Muscle samples from 105 marine mammals stranded along the Oregon-Washington coasts (2002-2009) were tested for levels of total mercury by Cold Vapor Atomic Fluorescence Spectrometry. The total mercury present is predominantly in the form of highly toxic methylmercury. After normalizing muscle tissue to 75% water weight, due to variance in water content, Steller sea lions (Eumetopias jubatus) and northern elephant seals (Mirounga angustirostris) exhibited the highest mean concentrations of total mercury followed by harbor seals (Phoca vitulina), harbor porpoises (Phocoena phocoena), and California sea lions (Zalophus californianus); 0.34 ± 0.278, 0.34 ± 0.485, 0.21 ± 0.216, 0.17 ± 0.169 and 0.15 ± 0.126 mg/kg normalized weight, respectively. Mean normalized values demonstrated limited muscle methylmercury accumulation in these species in the Pacific Northwest. Normalizing muscle mercury concentrations eliminated variability from desiccation, and allowed for a clearer indication of the amount of mercury the animal accumulated before stranding. However, actual wet weight concentrations in some of the stranded carcasses were high enough to pose a risk to scavengers.

Thesis (MScAgric (Zoology))--University of Stellenbosch, 1996. / A number of studies on the general physico-chemical character of the Eerste River, Western Cape, had previously been done, but the problem of heavy metal pollution had, by 1993, not been addressed. A study was therefore undertaken from 1993-1995 in order to investigate these aspects. Since several researchers have shown that freshwater crabs accumulate certain heavy metals in their bodies and may therefore be used as monitors of environmental heavy metal pollution, the present study concentrated mainly on metal concentrations (Mn, Zn, Cu, Pb and Cd) in the local freshwater crab species, Potamonautes perlatus, and its possible use as biomonitor in the Eerste River. Two localities in the Eerste River were chosen,. in order to make comparisons, namely a relatively uncontaminated site in the Assegaaibosch Nature Reserve, Jonkershoek, and a visibly polluted site downstream from Stellenbosch, behind Stellenbosch Farmers' Winery (SFW). Crabs, water and sediment samples were collected seasonally at both localities, and metal concentrations thereof determined by atomic absorption spectrophotometry. The results showed that the Eerste River down to the SFW locality is still relatively unpolluted in terms of heavy metals. It was, however, clear that runoff from the Stellenbosch municipal, industrial and agricultural areas do have an influence on other physico-chemical features of the river. The concentrations of heavy metals in whole crabs, tissues and carapace showed that Zn concentration was well regulated in P. perlatus from both localities, Mn and Cu were accumulated in individuals from SFW, and Pb and Cd accumulated in both populations. Compartmentalization of heavy metals was shown to occur in P. perlatus: the carapace was found to be the most important storage site for Mn, Zn and Pb, the carapace and gonads equally important for Cd storage, and the digestive gland the most important site for Cu storage. Whereas gender was shown, generally, to be of little importance in heavy metal uptake in P. perlatus, crab body size and seasonality were both shown to influence heavy metal uptake to some extent. However, only summer peaks in whole crab, carapace and tissue manganese concentrations were shown to correlate with peaks in environmental Mn concentrations. It was concluded that P. perlatus would possibly only be a Suitable monitor of environmental Mn, Pb and Cd pollution, although there is no guarantee that the crab body would accurately reflect environmental concentrations. It was also ascertained that, since a study of the sperm ultrastructure of P. perlatus showed a significantly larger number of abnormal spermatozoa in male crabs from ,SFW, and since these observed differences could possibly be related to heavy metal exposure, the sperm of this species might be a more reliable indicator of heavy metal pollution. It was finally concluded that more intensive research need to be undertaken on various aspects, especially the use of the spermatozoon as indicator of environmental heavy metal pollution, and that the results of the present study could serve as a basis for future studies.

Thesis (MSc (Botany and Zoology))--University of Stellenbosch, 2007. / The ability of various molluscan species to accumulate toxicants such as cadmium from natural waters in quantities that are many orders of magnitude higher than background levels are well-known. This phenomenon of bioaccumulation might cause certain stress responses in these organisms at the cellular level, which can be measured using biomarkers. A biomarker response test known as the neutral red retention assay was employed in this study to measure responses in four intertidal species. Specimens of Cymbula oculus (Born), Scutellastra longicosta (Lamarck), Cymbula granatina (Linnaeus) and Scutellastra granularis (Linnaeus) were collected at two localities on the coast of False Bay, South Africa. Laboratory exposures in static flow tanks at three different concentrations i.e. 0.8, 1 and 1.2 mg/L of CdCl2 were done respectively for each species over a three day exposure period i.e. each exposure concentration had an exposure period of 24, 48 and 72 hours. After every 24 hour exposure period the lysosomal membrane integrity was determined using the neutral red retention method to establish which species is the most sensitive to Cd. Both control and exposure groups for all species showed a decrease in retention times with an increase in Cd concentration over the exposure period. This decrease was particularly prominent at the highest exposure concentration after 72 hours. At 0.8 and 1.2 mg/L CdCl2 exposures an indirectly proportional relationship between neutral red retention time and heavy metal concentration was prominent in C. oculus, indicating a dose related response. In all species there was a moderate increase in heavy metal concentration over the 72 hour exposure period. EC50 values indicated that S. granularis and C. granatina had a “high” sensitivity to Cd contamination, while C. oculus had “medium” sensitivity and S. longicosta “low” sensitivity to Cd contamination. The sensitivity data obtained from the analysis of the experimental species in this study may contribute to the eventual establishment of a species sensitivity distribution model (SSD).

Lam, Shu Kee. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 206-219). / Abstracts in English and Chinese. / Abstract --- p.i / Abstract (in Chinese) --- p.iv / Acknowledgements --- p.vi / Table of contents --- p.vii / List of tables --- p.xii / List of figures --- p.xvi / List of plates --- p.xvii / Chapter CHAPTER 1 --- INTRODUCTION / Chapter 1.1 --- Research background --- p.1 / Chapter 1.2 --- Conceptual framework --- p.4 / Chapter 1.3 --- Objectives of the study --- p.8 / Chapter 1.4 --- Significance of the study --- p.9 / Chapter 1.5 --- Organization of the thesis --- p.10 / Chapter CHAPTER 2 --- LITERATURE REVIEW / Chapter 2.1 --- Introduction --- p.12 / Chapter 2.2 --- Use of hydroseeding in slope bioengineering works --- p.12 / Chapter 2.3 --- Problems associated with hydroseeded slopes --- p.12 / Chapter 2.4 --- Common Bermudagrass used in hydroseeding --- p.13 / Chapter 2.5 --- "Sludge disposal, potentials and problems" --- p.14 / Chapter 2.5.1 --- Properties and disposal of sludge --- p.14 / Chapter 2.5.2 --- Use of sludge and potential problems --- p.16 / Chapter 2.5.3 --- Heavy metals in sludge --- p.19 / Chapter 2.5.3.1 --- Cadmium --- p.22 / Chapter 2.5.3.2 --- Chromium --- p.22 / Chapter 2.5.3.3 --- Copper --- p.23 / Chapter 2.5.3.4 --- Nickel --- p.24 / Chapter 2.5.3.5 --- Lead --- p.24 / Chapter 2.5.3.6 --- Zinc --- p.25 / Chapter 2.5.4 --- Speciation of heavy metals --- p.25 / Chapter 2.5.5 --- Factors affecting the bioavailability of heavy metals --- p.26 / Chapter 2.5.5.1 --- Reaction pH --- p.26 / Chapter 2.5.5.2 --- Organic matter --- p.28 / Chapter 2.5.5.3 --- Fertilizers --- p.29 / Chapter 2.5.6 --- Effect of heavy metals on plant growth --- p.29 / Chapter 2.5.7 --- Effect of heavy metals on animals and water bodies --- p.31 / Chapter 2.6 --- "Lime, heavy metals and plant growth" --- p.32 / Chapter 2.6.1 --- Effect of lime on heavy metal dynamics --- p.32 / Chapter 2.6.1.1 --- Competition with heavy metals for adsorption sites --- p.32 / Chapter 2.6.1.2 --- Immobilization of heavy metals --- p.32 / Chapter 2.6.2 --- Effect of lime on plant growth --- p.34 / Chapter 2.7 --- Effect of precipitation on slopes --- p.35 / Chapter 2.7.1 --- Infiltration --- p.35 / Chapter 2.7.2 --- Surface runoff --- p.38 / Chapter 2.7.3 --- Soil erosion --- p.39 / Chapter 2.8 --- Summary --- p.42 / Chapter CHAPTER 3 --- EFFECT OF SLUDGE AND LIME ON ABOVEGROUND BIOMASS OF COMMON BERMUDAGRASS / Chapter 3.1 --- Introduction --- p.43 / Chapter 3.2 --- Materials and methods --- p.44 / Chapter 3.2.1 --- Materials --- p.45 / Chapter 3.2.2 --- Experimental design --- p.46 / Chapter 3.2.3 --- Grass clipping and pre-treatment --- p.49 / Chapter 3.3 --- Chemical analysis --- p.50 / Chapter 3.3.1 --- Properties of decomposed granite --- p.50 / Chapter 3.3.2 --- "Properties of sludge," --- p.52 / Chapter 3.3.3 --- Nitrogen of grass clippings --- p.52 / Chapter 3.4 --- Statistical analysis --- p.53 / Chapter 3.5 --- Results and discussion --- p.54 / Chapter 3.5.1 --- Properties of DG and sludge --- p.54 / Chapter 3.5.2 --- Aboveground biomass of grass --- p.56 / Chapter 3.5.3 --- Effect of sludge on aboveground biomass --- p.63 / Chapter 3.5.4 --- Effect of lime on aboveground biomass --- p.66 / Chapter 3.5.5 --- Synergic effect of sludge and lime on aboveground biomass --- p.68 / Chapter 3.5.6 --- "Effect of sludge on nitrogen uptake by grass shoots," --- p.69 / Chapter 3.6 --- Summary --- p.72 / Chapter CHAPTER 4 --- EFFECT OF SLUDGE AND LIME ON HEAVY METAL UPTAKE BY COMMON BERMUDAGRASS / Chapter 4.1 --- Introduction --- p.74 / Chapter 4.2 --- Materials and methods --- p.77 / Chapter 4.2.1 --- Materials and experimental design --- p.77 / Chapter 4.2.2 --- Analysis of heavy metals in grass shoots --- p.77 / Chapter 4.2.3 --- Reaction pH at the end of Part 1 --- p.77 / Chapter 4.2.4 --- Statistical analysis --- p.78 / Chapter 4.3 --- Results and discussion --- p.78 / Chapter 4.3.1 --- Cumulative uptake of heavy metals by common Bermudagrass --- p.79 / Chapter 4.3.2 --- Effect of sludge on heavy metal uptake --- p.84 / Chapter 4.3.3 --- Effect of lime on heavy metal uptake --- p.86 / Chapter 4.3.4 --- Synergic effect of sludge and lime on cumulative heavy metal uptake --- p.88 / Chapter 4.3.5 --- Effect of fertilizer addition --- p.91 / Chapter 4.3.6 --- Concentration of heavy metals in grass --- p.93 / Chapter 4.3.7 --- Effect of pH on heavy metal uptake --- p.98 / Chapter 4.3.8 --- Effect of heavy metal uptake on aboveground biomass --- p.100 / Chapter 4.4 --- Summary --- p.103 / Chapter CHAPTER 5 --- EFFECT OF SLUDGE AND LIME ON HEAVY METALS IN LEACHATE / Chapter 5.1 --- Introduction --- p.106 / Chapter 5.2 --- Materials and methods --- p.107 / Chapter 5.2.1 --- Leachate collection --- p.108 / Chapter 5.2.2 --- Analysis of leachate --- p.109 / Chapter 5.2.3 --- Statistical analysis --- p.109 / Chapter 5.3 --- Results and discussion --- p.110 / Chapter 5.3.1 --- Effect of sludge and lime on leachate volume --- p.110 / Chapter 5.3.2 --- Leachate pH and the effect of sludge and lime --- p.115 / Chapter 5.3.3 --- Heavy metal contents in leachate --- p.119 / Chapter 5.3.4 --- Effect of sludge and lime on the leaching of heavy metals --- p.121 / Chapter 5.3.5 --- Effect of pH on the leaching of heavy metals --- p.125 / Chapter 5.4 --- Summary --- p.126 / Chapter CHAPTER 6 --- "LEACHATE, SURFACE RUNOFF, SEDIMENT YIELD AND THEIR HEAVY METALS" / Chapter 6.1 --- Introduction --- p.128 / Chapter 6.2 --- Materials and methods --- p.130 / Chapter 6.2.1 --- Materials --- p.130 / Chapter 6.2.2 --- Experimental design --- p.132 / Chapter 6.2.3 --- Rainfall intensities in simulation experiment --- p.134 / Chapter 6.2.4 --- Selection of slope gradient --- p.136 / Chapter 6.2.5 --- Rainfall simulation --- p.136 / Chapter 6.2.6 --- "Leachate, surface runoff and runoff sediment" --- p.137 / Chapter 6.2.7 --- Properties of decomposed granite and sludge --- p.138 / Chapter 6.2.8 --- "Heavy metals in leachate, surface runoff and runoff sediment" --- p.139 / Chapter 6.2.9 --- Statistical analysis --- p.140 / Chapter 6.3 --- Results and discussion --- p.140 / Chapter 6.3.1 --- Properties of DG and sludge --- p.140 / Chapter 6.3.2 --- "Leachate, surface runoff and runoff sediment production" --- p.142 / Chapter 6.3.3 --- "Heavy metal concentrations in leachate, surface runoff and runoff sediment" --- p.153 / Chapter 6.3.3.1 --- Heavy metal concentrations in leachate --- p.153 / Chapter 6.3.3.2 --- Heavy metal concentrations in runoff --- p.163 / Chapter 6.3.4 --- Cumulative loss of heavy metals --- p.170 / Chapter 6.3.4.1 --- Cumulative loss of heavy metals from leachate --- p.170 / Chapter 6.3.4.2 --- Cumulative loss of heavy metals from runoff --- p.178 / Chapter 6.3.4.3 --- "Heavy metal loss from leachate, surface runoff and runoff sediment" --- p.185 / Chapter 6.4 --- Summary --- p.189 / Chapter CHAPTER 7 --- CONCLUSIONS / Chapter 7.1 --- Summary of major findings --- p.192 / Chapter 7.2 --- Implications of the study --- p.196 / Chapter 7.2.1 --- Potential use of sludge in slope bioengineering works --- p.196 / Chapter 7.2.2 --- Measures to optimize the benefits of sludge in land application --- p.198 / Chapter 7.3 --- Limitations of the study --- p.200 / Chapter 7.4 --- Suggestions for further study --- p.202 / REFERENCES --- p.206 / APPENDICES --- p.220

No description available.

Conventional wisdom in ecotoxicology predicts reductions in organismal fitness to follow from exposure-related physiological effects. This expectation may be appropriate for controlled laboratory environments, but may not necessarily reflect what is likely to take place in the wild. In an extensive review of the ecotoxicology literature, it was revealed that fish condition factor (an index of energetic fitness) is just as likely to respond favourably to pollutant exposure as it is to respond negatively. The remainder of this thesis examines some of the ecological reasons for this apparent paradox. One possible cause of altered energetic status in wild, pollutant-exposed fish is variable food availability. Addressing this possibility, I showed that consumption rates (estimated using a 137Cesium mass-balance approach) were not related to growth reductions in hormonally-impaired yellow perch ( Perca flavescens) from metal-contaminated lakes. Another possibility is that fish forage less efficiently in metal-polluted lakes as a result of lowered prey choice. In this thesis, I develop an enzymatic and individual-based biomarker for fish activity costs (muscle lactate dehydrogenase, LDH, activity) and show, through the use of this tool that the cost of fish activity is intimately tied to prey type and the ability to make normal ontogenetic diet shifts. Through the application of LDH measurements, as well as through bioenergetic modelling, diet and prey community analyses, a link between decreased prey choice and high perch activity costs leading to zero growth efficiency (energetic bottlenecks) was demonstrated in yellow perch from metal-contaminated lakes. This finding provided one of the first examples in ecotoxicology of a mechanistic link between community and organismal endpoints. The findings of this thesis emphasize the need for ecotoxicology to consider ecology when looking for and interpreting ecologically relevant endpoints. The final chapter of this thesis ex

Plants are able to take up and accumulate certain environmental contaminants such as heavy metals. When the plants are ingested by man, these contaminants are transferred along the food chain. Due to the poorly regulated medicinal plant trade in South Africa, many opportunities exist for heavy metal contamination of medicinal plants namely contaminated harvest sites as well as poor drying, processing, storage, transport and manufacturing conditions. The concentrations of five heavy metals (As, Cd, Co, Ni, Pb) and six microelements (B, Cu, Fe, Mn, Mo, Zn) were determined in some commonly used South African medicinal plants obtained from street markets. Elemental content was determined using inductively coupled plasma optical emission spectrophotometry (ICP-OES). Some of the medicinal plant samples investigated contained As and Cd at levels exceeding the World Health Organization limits of 1 and 0.3 mg kg-1 respectively. Lead and Ni were detected in all the samples. Elevated Fe and Mn levels were recorded in certain plant species. The results revealed multiple metal contamination in some medicinal plant parts sold in local markets and is thus grounds for concern. The effects of Cd application on growth parameters of some medicinal plant species belonging to the Hyacinthaceae (Albuca setosa, Eucomis autumnalis, Eucomis humilis, Merwilla plumbea) gave insight into heavy metal accumulation and distribution in these species. Application of Cd at 5 mg l-1 over a 12 week period reduced growth in A. setosa. The medicinally used A. setosa bulbs accumulated 37 mg kg-1 Cd after 12 weeks. Cadmium application at 2 mg l-1 over a six week period had no effect on growth parameters of E. autumnalis or E. humilis. However, a substantial difference in total Cd accumulation was detected in the plants (40.2 and 15.3 mg kg-1 respectively). Cadmium application at 2 mg l-1 significantly reduced the fresh weight of leaves, bulbs and roots of M. plumbea. Although most of the Cd was stored in the roots, the medicinally used bulbs accumulated up to 11.6 mg kg-1 when applied at 10 mg l-1. The antagonistic effect between Cd and Zn treatments and their effect on micronutrient distribution in M. plumbea were investigated. Five treatments were evaluated: (1) Hoagland’s nutrient solution (HS) (control) (2) HS + Cd 2 mg l-1 (single) (3) HS + Cd 2 mg l-1 + Zn 50 mg l-1 (combination) (4) HS + Cd 2 mg l-1 + Zn 100 mg l-1 (combination) (5) HS + Cd 2 mg l-1 + Zn 150 mg l-1 (combination). Cadmium readily accumulated in leaves, bulbs and roots of M. plumbea when supplied at 2 mg l-1. Zinc at 50 mg l-1 led to increased Cd accumulation. However, further increases in Zn concentration showed an antagonistic effect of Zn on Cd uptake and accumulation. Thus, increasing Zn levels in soils may be favourable for reducing toxic Cd accumulation in M. plumbea plants. Boron was not significantly affected by the addition of Cd to the media. However, with an increase in Zn, leaf B content increased while the B content in the bulbs and roots decreased. Copper and Mo levels were not significantly affected by treatments with Cd or Cd/Zn combinations. Compared to the control, Cd and Cd/Zn applications caused an increase in Mn content in leaves, bulbs and roots. Iron levels of M. plumbea were not significantly affected by Cd in the media. However, with an increase of Zn in the Cd-containing media, Fe content in the leaves, bulbs and roots increased. Tulbaghia violacea is one of the few medicinal plants that is also frequently used as a leafy vegetable. Application of Cd at 2 and 5 mg l-1 to T. violacea of varying sizes (small 8 - 10 g, medium 16 - 20 g, large 80 – 95 g) elicited a difference in growth response, Cd accumulation and micronutrient distribution. Leaf length and fresh weight of leaves of the medium-size plants decreased with application of Cd at 2 mg l-1 whilst 5 mg l-1 Cd significantly decreased the number of leaves in small-sized plants. Small plants accumulated more Cd in the leaves than medium- or large-sized plants. Application of Cd at 2 mg l-1 and 5 mg l-1 lowered the leaf Cu, Fe, Mo and Zn contents in small- and medium-size plants. This study indicated that T. violacea has the ability to accumulate Cd. In addition, plant size plays an important role with regards to Cd accumulation and elemental distribution. The effect of various nutrient applications (10%, 50% and 100% Hoagland’s nutrient solutions (HS); and HS deficient in N, P or K) on growth parameters and micronutrient distribution in Dioscorea dregeana were investigated. Irrigating plants with 50% HS resulted in better growth performance, whereas a deficiency of either N, P or K negatively affected seedling growth. Plants grown in 10% HS contained higher total B, Fe and Mo levels compared to seedlings grown in 50% and 100% HS. Compared to the control, P deficiency resulted in a Fe increase in the leaves, tuber and roots while a lack of P and K significantly increased total Mn content in D. dregeana. The effect of excess Zn (100, 200 and 300 mg l-1) on growth performance, chlorophyll content and microelemental distribution on Dioscorea sylvatica was investigated. Growth parameters showed a significant decrease when supplied with Zn at 100 mg l-1. Zinc phytotoxicity was evident by the reduction in chlorophyll content. Highest Zn concentrations were detected in the roots. Certain micronutrients appear to be redistributed due to Zn toxicity. The effect of microelements (Cu, Zn) and heavy metals (Cd, Pb, Hg) on germination and seedling development of Bowiea volubilis, Eucomis autumnalis and Merwilla plumbea was investigated. Copper and Zn applied at 1 mg l.1 significantly reduced the percentage germination of E. autumnalis. Low concentrations (. 1 mg l.1) of Cu and Zn negatively affected the root growth of all three species. Mercury concentrations of 0.5 and 1 mg l.1 significantly decreased the percentage germination of B. volubilis and E. autumnalis respectively. Cadmium and Hg at 2 mg l.1 showed a negative effect on the root growth of B. volubilis. Concentrations of 0.5 mg l.1 of all heavy metals tested significantly decreased shoot length of M. plumbea. The effect of Cd on biological activity (anti-inflammatory, antibacterial and antifungal) of medicinal plants with previously confirmed activity was evaluated. When supplied with Cd at 2 mg l-1, Eucomis humilis bulbous extracts showed lower anti-inflammatory activity than the control for both COX-1 and COX-2 activity. Eucomis autumnalis bulbous extracts had greater COX-1 activity compared to the control. However, Cd suppressed the activity of COX-2. Compared with non-Cd-treated Merwilla plumbea plants (control), those supplied with Cd at 10 mg l-1 showed increased antibacterial activity against Bacillus subtilis, Klebsiella pneumoniae and Staphylococcus aureus. However, no change in activity against Escherichia coli was observed. Cadmium accumulation in the bulbs had no effect on antifungal activity of Tulbaghia violacea. Thus, optimized agricultural practices are essential for quality control of cultivated medicinal plants. The studies presented in this thesis collectively answer several questions related to heavy metal involvement in South African medicinal plants. The findings substantiate the need to regulate and monitor the South African medicinal plant trade against heavy metal contamination which will in turn provide a product of safety and quality to the consumer. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.

Metal contamination can disrupt the trophic links in food webs by altering the taxonomic composition and size structure of benthic invertebrate communities. Benthic invertebrate samples and perch (Perca flavescens) were collected from six lakes along a gradient of metal pollution in Rouyn-Noranda, Canada. The benthic communities of the contaminated lakes were less diverse and had smaller individuals (0.09 mg d.w. and 0.16 mg d.w. vs. 0.22 mg d.w. in the reference lake). The stomach contents of perch from contaminated lakes were less diverse, showed a greater reliance on chironomids or zooplankton, and cannibalism than perch from less polluted lakes. The mean size of prey in perch from contaminated lakes was smaller than in reference lakes (3.7 mg d.w. and 7.39 mg d.w. vs. 47.7 mg d.w. and 67.1 mg d.w. in reference lakes). (Abstract shortened by UMI.)

Cupriavidus metallidurans CH34 is a Gram-negative & / Doctorat en Sciences agronomiques et ingénierie biologique / info:eu-repo/semantics/nonPublished

Tissue samples from spotted gar (Lepisosteus oculatus) and largemouth bass (Micropterus salmoides) were collected from Caddo Lake. Gar and bass livers were subjected to histological investigation and color analysis. Liver color (as abs at 400 nm) was significantly correlated with total mercury in the liver (r2 = 0.57, p = 0.02) and muscle (r2 = 0.58, p = 0.01) of gar. Evidence of liver damage as lipofuscin and discoloration was found in both species but only correlated with liver mercury concentration in spotted gar. Inorganic mercury was the predominant form in gar livers. In order to determine the role of mercury speciation in fish liver damage, a laboratory feeding study was employed. Zebrafish (Danio rerio) were fed either a control (0.12 ± 0.002 µg Hg.g-1 dry wt), inorganic mercury (5.03 ± 0.309 µg Hg.g-1 dry wt), or methylmercury (4.11 ± 0.146 µg Hg.g-1 dry wt) diet. After 78 days of feeding, total mercury was highest in the carcass of zebrafish fed methylmercury (12.49 ± 0.369 µg Hg.g-1 dry wt), intermediate in those fed inorganic mercury (1.09 ± 0.117 µg Hg.g-1 dry wt), and lowest in fish fed the control diet (0.48 ± 0.038 µg Hg.g-1 dry wt). Total mercury was highest in the viscera of methylmercury fed zebrafish (11.6 ± 1.86 µg Hg.g-1 dry wt), intermediate in those fed inorganic diets (4.3 ± 1.08 µg Hg.g-1 dry wt), and lowest in the control fish (below limit of detection). Total mercury was negatively associated with fish length and weight in methylmercury fed fish. Condition factor was not associated with total mercury and might not be the best measure of fitness for these fish. No liver pathologies were observed in zebrafish from any treatment.