are usually less contaminated than water quality. Water quality criteria are based surface water sources. Ground water has tra- on studies of growth, behavior, and health of ditionally been less contaminated than surface different species in various waters. One set of water. Contamination of ground water sources parameters which affect fish and shellfish are 1 2 Source Water Quality for Aquaculture: A Guide for Assessment Table 1.1 Advantages and disadvantages of common water sources Source Advantage Disadvantage Marine/coastal Constant temperature May contain contaminants High alkalinity May require pumping Estuarine May be readily available May contain contaminants Inexpensive May be subject to large fluctuations in temperature River/stream May be readily available Typically requires pumping Inexpensive Often have high silt loads Pumping costs lower than wells Can contain biological nuisances such as parasites and larvae of predatory insects May contain contaminants May contain excessive nutrient concentrations Have seasonal and possibly diumal fluctuations in flow, temperature, and chemistry Lake May be readily available Similar to river/stream, but chemistry is more stable due to the Inexpensive buffering effect of the large water volume Pumping costs lower than wells Bottom water may be anoxic in summer and contain reduced iron Surface runoff Inexpensive May contain contaminants Unreliable Requires 5-7 acres of watershed per surface acre of aquaculture water Spring Constant temperature Typically lacking oxygen and thus needs aeration May not require pumps Yield and reliability may be questionable Usually less polluted (see note) May contain dissolved gases Free of biological nuisances such as parasites May contain high iron concentrations or reduced iron and larvae of predatory insects May contain high hardness Inexpensive Well Constant temperature Typically lacking oxygen and thus needs aeration Usually less polluted (see note) Unless artesian, requires pumps which can be costly May contain dissolved gases May contain high iron concentrations or reduced iron Possible aquifer depletion Municipal High quality Expensive Typically have disinfecting chemicals which are poisonous to fish and expensive to remove Wastewater Inexpensive Medium to high pathogen concentrations May contain contaminants Note: Although ground water has traditionally been less contaminated than surface water, contaminabon of ground water sources has become common in industrialized natons. A similar trend may be likely for newly industrializing countries of Asia. Source: Swann 1993 and Lawson 1995. the basic characteristics of natural water other- Fish health can also be affected by pollutants wise referred to as its physio-chemical proper- typical of anthropogenic (as a result of human ties. These include properties such as turbidity, activity) discharges such as petroleum hydro- pH, and dissolved oxygen. For many of these carbons, metals and pesticides. It is possible for properties, fish have a limited range in which these discharges to also come from natural they can grow optimally. Hence, screening the causes. These pollutants can cause deleterious source water in respect to its physio-chemical behavioral and reproductive changes in fish properties is an important initial step in assess- and shellfish even at very low concentrations. ing the source-water suitability to fish health. To ensure good fish and shellfish health, source Assessing Source Water Quality 3 water must also be screened using water qual- pected, tests can be done by preparing a pilot ity criteria for these chemicals. study in which fish are grown in the source water and subsequently tested for contaminant Product Quality and Human Health concentrations in body tissue. The quality of the aquaculture product and its Guidelines for Evaluating Source suitability for human consumption may also Water Quality be affected by water quality. Even if culture species are able to grow and thrive in a given In evaluating the suitability of the quality of source water, low levels of pollutants may source water for new, improved, or expanded cause the aquaculture products to be contami- aquaculture developments, a three-phased nated or have off-flavor. Off-flavor or tainting screening process is recommended. For water occurs when certain pollutants such as petro- quality analysis it is recommended that those leum hydrocarbons or metals accumulate in methods defined in Standard Methods for Ex- fish or shellfish to a level at which the flavor amination of Water and Wastewater (APHA is affected, making the product undesirable for 1995) be followed which for many factors human consumption. would require an expert water quality analysis The process by which pollutants concentrate laboratory to do the assays. It is also important in seafood is called bioaccumulation (box 1.1, to note that the water quality suitable for hatch- p. 6). Many pollutants, especially those which ery, nursery, and grow-out systems for a par- are fat soluble, collect in the tissues of aquatic ticular species vary to some degree and are animals. This process results in higher concen- discussed in the text with the information trations of pollutants in body tissues of aquatic available for each type. organisms than in the surrounding water. For Phase I as illustrated in figure 1.1, the Accumulation of contaminants in fish and water quality criteria for the basic physio- shellfish is of great concern to the aquaculture chemical properties necessary to sustain the industry. Consumers are highly sensitive to the cultured organisms will be compared to meas- quality of food products and any potential urements made on the source water. This will health risks. Media reports of contamination of provide a simple means of screening the source seafood can seriously affect consumer percep- water without going through the more expen- tion, marketing, and production of all kinds of sive tests for anthropogenic pollutants. Ac- fisheries products. In addition, rejection of cordingly, if anthropomorphic pollution or aquaculture products which fail to meet import naturally occurring toxins (for example, arse- quality standards may have serious long-term nic, toxic algae) are not suspected and Phase I implications for the exporting country and pro- criteria are met, the source water can be con- ducers. sidered acceptable. If Phase I criteria are not Quality standards established by national met in this circumstance, a Phase III field trial governments are the means by which humans can be pursued. If the Phase III trial cannot be are protected from contaminated seafood. In- conducted, the water should either be rejected ternational and domestic commerce is regu- or accepted if a technically feasible and cost lated to prevent contaminated fish and effective water treatment is identified and shellfish from reaching the market. Thus meet- tested, bringing the source water within ac- ing these standards are an important goal for ceptable Phase I criteria. the products of a successful aquaculture pro- Phase II is designed to screen for criteria on ject from both an economic and public health anthropogenic pollutants in source water and perspective. Such water quality standards can would be conducted after the source water has be incorporated into a water quality assess- been tested and met the Phase I criteria. In ment. In cases where bioaccumulation is sus- addition, biological contaminants such as algal 4 Source Water Quality for Aquaculture: A Guide for Assessment Figure 1.1 Analytical process for evaluating source water quality for aquacuiture Qualitative Sit Assessment PHASE 1: isPHASE 1: Physlco-Chemlcal a Anlo9utonai Physlco-Chemlcal Water Quality Water Quality 1No WsQimiiy vWaeruly CurtIla Met? Criteile Met 5 7 // / ~~~~~~~~~~~~~~~~~~No PHASE II: Acc\tSbie? Anthroprogenic Are Risk \ N k-\7// | Pollutants l / No~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~I Ye WS V auab Field Trial and I Temst DNign Met?s MetI Trearert Do Not Accept Accept Source Water FY sb o SourCe Water inanciey Suc ae Pamible?~~ Assessing Source Water Quality 5 Box 1.1 Bioaccumulation Bioaccumulation is a process in which chemical pol- pollutants concentrated in their tissues. There is lit- lutants that enter into the body of an organism (by tle evidence that chemicals which bioaccumulate in adsorption through the gills and intestine or by di- the fatty tissues of aquatic species high in the food rect exposure through the skin) are not excreted, chain cause deleterious effects on these organisms. but rather collect in its tissues. However, it is thought that birds and mammals Rates of bioaccumulation in aquatic species vary which feed on these aquatic organisms experience greatly depending on species behavior and physi- deleterious effects. Therefore, there are considerable ology. For example, bottom feeders are more sensi- health concerns (for example, cancer, damage to the tive to pollutants associated with sediments. The nervous system) about the accumulation of such differences in the mechanism of regulating salt con- substances in the tissues of fish which are con- centration between fresh and salt water fish may sumed by humans. The U.S. Environmental Protec- affect exposure to water soluble contaminants. Dif- tion Agency conducted a national study of ferent species may also accumulate various pollut- accumulated toxins in fish caught in open waters ants in different tissues, such as muscle, kidneys, or which documents the concern (USEPA 1992). liver. The toxicity of contaminants, bioavailability, Sometimes pollutants can be naturally cleansed and rates of bioaccumulation are also influenced by from the tissue of aquatic animals by placing them environmental factors such as temperature, dis- in clean water for a given period of time. The rate solved oxygen, alkalinity, pH, redox potential, col- of cleansing, or depuration, depends upon the spe- loids, dissolved organics and suspended solids. cies and the contaminant in question. The only Species higher in the food chain tend to accumu- other way to address the problem of bioaccumula- late higher concentrations of many pollutants be- tion is to reduce exposure of the fish to the contami- cause they are feeding on organisms which have nant through improved water quality. toxins can also be screened. Because it is nei- criteria are met, it is not mandatory to pursue ther feasible nor desirable to test for every pos- Phase m. However it is advised that Phase m sible pollutant, only pollutants typical of be pursued, if possible, as a means of minimiz- current and historical industrial, municipal, ing the risk of project failure. and agricultural activities in the watershed Phase m involves a pilot study or field test should be tested. In some cases high concen- in which fish are grown in the selected source trations may occur in nature. This is common water, using similar management techniques in areas with large deposits of a particular min- as those of the proposed project, and then eral. If large natural sources are suspected in tested for bioaccumulated pollutants and off- the area, tests should be conducted to analyze flavor. The pilot study could also be replaced for the toxin(s). If the source water fails to meet by sampling fish and shellfish tissues from an Phase II criteria, the feasibility of pre-treating existing aquaculture facility, if available, in the the water before use could be considered as in vicinity that uses the same planned technology Phase I. A decision as to whether to pursue a and the source water in question. Following Phase III field trial or reject the source water Phase III where implemented, a final decision can then be made. If both Phase I and Phase II can be made on the use of the source water. CHAPTER 2 Phase I: Physio-chemical Water Quality Parameters Basic Factors peraturelimits;however, suboptimaltempera- ture conditions cause stress which affects be- Temperature, turbidity, salinity, alkalinity, havior, feeding, metabolism, growth, and acidity, hardness, dissolved oxygen, carbon di- immunity to disease. It is therefore preferable oxide, total gas pressure, nitrogen compounds, that water remain near optimum temperature, iron, hydrogen sulfide, methane, and water- and imperative that it never deviate beyond soil interactions are the basic physio-chemical lethal limits. properties tested in Phase I. Because these Listed in table 2.1 are general guidelines and physio-chemical properties of natural waters in table 2.2 species specific guidelines for affect the growth and health of fish and shell- source water temperature. The guidelines are fish, these parameters must be tested for in all based on the conditions at which optimal potential water sources. growth rates occur. Temperature Treatment. Since controlling the temperature of ponds in large-scale aquaculture facilities Effects. Water temperature affects a multitude is often not practical, sites should be selected of important processes in aquaculture. Physi- in geographic regions which provide an am- ological processes in fish such as respiration bient temperature conducive to the growth of rates, feeding, metabolism, growth, behavior, reproduction and rates of detoxification and Table 2.1 General temperature guidelines bioaccumulation are affected by tempera- Species Temperaturelcomment ture. Temperature can also affect processes important to the dissolved oxygen level in Tropical 29-300C / optimal growth water such as the solubility of oxygen, and the < 26280C / low growth rates rate of oxidation of organic matter. In addition < 10-150C / lethal limH the solubility of fertilizers can be affected by Warm-water 20-280C / optimal growth temperature. < oOC / lethal limit Cool-water 15-200C / optimal growth Guidelines. Each species has an optimum temperature at which its growth rate and Cold-water <150C/ optimal growth heartiness are best. Growth will still occur at >_25°C_/_lethal_limH very close to the upper and lower lethal tem- Source: Boyd 1990 and Lawson 1995. 6 Phase I: Physio-chemical Water Quality Parameters 7 Table 2.2 Optimal rearing temperatures for selected species est and grassland have lower rates of erosion Temperature (Boyd 1996, 220-21). Species (°C) Reference In addition to turbidity from source water, Brook trout 7-13 Piper et aL 1992 turbidity may also come during the aquacul- Brown trout 12-14 Petit 1990 ture operation. For example in the aquaculture Brown trout 9-16 Piper etal. 1982 pond turbidity can increase as a result of sedi- Rainbow trout 14-15 Petit 1990 ment resuspension, biological activity, the ad- Rainbow trout 10-16 Piper et aL 1982 dition of manure and feed, and erosion of the Atlantic salmon 15 Petit 1990 pond slopes. Chinook salmon 10-14 Piper et aL 1982 Coho salmon 9-14 Piper et aL 1982 Effects. Turbid waters can shield food organ- Sockeye salmon 15 Petit 1990 isms as well as cause gllU damage and fish stress. Turbot 19 Petit 1990 It can also clog filters. Turbidity levels affect the Plaice 15 Petit 1990 light available for photosynthesis by phyto- European eel 22-26 Petit 1990 plankton and the growth of undesirable organ- Japanese eel 24-28 Petit 1990 isms. In ponds with organisms that depend Common carp 25-30 Petit 1990 upon phytoplankton for feed, turbidity must be Mullet 28 Petit 1990 at sufficiently low levels to allow the penetra- Tilapia 28-30 Petit 1990 tion of light for photosynthesis. However, the Channel caffish 27-29 Tucker and turbidity must also be high enough to avoid the Channel catfish 21-29 Piperoet at. 1982 growth of undesirable rooted plants. The tur- Channel caffish hatcheries 78-82°F Boyd 1990 bidity necessary for prevention of the growth of Striped bass 13-23 Piper et at 1982 these plants can be typically provided by the Red swamp crawfish 18-22 Romaire 1985 phytoplankton themselves. P. vannamei 28-30 Clifford 1994 For ponds with organisms that derive a ma- Freshwater prawn 30 Romaire 1985 jority of their nutrition from feed inputs, light Brine shrimp 20-30 Romaire 1985 for phytoplankton growth is not imperative Brown shrimp 22-30 Romaire 1985 and therefore the turbidity can be higher. How- Pink Shrimp > 18 Romaire. .. Pink____Shrimp____>_______Romaire ___ ever, ff turbidity is too high in these ponds Source: Lawson 1995. photo-synthesis can be inhibited significantly enough to reduce oxygen levels. This can be marketable-sized products within a reasonable remedied by using mechanical aeration at a period of time (Lawson 1995,14). rate such that oxygenation occurs without ex- acerbating the turbidity problem through sus- Turbidity pension of sediment. Because many suspended solids will settle Turbidity is a measure of light penetration in out in ponds or canals, another major concern water. Turbid conditions result from dissolved besides turbidity itself is the arnount of sus- and suspended solids such as clay and humic pended particles that can potentially settle out compounds or microorganisms such as phyto- (that is, settlable solids). Sediments from highly plankton. In source water it is primarily a re- turbid source water may fill ponds and canals sult of erosion during runoff. Because of the within a few months. They can contain large significant contribution of erosion to turbidity, amounts of organic matter that exerts a high caution should be used when taking source oxygen demand resulting in oxygen depletion. water from areas where current and future Sedimentation can also smother eggs of some land use practices encourage erosion. Con- species in ponds used for natural reproduction. struction areas, deforested areas, and cropland Sedimentation of contaminated suspended have relatively high rates of erosion while for- particles is also of concern in areas affected by 8 Source Water Quality for Aquaculture: A Guide for Assessment pollutants such as heavy metals and pesticides end of the growing season, or dredging un- (Boyd 1990, 138). drainable ponds. Sediments removed from aquaculture facilities may be considered an en- Guidelines. Lethal levels of turbidity have virormental hazard and, hence, be difficult been shown to be 500-1,000 milligrams per liter and/or costly to dispose (Boyd 1990, 365-72). (mg l-l) for cold water fish (Alabaster and Lloyd 1982). Channel catfish have tested more tolerant Salinity with their fingerlings and adults surviving long-term exposures to 100,000 mg l-l with be- Salinity is a measure of the total concentration havioral changes occurring above 20,000 mg l-l of dissolved ions in water and measured in (Tucker and Robinson 1990). Listed in table 2.3 parts per thousand (%.). Salinity varies de- are the ranges in which good to moderate fish pending on where the water source lies in the production can be obtained. Recommended spectrum from seawater to freshwater. Typical suspended solids concentrations for salmonid salinity values are less than 0.5%. for fresh- culture from different literature sources are: less water, 0.5 to 30%o for brackish water and 30 to than 30 mg 1-1, less than 80 mg l-', and less than 40%. for marine water. 25 mg 1-'.1 In freshwater, the salinity and the elements contributing most significantly to salinity can Treatment. Colloids or very small suspended vary depending on the rainfall and the geology particles can be coagulated and precipitated by of the area. Freshwater commonly contains adding electrolytes such as aluminum sulfate relatively high concentrations of carbonate, (alum). While alum is very effective, it can cause silicic acid, calcium, magnesium and sodium other water quality problems by reducing alka- (Stumm and Morgan 1981, 551). linity and pH (see sections on pH and alkalin- The salinity of seawater varies depending on ity). Lime can be added to counteract these proximity to the coastline, rainfall, rivers, and effects. Turbidity caused by suspended clay can other discharges. The elements contributing be precipitated by the addition of organics such most to the salinity of seawater however do as barnyard manure, cottonseed meal, or super- not vary markedly. Chloride and sodium ions phosphate. However organic matter is often contribute most significantly with sulfate, difficult to obtain and apply; and it exerts an magnesium, calcium, potassium, and bicar- oxygen demand when decomposing. Avoiding bonate ions contributing to a lesser degree or addressing the source of turbidity is a better (Stunmm and Morgan 1981, 567). Optimum sa- strategy than chemical treatments which re- linities for selected species and general guide- quire frequent application and may result in lines are shown in table 2.4. other water quality problems. Current methods of sediment (settlable sol- Effects. Salinity is tremendously important ids) control involve using sediment ponds or to fish which must maintain the concentration canals to reaove the bulk of sediment before of dissolved salts in their bodies at a fairly water enters the culture area, draining ponds constant level. Through the process of osmo- and removing sediments periodically at the regulation the fish expends energy in order to maintain this level. Each organism has a range Table 2.3 Turbidity tolerance levels for aquaculture of salinity in which it can grow optimally, and Effect Suspended solids concentration when it is out of this range, excess energy needs to be expended in order to maintain the No harmful effects on fisheries 25 mg j1 desired salt concentration. This is done at the Acceptable range 25-80 mgr Detrimental to fisheries 80 mg i" expense of other physiological functions, if the salinity deviates too far from the optimum Source: Boyd 1990. range. Phase I: Physio-chemical Water Quality Parameters 9 Table 2.4 Optimal salinities for selected species and general guidelines Species Salinity Comment Reference Salmon > 24%o Optimum Black 1991 Trout < 200/%o Survival and growth decrease above 200/%o McKay and Gjerde 1985 Grass carp < 10-140/%o Upper salinity tolerance Maceina and Shineman 1979 Tilapia aurea and Tilapia nilotica 0-10%o Optimum salinity Stickney 1986 Red hybrid tilapia < 170/% Lawson 1995 Channel catfish 1 1-14%0/o Can survive Perry and Avault 1970 > 6-80/o. Growth is poor 0.5-3.00/o. Optimal salinity < 0.50/co Can still grow well Boyd 1990 < 30/o Optimal for egg and fry 0.1-8.00/%o Optimal for hatcheries Freshwater prawn 1 2.00/co Eggs and larval stage Tansakul 1983 M. rosenbergii < 0.5%/o Postlarval stages Brackish water prawn 15-250/oo Optimum 1 0-350/oo Acceptable range P. vannamei 15-250/oo Optimum Clifford 1994 General Guidelines Most freshwater fish < 0.50/oo Optimal < 2%o Can survive at <70/c but growth poor Lawson 1995 Marine fish 33-340/oo Optimum 30-400/oo Acceptable range Treatment. Salinity may be increased by add- culture, it is a convenient measure of the de- ing gypsum or sodium chloride, though costs gree to which a water can neutralize acidic could be prohibitive. Due to its high solubility, wastes and other acidic compounds and sub- large increases in salinity can be obtained using sequently prevent extreme pH shifts, which sodium chloride. Generic rock salt can be used can disturb the biological processes of the for this purpose. Gypsum is only soluble up to aquaculture species.2 Any chemical species about 2%o and therefore is more appropriate for which can neutralize an acid can contribute affecting smaller changes in salinity (Boyd to alkalinity. In natural waters, the chemical 1979). It should be noted that because increases species most responsible for alkalinity are car- in salinity cause particles to settle, the effect of bonate species (COy HCO). Hydroxides, am- increased sedimentation rates must be consid- monium, borates, silicates and phosphates also ered in any treatment to increase salinity. Low- contribute to alkalinity.3 Total alkalinity, or the ering salinity would require advanced total amount of titratable bases, is expressed in treatment processes such as reverse osmosis mg 1-1 of equivalent calcium carbonate and electrodialysis, which are too expensive to (CaCO3). Alkalinity in natural freshwater sys- be practical for most aquaculture operations. tems ranges from 5 mg 1-1 to 500 mg 1-1. Sea water has a mean total alkalinity of 116 mg l-l Alkalinity (Lawson 1995, 24). Alkalinity is a measure of the acid neutralizing Effects. There are no direct effects of alkalinity capacity of a water. For the purpose of aqua- on fish and shellfish, however it is an important 10 Source Water Quality for Aquaculture: A Guide for Assessment parameter due to its indirect effects. Most im- water but to processes that occur during the portantly, alkalinity protects the organism from aquaculture operation.5 However, source major changes in pH. The metabolism and res- water with a proper pH is imperative, and the piration of fish and micro-organisms, particu- pH of any potential source water should be larly phytoplankton and bacteria, can produce screened. wastes and by-products which can change pH. In addition some biological processes can Effects. The pH of water used in aquaculture change alkalinity itself by producing or con- can affect fish health directly. For most species, suming acids or bases.4 A summary of some a pH between 6.5 and 9 is ideal. Below pH 6.5 processes are shown in appendix table 1. species experience slow growth (Lloyd 1992, Alkalinity may have another indirect effect 64). At lower pH, the species ability to maintain on aquaculture through its effect on photo- its salt balance is affected (Lloyd 1992, 87) and synthesis. If alkalinity is too low (less than 20 reproduction ceases. At approximately pH 4 or mg l-1), the water may not contain sufficient below and pH 11 or above, most species die carbon dioxide (CC2) or dissolved carbonates (Lawson 1995, 26). for photosynthesis to occur, thus restricting The pH can also indirectly affect fish and phytoplankton growth (Lawson 1995, 24). shellfish through its effects on other chemical parameters. For example, low pH reduces the Guidelines. Listed in table 2.5 are the recom- amount of dissolved inorganic phosphorous mended general guidelines for the alkalinity of and carbon dioxide available for phytoplank- source water used in aquaculture. ton photosynthesis. Also at low pH, metals toxic to fish and shellfish can be leached out of pH the soil. At high pH, the toxic form of ammonia becomes more prevalent. In addition phos- The pH of water is its hydrogen ion concentra- phate, which is commonly added as a fertilizer, tion ([H+]). It is expressed as the negative loga- can rapidly precipitate at high pH (Boyd 1990, rithm of the hydrogen ion concentration 154). (log[H+]). Natural waters range between pH 5 and pH 10 while seawater is maintained near Guidelines. The effects of pH on warm water pH 8.3. The pH problems associated with pond fish are summarized in table 2.6 along aquaculture are usually not due to the source with recommended levels for salmon culture. Table 2.5 Alkalinity tolerance levels for aquaculture Treatment. Low pH waters are often treated Total alkalinity using lime (Boyd 1981, chapter 5). Alum can be (mg l.1) Effect Reference used to treat high pH waters. In cases where the high pH problem is due to excess phytoplank- 15-20 Phytoplankton produc- Boyd 1974 ton photosynthesis in waters with high alkalin- tion low ity and low calcium hardness, gypsum can be < 30 Poorly buffered against Meade 1989, added as a source of calcium. Another option is rapid pH changes Tucker and Robinson to kill off phytoplankton with algaecides, but 1990 low dissolved oxygen conditions, residual ad- 20-400 Sufficient for most Meade 1989, verse effects of the algicide, and high costs may aquaculture purposes Tucker and Robinson result (Boyd 1990, 378). 1990 2100 or 150 Desirable Meade 1989, Hardness (Calcium and Magnesium) Tucker and Robinson 1 990 1990_______________ Total hardness is a measure of the concentra- Source: Lawson 1995. tion of all metal cations with the exception of Phase I: Physio-chemical Water Quality Parameters 11 Table 2.6 pH tolerance levels and effect for aquaculture for bone and exoskeleton formation and for pH levels Effect osoregulation. Crustaceans absorb calcium Warmn water pond fish from the water when molting, and if the water <14.0 Acid death point is too soft their exoskeletons begin to soften and 4.0-5.0 No reproduction they may cease to molt. In addition, bone de- 4.0-6.5 Slow growth formities and reduced growth rates may result if water is too soft.6 6.5-9.0 Desirable range for fish Hardness also affects aquaculture species production and operations through its chemical interac- 9.0-11.0 Slow growth tions with other species in water. Calcium re- > 11.0 Alkaline death point duces the toxicity of metals, ammonia, and the Salmonid culture hydrogen ion. In addition, due to the higher 6.4-8.4 Recommended range for fish ion concentration m hard waters, suspended production soil particles settle faster in hard waters than soft waters. For waters where alkalinity is high 6.7-8.6 Recommended range forpfish and calcium is low, photosynthesis may in- crease the pH to levels that are toxic to fish 6.7-7.5 Recommended range for fish (Boyd 1990, 143, 377). production Sources: Lawson 1995, Tarazona and Munoz 1995. Guidelines. In general the most productive waters for fish culture have roughly equal mag- the alkali metals. Calcium and magnesium are nitudes of total hardness and total alkalinity.7 the most common cations contributing to hard- Listed in table 2.8 are general and species spe- ness in fresh water systems. To a much lesser cific guidelines for freshwater aquaculture. extent, hardness also includes other divalent Hardness averages 6,600 mg Pl in ocean water ions such as iron (Fe2+) and barium (Ba2+). and therefore is not a problem in seawater or Water is classified with respect to its hardness brackish water systems (Lawson 1995, 25). and softness as shown in table 2.7. These categories were originally developed Treatment. Insufficient hardness is easily for municipal water treatment and thus have overcome. Calcium hardness can be raised by no biological relevance. It should be noted that adding agricultural gypsum or calcium chlo- much of the concern about hardness in water ride. Gypsum is preferable because it costs less, treatment is with all the ions involved, while is more readily available, and does not affect in aquaculture the concern is mostly with the alkalinity. Its disadvantages include the vari- calcium concentration. able purity of agricultural gypsum (70-98 per- cent) and its slow reaction rate relative to Effects. Calcium is the most important compo- calcium chloride (Boyd 1990,383). nent of hardness to aquaculture. It is necessary Dissolved Oxygen Table 2.7 Hardness tolerance levels for aquaculture Concentration Dissolved oxygen (DO) is a very basic require- Water classification (CaCOa per liter) ment for aquaculture species. It is usually the first limiting factor to occur in pond culture. Soft 0-75 mg Dissolved oxygen is a complex parameter be- Moderate 75-150mg cause its concentration is dependent upon Hard 150-300 mg Very hard > 300 mg many processes. In an aquaculture system the sources of dissolved oxygen are photosynthe- Source: Sawyer and McCarty 1978. sis and reaeration from the atmosphere. The 12 Source Water Quality for Aquaculture: A Guide for Assessment Table 2.8 Optimal ranges for total hardness Total hardness Species (mg 1-1) Comment Reference Hatchling silver carp 300-500 Optimum Boyd 1990 Channel catfish hatchery > 20 Optimum Boyd 1990 Trout hatchery 10-400 Suggested Piper eta!. 1982 Warm water hatchery 50-400 Suggested Piper et aL 1982 Freshwater crustaceans > 50 Some species need more Boyd 1990 Freshwater crayfish > 100 For optimum production De la Bretonne et a/. 1969 General guideline 20-300 Hardness = alkalinity Boyd and Walley 1975 Romaire 1985 sinks include oxygen-consuming processes in slow growth. As dissolved oxygen gets be- such as respiration from microbial life, fish, low 1 mg l-l, it becomes first lethal after long- and plants, and the degradation of organic term exposure; and at lower dissolved oxygen, matter by microorganisms (biological oxygen only small fish can survive short-term exposures demand or BOD). These processes are influ- (Lawson 1995, 23). At high oxygen concentra- enced by other factors. Photosynthesis, respi- tions, oxygen supersaturation can contribute to ration, the degradation of organic matter, gas bubble trauma (see section on total gas pres- and the solubility of oxygen are all influenced sure). Although when combined with other by temperature. The type of fish, life stage, gases, oxygen can cause gas bubble trauma. feeding practices, level of activity and dis- High oxygen concentrations alone do not result solved oxygen concentration also influence the in gas bubble trauma, but high dissolved oxygen respiration rate. In addition to temperature, concentrations occurring at times when water oxygen solubility is also affected by salinity, temperature increases rapidly can augment the barometric pressure and impurities. The most phenomenon (Tarazona and Munoz 1995, 124). common cause of low dissolved oxygen in an Oxygen supersaturation occurs due to high aquaculture operation is a high concentration dams, aerators, and rapid photosynthesis when of biodegradable organic matter (and thus saturated groundwater is warmed naturally to BOD) in the water. This is especially true at ambient temperatures, or when saturated water high temperatures. Hence BOD is possibly a is heated in hatcheries (Boyd 1990, 150-52). more important parameter to dissolved oxygen than dissolved oxygen itself. Guidelines. Setting guidelines for dissolved oxygen for source water is difficult because dis- Effects. Dissolved oxygen concentrations near solved oxygen in aquaculture operations is af- saturation levels are generally healthiest for fected by many processes independent of the fish. Romaire (1985) believes that growth is im- initial source-water dissolved oxygen. At the paired if dissolved oxygen concentrations re- screening stage, the initial dissolved oxygen main below 75 percent saturation for long and BOD can be used to assess the ability of the periods, and Colt and Orwicz (1991) recom- source water to maintain proper oxygen levels. mend that dissolved oxygen be maintained at a Other factors affecting dissolved oxygen con- minimum of 95 percent saturation for optimum centration in the aquaculture operation can growth. The following generalizations were de- only be assessed and mitigated once the opera- rived for warm water pond fish. For dissolved tion is running. oxygen concentrations approximately 1-5mg 1-, Listed in table 2.9 are the tolerances for dis- the dissolved oxygen is still high enough for solved oxygen for different species. These survival; however, long-term exposure results should be considered as a minimum for source Phase I: Physic-chemical Water Quality Parameters 13 Table 2.9 Recommended levels of dissolved oxygen for aquaculture Species DO (mg 1-') Comment Reference Tilapia > 5.0 Preferred Lloyd 1992 3.0-4.0 Tolerable Trout 10.0 Normal at 150C Lloyd 1992 5.0 Limit for acclimation Marine fish > 6.0 Minimum Huguenin and Colt 1989 Cold water fish > 6.0 Minimum Lawson 1995 Salmonids > 5.0 Can only survive lower DO for a few hours Lloyd 1992 > 5.5 fish Roberts and Shepherd 1974 > 7 eggs Salmon > 8.5 Optimal Black 1991 100% saturation Warm water crustaceans > 5 Can only survive lower DO for a few hours Lloyd 1992 Eel > 5 Preferred Uoyd 1992 3.0-4.0 Tolerable Carp >5.0 Preferred Lloyd 1992 3.0-4.0 Tolerable Fish in muddy ponds or Resistant to Example: goldfish Lloyd 1992 warm, slow rivers low DO Warm water fish More tolerant to low DO than cold water species Lloyd 1992 > 5.0 Recommended Lawson 1995 > 1.5 Live for several days > 1.0 Live for several hours < 0.3 Lethal concentration Channel caffish < 0.5 (fingerlings) Survive short exposure Lawson 1995 0.5 (adults) Survive short exposure Lawson 1995 2.0-3.0 Adults survive, eggs die Lawson 1995 < 5.0 Feed poorly, grow slowly Lawson 1995 < 6.0 (hatchery) Boyd 1990 Red swamp crawfish < 1.0 (uveniles) Survive short exposure Avault eta. 1974 < 2.0 Adults crawl out Lawson 1995 Penaeid shrimp species low DO Like freshwater fish Boyd 1990 0.7-1.4 Lethal concentration Lawson 1995 P. vannamei 6.0-10.0 Optimum Clifford 1994 General guideline > 5.0-6.0 Lawson 1995 water. In addition the dissolved oxygen and aerators. These systems typically employ me- BOD should be used together to assess the abil- chanical mixing in order to increase the surface ity of the source water to maintain proper oxy- area of the water exposed to the air and thus the gen levels. transfer of oxygen. These can take many forms including running the water over baffles or em- Treatment. Treatment of source water for low ploying power aerators such as paddlewheel dissolved oxygen can be accomplished using aerators and spray aerators.8 14 Source Water Quality for Aquaculture: A Guide for Assessment Biochemical Oxygen Demand treatment is controversial because potassium permanganate is also an algicide; it may further The biochemical oxygen demand is a measure decrease oxygen levels by killing algae. The of the amount of organic compounds that can lower oxygen levels are due to reduced photo- be biologically oxidized by naturally occurring synthesis and the decomposition of the dead microorganisms in water.9 It is important in algae. aquaculture because the degradation of or- The most effective method for reducing BOD ganic matter by microorganisms is a major sink is providing oxygen through aeration, thus ac- for dissolved oxygen, a parameter of funda- celerating the degradation of the BOD by mi- mental importance to aquaculture. croorganisms. The methods of aeration are similar to aeration in dissolved oxygen treat- Effects. As indicated earlier, the major concern ment. For rapid removal, rigorous aeration to of BOD is the potential for it to deplete oxygen remove BOD can be followed up by a settling to levels which are dangerous to fish. If a source basin and a sand filter to remove the microor- water contains a large amount of BOD, micro- ganisms and any other particulates (Boyd 1990, bial growth will be enhanced especially at 356, 386). Another method which is less costly high temperatures. With this microbial growth and less efficient is to use retention ponds in and the corresponding degradation of or- which the water is held for one or two days to ganic matter, oxygen will be consumed. This allow settling and oxidation of the BOD. can lead to the depletion of oxygen in the pond and its associated effects on fish including Carbon Dioxide death. Carbon dioxide (CO2) is a natural component Guidelines. Like dissolved oxygen, it is diffi- of surface waters. Diffusion from the atmos- cult to establish guidelines for BOD concentra- phere, fish respiration, and the biological oxi- tions in source water because the effects of the dation of organic compounds are the major BOD are dependent upon many processes. sources of carbon dioxide in surface waters. BOD5 indicates the rate of oxygen consumption Extraordinarily high levels of carbon dioxide in water over a 5-hour period. The optimal are of concern in aquaculture. This can occur range of BOD5 for cyprinid culture is recom- in source water taken from groundwaters. In mended to be less than 8-15 mg 1-'.10 For waste- addition, surface water sources can have high water-fed ponds the recommended range of levels of carbon dioxide when respiration is BOD5 concentrations is 10-20 mg l-l (Ghosh and occurring at high rates. Thus, if a source water others 1990, 181). is taken from surfaces waters at night or in the These guidelines can be used while taking summer when respiration is high, there may into consideration factors such as the dis- be reason for concern. solved oxygen, the likely DO requirements of the culture, the degree of aeration of the pond, Effects. When carbon dioxide concentrations seasonal temperature changes, expected pho- are too high, the blood CO2 levels of fish in- tosynthesis, and the oxygen solubility. A judg- crease subsequently impairing the ability of ment can then be based on the appropriate their hemoglobin to carry oxygen, and causing BOD level for the source water. respiratory distress (also known as the Bohr- Root effect). The severity of the Bohr-Root effect Treatment. Two common options for treat- is dependent upon the oxygen level. It occurs ment are potassium permanganate and aera- even at high oxygen levels and becomes more tion. Potassium permanganate chemically severe at lower oxygen levels. A species toler- oxidizes organic matter, thus reducing the ance to the Bohr-Root effect can vary. Some BOD. However results are often mixed and the species are able to survive high carbon dioxide. Phase I: Physio-chemical Water Quality Parameters 15 Table 2.10 Carbon dioxide tolerance levels for aquaculture Effects. Under supersaturated conditions, Free COa gases will come out of solution by forming bub- Aquaculture type (mg /-t) Comment bles, both in the water column and in the blood and tissues of aquatic animals. Fish in shallow HaTcrhety <10 Ideal tanks and cages are particularly susceptible be- Warm water < 15 cause they are unable to dive to greater depths Channel caffish hatchery <10 Ideal where they would be protected by higher pres- Finfish < 10-15 Maximum sure. Fish in flow-through and closed recircu- Trout 9-10 Toxic effects lating systems are also susceptible because sufficient degassing does not occur. Gas bubble Source: Lawson 1995, Piper and others 1982, Boyd 1990, and Petit 1990. trauma is rarely a problem in pond culture sys- tems because supersaturated water added to The channel catfish can survive CO2 levels up to ponds rapidly degasses (Lawson 1995, 20). 50 mg l-l provided that sufficient oxygen is pre- sent (Tucker and Robinson 1990). Many species Guidelines. A total gas pressure over 105 per- can tolerate high levels for short periods cent saturation is considered undesirable and (Lawson 1995, 27). High carbon dioxide levels ideally the total gas pressure should be below can also lower the pH, which as mentioned 100 percent (Lawson 1995,20). If a source water earlier can affect fish adversely. does not meet these conditions and methods are used where insufficient degassing is expected, Guidelines. Table 2.10 lists guidelines for carb- then degassing of the source water should be on dioxide levels for aquaculture operations. considered. Treatment. Either calcium hydroxide, also Treatment. Supersaturated source water can known as salked or hydrated lyme, or sodium be degassed by flowing the water through a carbonate may be added to reduce high levels of packed column or providing vigorous agitation carbon dioxide. Sodium carbonate is safer be- (Lawson 1995, 20). cause, unlike calcium hydroxide, it is not caustic and will not cause a substantial rise in pH. How- Nitrogen Gas ever, calcium hydroxide is cheaper and more widely available (Boyd 1990,379,380). Vigorous Nitrogen gas, which is the principal gas in air, mixing and aeration is also a good method for readily diffuses in and out of surface water to removing excess carbon dioxide. reach equilibrium with the atmosphere. At nor- mal culture temperatures, water contains Total Gas Pressure about 10-20 mg 1-l nitrogen gas at equilibrium. Nitrogen gas is not toxic to fish or inverte- Total gas pressure (TGP) is the sum of the par- brates, but supersaturation can cause gas bub- tial pressures of all dissolved gases. If TGP is ble trauma. greater than the barometric pressure, then the water is considered supersaturated. This is of Ammonia concern to aquaculture operations due to its effects on fish health. It can occur via many Ammonia is the initial product of the decom- processes including a temperature increase, position of nitrogenous organic wastes and res- mixing waters of different temperatures, air piration, and may indicate the presence of entrainment such as in a waterfall, photosyn- decomposing urea, feces, and organics. High thesis, high pressures such as those found in ammonia concentrations in source water are deep groundwater, and bacterial activity often found in groundwaters in reducing con- (Lawson 1995, 254). ditions such as those taken from deep wells.1 16 Source Water Quality for Aquaculture: A Guide for Assessment Ammonia can be a larger problem for recircu- rium depending on pH, temperature and sa- lating systems than for ponds because these linity. Analytical procedures normally meas- systems do not often have phytoplankton and ure TAN, so pH, temperature, and salinity rooted plants to assimilate ammonia unless an must be known to calculate the concentration adequately sized nitrifying filter is included. of unionized ammonia. In pulsed flow systems such as those in irri- The proportion of total ammonia nitrogen in gation ditches, high stocking densities result the form of unionized ammonia increases as in high ammonia concentrations (D'Silva and pH increases, so at a higher pH a smaller Maughan 1995). amount of total ammonia nitrogen causes toxic effects (Boyd 1990, 156). At lower pH Effects. High concentrations of ammonia TAN is less toxic because more ammonia ex- cause an increase in the ammonia concentration ists as ammonium. The effect of pH on am- and pH in fish blood. This can cause gill dam- monia toxicity can be pronounced. A change age, reduce the oxygen-carrying capacity of in pH levels from 7.0 to 8.0 increases the tox- blood, increase the oxygen demand of tissues, icity of a given concentration of ammonia by a damage red blood cells and the tissues that factor of 10 (Lloyd 1992,37). Ammonia toxicity produce them, and affect osmoregulation can be influenced by other factors such as tem- (Lawson 1995,32-33). perature and salinity. These are summarized Ammonia toxicity is greatly affected by the in table 2.11. solution chemistry. The toxicity of total ammo- nia nitrogen (TAN which is equal to NH4+ + Guidelines. In general warm water fish are NH3) depends on what fraction of the total is more tolerant to ammonia than cold water fish, unionized, since this is the more toxic form. and freshwater fish are more tolerant to ammo- Ammonium may also be toxic, but only at very nia than marine fish (Lawson 1995, 33). Toxic high concentrations (Boyd 1990, 156). Ionized effects of unionized ammonia are usually felt at and unionized ammonia exist at an equilib- concentrations between 0.6 and 2.0 parts per Table 2.11 Factors affecting the toxicity of ammonia to fish Factor Effect Physlo-chemical properties Temperature Controls ratio of toxic NH3 to NH4+ Increasing temperature increases ammonia toxicity pH Controls ratio of toxic NH3 to NH4+ Increasing pH increases ammonia toxicity DO Low DO increases ammonia toxicity Plants Photosynthesis Increases DO Reduces carbon dioxide; increases pH of water Respiration Reduces DO Increases carbon dioxide; decreases pH of water Gill Surface C02 excretion Increased respiration increases C02 excretion; reduces pH of water Increased C02 in incoming water lessens pH reduction Acclimation Environmental ammonia May increase detoxification capability May be linked with protein content of food Sou8e: Uoyd 1992. Phase I: Physio-chemical Water Quality Parameters 17 Table 2.12 Ammonia tolerances for aquaculture Ammonia Species (mg 1' of NH3) Comment Reference M. rosenbergii 0.09 Reduced growth rates Boyd 1990 Penaeidshrimp 0.45 50% growth reduction Boyd 1990 P. monodon < 0.13 Safe concentration Boyd 1990 P. vannamei < 0.1 Optimum Clifford 1994 0.1-1.0 mg Il TAN Optimum Freshwater fish <0.05 Safe concentration Lawson 1995 < 1.0 mg 1.1 TAN Channel cat. hatchery < 0.05 Optimum Boyd 1990 Salmonid hatchery <0.0125 Upper limit Piper et al. 1982 Salmonids <0.02 EU 1979 Marine fish < 0.01 Safe concentration Huguenin and Colt 1989 General guidelines < 1.0 mg 11 TAN Permissible level Meade 1989 0.1 Max tolerable level Pillay 1992 < 0.012 Permissible level Boyd 1990 <0.02 Permissible level Meade 1989 million (mg 1-l), but some species may be less Because it gets converted to the nitrate end- tolerant. Because there is little consensus re- product quickly, high nitrite concentrations are garding permissible levels of ammonia, it is not common in aquatic systems. Nitrite is not best to be conservative. Listed in table 2.12 are a common source water problem. More com- species-specific ammonia tolerances to use in monly, it becomes a problem during operation assessing the suitability of the source water. of recirculating systems where the water is con- tinually reused (Lawson 1995, 35). Treatment. As mentioned earlier, ammonia is primarily a problem in recirculating systems Effects. High nitrite concentrations deactivate where ammonia is produced at a faster rate than hemoglobin in the blood of fish thus causing it is oxidized. In these cases biological filters are hypoxia. This condition is referred to as brown used (Lawson 1995, 215-47). In brackish water blood disease. A similar effect is found in crus- shrimp farms, zeolites are known to be added taceans (Lawson 1995,34). to control ammonia concentrations. Zeolites Nitrite toxicity is affected by many chemical have been shown to be technically effective in factors. Among the most important is the re- freshwater; however recent research has put duction of toxicity by ions such as calcium, into question the efficacy and cost effectiveness chloride, bromide and bicarbonate. As a result, of this method in salt water and brackish water it is rarely a problem in saltwater and brackish systems (Briggs and Funge-Smith 1996). Other water. For example, nitrite is 55 times more options include using aeration to oxidize the toxic to milkfish (Chanos chanos) in freshwater ammonia to nitrate (nitrification) or to adjust than in water with 16%o salinity (Boyd 1990, the pH and use air stripping to volatilize the 161). It has also been found that the combina- ammonia.'2 tion of high nitrite concentrations and low chloride levels can result in reduced feeding Nitrite activities, poor feed conversions, lower resis- tance to disease, and mortality (Lawson 1995, Nitrite is formed primarily as an intermediary in 34). Other evidence shows increasing pH, low the conversion of ammonia to nitrate, a process dissolved oxygen and high ammonia increases known as nitrification (see appendix table 1). the toxicity.13 18 Source Water Quality for Aquaculture: A Guidefor Assessment Table 2.13 Optimal nitrite concentrations for aquaculture Treatment. Nitrate can be converted to nitro- Species or Concentration gen gas by the process of denitrification. It can water (mg 1.-) Comment Reference then be removed by volatilization. These treat- ment systems can be difficult to run and are Hard freshwater < 0.1 Pillay 1992 Soft water <0.1 Meade 1989 generally expensive.' Freshwater fish <0.5 Hatcheries Swann 1993 Other Critical Factors Brackish water shrimp <45 Boyd 1990 P. monodon <4.5 Postlarval Boyd 1990 IronandManganese growout P. vannamei < 1.0 Optimum Clifford 1994 Iron (Fe) is found in two oxidation states in Salmonid <0.01 Soft water Pillay 1990 natural systems. Ferrous iron (Fe2+) is the re- <0.1 Hard water duced form and ferric iron (Fe3+) is the oxi- dized form. The reduced form of the metal which predominates in nonoxygenated (an- Guidelines. Listed in table 2.13 are recom- oxic) waters is relatively soluble while the mended levels of nitrite in aquaculture facili- oxidized form which predominates in oxy- ties. They can be used as a guide to assess the genated waters is very insoluble. The differ- suitability of a given source water for aqua- ence in solubility causes problems when culture. using source water with high concentrations of reduced iron. If a source water contains a Treatment. In recirculating systems the bio- lot of reduced iron, the iron will precipitate logical filters mentioned for ammonia removal once the source water is oxygenated. The pre- are also used for nitrite. If treatment of source cipitate can then have deleterious effects water before use is desired, aeration can be used upon the operation. Common sources of fer- to promote the nitrification process and conver- ric iron are bottoms of large reservoirs during sion to nitrate.'4 summer, and deep ground water (Boyd 1990, 165). Nitrate A very similar situation exists for manganese (Mn). The oxidized form (Mn4+) is much less Nitrate is the least toxic of the major inorganic soluble than the reduced form (Mnn+). If high nitrogen compounds. It is formed as the end concentrations of reduced manganese exist in product of the nitrification process and concen- a source water, it will oxidize and precipitate trations are generally higher than both ammo- causing similar problems as iron. nia and nitrite. Effects. High levels of nitrate can affect os- Table 2.14 Optimal nitrate concentrations for aquaculture moregulation and oxygen transport, but toxic Concentration concentrations are much higher than for ammo- Species (mg 1I) Comment Reference nia and nitrites (Lawson 1995, 35). High nitrate Carp < 80 Optimum Svobodova et levels can also result in eutrophication and ex- aL 1993 cessive growth of algae and aquatic plants Trout <20 Optimum Svobodova et which might have a negative impact on culture aL 1993 species. P. vannamei 0.4-0.8 Optimum Clifford 1994 Freshwater < 3 Optimum Piper et aL hatchery 1982 Guidelines. Listed in table 2.14 are recom- mended nitrate levels on a species specific and General < 3 Permissible Meade 1989 general basis. guidelines < 100 Pillay 1992 Phase 1: Physio-chemical Water Quality Parameters 19 Effects. If waters which have high concentra- necessary, water can be vigorously agitated tions of reduced iron or manganese are used with mechanical devices or spilled through directly for filling aquaria or tanks for holding towers, and then passed through a sand filter fish, the precipitates may occlude gills and or settling basin. In small-scale operations, iron cause stress or mortality. This is less of a prob- can be removed with filters and water softeners lem in earthen ponds where the volume of alone, but this method is not practical for large- water is greater and the iron or manganese scale aquaculture facilities (Lawson 1995, 38). precipitates near the inflow and does not harm fish. Channel catfish ponds can even be filled Hydrogen Sulfide with water containing 20 to 50 mg 1-1 of ferrous ion, but such waters are not suitable for direct Hydrogen sulfide (H2S) is produced by bacte- use in hatcheries (Boyd 1990, 165). In general ria under oxygen starved (anoxic) conditions. manganese is in lower concentrations in the It can be found in source water taken from environment than iron and therefore is less of a ground water and oxygen-starved areas of sur- concern than iron. In addition to the problems face water. It is of great concern to aquaculture with precipitation, iron also encourages the as it is very toxic to fish. growth of iron-metabolizing bacteria which form an orange slime that can clog pipes, filter, Effects. Even extremely low concentrations of and other equipment (Lawson 1995, 36). hydrogen sulfide cause hypoxia and are deadly or extremely harmful to fish. Concentrations as Guidelines. Iron concentrations less than 0.5 little as 0.05 mg 1-1 have caused death after only mg Pl would be appropriate for hatcheries of a brief exposure and concentrations less than channel catfish and other warm water species, 0.01 mg 1-1 have inhibited reproduction.8 while the optimal iron concentration for cold water hatcheries is less than 0.15 mg t1.'6 Iron Guidelines. While hydrogen sulfide produced concentrations of less than 0.2 mg 1-1 are recom- by heterotrophic bacteria under anaerobic con- mended for cyprinid culture and concentra- ditions inside culture facilities can be treated, tions of less than 0.1 mg P1 are recommended for any sign of hydrogen sulfide in source water is marine aquaculture systems.17 But Meade cause for alarm. Source water found to contain (1989) conservatively recommends a general even the lowest levels of hydrogen sulfide is ques- standard of less than 0.01 mg 1-1. A general tionable as to its suitability as a source water. standard for manganese concentrations in source water is less than 0.01 mg 1-1. Treatment. Oxidation with potassium per- manganate or dilution through water exchange Treatment. Ferrous iron can be removed with are the best methods of hydrogen sulfide re- potassium permanganate (KMnO4), but the pro- moval. The formation of hydrogen sulfide in cedure is seldom practical because potassium ponds can be prevented by vigorous aeration permanganate is toxic to phytoplankton and and circulation to eliminate anaerobic zones expensive. Orthophosphate is adsorbed by the (Lawson 1995, 38). As a method of hydrogen precipitating ferric hydroxide, so ponds must sulfide removal, some companies in Asia are often be fertilized after treatment (Boyd 1990, selling photosynthetic bacterial additives 358). which claim to convert hydrogen sulfide to sul- The simplest method for removing reduced fate. There is no evidence that these bacterial iron and manganese is to retain water for one supplements can lower concentrations of hy- or two days in a holding pond, which will al- drogen sulfide in ponds. In fact, the commer- low the reduced forms (ferrous iron) to natu- cially sold bacteria are naturally abundant in rally oxidize to the oxidized forms (ferric iron), aquaculture environments and do not need to precipitate and settle out. If rapid removal is be added (Boyd 1990, 387). 20 Source Water Quality for Aquaculture: A Guidefor Assessment Methane Table 2.15 Optimal mud characteristics for aquaculture Potential for fish Optimum for Methane, also known as marsh gas, results Variable and range production P. monodon from anaerobic decomposition in pond muds. pH Odorless and flammable, methane might be <5.5 Low found in water taken from the bottom of lakes 5.5-6.5 Average and reservoirs during summer. 6.5-7.5 High 7.5-8.5 Average Guidelines. Methane concentrations below 65 > 8.5 Low mg 1-l are not harmful to fish (Boyd 1990, 163). Available phosphorus > 13 mg i <30 mg 1-1 Low Water-Soil Interactions 30-60 mg I Average > 60 mg r High The chemistry of natural waters is affected by Available nitrogen > 124 mg l-1 the chemistry of the soil and sediment in the < 250 mg r Low water. Exposing water to soils and sediments 250-759 mg i" High often results in chemistry which may be very Organic carbon > 1.0% different from that of the original source water. <0.5% Low Although little is known about these interac- 0.5-1.5% Average tions, they may have important consequences, 1.5-2.5% High either advantageous or deleterious, for the suc- > 2.5% Low cess of an aquaculture project. CIN ratio < 5.0 Low Effects. From the limited studies performed, 5.0-10.0 Average mud may have a large influence on productiv- 10.0-15.0 High ity, especially in brackish water paddy culture Sources: Baneriea and Gosh 1963, and Banerjea 1967 in Boyd 1990, and systems, such as those in India, which use Chakraborli and others 1985. little or no input of nutrients. In pond culture of Penaeus monodon, the highest yields were tion were not addressed, the data (shown in obtained with muds containing greater than appendix tables 2 and 3) provides typical soil 1.0 percent organic carbon, greater than 124 and sediment characteristics for working mg 1-' available nitrogen, and 13 mg 1-l available aquaculture facilities throughout the world. By phosphorous. Other possible water-soil interac- comparing soil characteristics in the source tions include ammonia release during organic water and at the proposed site with these val- decomposition, phosphorous release, increased ues, potential problems may be able to be red- oxygen demand, changes in redox potential and flagged during the screening process. production of reduced substances, and changes in pH.'9 Soil Acidity Guidelines. Because there is not enough re- Soils may be acidic and subsequently reduce search on the effects of soils and sediments on the pH of the water causing deleterious effects aquaculture, it is difficult to subscribe definitive upon the aquaculture operation. Acidic soils in guidelines. Listed in table 2.15 are the results of aquaculture are typically due to either the ex- one study that provides some recommenda- istence of iron pyrite in the soil or due to a large tions. A more thorough study completed re- proportion of exchangeable acidic cations (pri- cently also provides useful information. This marily aluminum ion, A13+) adsorbed to the soil. study sampled soils and sediments from all Under oxygenating conditions, iron pyrite in over the world. Although the effects on produc- soils forms sulfuric acid thus causing a de- Phase I: Physio-chemical Water Quality Parameters 21 crease in pH to typically less than 3.5.20 A soil upon drying for several days.21 For acidity in which is in this state is referred to as an acid- general, it has been suggested that for a soil pH sulfate soil. Acid-sulfate soils typically de- of less than 6.5 and a source water with a low velop in brackish water swamps that are high total alkalinity (less than 20 mg 1-1), treatment in iron pyrite and they also result from acid (using liming) will be required. In addition the mine drainage (Boyd 1990, 182). In addition, pH guidelines given under water-soil interac- acid-sulfate soils are particularly prevalent in tions and the average soil pH of aquaculture ponds constructed on former mangrove operations in Appendixes 2 and 3 can provide swamps. Acidic soils not containing iron py- some guidance. rite lower the pH of the solution as a result of exchangeable acidic cations which disassociate Treatment. There is no feasible way of treating with the soil and react with the water as an the soil to remove iron pyrite. However, meas- acid. ures can be taken to mitigate the effects. These include: draining soils and waiting until natural Effects. Acid soils can reduce the pH of the oxidation and leaching removes the acidity, us- water and causing the deleterious effect of low ing lime to neutralize the acidity, and preven- pH mentioned earlier. Acid-sulfate soil condi- tion of the oxidation of iron pyrite so that tions also tie up nutrients (including fertilizers), sulfuric acid is not produced. It should be noted thus reducing primary production and wasting that the time to remove the acidity in first tech- fertilizer (Joseph 1990, 319). nique is several years and the lime require- ments for the second technique are so large it is Guidelines. Potential acid-sulfate soils may be often unfeasible. Acid soils other than those identified as either having a sulfur concentra- caused by the presence of iron pyrite can be tion greater than 0.75 percent or a low pH (2-3) treated using lime.2 CHAPTER 3 Phase II: Anthropogenic and Biological Water Quality Parameters M etals, metalloids, organic com- form complexes with particulates such as ox- pounds, pathogens and biological ides, clays and particulate organic matter. Tox- contaminants are the parameters ad- icity is usually related to the dissolved, dressed in Phase II. Because testing for all of uncomplexed forms of the metals, rather than these parameters can be expensive, identifica- to the adsorbed, chelated, or complexed forms tion of the parameters of greatest concern will which are more common. In addition to its re- be made. This is done by determining the pol- duction through binding to particulates and lutants expected from past, present and future complexing ligands, the concentration of the agricultural, industrial, and domestic activities toxic dissolved, uncomplexed forms are re- in the area. In addition any historical evidence duced at high pH. Toxicity of metals are also for algal or phytoplankton blooms in the area reduced at high salinity due to competition of can be reviewed. The parameters of concern ions with the metals.23 Therefore metals are less can then be tested for and compared to the likely to be a problem in marine aquaculture guidelines presented here. systems than in freshwater systems. Some met- als bioaccumulate in fish and shellfish thus Metals causing a potential threat to public health. The following sections summarize the Major anthropogenic sources of metals include sources, environmental behavior, background ore mining and processing, smelters, plating levels, and toxicities of the metals. In addition, industries, tanneries and textile industries. The guidelines to assess the source water are also resulting metal pollution is of concern to presented. It should be noted that although this aquaculture because of the potential toxic ef- document treats contaminants in isolation, fects and the ability of many metals to bioac- they are likely to occur in concert with other cumulate, thus reducing product quality and contaminants and water quality problems. A causing public health risks. mixture of metals at concentrations below their In general the effects of metals are dependent individual toxicity thresholds may produce upon which form predominates of the many toxic effects through their joint action (Fumess different aquatic chemical forms of metals. In and Rainbow 1990,116). The following section solution metals form complexes with ligands reflects the bias in the literature towards the such as hydroxide ions and carbonate ions. focus on criteria for contaminant concentra- Stronger complexes are also formed with tions in the water column, but concentrations chelating agents such as organic matter. Metals in sediments may be as important, if not more 22 Phase II: Anthropogenic and Biological Water Quality Parameters 23 so. In some instances sediments may be the Effects on bioaccumulation. While methyl mer- most appropriate measure of contamination, cury accounts for more than 90 percent of the yet few standards exist for sediment contami- mercury found in fish at higher trophic levels, nation. it constitutes less than 1 percent of the total mercury found in aquatic systems (Malm and Mercury others 1990, 12). Methyl mercury is 1,000 times more soluble in fats than in water and concen- Mercury (Hg) naturally occurs in the environ- trates in muscle tissue, brain tissue, and the ment as a result of the volcanic degassing of central nervous system. Hence mercury levels the Earth's crust and weathering of mercury- in fish may be in excess of 10,000 to 100,000 rich geology. While water from areas rich in times the original concentration in surrounding mercury ores may exhibit high local mercury waters. The contaminant rises through the food concentrations, industrial processes, agricul- chain and high concentrations of mercury accu- ture, and the combustion of fossil fuel are the mulate in predators such as trout, pike, walleye, most significant sources of aquatic contamina- bass, tuna, swordfish, and shark. In highly con- tion. Common sources include caustic soda, taminated areas methyl mercury may be accu- pulp and paper, and paint manufacturing. mulated in smaller species which are lower in Mercury is also used in batteries, dental amal- the food chain such as those found in aquacul- gam, and in bactericides. ture (Philips 1993, 302). In addition to fish, aquatic invertebrates also accumulate mercury Environmental behavior. Mercury occurs in to high concentrations.26 both inorganic and organic forms in water. Its Accumulation is fast while depuration is most predominant forms in freshwater are hy- slow. Slightly contaminated shrimp are slow droxide complexes and in saltwater as a chlo- to depurate mercury, while contaminated oys- ride complex (Stumm and Morgan 1981, 372). ters depurate rapidly. Unlike oysters, shrimp Mercury also exists as the mercuric ion (Hg2+) consume sediment-dwelling organisms which and under anoxic conditions, as the neutral, may contain a higher proportion of methyl reduced form (Hg°). In soils it can precipitate mercury than plankton and detritus in the out as stable mercuric sulphide (Dojlido and water column. Mercury depuration in fish is Best 1993, 92). Methyl mercury is formed by also extremely slow. The half-life of methyl bacteria from mercuric ions under both aerobic mercury in fish is estimated at two years (Pal- and anaerobic conditions. It is this form that mer and Presley 1993, 566). bioaccumulates in fish and shellfish. Levels of methyl mercury in fish have also been correlated with the age and size of the Background levels. Mercury levels in water are fish, the species, pH of the water, and mercury much lower than levels in sediments. Natural content of water and sediments (WHO 1989b, background concentrations average 0.1 mg 1-l 33). However the processes affecting mercury dry weight in soils, and 0.19 mg 1-l dry weight behavior in the environment are too complex in sediments.24 Background levels for unpol- for prediction with the current state of knowl- luted waters fall in the range of 0.001 to 0.003 edge. parts per billion (ppb) for lakes and rivers, 0.002 to 0.015 ppb for coastal waters, and 0.0005 to Effects on human health. The general popula- 0.003 ppb for the open ocean. tion does not face a significant health risk from mercury. Exposure is primarily through diet. In Effects on fish health. The lethal levels of mer- most foodstuffs mercury is largely in the inor- cury for fish range from 1 mg l-' for tilapia to 30 ganic form and at very low levels. Fish and fish mg l-l for guppies and 2 mg l-1 for a crustacean products are the dominant dietary sources; (Cyclops abyssorum).25 hence mercury is of greater concern in areas 24 Source Water Quality for Aquaculture: A Guide for Assessment where fish and shellfish account for a major Cadmium proportion of the diet (Philips 1993, 303). Very high levels (more than 1 mg 1- wet weight) have Cadmium (Cd) is a highly toxic metal which been found in the flesh of fish from contami- plays a role in a variety of industrial processes nated waters, resulting in bans on fishing, fish such as electroplating, nickel plating, smelting, sale, and fish consumption in polluted areas. engraving, and battery manufacturing. It is Groups of people with high fish consump- also a constituent of easily fusible alloys, soft tion rates may accumulate blood-methyl mer- solder, electrodes for vapor lamps, photoelec- cury levels associated with a low risk of tric cells, nickel-cadmium storage batteries, neurological damage in adults. The health ef- pigments and plastics. Inorganic fertilizers fects of mercury poisoning are essentially irre- such as phosphate fertilizers, sewage sludge versible. Symptoms include numbness and used on agricultural land, and tailings from tingling, loss of vision and hearing, delirium, zinc mines are also important sources of cad- and disturbance of gait and speech (Philips mium contamination. Cadmium is usually 1993, 298). Of particular concern is that methyl found along with zinc in surface waters, but at mercury is almost completely absorbed from much lower concentrations (Svobodova and the intestine and stable in the body, and circu- others 1993, 26). Municipal sewage effluents lates unchanged in the blood. It remains in the and sludge are another important source of body for extended periods of time (biological cadmium in aquatic environments. half-life is estimated at 70-76 days in human and 200 days to two years in fish), penetrates Environmental behavior. The predominant easily through the blood-brain barrier and ac- form of cadmium in the environment is as the cumulates in the brain. Pregnant and nursing cadmium ion (Cd2+). It also can complex with women are at a greater risk of adverse effects organic matter and particulates to a significant than the general population (WHO 1989b, 33). extent (Dojlido and Best 1993, 84-85). In anoxic Methyl mercury easily penetrates the placenta sediments, cadmium precipitates as cadmium and accumulates in the fetus (Philips 1993, sulfide. Unlike mercury, cadmium does not 303), causing critical prenatal exposure which form organometallic species. may lead to brain damage (Fitzgerald and Clarkson 1991). Because it is highly fat soluble, Background levels. In general natural waters methyl mercury also accumulates in mother's contain very low levels of cadmium unless they milk. are polluted. For unpolluted waters of any type, cadmium concentrations generally range from Guidelines. Because the concentrations which 0.0 to 0.13 ppb.27 Saline water levels are less than may present a public health risk are signifi- 0.2 ppb in estuaries (less than 2.0 in estuarine cantly lower than those that affect the health of sediments) and less than 0.15 ppb in coastal the culture species, the guidelines are based on areas (less than 1.5 in sediments)-8 the public health risks. Because the chemical and biological interactions of mercury are so Effect onfish and shellfish health. The cadmium complex, it is not possible to calculate a single ion and some organic and inorganic complexes mercury criteria for source water that will pro- are toxic to fish. Acute toxic exposure of fish duce aquaculture products with a mercury damages the central nervous system and concentration less than those which present a parenchymatous organs. Chronic exposure ad- risk to public health. Therefore a Phase III pilot versely affects the reproductive organs of study is advisable if total mercury concentra- aquatic organisms, as well as maturation, tions in fresh or estuarine water are greater hatchability, and development of larvae than 0.01 ppb or greater than 0.02 ppb in salt (Svobodova and others 1993,26). Continuation water. of exposure causes mortalities at concentrations Phase II: Anthropogenic and Biological Water Quality Parameters 25 considerably lower than the lethal count level Effects on human health. Cadmium is excep- (96-hour LCJ), probably because the efficiency tionally persistent in humans, and even low of the cadmium detoxification mechanism in levels of exposure may result in considerable fish has a limited duration (Lloyd 1992, 84). accumulation over time especially in the kid- However, most of the cadmium which binds neys (WHO 1989b, 29). The major symptoms of with solid particles ends up in sediments cadmium poisoning, also known as itai-itai syn- where its biological availability is limited and drome, are softening of the skeletal bones, thus less toxic. Calcium also reduces the toxic- pseudo-fractures of the bones, possible skeletal ity of dissolved cadmium, so it is somewhat deformation, and kidney damage (Phillips less toxic in hard water (Lloyd 1992, 84). Be- 1993, 299). Subclinical effects include liver and cause carbon and cadmium compete for bind- renal tubular dysfunction (Phillips 1993, 300, ing sites, higher concentrations of carbon 304). dioxide may reduce the bioavailability and Exposure is likely to vary among individuals hence the toxicity of cadmium.29 depending on food preferences. Bivalve mol- lusks (oysters and clams), some crustaceans, Effects on bioaccumulation. Some species have kidneys and livers of terrestrial animals, and greater capacity for accumulation of cadmium tobacco are common pathways of cadmium ex- than other species. Unlike mercury, accumula- posure for humans (Phillips 1993, 304). While tion rates for cadmium vary greatly among cadmium poisoning has not been known to oc- groups (Phillips 1993, 304). The bioconcentra- cur as a result of consumption of fisheries tion factors (concentration in organism/con- products, significant concern exists over this centration in water) for many species are on possibility. the order of thousands. For some mollusks and arthropods, they are on the order of tens Guidelines. Listed in table 3.1 are guidelines of thousands, and on the order of hundreds of for cadmium in source water. Meade's (1989) thousands for certain tissues (few of which cadmium criteria of 0.5 ppb for soft water and are usually eaten by man).30 Depuration is 5 ppb for hard waters are good for most slow and incomplete, so animals contami- aquaculture with the exception of mollusks. nated in culture facilities are not commercially Linear uptake of cadmium was recorded for salvageable. mollusks growing in 5 ppb of hard saline water Significant levels of cadmium may be accu- (UNEP 1985,11). Therefore a more conservative mulated by bivalve mollusks and certain spe- upper limit of 0.5 ppb, regardless of the hard- cies of crustaceans (Phillips 1993, 304). In ness, is recommended for mollusks. polluted waters, oysters (Crassostrea gigas and C. commercialis), clams, cockles, and some spe- Lead cies of crab (particularly in the brown meat) can accumulate significant amounts of cad- The major sources of lead (Pb) to aquatic sys- mium.ix The Pacific oyster (Crassostrea gigas) tems include atmospheric deposition of ex- has exhibited consistently high concentrations haust from vehicles, disposal of batteries, lead of cadmium, especially in China. Cadmnium ore mine wastes, lead smelters, sewage dis- concentrations in shrimp and prawns are un- charge, highway runoff, and agricultural run- likely to be high. Although, studies of Penaeus off from fields fertilized with sewage sludge. japonicus have revealed high concentrations in areas where fin fish concentrations were com- Environmental behavior and background levels. paratively low. In marine vertebrates, cad- At pH 6 the lead ion (Pb2+) and hydroxide spe- mium tends to accumulate in the kidneys, cies dominate. At higher pH, lead hydroxide leaving the concentration low in the axial mus- and carbonate species begin to dominate. Lead cle tissue.32 also commonly forms sulfate and carbonate 26 Source Water Quality for Aquaculture: A Guide for Assessment Table 3.1 Maximum cadmium concentrations for aquaculture Concentration Species (ppb) Comment Reference Salmonids <0.2 Svobodova etaaL 1993 Salmonid hatcheries < 0.4 Alkalinity < 100 mg 1-1 Piper et aL 1982 < 3.0 Alkalinity > 100 mg I" Cyprinids < 1.0 SvobodovA et aL 1993 Crustaceans < 2.0 UNEP 1985 Freshwater < 1.1 USEPA 1986 Saltwater < 9.3 USEPA 1986 General guidelines < 0.5 Alkalinity < 100 mg I" Meade 1989 < 5.0 Alkalinity > 100 mg I1 Human drinking water < 10.0 Maryland 1993 precipitates. It also forms complexes with or- to be a public health threat (Phillips 1993, 305). ganic matter and particulates. Dissolved lead However mollusks are known to accumulate concentrations in the environment are generally high concentrations of lead in polluted areas low due to either precipitation of carbonate spe- (Pastor and others 1994,53). The half-life of lead cies or adsorption to particulate matter (Dojlido in marine organisms is shorter than the half- and Best 1995, 109-10). There is some evidence lives of other heavy metals. Lead in black-lip that lead forms organometalic compounds in oysters has a half-life of 26 to 34 days. In 40 days natural systems which can accumulated in fish mussels lose 33 percent of their accumulated. It (Schmidt and Huber 1976). The backgrounds is believed that the rate of lead depuration is levels of dissolved lead in surface waters rarely dependent upon the initial exposure conditions exceeds 20 ppb (Dojlido and Best 1993, 110). and detoxification mechanism (UNEP 1985,35). Effects onfish and shellfish health. Chronic lead Effects on human health. As mentioned earlier, toxicity in aquatic organisms leads to nervous fish and shellfish are not a major pathway for system damage while acute toxicity causes gill lead exposure to human populations. The ef- damage and suffocation (Svobodova and others fects which primarily arise from exposure to 1993, 27). Chronic lead toxicity is easily identi- exhaust fumes includes impaired neurologic fied in fish by the blackening of the fins (Dojlido and motor development and damage to kid- and Best 1993, 112). The toxicity of lead is de- neys (Dojlido and Best 1993, 112-13). Severe pendent on the alkalinity, hardness and pH of lead poisoning can also occur in cases where the water. Toxicity is decreased by high alkalin- lead-based paints are ingested. ity (that is, high calcium carbonate) because calcium carbonate competes for uptake at the Guidelines. The lead criteria in table 3.2 repre- gill surface (Lloyd 1992, 39). The solubility of sent the range of opinions regarding maximum lead and thus its toxicity is lower in hard waters concentrations of lead in source water. The per- than in soft waters (Dojlido and Best 1993,112). missible level of lead in drinking water is also For the same reason, lead toxicity is higher at included for comparison. However, saltwater lower pH levels which would be common par- mussels (Mytilus edulis) have been shown to ticularly at ponds bottoms and among benthos accumulate significant concentrations of lead in and nutrients (Svobodova and others 1993, 27). water with a concentration of 10 ppb; so it is questionable whether any of the criteria above Effects on bioaccumulation. Background levels are conservative enough for mollusks (UNEP are low in most marine products and unlikely 1985, 35). The safest strategy is to conduct a Phase II: Anthropogenic and Biological Water Quality Parameters 27 Table 3.2 Maximum lead concentrations for aquaculture Species Lead concentration Reference Salmonids 4.0-8.0 ppb Svobodova et aL. 1993 < 4.0 ppb annual mean; hardness < 50 mg 1I EC 1979 < 0.0 ppb annual mean; hardness 50-150 mg < 20.0 ppb annual mean; hardness > 150 mg l-1 Cyprinids < 70.0 ppb Svobodova et aL 1993 < 50.0 ppb annual mean; hardness < 50 mg 11 EC 1979 < 25.0 ppb annual mean; hardness 50-150 mg 1 < 250.0 ppb annual mean; hardness 150-250 mg I' Freshwater < 3.2 ppb USEPA 1986 Saltwater < 8.5 ppb USEPA 1986 < 5.6 ppb Maryland 1993 All species < 20.0 ppb Meade 1989 Drinking water < 50.0 ppb Maryland 1993 Phase III pilot study if lead concentrations in Background levels. Concentrations of copper in proposed source water exceed 3.2 ppb for fresh- water are typically around 2 ppb. Higher con- water or 5.6 ppb for saltwater. centrations occur in polluted areas (Dojlido and Best, 1993, 66). Copper Effect on fish and shellfish health. Copper has a Copper (Cu) was formerly used in antifouling low toxicity to mammals and does not bioaccu- paints, though it has largely been replaced by mulate readily. However copper is very toxic to organotin. By leaching from paints on the hulls aquatic organisms. Therefore rather than caus- of ships, copper has entered the aquatic envi- ing a human health risk, the main concern re- ronment (Lloyd 1992, 92). In addition copper garding copper contamination is its toxicity to is used as fungicides and algicides. Mining is aquatic organisms. also an important source of copper in the Copper is most toxic to aquatic organisms in aquatic environment. its cupric ion form. Hardness and dissolved organic matter reduce the amount of cupric ion Environmental behavior. Copper species in and thus reduce the toxicity of copper. In hard natural waters commonly include the cupric ion water, copper forms carbonate precipitates and (Cu2+), and copper hydroxide and carbonate is very slow to redissolve. Also, calcium in complexes. In addition, copper forms strong hard waters competes with copper for binding complexes with dissolved organic matter and sites, further reducing toxicity. Dissolved or- particulate matter. These complexes typically ganic matter binds strongly with copper result- control the aqueous copper and/or cupric ion ing in reduced cupric ion concentration and concentration in freshwater systems. Precipita- thus lower toxicity. tion of copper carbonate may also control the concentration at higher pH levels. In seawater Guidelines. The maximum recommended con- there is evidence that complexation to solids and centrations for copper in source water range organic matter is less due to the high concentra- from 1 to 10 ppb or more depending on the tion of ions competing for complexation sites. In physical and chemical properties of the water bottom sediments, copper can precipitate out as and the species of the fish (Svobodova 1993,25). sulfides, hydroxides and carbonates.33 Listed in table 3.3 are the European Union (EU) 28 Source Water Quality for Aquaculture: A Guide for Assessment Table 3.3 Maximum copper concentrations for production speciation which in turn is pH dependent. of salmonil fish Maximum toxicity occurs at pH 5.6 Species Copper concentration Salmonids < 1 ppb; hardness 0-50 mg I" Effects on bioaccumulation and public health. <6 ppb; hardness 50-100 mg Fish will die from aluminum poisoning long < 10 ppb; hardness 100-250 mg 11 before they would be able to accumulate con- < 28 ppb; hardness > 250 mg l centrations which would be harmful to hu- mans. Therefore bioaccumulation is not a major Source: EU 1979. concem. If exposed, there is very little cause for concern. Aluminum which does accumulate in guidelines specifically for salmonids. The fol- the body is stored in the heart, spleen and bone, lowing are general copper concentration guide- and has not proven to be a serious health risk. lines collected from different literature sources: It should be noted though that there is a possible less than 2.9 ppb for saltwater; less than 6 ppb but unproven association between aluminum for soft freshwater (alkalinity less than 100mg 1-); intake and disorders such as Alzheimer's dis- less than 12 ppb for hard fresh water alkalinity ease (WHO 1989b, 27). greater than 100 mg l-1.34 Guidelines. A guideline for aluminum in Aluminum source water is less than 10 ppb (Meade 1989). Aluminum (Al) is among the most abundant Chromium naturally occurring metals. Its most common forms in the environment are as alumino-sili- Chromium (Cr) is principally used in plating cates or aluminum oxides. Anthropogenic and chrome alloy production. Chromium is emissions to water include its use as a coagu- also used in pigments, paints, ceramics, textile lant in water treatment. It is also commonly dyes, fungicides, fireproof bricks and catalysts. used in chemical industries (Dojlido and Best Chromate compounds are also used for corro- 1993, 100). sion control in heating and cooling systems (Dojlido and Best 1993, 175). Environmental behavior and background levels. Aluminum is more soluble at pH below 6 than Environmental behavior and background levels. at higher pH where it precipitates as aluminum Under reduced conditions chromium is in the hydroxide (Svobodova and others 1993, 23). ion form, Cr3+. Under oxidizing conditions such Generally at pH levels common to natural wa- as those commonly found in an aquaculture ters (pH 5 to 9), aluminum concentrations are operation, it is in the hexavalent (Cr+) form. A low due to the low solubility of aluminum hy- large proportion of chromium in natural waters droxide. Normal concentrations of dissolved is found associated with suspended solids and aluminum in natural waters with near neutral sediment. In natural waters chromium typically pH and low concentration of complexing agents has concentrations less than 5 ppb and they range from 0.0003 ppb to 0.3 ppb.35 Acidified rarely get above 20 ppb (Dojlido and Best 1993, waters would have higher dissolved aluminum 175-76). Chromium can also bioaccumulate in concentrations. Complexing agents such as hu- aquatic organisms. mic acids would increase the solubility of alu- minum, thus increasing the dissolved Effects onfish and shellfish health. Chromium is aluminum concentration. highly toxic to aquatic organisms, especially in the hexavalent form.37The toxicity of chromium Effects on fish and shellfish health. The toxicity is greater in soft, acidic water (Svobodova and of aluminum to fish is dependent upon the others 1993,24). Therefore chromium poisoning Phase I1: Anthropogenic and Biological Water Quality Parameters 29 is less of a problem in marine waters, and back- waters (Dojlido and Best 1993, 201). Typical ground levels are low in most marine organisms concentrations of nickel in surface water ranges (Phillips 1993, 305). The 96-hr LC50 for salmonid from 1-3 ppb with higher concentrations (10-50 fish ranges from 3.3 to 65 mg 1.38 For longer ppb) in industrialized areas.40 exposures it was found that a concentration of 13 ppb adversely affected the growth of rain- Effects onfish and shellfish health. Nickel is only bow trout.39 moderately toxic to fish. For salmonid culture, Chromium is not very toxic to humans. nickel has a 96-hr LC50 value of 8 mg l-l in soft There is little evidence that significant expo- waters and 50 mg 1-' in hard waters.4' sure can occur via the ingestion of seafood products. There have been some incidences Effects on bioaccumulation. Fish have little ca- where large exposures via inhalation of salts pacity for bioaccumulation of nickel. Inverte- caused lung cancer (Forstner and Wittman brates have been shown to accumulate nickel 1981, 25). Table 3.4 lists water quality criteria (EIFAC 1984, 6-9). for chromium in aquaculture. Effects on human health. At high doses nickel Nickel can be carcinogenic and teratogenic to humans (Dojlido and Best 1993, 202). Nickel (Ni) is introduced to surface waters through effluents from metal plating and ore Guidelines. Recommended water quality cri- processing facilities. It is also emitted by the teria are: less than 10 ppb (95 percentile less than combustion of petroleum products and is used 30 ppb) for soft water (20 mg 1-1 CaCO) and less to make batteries. than 40 ppb (95 percenfile less than 120 ppb) for hard water (320 mg I-f CaCO).42 Environmental behavior and background levels. The dominant form of nickel in aquatic systems Silver is Ni2+. It forms moderately strong complexes with humic acids and can adsorb to particu- The main industrial sources of silver (Ag) are lates. However, in general, nickel is found pre- ore processing, photography, dentistry, and dominantly in the dissolved form in natural electronics. In industrialized areas anomal- ously high concentrations of silver can be found in surface waters wherever human be- for aquaculture ings are found. In fact silver is often a good Species Chromium concentration tracer for sewage. Salmonid < 5 ppb annual mean; Hardness 0-50 mg Ir Environmental behavior and background concen- < 10 ppb annual mean; Hardness 50-100 mg I1 trations. Common aqueous forms of silver un- < 20 ppb annual mean; Hardness 100-200 mg I1 der aerobic conditions are the silver ion (Ag+) < 50 ppb annual mean; Hardness > 200 mg Ir1 in freshwater and silver chloride complexes in Cyprinid < 150 ppb annual mean; Hardness 0-50 mg I1 seawater (Stumm and Morgan 1981, 372). It < 175 ppb annual mean; Hardness 50-100 mg l11 also readily forms precipitates such as silver < 200 ppb annual mean; Hardness 100-200 mg 1-1 sulfide, silver oxide, silver chloride and silver < 250 ppb annual mean; Hardness > 200 mg i"1 nitrate (Dojlido and Best 1993, 70). Mollusks, such as oysters, accumulate silver quickly, but General <210"ppb chromium (III) take a long time to depurate. Typical concentra- guidelines < 11 ppb chromium (VI) in freshwater tions of silver in surface waters in the Urited < 50 ppb chromium (VI) in saltwater States range from 0 to 1 ppb (Durum and Haffty Sources: EU 1979 and USEPA 1993. 1961). 30 Source Water Quality for Aquaculture: A Guide for Assessment Effects on fish and shellfish health. Silver is in freshwater areas where there is considerable highly toxic to aquatic life. Its toxicity is de- boating activity, especially in marinas (Lloyd pendent upon which salt is present. Silver ni- 1992, 92). trate is most toxic followed by silver chloride and iodide, sulfide, and thiosulfate. Concentra- Effects onfish and shellfish health. Tin, which is tions as low as 0.5 ppb have caused mortalities of low toxicity to mammals, is toxic to aquatic and interfered with the hatching of rainbow organisms (Phillips 1993,306). A toxic level has trout.43 been reported at 2 mg l-l for fish (Liebman 1958). Organotin compounds are considerably more Effects on human health. Silver can be absorbed toxic than tin and are of considerable concern as by skin tissue. When this occurs in large a result. amounts, discoloration of both skin and eye tissue, a condition known as argyria, can result Effects on bioaccumulation. Organotin com- (Forstner and Wittman 1981,16). pounds readily bioaccumulate in aquatic or- ganisms (Dojlido and Best 1993,107). Guidelines. Areas with high silver concentra- tions should be avoided for culture of mollusks. Effects on human health. Gastric irritation is the Guidelines for silver concentrations in source main human health problem associated with water are: less thanO.12ppb for freshwater and less consumption of foods containing elevated lev- than 2.3 ppb for saltwater (Maryland 1993,11). els of tin (WHO 1989b, 34). Most of the tin ingested by humans is derived from packaging Tin in tin cans. Fisheries products are considered a negligible source of tin in the human diet. How- Industrial sources of tin (Sn) include process- ever standards for tin in fish and shellfish do ing ore and manufacturing paint and rubber exist and can be considered directly if a Phase products. Sources of organotin include most III study is pursued. predominantly the use of tributyl tin (TBT) as an antifouling paint for boats. It can also come Guidelines. A water quality standard for fish from plastics industries where it is used as a for tin is 2 mg l-'.45 For organotins, sediments catalyst, fungicide, and disinfectant (Dojlido with TBT concentrations of 1 ppb are toxic to and Best 1993, 107). There are also tin-based clams (Furness and Rainbow 1990, 118). Pro- molluscicides that are often excessively used to posed environmental quality standards for fish control snail populations (Acosta and Pullin for organotins are 0.02 ppb for tributyl tin and 1991). triphenyl tin in freshwater fish."6 Other stand- ards state TBT concentrations in source water Environmental behavior and background levels. should be less than 0.026 ppb for freshwater and In natural waters under aerobic conditions, tin less than 0.010 ppb for saltwater (Maryland is most commonly complexed with hydrox- 1993, 11). ides.' In natural waters, TBT remains in a slowly degrading toxic form which accumu- Zinc lates in sediments (Lloyd 1992,92). Typical con- centrations of tin in natural waters are very low, Zinc (Zn) enters surface waters primarily as a ranging from approximately 0 to 2 ppb (Durum result of discharges from metal treatment and Haffty 1961). Because organotins do not plants, chemical plants, and foundries (Dojlido occur in nature, levels of organotin should be and Best 1993, 79). Mining can also be a source. negligible unless contamination exists. Most TBT contamination occurs in the marine envi- Environmental behavior and background levels. ronment, but high concentrations can also occur In low alkalinity waters, zinc exists as the zinc Phase 11: Anthropogenic and Biological Water Quality Parameters 31 ion (Zn2+) and hydroxide complexes. In high Table 3.5 Maximum zinc concentrations for aquaculture alkalinity waters, it forms complexes with car- recommended by the European Union bonate and sulfate. Zinc can precipitate at high Annual 95th pH as zinc hydroxide and coprecipitate with S Hardness average percentile calcium carbonate (Dojlido and Best 1993, 80). It also readily forms complexes with organic Salmonid fisheries 10 8 30 matter or particulate matter. Ten to seventy- 50 50 200 eight percent of zinc in the world's rivers is 100 75 300 adsorbed to suspended solids and very little is 500 125 500 in the form of precipitates.47 The concentration Coarse fisheries 10 75 300 of zinc in surface waters is generally low. Its 50 176 700 range in uncontaminated waters is 5 to 15 ppb 100 250 1,000 (Moore and Ramamoorthy 1984). 500 500 2,000 Source: EU 1979. Effects onfish and shellfish. There is very little evidence to indicate any significant human concentrations high enough to cause human health effect of zinc. It is however toxic to health problems. aquatic organisms. Zinc concentrations less than 100 ppb had little effect on oyster larvae Environmental behavior and background levels. (Ostrea edulis), but concentrations of 300 ppb Arsenic chemistry in water is complex. Arsenic considerably reduced larval growth, and at can exist in four different oxidation states de- concentrations of 500 ppb larvae either died pending on whether the conditions are oxidiz- or failed to metamorphose (Milne 1972, 165). ing or reducing. Arsenic binds strongly to Hardness (or high calcium concentration) re- particulate matter, can coprecipitate with iron duces the toxicity of zinc (Lloyd 1992, 79). The oxides, and under reducing conditions can pre- LC50 (48-96 hours) varies between 0.5 and 5 cipitate as arsenic sulfide or elemental arsenic. mg l-1 for fish (Moore and Ramamoorthy 1984, Arsenic also forms methylated species through 82). the action of microorganisms. In natural waters a significant portion of the total arsenic is asso- Guidelines. Listed in table 3.5 are the EU ciated with particulates. For example, 33 per- guidelines for specific fisheries. General guide- cent of the arsenic in Puget Sound and 67 lines are: less than 50 ppb for warm water hatch- percent in Rhine River is associated with par- eries; less than 110 ppb for freshwater; and less ticulates.49 Arsenic tends to accumulate in bot- than 86 ppb for saltwater.' tom sediments. Unpolluted river waters usually do not contain concentrations greater Metalloids than 1 ppb.50 The coastal waters in the United Kingdom have concentrations of arsenic less Arsenic than 5 ppb (Musselwhite 1982). The main sources of contamination of arsenic Effects on fish and shellfish health. There is only (As) in the environment are smelting, power limited information on the toxicity of arsenic to generation, the burning of crude oil and coal, aquatic species. Based on existing information, and washing of products such as detergents arsenic is relatively non-toxic to aquatic organ- (Dojlido and Best 1993, 144).- Arsenic is com- isms. A short-term exposure of approximately monly used in insecticides, herbicides and 1,000 ppb is necessary for mortalities to occur. wood preservatives. There are also some natu- However arsenic may affect phytoplankton ral groundwater sources of arsenic from arse- growth at levels as low as five times the back- nic ores and volcanic activity which can reach ground concentration.5' 32 Source Water Quality for Aquaculture: A Guide for Assessment Effects on bioaccumulation. The organic forms cement production (Dojlido and Best 1993, of arsenic are bioaccumulated in fish and shell- 172). fish. However, the bioaccumulation is much less significant than that of methyl mercury. Environmental behavior and background levels. The primary forms of arsenic in fish and shell- Like arsenic, selenium exists in the environment fish are methylated arsenicals and arseno-sug- in many different oxidation states. Its most ars in primary producers and arsenobetanine in common forms in the environment are as se- higher organisms. Relatively high concentra- lenites and selenates which have similar chemi- tions of organic arsenical compounds are pre- cal behavior as sulfites and sulfates. The sent in some seafoods. However the World breakdown of organic matter containing sele- Health Organization (WHO) has announced nium results in the formation of organose- that there is little evidence to suggest that peo- lenium compounds. Typical background ple who consume large amounts of seafood concentrations of selenium are around 0.1 suffer adverse effects related to its organic arse- ppb.53 nic content. Levels of inorganic arsenic in aquatic organisms are low, frequently below Effects onfish and shellfish health. Selenium pre- 0.5-1.0 mg l-l wet weight.52 sents few problems for marine organisms, and it may even help in detoxifying accumulated Effects on human health. The human health mercury.54 effects of arsenic are primarily neurological and nephrological and may linger. The toxicity of Effects on bioaccumulation and human health. arsenic is related to its chemical form. Inorganic Organic forms of selenium can bioaccumulate forms are toxic to mammals and many organic and are harmful to humans. Selenium is also a forms are of insignificant toxicity (Phillips 1993, necessary nutrient to humans and the differ- 300). Human populations consuming large ence between the amount that results in a nutri- quantities of marine fish contamninated with or- ent deficiency and the amount that results in ganoarsenic compounds (weekly intakes of 0.05 toxicity is very small (Dojlido and Best 1993, mg/kg of body weight) did not experience ad- 173). verse effects (WHO 1989b, 28). In laboratory tests, rats which consumed enough contami- Guidelines. Concentrations of selenium in nated fish to produce a daily organoarsenic in- source waters should not exceed 5 ppb in fresh- take of 3 mg/kg of body weight showed no water and 71 ppb in saltwater (USEPA 1993). toxic effects. WHO does not recommend a change in dietary habits due to organoarseni- Chlorine cals in marine fish; however the organization indicates further investigations of the type and Chlorine (Cl) is discharged into surface waters levels of organoarsenicals present in marine from municipal and agricultural water treat- fish are suggested. ment operations and from textile and paper plants. Chemical industries which use chlorine Guidelines. Concentrations of arsenic (III) in gas can also be a significant source. If a source source water should not exceed 190 ppb in water is taken from a municipal water supply freshwater and 36 ppb in saltwater (USEPA which chlorinates, high chlorine concentra- 1993). tions should be expected. Selenium Environmental behavior and background levels. Upon entering water, chlorine gas dissociates to The principle sources of selenium (Se) in the form hypochlorous and hydrochloric acids. Hy- environment are the burning of fossil fuels and pochlorous acid (HOCl) partially dissociates Phase II: Anthropogenic and Biological Water Quality Parameters 33 creating water with some hypochlorite (OCI-) Environmental behavior and background levels. which is the less toxic species and some HOCI, Cyanide in water is typically in the form of the more toxic species. The proportion of each hydrogen cyanide, HCN, or the ion form CN-. species is dependent upon the pH. As pH in- The ion form can take on a variety of complexes creases, the proportion of hypochlorite in- with metals. These complexes are of varied sta- creases until about pH 9 where it dominates. bility with the most stable complexes forming Chlorine commonly reacts to form chloramines with iron and cobalt. Because HCN is the most in solution. In general the high reactivity of toxic form, it is these complexes which regulate chlorine makes it relatively short lived in the toxicity of cyanide. Cyanides do not gener- aquatic systems. ally occur in surface waters because of their The amount of chlorine added to municipal rapid breakdown and evaporation. They are water supplies depends upon the pH and the typically found only near discharge points (Do- amount of organic matter and complexing jlido and Best 1993,208-9). agents in the water supply. However, it tends to range between 0.1 to 1.0 mg 1-1 of residual free Effects. Due to the rapid breakdown of cya- chlorine (chlorine which has not reacted with nide in water, toxicity is of primary concern complexes or organic compounds in solution).55 for fish and shellfish. The toxicity of cyanide is dependent upon the complexes formed Effects. Chlorine and chloramines are very with metals in solution. The weaker the com- toxic to fish. Concentrations as low as 4 ppb as plex, the higher the toxicity. Therefore, high HOCl can be harmful to fish within four days concentrations of metals which form strong of exposure (Alabaster and Lloyd 1980,185). complexes with CN [for example, Ni, Fe (II), Fe (III), CO] would reduce the toxicity of CN. Guidelines. The USEPA recommends chlorine Toxicity is also increased by low pH and by residuals not exceed 11 ppb in freshwater or high temperature.55 7.5 ppb in saltwater. For freshwater fisheries at a pH of 6, the EU recommends a residual Guidelines. Maximum permissible cyanide free chlorine concentration of 6.8 ppb or less. concentrations range from 0.2 to 20 ppb Higher pH can tolerate more. However it is depending on the compounds involved. Sug- more prudent to follow the more conservative gested general guidelines are 5 ppb in fresh- general criteria of 3 ppb suggested by some water or 1 ppb in saltwater.59 researchers.56 Organic Compounds Treatment. Addition of sodium thiosulfate is the most effective method for chlorine removal. Off-flavor It takes approximately 7 mg l-l of sodium thio- sulfate pentahydrate to remove 1 mg 1-1 of free Odorous organic compounds such as those residual chlorine. Chlorine also can be removed from petroleum distillates and discharges from by simply holding water in a storage reservoir paper processing are a common source of off- until the chlorine dissipates through exposure flavors in fish. Pulp and paper mill wastes to sunlight.57 contain polymeric lignins, phenolic com- pounds, mercaptans, terpenes, and other Cyanide residues of chemically digested wood chips which can contain chlorinated derivatives Cyanide (CN) may be discharged into surface and degradation products of chlorolignins waters from a variety of industries including such as chloroform, carbon tetrachloride, and coking plants, gasworks, galvanizing plants, chloroethylenes. Petroleum products enter wa- and petroleum refineries. ters via discharges from petroleum refineries 34 Source Water Quality for Aquaculture: A Guide for Assessment or petrochemical industries as runoff contami- Pesticides nated by motor oils and fuels, from wastes and spills of boat fuels, and from oil spills or dis- Pesticide is used to refer to any chemical em- charge of ballast water off oil tankers and other ployed to control unwanted nonpathogenic or- large ships. Phenols in source water may also ganisms including insecticides, acaricides, cause off-flavor. Phenols result from dis- herbicides, fungicides, algicides, and even ro- charges of industrial effluents (especially from tenone which is used to kill unwanted fish thermal processing of coal), from petroleum (Svobodova 1993, 30). Pesticides have tradi- refineries, and from the production of synthetic tionally been designed to be not only toxic but fabrics.60 persistent. The persistence allows for less frequent application of the pesticide. These Effects. The primary effect is on the flavor of properties are precisely the reasons for the en- the product because fish grown in water con- vironmental concern over pesticides. Pesticides taminated with these compounds will be unpal- are of concern because of the risks they pose atable before contaminant concentrations reach to fish and shellfish health, as well as the risks an unhealthy level. The exception to this is phe- their bioaccumulation pose to product quality nols which can have significant behavioral ef- and public health. fects on fish.6' Pesticides can be split into seven main cate- The majority of off-flavor in fish exposed to gories: inorganic pesticides, organophospho- petroleum products are caused by unsaturated rus pesticides, carbamates, derivatives of alkanes, aromatic hydrocarbons, and sulfur phenoxyacetic acid, urea pesticides, pyrid- containing organic contaminants. However not inium pesticides, and derivatives of triazine all petroleum contaminants result in off-flavor. (Dojlido and Best 1993, 234). The chlorinated Saturated aliphatic hydrocarbons are not very pesticides are of particular concern due to their odorous and do not cause unpalatable flavors persistence and tendency to bioaccumulate in in fish (Tucker and Martin 1991, 137). fish and shellfish. Phenols act as anesthetics on the central The major source of pesticide contamination nervous system. Chronic exposure to phenols in surface waters is runoff from agriculture. may result in necrobiotic changes in the brain, Pesticide manufacturing operations can emit parenchymatous organs, circulation system, wastes with extremely high pesticide concen- and gills. The symptoms of phenol poisoning trations. Because of the persistence of many in aquatic species are increased activity, leap- pesticides, special attention must be made to ing out of the water, loss of balance, and mus- potential past sources of pesticides in identify- cular spasms. ing potential contamination sources to aquaculture source water. Guidelines. Admissible concentrations for oils Some chlorinated pesticides, namely di- range between 0.002 and 0.025 mg 1-1. Admissi- chloro-diphenyl-trichloro-ethane or DDT, ble concentrations for phenols are 0.001 mg P' aldrin, dieldrin, heptachlor, and chlordane are for chlorophenol, 0.003 mg 1-1 for cresol, 0.004 prohibited in the United States and their use mg 1-1 for resorcine, and 0.001 mg 1-1 for hydro- continues to decline worldwide.62 However quinone (Svobodova 1993, 27-28,35). they are still used in some developing coun- The simplest test for off-flavor producing tries where problems of agricultural pests and organics requires neither equipment nor re- insect-transmitted disease are severe and alter- agents: water which tastes or smells unusual native methods are expensive or insufficiently may result in off-flavor. Therefore a sensory developed. assessment can often be preferable to chemi- cal analysis in assessment of the source Environmental behavior. The persistence of water. pesticides varies depending on the chemical Phase II: Anthropogenic and Biological Water Quality Parameters 35 Table 3.6 Persistence of pesticides Readily degradable Slightly degradable Moderately persistent Persistent 1/2 life < 2 wks 1/2 life = 2-6 wks 1/2 life = 6 wks-6 mos. 1/2 life > 6 mos. Captan Chloramben Carbofuran DDT Carbaryl Chlorpropham Carboxin y-HCH Chlorpyrifos Dalapon Chlordane Aldrin Dichione Diazinon Chlorfenvinfos Dieldrin Dicrotophos Disulfoton Chloroxuron Heptachlor Endotol Fenuron Dimethoate Isodrin Endosulfan MCPA Diphenamid Monocrotophos Fenitrothion Methoxychlor Diuron Benomyl Malathion Monuron Ethion Methiocarb Phorate Fensulfothion Methylparathion Propham Linuron Parathion Prometion Phosphamidon Propazine Propoxur Simazine 2,4-D Toxaphene Source: McEwan and Stephenson 1979. structure. In general the more insoluble pesti- ated pesticides are listed in table 3.7. The toxic- cides such as organochlorine pesticides tend to ity of a pesticide can be reduced by high concen- be more persistent, while the water soluble pes- trations of particulate matter. Adsorption to ticides tend to be less persistent (Dojlido and these particulates, as well as sediments, reduces Best 1993, 239-41). Table 3.6 shows the relative the availability and toxicity of a given pesticide. persistence of a range of pesticides. Pesticides also affect aquaculture species indi- The primary mechanism of pesticide degra- rectly through their toxicity to phytoplankton. dation is biological, however chemical and photochemical degradation also occurs. The Table 3.7 Toxicity to aquatic life of selected chlorinated processes controlling biodegradation are com- hydrocarbon insecticides plex and poorly understood. Among the limit- 96-hr LC5o Safe level ing processes are presence of organisms which Pesticide (ppb) (ppb) can degrade the chemicals, existence of condi- tions in which the organisms can grow to sig- Aldrin 0.20-16.0 0.003 nificant populations, and availability of BHC 0.17-240.0 4.0 sediment-bound pesticides to the organisms. 0.08 Another process affecting the fate of pesticides Chlordane 5.0-3,000.0 0.01 is their high affinity for particulates, especially 0.0043 (fresh) 0.004 (salt) those containing organic matter. This is par- DDT 0.24-2.0 0.001 ticularly true for the pesticides with low solu- Dieldrin 0.20-16.0 0.003 bility such as the organochlorine pesticides. As 0.0019 a result, these pesticides commonly accumu- Endrin 0.13-12.0 0.004 late in bottom sediments where biodegrada- 0.0023 tion is often slow because of factors such as Heptachlor 0.10-230.0 0.001 reduced bioavailability, non-ideal redox condi- 0.0038 (fresh) tions, or nutrient limitations. 0.0036 (salt) Toxaphene 1.0-6.0 0.005 Effects onfish and shellfish health. The toxicities 0_0002 (96-hr LCJ) and safe levels of selected chlorin- Source: Boyd 1990 and USEPA 1993. 36 Source Water Quality for Aquaculture: A Guide for Assessment Herbiciides are particularly toxic to phyto- Guidelines. The safe levels for selected pesti- plankton (Boyd 1990, 166). cides in table 24 include only a partial list of the hundreds and potentially thousands of com- Effects on bioaccumulation. Many pesticides, mercially available pesticides. If the pesticides including most significantly chlorinated pesti- used in the watershed from which source water cides, have a low solubility in water; however is derived are not among those listed, further they readily dissolve in hydrophobic environ- investigations should be conducted to deter- ments such as the fats of aquatic organisms. In mine permissible levels. general lower solubility results in a higher ten- Depending on the pesticides of concern, the dency for a pesticide to accumulate in fish and testing required to determine permissible levels shellfish. Efforts to experimentally quantify the may range from simple to complex. Because bioconcentration factors (BCF) have not yielded many persistent pesticides bind strongly to exact results due to the variability in experi- sediments and suspended particulate matter, mental conditions. The BCF equals concentra- testing of concentrations which occur in solu- tion of pesticide in organism divided by tion may be misleadingly low in comparison concentration of pesticide in water. However with their bioavailability (Lloyd 1992, 90). they have yielded general BCF ranges for a Therefore if the presence of persistent pesticides particular compound. Listed in table 3.8 are the is suspected in source water or sediments, a solubility of selected pesticides and the corre- Phase III field study should be conducted to sponding ranges of experimentally derived determine the effects of potential pesticide ac- BCF for fish. cumulation on culture species and consumers. Effects on human health. Organochlorine pesti- Treatment. Options include those used in cides are absorbed in humans by the gastroin- treatment of municipal water supplies such as testinal tract, and some may also be absorbed reverse osmosis, ion exchange, air stripping, through the skin. The toxic mechanisms are not adsorption, and oxidation. However these are yet fully understood, but the major toxic action often very expensive. Finding another source of organochlorine pesticides is on the central water may be the most viable choice. and peripheral nervous system. Exposure to Water from an uncontaminated source can chlorinated cyclodiene insecticides (that is, be contaminated by insecticides after it is in- aldrin, dieldrin, endrin, chlordane, heptachlor, troduced into culture facilities. Pesticides endosulfan, and isodrin) causes headaches, diz- sprayed onto crops may drift over considerable ziness, nausea, vomiting, jerking muscles, and distances to ponds and canals (Boyd 1989, 47). convulsions. In addition many pesticides are Box 3.1 describes measures to prevent pesticides suspected carcinogens.63 from contaminating the aquaculture ponds. Table 3.8 Pesticide solubility and experimentally derived bioaccumulation factors in fish Pesticide Solubility in water (mg 1-') BCF in fish References Aldrin 0.02 3,890-10,715 Suntio et al. 1988 and Howard 1991 Atrazine 33 3-10 Khan 1977 BHC low 1,160-3,740 Khan 1977 Chlordane 0.1 5,200-38,000 Worthing 1987 and Howard 1991 Dieldrin 0.17 3-6,000 Suntio 1988 and Howard 1991 Endrin 0.00025 1,335-10,000 Biggar and Riggs 1974 and Howard 1991 Heptachlor 0.18 5,744-21,379 Biggar and Riggs 1974 and Howard 1991 Toxaphene 0.55 3,100-33,300 Murphy etal. 1987 and Reish et aL 1978 Note: BOF factors partially taken from Howard (1991), in which literature values are included for a long list of pesticides. Ranges listed here were taken from the literature values quoted for fish that did not specify an unusually short equilibrium time (that is, on the order of hours.) Phase II: Anthropogenic and Biological Water Quality Parameters 37 Box 3.1 Protecting aquaculture ponds processed and distributed chemical products from pesticides in the world. Primary sources include runoff from roads and discharge from industries us- • Place ponds a considerable distance from ing oil (Dojlido and Best 1993, 231). As men- pesticide treated fields. tioned earlier, the major concern of petroleum . Plant trees or other tall plants between pes- hydrocarbons to aquaculture is producing off- ticice treated fields and aquaculture facili- flavor. Crude oil, either released from tankers ties to intercept airborne drift of sprayed at or stc al oil fied or shore pesticides. at sea or spilt accidentally at oil fields or shore . Construct topographic barriers (ditches or terminals, is a major pollutant in the intertidal terraces) to prevent agricultural runoff zone which can devastate oyster beds (Milne from entering ponds. 1972, 163). The risks of potential aquaculture . Use proper methods of pesticide applica- source water taken from areas with high oil tion to fields. . Properly dispose of all pesticides and pes- tanker traffic should be considered carefully. ticide containers. Polychlorinated Biphenyls Source. Boyd 1990. Polychlorinated biphenyls (PCB) were heavily used in transformers and capacitors of heavy Antibiotics and Antimicrobials electrical equipment as lubricants for compres- sors and in the production of varnishes, dye- Agriculture is one example of industries re- stuffs and plastics (EIFAC 1993, 28). Common quiring control of microbes which may con- worldwide PCB trade names are Aroclor taminate source water with unwanted anti- (USA), Clophen (Germany), Delor (Czechoslo- biotics and antimicrobials. Iodine, for example, vakia), Kaneclor Japan), and Savol and Sovtol is often used in veterinary drugs, agricultural (Russia and the former Soviet republics).65 In chemicals, and sanitizing solutions (WHO the 1970s severe restrictions were made on its 1989b, 32). These chemicals may damage the production and as a result worldwide produc- natural micro-biological conununities which tion has gone down drastically. However PCB are necessary for the health of the culture spe- is considered among the most persistent pol- cies; or they may disturb the natural microbio- lutants and contamination is widespread. Be- logical environment, creating an opening for cause of their persistence, it is of particular opportunistic pathogens. importance to identify older companies which Bioavailability is a particularly important is- may have been producing the chemical in or- sue for antibiotics and antimicrobials. Testing der to identify if PCBs are potentially contami- procedures for these compounds are so sensi- nating the source water. It should also be noted tive that even a few molecules can be detected. that PCBs can travel great distances and there- However molecules which are bound to sedi- fore industries outside the immediate locality ments and other substrates, and thus biologi- may be contaminating the source water of cally unavailable, must be detached in order to concern. be detected. Therefore the levels which are shown by testing may be representative of Environmental behavior. PCBs are extremely many antibiotic and antimicrobial chemical persistent in the environment. Although they complexes which are not biologically active.64 can be biodegraded, degradation is slow under natural conditions. The PCBs are able to volatil- Petroleum Hydrocarbons ize from water; however the more common des- tiny for these molecules is in sediments and As components of liquid and gaseous fuels, body tissues. This is due to their extremely low hydrocarbons are among the most widely solubility which encourages adsorption to sedi- 38 Source Water Quality for Aquaculture: A Guide for Assessment ments and accumulation in the fat tissues of fish pared to that in the tested formulations (Svobo- and mammals. As a result, concentration of dova 1993, 28). PCBs in the water column are typically much General water criteria for aquatic organisms lower than in the sediments (Dojlido and Best as set by the USEPA are less than 0.014 ppb for 1993, 183, 282). freshwater and less than 0.03 ppb for saltwater. Meade (1989) suggests that levels up to 2 ppb Effects on fish and shellfish health. Chronic ex- may be acceptable. Due to their high toxicity, posure to low levels of PCBs may result in if levels of any PCBs exceed those set out by skeletal deformities, skin and fin damage (pos- the USEPA, a Phase Im pilot project should be sibly disintegration), damage to the liver and pursued to identify and quantify a number of gonads, high mortality during hatching, and key types of PCBs for an expert evaluation of high mortality of early fry (Svobodova 1993, the potential hazard.68 29). The eggs and larvae of aquatic organisms are more sensitive to these pollutants. The solu- Dioxins and Furans bility and thus toxicity of PCBs are enhanced by increases in temperature. Dioxins is a general term for 75 different poly- chlorinated dibenzo-o-dioxins. Similarly, Effects on bioaccumulation. Because of their low furans is a general term for 135 different poly- solubility in water and high solubility in fat, chlorinated dibenzofurans. Furans are typi- these compounds have a large tendency to ac- cally found in conjunction with dioxins. cumulate in the food chain, especially in lipid Dioxins and furans can enter water via the rich eggs and fatty fish such as eels. The BCF for wastewater of industries such as wood proc- PCBs in aquatic organisms ranges from 103 to essing plants, pulp and paper mills, tanneries, 105. Shellfish and mussels are known to accu- and the production of pesticides and wood mulate PCBs in contaminated waters.66 preservatives. Also, combustion of wastes, coal and chlorinated pesticides can produce dioxins Effects on human health. When ingested, less and furans (Dojlido and Best 1993, 287). highly chlorinated PCBs are metabolized in the liver and excreted, but more highly chlorinated Environmental behavior. Dioxins and furans are biphenyls are metabolically stable and accumu- widespread in the water environment. Sediments late in body fat. However the toxicity of PCBs are a major sink for these compounds. Their to humans is generally low. In Japan in 1968 an biodegradation is slow and because of their low accidental consumption of PCB-contaminated solubility, they readily adsorb to sediments. edible oil by 1,000 people resulted in no mortali- ties but adverse health symptoms were ob- Effects on fish and shellfish health. In rainbow served for three years.67 trout, coho salmon, guppy, and pike, chronic exposure to tetrachloro dioxin (TCDD) through Guidelines. Because there are over 200 PCBs diet or water caused decreased growth and with individual toxicological properties caused fin necrosis and death.69 which are often mixed together, it is difficult to determine toxicity standards for either hu- Effects on bioaccumulation. Dioxins and furans man or aquatic species. Most toxicity tests are have low solubility and therefore are capable of carried out on commercial formulations bioaccumulation in fish. Bioaccumulation fac- which are normally identified by the extent to tors up to 10,000 have been reported (Isensee which they are chlorinated rather than by the 1978). PCBs that they contain. Differential uptake of the individual components leads to a different Effects on human health. Of the dioxins the 2,3, ratio being found in the organisms when com- 7, 8 tetrachloro isomer (2,3,7,8 TCDD) is the Phase II: Anthropogenic and Biological Water Quality Parameters 39 most toxic. The primary human health effects of one order of magnitude takes place in-pond, so dioxins are chloracne and possible birth defects. that in-pond concentrations should be less than They have also been shown to affect the liver 103 per 100 ml. If pond temperature and reten- and nervous system.70 tion time indicate that a higher reduction can be However, it should be noted that the effects achieved, this guideline may be relaxed. At con- of dioxins and furans in the above areas are centrations above 104 and 105 per 100 ml, the not certain and a point of great controversy in potential for fecal coliform and other pathogens politics and in the scientific community. to invade muscle tissue is very high.7" Guidelines. It is difficult to prescribe guide- Guidelinesfor total bacteria. The validity of fecal lines considering the controversial nature of coliform as an overall indicator of bacteriologi- dioxin effects. It is recommended that dioxins cal contamination is debatable, especially in the be evaluated on a case-by-case basis. If their tropics. Reliance on coliform standards may presence is suspected, a Phase Im field study overestimate potential health risks, unduly bur- should be pursued. dening developing countries in their efforts to develop shellfish resources in tropical waters Pathogens and Biological Contaminants (Rice 1992, 195). Some researchers recommend that the concentration of total bacteria (not total High concentrations of pathogenic organisms coliforms or fecal coliforms, but standard plate are commonly found in waters polluted by hu- count per ml) be used to assess the risk of mi- man sewage and animal wastes. Thus a major crobial contamination. They point out that if source of contamination is sewage outfalls in total bacteria reaches 1.0 to 5.0 multiplied by 104 populated areas and livestock facilities. per ml, then bacteria are likely to appear in muscle tissue (Buras and others 1985). Human Pathogens in Fish and Shellfish Guidelines for specific pathogens and parasites. In many countries untreated wastewater or Other pathogens associated with human dis- animal wastes are used directly in aquacul- eases such as salmonella, streptococcus, Aero- ture; in these cases contamination is of particu- monas, Pseudomonas, Klebsiellae, and Escherichiae lar concern. are often found in the gut of fish cultured in wastewater, but rarely in the muscle tissues or Effects. Human pathogens are of concern in visceral organs. WHO recommends that salmo- aquaculture because they can accumulate in nella count in source water not exceed 103 per fish. These organisms do not cause disease in 100 ml. Mara and Cairncross (1989) recommend the fish. However, the fish can serve as a vector that the concentration of viable trematode eggs for the disease thus infecting humans who con- (arithmetic mean number per liter or kg) be sume them or handle them. Many pathogens, equal to zero, because the only feasible means of including salmonella, E. coli and Clostridium controlling Clonorchis sinensis, Fasciolopsis buski, botulinum, have been found to survive in fish and Schistosoma japonicum (species which are tissues (Buras 1990). endemic to Asia) is to remove all viable eggs before the wastewater is applied to ponds.72 Guidelinesforfecal coliforms. WHO (1989) rec- Botulism, typhoid, hepatitis, cholera, non- ommends that fecal coliform counts in source specific gastroenteritis, and a host of other dis- water not exceed 103 per 100 ml. Mara and eases may also result from ingestion of raw or Cairncross (1989) indicate that in wastewater- insufficiently cooked fish and shellfish. There- fed ponds, concentrations of 104 per 100 ml are fore if wastewater or other sources which are acceptable for culture of both fish and aquatic likely to be contaminated with pathogens are macrophytes. They assume that a reduction of used, source water should be tested for a range 40 Source Water Quality for Aquaculture: A Guide for Assessment of pathogens which might influence project Because such pathogens are difficult and expen- viability. sive to monitor, standards are set for depura- tion processes rather than for the concentration Standards for shellfish. The United States has of pathogens in the flesh of cultured organisms established standards for waters that can be (Pillay 1992, 104). For example, only shellfish used to culture or harvest shellfish. For these grown from certified operations can be sold on waters the total coliform median or geometric the United States and Canadian markets. mean most probable number (MPN) of the The two most common methods of depura- water should not exceed 70 per 100 ml and not tion are relaying in clean water or depuration more than 10 percent of the samples can exceed in specially designed plants. Relaying entails an MPN of 230 per 100 ml for a 5-tube decimal transplanting shellfish into a clean area for a dilution test (or an MPN of 330 per 100 ml for a minimum period of time, usually 30 days; 3-tube decimal dilution test). In addition the however, depuration of highly contaminated fecal coliform median or geometric mean MPN shellfish requires longer purging periods and of the water should not exceed 14 per 100 ml and is not feasible on a commercial basis. Depura- not more than 10 percent of the samples can tion plants store the shellfish in tanks of seawa- exceed an MPN of 43 per 100 ml for a 5-tube ter disinfected with filters, chlorine, ozone, or decimal dilution test (or an MPN of 49 per 100 ultra-violet radiation (Pillay 1992,104). Despite ml for a 3-tube decimal dilution test).73 its acceptance in many countries, depuration alone without attention to water quality in the Water treatment. Wastewater usage can be initial growing areas is not sufficient to assure treated through traditional wastewater treat- safe shellfish. Careful attention must be given ment processes. These processes can be a com- for developing unpolluted areas and culture bination of primary sedimentation, activated practices which will minimize the risk of mi- sludge, biofiltration, aerated lagoon, oxidation crobial contamination of shellfish. ditch, disinfection, waste stabilization ponds, or effluent storage reservoirs. Treated waste- Phytoplankton and Algal Toxins waters have been shown usable for aquaculture and, in some cases, as a better altemative than Off-flavor. The muddy, earthy flavor of fish the local contaminated surface water.74 grown in fresh or brackish water is one of the In addition, chlorination of aquaculture most common types of environmental contami- ponds to remove pathogens can be performed. nation of aquaculture fish; it can often be antici- The chlorine dose will vary depending on pH pated by smelling or tasting the source water. and the concentration of organic matter and This muddy off-flavor, which is easily detected ammonia. However, when chlorinating in mild-flavored fish, is not harmful to human aquaculture ponds, one has to be careful the health, but can result in lower prices for concentrations of chlorine are reduced below aquaculture products. Off-flavor in pond-cul- toxic levels before the fish are exposed to the ture fish is characteristic of geosmin, 2-methyl- disinfected water (Boyd 1996, 44). isobomeol, mucidone, or similar compounds produced by blooms of actinomycetes and blue- Treatment by depuration of shellfish. Filter-feed- green algae. Algal blooms are often times un- ing shellfish grown in polluted or low-quality predictable and hard to prevent. The offending water accumulate pathogenic micro-organisms algae can be killed with copper sulfate, but the and have to be depurated before sale, especially best strategy is to remove the muddy flavor in areas where shellfish is eaten raw or partially through depuration in clean water prior to har- uncooked. Depuration also reduces the risk of vesting. Catfish, for example, can depurate in 5 viral pathogens, such as hepatitis, which are to 15 days depending on water temperature and often transmitted through oysters and clams. the severity of the off-flavor. Algae which cause Phase II: Anthropogenic and Biological Water Quality Parameters 41 muddy off-flavor do not thrive in saline water muscle, rarely becomes toxic. Depuration is (Pillay 1992, 100-1). feasible for rapidly detoxifying species. How- ever detoxifying shellfish on a large scale is not Red tide. Red tides (blooms of toxic dinoflag- economically promising.76 ellates) are a major source of fish and shellfish mortality and a serious public health hazard. Toxic algal blooms. Toxic algal blooms are dif- The most common algal blooms in tropical wa- ficult to prevent or predict. Algal blooms origi- ters are caused by the dinoflagellate Pyrodinium nate in the oceans far from shellfish beds, and bahamense var. compressa.75 the mechanisms which cause them are not well Shellfish rapidly accumulate these toxins understood. The toxins associated with these and become vectors of various forms of shell- algae can cause shellfish to become toxic over- fish poisoning, such as paralytic shellfish poi- night. These toxins can persist for months after soning (PSP), diarrhetic shellfish poisoning blooms have disappeared, resulting in major (DSP), neurotoxic shellfish poisoning (NSP), economic disasters (Pillay 1992,105). and amnesiac shellfish poisoning (ASP). Rates of toxin accumulation and depuration vary Guidelines. Because it is difficult to predict with species, temperature, and intensity of if a given source water will be a victim of algal blooms. Mussels both accumulate and depu- or phytoplankton blooms, guidelines need to rate PSP toxins more quickly than other spe- be based on historical monitoring data. If data cies, while oysters take a longer time to exist on location and extent of algal or phy- accumulate and to detoxify. Some species have toplankton blooms, then it should be deter- been reported to remain toxic for up to two mined if the area of the proposed source years. The hard clam or quahog, on the other water is susceptible to blooms. If so, the hand, can avoid toxic algae by burying itself risks must be considered carefully. The ef- deep within the sand and closing its shell. Scal- fects may be mitigated by restricting the lops are also safe to eat during algal blooms types of species farmed or the time of year because the part normally eaten, the abductor farms can operate using this source water. CHAPTER 4 Phase III: Field Study P hase m should be pursued if Phase I or processes, and the project species. The fish Phase II criteria are not met and the risks growth, health, and contaminant residues can are either considered acceptable or a then be measured. A design and cost analysis treatment method which is technically and fi- can be made of any proposed treatment nancially viable is found. The purpose of processes. Phase III is to provide a field test of aquacul- In both cases it is important to emulate the ture operation when the success of the project conditions to be used in the final project. This is in question based on water quality. The includes not only source water and species field study will help render a decision on but, if possible, the soil. Because quality in whether or not to use the selected source surface waters can vary seasonally, it is im- water. In the case where the source water is portant to run the study over a representative accepted, any operational problems or ad- time period which reflects these changes. Typi- justments can be anticipated before the pro- cally this would be one year. In order to make ject begins. The field study specifically focuses sure the influence of source water quality on on evaluating the fish growth and health, the project outcome is being tested, efforts should contaminant residues in the fish, and the tech- be made to eliminate other possible sources of nical and economic feasibility of a treatment failure. operation. Criteria for Fish Growth and Health Study Design Fish should be of sufficient size to be market- There are two options for the type of field able and production should operate at a high study. The more cost efficient method is to find enough rate to be profitable. The fish should an operating aquaculture facility in the area be sufficiently healthy so disease or its risk is which is using the same source water and man- low. The fish should undergo examination for agement techniques to grow a similar species. any specific symptoms based on the pollutants Tests for species growth and health and con- present. More general examination for dis- taminant residues can then be made on the eases, stress, or abnormalities should be per- product of this facility. In addition, a detail formed. Recent research has pointed to the design including cost analysis can be made of utility of biomarkers in assessing a potential any proposed treatment processes. effect of water quality on fish. These markers, The second option is to set up a pilot study which are listed in appendix table 4, may be of of the aquaculture facility, using the pro- use depending on the pollutant. In particular posed source water, any proposed treatment those measuring stress such as the corticos- 42 Phase III: Field Study 43 teroids/cataecholamines biomarkers have biological contaminants for the United States, been suggested as a good measure of general Canada, Japan, and the European Union. stress as a result of water quality problems (Tarazona and Munoz 1995). Fish and Shellfish Intended for Local Consumption Criteria for Contaminant Residues Because diet and possible exposure to contami- In the case of fish intended for export, contami- nants differ from country to country, standards nant residues should be sufficiently low to for contaminant residues set as import stand- meet the standards of the importing country. ards by some countries in food may not be For fish intended for consumption locally, appropriate for the project area. Both where standards should be adopted based on protec- aquaculture products will be consumed and tion of public health. what product parts will be consumed must be taken into account when considering permis- Basisfor Standards sible levels of contaminant residues. If a prod- uct is going to be consumed heavily in a local Levels of contaminants allowed in food and area, the residues will have to be lower to be drinking water are based upon provisional tol- safe. In addition all edible parts should meet erable weekly intake (PTWI) standards. These consumption standards and the parts of a fish standards, expressed in micrograms per per- deemed edible vary from market to market ac- son or micrograms per person per kilogram of cording to custom and taste. Consumers in body weight, depend upon the average rate of some regions may eat kidneys, livers, or other human bioaccumulation from contaminated organs, while consumers in other regions will foodstuffs. Standards for contaminant residues eat only muscle tissues. In addition, certain in food are calculated on the basis of the PTWI, contaminants may accumulate in the kidney, rate of consumption of the foodstuff, and prob- liver, and muscle tissues of a fish at different able extent of exposure to the contaminant via rates. Hence a single fish may contain some other pathways. PTWI for selected contami- parts which meet standards and others which nants are listed in appendix table 5. do not. If no standards are set for the project area, Fish and Shellfish Intendedfor Export the above factors should be considered to the extent possible in establishing standards. In ar- For fish and shellfish intended for export, the riving at these standards the list of PTWI in contaminant residues should meet the stand- appendix table 5 may be useful along with the ards of the importing country. Appendix tables import standards for different countries listed 6 and 7 list these standards for chemical and in appendix tables 6 and 7. APPENDIX TABLES Appendix table 1 Effect of biological processes on alkalinity Process Alkalinity change for forward reaction pH change for forward reaction Photosynthesis (forward reaction) and respiration (reverse reaction) (la) nCO2 + nH20 <=> (CH20)n + nO2 No change No change (lb) 106C02 + 16 NO3- + HP042- + 122H20 + 18H {CI06H2630110N16Pl) + 13802 Increase Increase 'algae' (1c) 106C02 + 16NH4+ + HPO42- + 108H20 (C{06H2630110N16P) + 10702 + 14H+ Decrease Decrease Nitrification (2) NI-14 + 202 = NO3- + H20 + 2H+ Decrease Decrease Denitrification (3) 5CH20 + 4NO3- + 4H+ = 5CO2 + 2N2 + 7H20 Increase Increase Sulfide oxidation (4a) HS- + 202 = S042- + H+ Decrease Decrease (4b) FeS2(s) + 3.7502 + 3.5H20 => Fe(OH)3(S) + 4H+ + 2SO42- Decrease Decrease pyrite Sulfate reduction (5) S042- + 2CH20 + H+= 22 + HS + H20 Increase Increase CaCO3 dissolution (6) CaCO3 + CO2 + H20 Ca2+ + 2 HC03- Increase No change Source: Stumm and Morgan 1984. Appendix Tables 45 Appendix table 2 Relative abundance categories of soil chemical variables in brackish water ponds 1st decile 2nd-3rd decile 4th-7th decile 8th-9th decile 10th decile Variable (very low) (low) (medium) (high) (very high) pH < 4 4-6 6-8 8-9 > 9 Carbon (%) < 0.5 0.5-1 1-2.5 2.5-4 > 4 Nitrogen (%) < 0.15 0.15-0.25 0.25-0.4 0.4-0.5 > 0.5 Sulfur (%) < 0.05 0.05-0.1 0.1-0.5 0.5-1.5 > 1.5 Phosphorus (mg 11) < 20 20-40 40-250 250-400 > 400 Calcium (mg 11) < 1,000 1,000-2,000 2,000-4,000 4,000-8,000 > 8,000 Magnesium (mg 1") < 700 700-1,500 1,500-3,000 3,000-4,000 > 4,000 Potassium (mg 1") < 100 100-400 400-1,200 1,200-1,700 > 1,700 Sodium (mg 11) < 2,500 2,500-7,000 7,000-15,000 15,000-25,000 > 25,000 Iron (mg 1.) < 60 60-200 200-750 750-1,200 > 1,200 Manganese (mg 11) <10 10-50 50-150 150-350 > 350 Zinc (mg [-1) < 2 2-5 5-8 8-14 > 14 Copper (mg l') <1 1-2 2-8 8-11 >11 Silicon (mg 11) < 30 30-100 100-500 500-750 > 750 Boron (mg 1-) < 4 4-8 8-18 18-24 >24 Cobalt (mg 11) < 0.5 0.5-1 1-2.5 2.5-3.5 > 3.5 Molybdenum (mg 11) < 0.3 0.3-0.5 0.5-0.9 0.9-1.2 > 1.2 Aluminum (mg -1) <100 100-200 200-500 500-600 >600 Barium (mg 1.1) < 0.5 0.5-1 1-1.5 1.5-3.5 > 3.5 Chromium (mg 11) < 1 1-2 2-4 4-7 > 7 Lead (mg 11) < 2 2-4 4-7 7-9 > 9 Note: Series of soil samples from 346 brackish water aquaculture ponds. Source: Boyd and others 1994. 46 Source Water Quality for Aquaculture: A Guide for Assessment Appendix table 3 Relative abundance categories of soil chemical variables in freshwater ponds 1st decile 2nd-3rd decile 4th-7th decile 8th-9th decile 10th decile Variable (very low) (low) (medium) (high) (very high) pH < 5 5-6 6-7 7-8 > 8 Carbon (%) < 0.5 0.5-1 1-2 2-3.5 > 3.5 Nitrogen (%) < 0.2 0.2-0.3 0.3-0.4 0.4-0.5 > 0.5 Sulfur (%) < 0.01 0.01-0.025 0.025-0.05 0.05-0.125 > 0.125 Phosphorus (mg 11) < 5 5-10 10-20 20-40 > 40 Calcium (mg l-1) < 600 601-1,200 1,200-3,400 3,400-7,600 > 7,600 Magnesium (mg 1.1) < 45 45-80 80-120 120-230 > 230 Potassium (mg 1-1) < 30 30-60 60-80 80-110 >110 Sodium (mg 1') < 15 15-35 35-60 60-100 > 100 Iron (mg 11) <10 10-50 50-130 130-210 > 210 Manganese (mg 11) < 5 5-20 20-40 40-75 > 75 Zinc (mg 1-1) < 0.2 0.2-1.5 1.5-2.5 2.5-5 > 5 Copper (mg 11) < 0.3 0.3-1.25 1.25-2.5 2.5-6 > 6 Silicon (mg 11) < 20 20-40 40-60 60-100 > 100 Boron (mg 1") < 0.3 0.3-0.5 0.5-0.75 0.75-1.25 > 1.25 Cobalt (mg i1) < 0.1 0.1-0.2 0.2-0.35 0.35-0.8 > 0.8 Molybdenum (mg 1) <0.1 0.11-0.15 0.15-0.2 0.21-0.35 >0.35 Aluminum (mg 1.1) < 3.5 3.5-75 75-120 120-200 > 200 Barium (mg 11) < 0.5 0.5-1 1-1.5 1.5-4 > 4 Chromium (mg 1") < 0.5 0.5-0.75 0.75-1 1-1.75 > 1.75 Lead (mg 1.1) < 1 1-1.25 1.25-1.5 1.5-2.5 > 2.5 Note: Series of soil samples from 358 freshwater aquaculture ponds. Source: Boyd and others 1994. Appendix Tables 47 Appendix table 4 Selected blomarkers proposed in study of environmental and/or toxicological responses In tish Type Biomarker Comments DNA alterations DNA adducts Specific for genotoxic chemicals DNA alterations Strand breaks in DNA Specific for genotoxic chemicals DNA alterations Hypomethylation of DNA Specific for genotoxic chemicals DNA alterations Cyotgenetic effects Specific for genotoxic chemicals Biochemical Induction of Cyt. P-450 Organic planar compounds Biochemical Metallothioneins Selected metals Biochemical ATPases Nonspecific Biochemical Aminolevulinic acid dehyd. Specific for lead Biochemical Methemoglobin Specific for nitrite and other chemicals Biochemical Acetylcholinesterase Specific for organophosphorous and carbamates Physiological Adenylate energy change Nonspecific Physiological Glycogen Nonspecific Physiological Scope for growth Nonspecific Physiological Corticosteroidslcatecholamines Nonspecific-primary stress response Physiological Plasma thyroid hormone Developmental alterations in growth Physiological Growth hormone Growth inhibitors: chlorpyrifos and phenol Physiological Stress (heat shock) proteins Nonspecific Immunological Leucokrit General screen assay Immunological Macrophage phagocytosis Immunological Macrophage pinocytosis Immunological Native immunoglobulin Humoral comprehensive assay Immunological Specific antibody quantitation Humoral host resistance challenge assay Immunological Increase disease susceptibility Comprehensive host resistance challenge assay Histopathological Hepatic biomarkers Different lesions depending on the chemical Histopathological Vertebral abnormalities Temperature, oxygen, metals Source: Tarazona and Munoz 1995. 48 Source Water Quality for Aquaculture: A Guide for Assessment Appendix table 5 Provisional tolerable weekly intake for selected elements Unit per kg of body Element weight Comment Source Aluminum 7mg WHO (1989b) Arsenic (inorganic) 0.015 mg Narrow margin between PTWI and levels that have toxic WHO (1989b) effects. Cadmium 7 g Highly dependent on rates of consumption of contaminated WHO (1 989b) food products.a Copper 3.5 mg WHO (1982) Iron 5.6 mg WHO (1983) Lead 25 g WHO (1993) Mercury (total) 5 g WHO (1 989b) Methyl mercury 3.3 g WHO (1 989b) Tin (inorganic) 14 mg No PTWI set for organotin compounds. WHO (1989b) Zinc 7mg WHO (1982) PCBs 0.28 mg No-effect level in monkeys. WHO (1990) a. Considerable portions of many populations ingest more Cd than the limit so one might argue for the avoidance of any fish product containing excessive Cd (Phillips 1993, 304). Appendix table 6 Import standards for contaminant residues in fish and shelffish United States Canadian Japanese European Union Median standard Range of import standard import standard import standard impont standard Contaminant Shelffish Fish standards' Shellfisht Fisht Shellfish Fish Shellfish Fish4. Shellfish52'3 Fish5,21 Arsenic (AS) 1.5 0.1-5.0 766 3,529 3,529 -17,18,20 "18,20 Cadmium (Cd) 1 0.3 0.05-2.0 36 "17,18,20 **18,20 Chromium (Cr) 1 1 1 126 "17,18,20 "18,20 Copper (Cu) 20 20 10-100 "17,18,20 18,20 Lead (Pb) 2 2 0.5-10 1.56 0.529 0.529 -17,18,20 *18,20 Mercury (Hg) 0.5 0.5 0.1-1.0 1.0.0 7'f 0.5 8230 0.4,0.321,26 0.4,0.325,26 0.58,13,15,18.20 0 85,1 08,13,14,15,18,20 Nickel (Ni) 706 "17,18,20 *-18,20 Selenium (Se) 0.3 2 0.3-2.0 -17,18,20 -18,20 Tin (Sn) 190 150 50-250 -17,18,20 "18,20 Zinc (Zn) 70 45 40-100 -17,18,20 "18,20 Paralytic shellfish 0.88 4.0 MU/g8,27 0.816 poison (PSP) Neurotoxic shellfish poison (NSP) Diarrhetic shellfish 0.05 MU/g5,27 "16,22 poison (DSP) Dyes "18 Petroleum hydro- `17 carbons Organophosphorus "18 18 compounds Organohalogenated "17,18.19 "18,19 compounds PCBs 2.08 2.08 2.08 0.500.5,3.08,24 *18,19 *18,19 2,3,7,8 - TCDD 0.02 ppb2 DDT and dervatives 5,o8 5.08 Dieldrin 0.38,81 2 o.38,9.12 0.128 Chordane 0.38 0.38 Chlordecone 0.3,0.48.10 0.38 Heptachlor/Hepta- 0.3' 0.38 chlor Epoxide 2,4-D 1.0 1.0 Mirex 0.18 0.18 Diquat 0.1 0.1 Fluridone 0.511 059 Glyphosate 3.0 0.259 Simazine 129 (Table continues on next page.) Appendix table 6 (continued) * Limits are in mg i'l unless otherwise specified. In the case of contaminant residues in fish, mg I" is mg (of contaminant) per kg of fish weight. 1. Median intemational standards and their ranges adapted by Pullen et al., 1993 from Nauen, 1983. 2. USFDA and EPA tolerances, action levels and guidance levels relating to safety attributes of fish and fishery products. In many cases, these levels represent the point at or above which the agency will take legal action to remove products from the market (Fish and Fishery Products Hazards and Controls Guide, USFDA, January 1998). 3. Bureau of Food Regulatory, Intemational and Interagency Affairs, Health Protection Branch, Health Canada. 4. Specificatons and Standards for Foods, Food Additives, under the Food Sanitation Law, JETRO, 1996. 5. Based on EU Directives 91/492/EEC, 91/493/EEC, 96/325/EC, 79/923/EEC and Commission Decision 931351/EEC. 6. For crustacea only. 7. Methylated mercury. 8. Specifies edible portion. 9. Fin fish only. 10. 0.4 mg r'1 for crabmeat and 0.3 mg r1 for all other fish. 11. Crayfish only. 12. Includes dieldrin and aldrin. 13. Contaminant concentration should be measured per fresh weight of the fish. 1 14. All fish have a standard of 0.5 mg I except the following which have a 1.0 mg I standards: Sharks (all species), Tuna (Thunnus spp.), Little tuna (Euthynnus spp.), Bonito (Sarda spp.), Plain bonito (Orcynopsis unicolor), Swordfish (Xiphias gladius), Sailfish (Istiophorus playpterus), Martin (Makaira spp), Eel (Anguilla spp.), Bass (Dicentratchus labrax), Sturgeon (Acipenser spp.), Halibut (Hippoglossus hippoglossus), Redfish (Sebastes marinus, S. mentella), Blue ling (Molva dipterygia), Attantic catfish (Anarhichas lupus), Pike (Esox lucius), Portuguese dogfish (Centroscymnes coelolepis), Rays (Raja spp.), Scabbardfishes (Lepidopus candatus, Aphanopus carbo), Anglerfish (Lophius spp.) Commission Decision 93/351/EEC. 15. Total mercury. 16. For live bivalve mollusks only (Council Directive, 91/492/EEC). 17. The standards for these chemicals for live bivalve mollusks have yet to be established, however they have been specified as parameters that will be regulated in live bivalve mollusks based on the permissible daily intake for each chemical and any deleterious effects on taste (Council Directive 91/492/EEC). 18. Countries exporting to the EU must submit a plan to monitor in these chemicals and their metabolites in live aquaculture animals, their excrement, body fluids and all places the animals are bred or kept. Plans to monitor the aquacufture products must also be submitted (Council Directive 96/325/EC). 19. Monitoring requirement referred to in above note 18 specifies that Aorganochlorine compounds (including PCBs)A be monitored. 20. Monitoring requirement referred to in above note 18 specified that Achemical elements@ be monitored. 21. The EU has not set standards for many contaminants however national laws may apply. 22. The standard specifies that the customary biological testing methods must not give a positve result for the presence of DSP in the edible parts of the mollusk. 23. A country exporting to the EU must identify production areas from which live bivalve mollusks may be harvested for exportation to the EU. Monitoring of these areas for microbiological and environmental contamination and the presence of biotoxins is an important consideration in granting approval for a country to export live bivlve mollusks to the EU (Council Directive 91/492/EEC). 24. The PCB standard specifices 0.5 mg lr1 for fishes and shelfishes from the ocean and open sea and 3.0 mg r' for fishes and shellfishes from inland seas and bays. 25. The mercury standard specifies 0.4 mg I1 for total mercury and 0.3 mg I1 for methyl mercury (as mercury). 26. The mercury standard does not apply to tuna fishes (tuna, swordfish, bonito), fishes and shellfishes trom inland rivers and fishes and shelHfishes from the deep sea (rockfishes, Bdryx splendens, gindara, benizuwaigani, ecchubaigai and sharks). 27. One MU (mouse unit) represents the amount of toxin that kills a mouse of 20 g in 15 minutes. 28. Applies to hard shell mussels only. 29. In fish protein. 30. Swordfish and shark are exempted from the mercury guideline. 31. For clams, oysters and mussels only. 32. Ppb equals parts per billion or micrograms of contaminant per kilogram of fish weight. Appendix table 7 Import bacteriological standards for fish and shellfish United States import standard Canadian import standard Japanese import standard European Union import standard Contaminant Shellfish Fish Shellfish/ Fish Shellfish3 Fisht Shellfish4 Fish4 Bacteria count 50,000, 100,000/1g7 100,000/gt7 E. coli spp. 230/100 40 CFU/g13 40 CFU/g'3 230/100g18 100 CFU/g22'23'26 MPN/g 12'31 230 MPN/'100g29,30 Enterotoxigenic E. Coli 1x103 ETEC/ga32 1x103 ETEC/g5'32 Coliform group presence of presence of organism organism'9 Fecal coliform 330/100 g12,31 330 MPN/1 00g29'30 Staphylococcus spp. 104 MPN/g or 104 MPN/gor 10,000 CFU/g14 10,000 CFU/g14 1,000 CFU/g22'23'24 presence of presence of toxin 831 toxin8'1 Salmonella spp. presence of presence of presence of presence of presence of organism organism organism 5 organism5f organism 21 3 ListeNa spp. presence of presence of 100 CFU/g"6 100 CFU/g'6 organism5'8 organism5 ' Clostridium spp. presence of presence of organism or organism or toxin7 toxin7 Vibrio cholerae presence of presence of organism5,9 organism5-9 Vibrio paraphaemolyticus 104/g5,10 104/9 5,1 Vibrio vulnifficus presence of presence of organism 5' organism5,11 Thermotolerant bacteria 100 CFU/g22'23'25 Mesophilic aerobic bacteria 100,000, 500,000, C F'°°°2,2°3,27 CFU/g~2 * Limits are in mg l- unless otherwise noted. 1. USFDA and EPA tolerances, action levels, and guidance levels relating to safety atributes of fish and fishery products. In many cases these levels represent the point at or above which the agency will take legal action to remove products from the market (Fish and Fishery Products Hazards and Controls Guide, USFDA, January 1998). 2. Bureau of Food Regulatory, Intemational and Interagency Affairs, Heafth Protection Branch, Health Canada. (Table continues on next page.) Appendix table 7 (continued) 3. Specifications and Standards for Foods, Food Additives, under the Food Sanitation Law, JETtRO, 1996. 4. Based on EU Directives 91/492/EEC, 91/493/EEC, 961325/EC, 79/923/EEC and Commission Decision 93/351/EEC. 5. For ready to eat fishery products (minimal cooking by consumer). 6. Specifies presence of Usteria monocytogenes. 7. For Clostridium Botulinum, specifies either (a) presence of viable spores or vegetative cells in products that will support their growth or (b) presence of the toxin. 8. Specifies either (a) positive for staphylococcal enterotoxin or (b) Staphylococcus aureus level is equal to or greater than 104/g (MPN). 9. Presence of toxigenic 01 or non-1. 10. Specifies 104/g (Kanagawa positive or negative). 11. Specifies presence of pathogenic organism showing. 12. For clams and oysters, fresh or frozen, guideline specificies (a). E coli MPN of 230/100g (average of subsamples or 3 or more of 5 subsamples); (b) APC- 500,000/g (average of subsamples or 3 or more of 5 subsamples). 13. For cooked fish: out of five sample units 1 sample can be >4 CFU/g but none can be over 40 CFU/g. For all fish except cooked: out of two sample units 1 sample can be >4 CFU/g but sample units 1 sample can be >4 CFU/g but none can be greater than 40 CFU/g. 14. Out of five sample units, 1 can be greater than 1,000 CFU/g and none can be greater than 10,000 CFU/g. 15. Out of five 50-g samples, no Salmonella can be present. 16. Out of five samples none can exceed 100 CFU/g. 17. For raw consumption oysters the standard is 50,000/g. For frozen fresh fish and shellfish for raw consumption the standard is 100,000/g. 18. For raw consumption oysters. 19. For frozen fresh fish and shellfish for raw consumption. 20. For cooked crustaceans and cooked molluskan shellfish. 21. For shelled and shucked products: out of 5 samples, 25 g samples no Salmonella can be present. For live bivalve mollusks: a 25 g sample of mollusk flesh must not contain Salmonella. Bacteral counts should be determined using the MPN method (see note 31). 22. For shelled and shucked products. 23. The criteria for these EU standards is specified by four varables: M, m, n, c, the values of which are listed in the footnotes of the particular standards. The variable n refers to the number of fish or shellfish samples to be tested. For all the criteria listed here n=5 and therefore is recommended that 5 samples be tested. If 5 samples are not tested, n would have to be changed accordingly. The other variables are used to specify the criteria as follows: the samples tested (# samples = n) are considered (a) satsfactory if all the values are 3 m or less; (b) acceptable if the values observed are between 3m and M and c/n is 2/5 or less. The quality of the samples is considered unsatisfactory if any of the values are above M or if c/n is greater than 2/5. 24. Specifies for Staphylococcus aureus. M=1000, m=100, n=5, c=2 (refer to note 23). 25. Specifies growth should be done at a temperature of 44.5 C on solid medium. M=100, m=10, n=5, c=2 (refer to note 23). 26. Specifies growth on solid medium. M=100, m=10, n=5, c=1 (refer to note 23). 27. Specifies growth should be at a temperature of 30.5 C. For whole products M=100000, m=10000, n=5, c=2; For shelled or shucked products with the exception of crabmeat, M=500000, m=50000, n=5, c=2. For crabmeat M=1,000,000, m=100,000, n=5, c=2 (refer to note 23). 28. Are guidelines to help manufacturers decide whether their plants are operating satisfactorily and to assist them in implementing the production monitoring procedures. 29. For live bivalve mollusks. 30. The standard specifies that the sample must contain, fecal coliforms or less than 230 E.Coli per 100 g based on five tube, three dilution MPN test or test with equivalent accuracy. 31. Determined by most probable number (MPN). See Glossary. (APHA, 1995) 32. Specifies Enterotoxic E. Coli (ETEC) 1 x 103/g, LT or ST positive. 33. Determined by colony forming units (CFU). See Glossary. (APHA, 1995). Notes 1. Bromage and Shephered 1974; Pillay 1990; EU 7. Romaire 1985 as cited in Lawson 1995, 25. 1979. 8. For more information on aeration see Lawson 2. Functionally alkalinity is the amount of a strong (1995). acid necessary to titrate a water to the equivalence point 9. BOD is often measured as the five day BOD (BODs of atmospheric CO2 which occurs at about a pH of 4.5. in mg/i) which is defined as the amount of dissolved Because the pH of 4.5 is approximately the limit at oxygen used up by microorganisms in the biochemical which fish and shellfish can survive, alkalinity is a good oxidation of organic matter over a 5 day period at 20°C. measure of the ability of the water to prevent reductions (Metcalf and Eddy, Inc. 1991, 71.) BOD for aquaculture in pH to the level at which the fish undergo extreme operations can also be measured using a shorter period disturbance. Adapted from Stumm and Morgan 1981, of time than 5 days and a temperature equivalent to that 185. of the pond. The result is expressed as a function of time 3. Alkalinity can be represented as [Alk] = [HCO3-1 + (mg 1-1 hr-1). (Boyd 1981, p130.) COD which represents 2[CO32-] + [OH-] - [H+] + Cb - Ca where Cb represents the amount of organic matter that can be chemically the total equivalents of bases other than the carbonate oxidized in a given water is also commonly used be- and hydroxide species. This can include species such as cause of the ease of its measurement. BOD can be esti- ammonium, borates, silicates and phosphates. Ca rep- mated from COD in using the following correlation resents the total equivalent concentration of acids other developed for channel catfish ponds: BOD (mg r' hr1) = than the hydrogen ion. Note that because the hydrogen -1.006 - 0.00148C - 0.0000125C2 + 0.0766T + 0.000253CT; ion contributes to alkalinity, a change in pH can result C = COD mg/l T = temp (°C). Boyd and others 1978 as in a change in alkalinity. cited in Boyd 1981, 130. 4. Production of an acid by a metabolic process neu- 10. Svobodova and others 1993,9. A maximum COD tralizes some of the bases, reducing the acid neutraliz- concentration of 20-30 mg/1 is also recommended. ing capacity of the water and thus decreasing alkalinity. 11. Ammonia is also a waste product excreted by fish The production of a base results in an increase in the and shellfish, and hence ammonia will be produced acid neutralizing capacity of the water and thus an during an aquaculture operation. increase in alkalinity. This also applies to H+ and OH-. 12. For more information on these methods, see Met- Because H+ is an acid and OH- is a base, a reduction in calf and Eddy, Inc. 1991. pH(adecreaseinOH andanincreaseinH+)willresult 13. EIFAC 1984, 8; Lawson 1995, 34; Boyd 1990, in a reduction in alkalinity and vise versa. 161. 5. In aquaculture low pH is often a result of sulfuric 14. For more information, see Metcalf and Eddy, Inc. acid formation by the oxidation of sulfide-containing 1991. bottom soils. This occurs most commonly where iron 15. Peavy and others 1985. For detailed design, see pyrite is present (Lawson, 1995, 26). High pH in Metcalf and Eddy, Inc. 1991. aquaculture is commonly a result of excess photoplank- 16. Tucker and Robinson 1990; Swann 1993, 2. ton photosynthesis in waters with high alkalinity and 17. Huguenin and Colt 1989; Svobodova and others low calcium hardness. 1993, 24. 6. Boyd 1990, 143; Lawson 1995, 25. 18. Smith and others 1976; Lawson 1995,35. 53 54 Source Water Quality for Aquaculture: A Guide for Assessment 19. Boyd 1990,185-187. For more information on soils 53. Dojlido and Best 1993, 172; Forstner and Wittman and sediments in aquaculture, see Boyd 1995. 1981. 20. Boyd 1995, 49. Specifies a pH of less than 3.5 in a 54. Phillips 1993,306; Furness and Rainbow 1990,119. 1:1 mixture of soil and distilled water. 55. Dojlido and Best 1993, 184. 21. Boyd 1995, 272. Field identification of potential 56. USEPA 1993; EU 1979; Meade 1989. acid sulfate soils can be made by mixing a few grams of 57. Boyd 1990, 387; Boyd 1996; Boyd 1979, 187. fresh soil with a few milliliters of fresh, 10-30% hydro- 58. Dojlido and Best 1993,209; Svobodova and others gen peroxide. If pyrite is present there will be a rigorous 1993,21. reaction with the production of bubbles. This followed 59. Svobodovf and others 1993, 22; USEPA 1993. by measurement of a pH of less than 3 for the hydrogen 60. Brune and Tomasso 1991, 137; Svobodova 1993, peroxide solution is confirmation of a potential acid- 27-28. sulfate soil. 61. Not all instances of off-flavor are caused by water 22. Boyd 1995,276. quality problems. Off-flavor may also result from post- 23. Shazili 1995; Eisler 1971; Sunda 1978. mortem oxidation of fats due to prolonged or improper 24. Salomons and F6rstner 1984; Malm and others 1990, storage, or from certain feed ingredients such as those 12. high in marine fish oil. However, if source water has an 25. Mance 1987. unusual odor or if the presence of compounds which 26. For more information see Cunningham and Tripp might cause off-flavor is suspected, off-flavor should be 1973 or Sayler and others 1975. tested for. 27. WHO 1973, cited in Dojlido and Best 1993, 85. 62. For more information on pesticides see Macrae 28. UNEP 1985, 13. and others 1993, 3521-41. 29. Rosenthal, personal communication. 63. Manahan 1991,522; USGPO 1987. 30. UNEP 1985, 10. 64. Rosenthal, personal communication. For more 31. Pillay 1992, 102; Phillips 1993, 305. information, contact the International Council for the 32. Phillips 1993,304-5; Fumess and Rainbow 1990,150. Exploration of the Sea, which is conducting research on 33. Mantoura and others 1978; Dojlido and Best 1993, biologically active complexes. 65-6. 65. Svobodova 1993,28. 34. USEPA 1993; Piper and others 1982; Meade 1989. 66. Lloyd 1992, 59. See also MAFF 1989; Svobodova 35. Nordstrom 1982, cited in Dojlido and Best 1993, 1993,28; Pillay 1992, 102. 101. 67. Bailey and others 1978, cited in Dojlido and Best 36. Hermann 1987, cited in Dojlido and Best 1993,102. 1993,285. 37. Phillips 1993,300. 68. USEPA 1993; Svobodova 1993, 29. 38. Mance 1987, cited in Dojlido and Best 1993, 177. 69. Lobel and others 1994,3-4. See also, Kleeman and 39. Mance 1987, cited in Dojlido and Best 1993, 177. others 1988. 40. Nriagu 1980, cited in Dojlido and Best 1993, 201. 70. Phillips 1993,302; Dojlido and Best 1993,287. 41. Mance 1987, cited in Dojlido and Best 1993, 202. 71. WHO 1989a, 43; Mara and Cairncross 1989,89,116. 42. EIFAC 1984, 15. 72. Pillay 1992, 52; WHO 1989a, 43; Mara and Cairn- 43. Mance 1987, cited in Dojlido and Best 1993, 70. cross 1989, 89. For maps of areas of endemism see Mara 44. Dojlido and Best 1993, 107; Stumm and Morgan and Cairncross 1989, 85-87. For treatment procedures 1981, 372. see Mara and Cairncross 1989, 112-113. 45. Liebman 1958, cited in Dojlido and Best 1993,107. 73. USDHH, USPHS, USFDA 1995, c-9. 46. Zabel and others 1988, cited in Dojlido and Best 74. WHO 1989, 44 48; Shereif and Mancy 1995. 1993, 107. 75. Pillay 1992, 71, 105. Other common species in- 47. Wilson 1976, cited in Dojlido and Best 1993, 80. clude toxic marine dinoflagellates (Ptychodiscus and 48. Piper and others 1982; USEPA 1993. Gonyaulax.), some blue-green algae (Microcystis aerugi- 49. Dojlido and Best 1993, 145; Moore and nosa),andthebrackishwaterchrysophyte(Prymnesium Ramamoorthy 1984. parvum.). Boyd 1990, 163. 50. Dojlido and Best 1993, 147; Moore and 76. Other methods employing temperature and Ramamoorthy 1984. salinity stress and chlorination have not been very suc- 51. Dojliclo and Best 1993, 147; Fumess and Rainbow cessful. Ozonation has met with limited success, but 1990, 119. there is controversy over its usefulness. Pillay 1992, 52. Phillips 1993,305; WHO 1983,29; Pillay 1992,102. 106. Bibliography and Related Sources Acosta, B. O., and R. S. V. Pullin, eds. 1991. 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Species Index Aeromonas, 40 Fasciolopsis buski, 40 Arthropods, 25 Freshwater crayfish, 13 Atlantic salmon, 8 Freshwater crustaceans, 13 Freshwater prawn, 8, 10 Bass, 8, 24, 60 Brackishwater prawn, 10 Grass carp, 10, 58 Brine shrimp, 8 Guppy, 39 Brook trout, 8 Hatchling silver carp, 13 Brown shrimp, 8 Japanese eel, 8 C. commercialis, 26 Carp, 14, 20 Klebsiellae, 40 Catfish, 41, 56, 57, 61 Channel catfish, 8, 10, 13, 14, 16, 20 M. rosenbergii, 10 Chanos chanos, 18 Marine fish, 10, 14, 18 Chinook salmon, 8 mollusks, 25, 26, 27, 28, 30, 31 Clams, 26, 31, 41 Mullet, 8 Clonorchis sinensis, 40 mussels, 27, 28, 39, 42 Clostridium botulinum, 40 Mytilus edulis, 28 Cockles, 26 Coho salmon, 8, 39 Ostrea edulis, 32 Cold water fish, 14 Oyster, 24, 26, 27, 30, 32, 38, 41, 42, 57, 60 Common carp, 8 Crab, 26 P. monodon, 18, 19, 22 Crassostrea gigas, 26 P. vannamei, 8, 10, 14, 18, 19, 20 Cyclops abyssorym, 24 Pacific Oyster, 26 Cyprinid, 15, 20, 27, 30 Penaeid shrimp, 14, 18 Penaeus japonicus, 26 E. coli, 40 Penaeus monodon, 21, 57 Eel, 14 Pike, 24, 39 Escherichiae, 40 Pink Shrimp, 8 European eel, 8 Plaice, 8 61 62 Source Water Quality for Aquaculture: A Guide for Assessment Pseudomnonas, 40 Sockeye salmon, 8 Pyrodinium bahamense var. compressa, 42 Sole, 8 Streptococcus, 40 Quahog, 42 Striped bass, 8 Swordfish, 24 Rainbow trout, 8, 29, 30, 39, 59 Red hybrid tilapia, 10 Tilapia, 8, 10, 14, 24, 57, 60 Red swamp crawfish, 8, 14 Trout, 10, 13, 14, 16, 20, 60 Tuna, 24 Salmonella, 40 Turbot, 8 Salmonid, 8, 11, 12, 14, 18, 19, 27, 28, 29, 30, 32, 60 Walleye, 24 Schistosoma japonicum, 40 Warm water crustaceans, 14 Shark, 24 Warm water fish, 14 THE WORLD BANK 1 8 11I Sti-c.t .WV. NVashimiton, 1).( . 20433 USA 'I'elephlotnC: 20J2-4-77-1234 IFacsimile: 202-477-6391 TIelex: NMC(I1 64145 WMLIA) NIN M1CI 248423 XV()RI .L)lANIk I-n-mail: hooks@ Cvorldhank.orlg ENVIRONMENTALLY AND SOCIALLY SUSTAINABLE DEVELOPMENT RSBN O-8 4 3D - /9/ ISBN 0-8213-4319-X