Endosulfan acute toxicity and histomorphological alterations in Jenynsia multidentata (Anablepidae,Cyprinodontiformes)

Toxicity tests using adult specimens of Jenynsia multidentata were carried out during 96 hours in order to determine the lethal concentration (LC50) of endosulfan. Histological alterations were determined in gills and liver. Gill damage was quantified as secondary lamellae thickness. The 96 hr LC50 values were significantly different between males (0.719 μ g.L^{? 1}) and females (1.317 μg.L^{? 1}). The sex difference was attributed to the dimorphism in the lipid content in females (2.16%) and males (1.79%). Histological alterations in gills included hypertrophy and lifting of the epithelium of the secondary lamellae and aneurisms. These alterations caused a significant increase of the secondary lamellae thickness in treatment versus control fish. Finally, reversible histological alterations (such as hydropic degeneration and dilation of sinusoids) were observed in the liver of exposed fish as well as an irreversible change such as necrosis at the highest concentrations.     

Histopathology of gills in mosquitofish,Gambusia affinis after long-term exposure to sublethal concentrations of malathion

The histopathological effects of malathion, an organophosphate pesticide, on the gill tissues in mosquitofish, Gambusia affinis, were determined by light microscope. The fish were exposed to sublethal concentrations (0.01 and 0.02 mg/L) of malathion for 10, 20 and 30 days. Histological examination of the gills treated with malathion showed a variety of histopathological effects. The gill lesions included necrosis and desquamation of secondary lamellar epithelium, lifting up of epithelium, intraepithelial oedema, fusion of adjacent secondary lamellae, haemorrhage at primary lamellae, disorganization and rupture in seconder lamellae, hypertrophy and hyperplasia of epithelial cells. These alterations were time- and dose-dependent.     

Water quality and fish size affect toxicity of endosulfan, an organochlorine pesticide, to rainbow trout

The acute toxicity of endosulfan in juvenile rainbow trout (Oncorhynchus mykiss, 10.61+/-1.69 g) was evaluated in glass aquaria under static conditions. Nominal concentrations of endosulfan in the toxicity test ranged from 1.3 microg l(-1) to 29 microg l(-1). The concentrations of endosulfan that killed 50% of the rainbow trout within 24-h (24-h LC50), 48-h LC50, 72-h LC50, and 96-h LC50 were 19.78, 8.89, 5.28, and 1.75 microg l(-1), respectively. None of the unexposed control fish died, and the first fish died 4 h after exposure to 26.3 microg l(-1) of endosulfan. Survival of fish was significantly increased with increasing fish size and decreased with decreased fish size at the same temperature (p<0.001). Temperature also had a significant effect on survival of fish. Alkalinity at levels above 20 mg l(-1) as CaCO3 significantly increased survival of fish at 19.78 microg l(-1) of endosulfan. Increasing alkalinity from 20 mg l(-1) as CaCO3 to 42 or higher concentrations tested in this study (121 mg l(-1) as CaCO3) significantly increased survival of fish (p<0.01). Total hardness ranging from 55 mg l(-1) as CaCO3 to 126 mg l(-1) as CaCO3 did not affect survival of fish exposed to endosulfan. Endosulfan toxicity was found to be irreversible when fish were exposed to minimum concentrations of endosulfan tested. Histologically, fish gills had lamellar edema, separation of epithelium from lamellae, lamellar fusion, and swelling of the epithelial cells. Melanomacrophage centers were scattered throughout the trunk kidney, head kidney, and spleen. The liver of endosulfan-exposed fish had severe focal necrosis. None of these lesions were seen in unexposed control fish. Results indicate that alkalinity, temperature, and fish size affect endosulfan toxicity of rainbow trout.     

Histopathological alterations of white seabass,Lates calcarifer,in acute and subchronic cadmium exposure

Histopathological alterations to white seabass, Lates calcarifer aged 3 months in acute and subchronic cadmium exposure were studied by light and scanning electron microscopy. The 96-h LC50 values of cadmium to L. calcarifer was found to be 20.12 +/- 0.61 mg/l and the maximum acceptable toxicant concentration (MATC) was 7.79 mg/l. Fish were exposed to 10 and 0.8 mg/l of Cd (as CdCl,H2O) for 96 h and 90 days, respectively. The study showed that gill lamellae and kidney tubules were the primary target organs for the acute toxic effect of cadmium while in the subchronic exposure, the toxic effect to gills was less than that of kidney and liver. Gill alterations included edema of the epithelial cells with the breakdown of pillar cell system, aneurisms with some ruptures, hypertrophy and hyperplasia of epithelial and chloride cells. The liver showed blood congestion in sinusoids and hydropic swelling of hepatocytes, vacuolation and dark granule accumulation. Lipid droplets and glycogen content were observed in hepatocytes at the second and third month of subchronic exposure. The kidney showed hydropic swelling of tubular cell vacuolation and numerous dark granule accumulation in many tubules. Tubular degeneration and necrosis were seen in some areas.     

Toxic effects of 2,4‐D herbicide on fish

Abstract

Acute and subacute 2,4‐D toxicity to carp (Cyprinus carpio L.) were investigated. Acute toxicity (LC‐ 50) was investigated in semi‐static test during a 24, 48, and 96‐ hours exposition. Subacute toxicity was investigated by exposing fish to different 2,4,‐D concentrations (150, 200, and 250 mg/L) for 14 days. Biochemical and morphological changes in certain organs and tissues were investigated.

LC‐ 50 values at 24 hours exposure was 310.0 mg/L, 295.0 mg/L for 48 hours, and 270.0 mg/L for 96 hours exposure.

Subacute toxicity tests show that 2,4‐D induce changes in the enzyme activities (AP, GOT, GPT) and morphological changes in the gills, liver and kidneys, but changes are of limited biological importance.     

Cypermethrin induced alterations in nitrogen metabolism in freshwater fishes

In the present study, two fresh water fishes namely, Channa punctatus and Clarias batrachus, were exposed to three sub-acute concentrations of synthetic pyrethroid, cypermethrin, for 96 h to evaluate the role of amino acids in fulfilling the immediate energy needs of fishes under pyrethroid induced stress as well as to find out the mechanism of ammonia detoxification. The experiments were designed to estimate the levels of free amino acid, urea, ammonia and the activities of aspartate aminotransferase (AAT), alanine aminotransferase (AlAT), glutamate dehydrogenase (GDH), glutamine synthetase (GS) and arginase in some of the vital organs like brain, gills, liver, kidney and muscle of both fish species. The significant decrease in the levels of amino acids concomitant with remarkable increase in the activities of AAT, AlAT and GDH in these vital tissues of fish species elucidated the amino acid catabolism as one of the main mechanism of meeting out the immediate energy demand of the fishes in condition of cypermethrin exposure. The levels of ammonia were significantly increased at 10% of 96 h LC(50) of cypermethrin in the different organs such as brain, gills, liver, kidney and muscle of both fish species while 15% and 20% concentrations of 96 h LC(50) of cypermehrin registered remarkable decline in both fish species. The differential increment in the activities of GDH, GS and arginase and in the level of urea established three different alternative mechanisms of ammonia detoxification. The results indicated that in C. punctatus, the prevalent mode of nitrogen excretion is in the form of conversion of ammonia into glutamine and glutamate while in C. batrachus, the excessive nitrogen is excreted in the form of urea synthesized from ammonia.     

Effects of experimental terbuthylazine exposure on the cells of Dicentrarchus labrax (L.)

The effects of acute exposure to the herbicide terbuthylazine (3.55, 5.01 and 7.08 mg l(-1)) on the cells of farmed European sea bass, Dicentrarchus labrax L., were investigated by means of light and electron microscopy. In gills of treated fish, the number of chloride cells (CCs) and rodlet cells (RCs) increased significantly within 24 h and 48 h, respectively; the intestine showed the largest increase in RCs linked to treatment and exposure time. In kidney, 24 h exposure induced a significant increase in RCs and the number and global area of macrophage aggregates (MAs). Treated fish displayed cellular and/or ultrastructural alterations in all the organs examined. In the gills necrosis, lamellar and cellular oedema, epithelial lifting, telangectasia, and fusion of secondary lamellae were encountered. The liver presented myelin-like figures, cytoplasmic rarefaction and acute cell swelling of hepatocytes. In both organs, the severity of damage was dose-dependent. In RCs of gills, the intestine and kidney of exposed sea bass, high cytoplasmic vacuolization, myelin-like figures, cristolysis and varying degrees of rodlet degeneration were observed. Extensive rodlet expulsion occurred in the gut lumen. Exposure to terbuthylazine also affected the renal tubular epithelial cells, which exhibited 'blebs'. Damage to the intestinal epithelial cells was also observed.     

Sublethal effects of monocrotophos on locomotor behavior and gill architecture of the mosquito fish, Gambusia affinis

Subacute studies of monocrotophos [Dimethyl (E)-1-methyl-2-(methyl-carbamoyl) vinyl phosphate] on mosquito fish, Gambusia affinis, were carried out in vivo for 24 days to assess the locomotor behavior, structural integrity of gill, and targeted enzyme acetylcholinesterase (AChE, EC: 3.1.1.7) interactions. Monocrotophos (MCP) can be rated as moderately toxic to G. affinis, with a median lethal concentration (LC(50)) of 20.49 +/- 2.45 mgL(-1). The fish exposed to sublethal concentration of LC(10) (7.74 mgL(-1)) were under stress and altered their locomotor behavior, such as distance traveled per unit time (m min(-1)) and swimming speed (cm sec(-1)) with respect to the length of exposure. Inhibition in the activity of brain AChE and deformities in the primary and secondary lamellae of gill may have resulted in failure of exchange of gases. The maximum inhibition of 95% of AChE activity was observed on days 20 and 24.Morphological aberrations in the gills were also studied during exposure to the sublethal concentration of monocrotophos for a period ranging from 8 to 24 days. The extent of damage in gill was dependent on the duration of exposure. The findings revealed that inhibition in brain AChE activity and structural alteration in gill were responsible for altering the locomotor behavior of exposed fish.     

Lethal and sub-lethal effects of the fungicide chlorothalonil on three life stages of the grass shrimp,Palaemonetes pugio

Chlorothalonil (2,4,5,6-tetrachloroisophthalonitrile) is the second most widely used fungicide in the United States. Due to the widespread use of chlorothalonil, it is important to investigate the effects chlorothalonil may have on estuarine species such as the grass shrimp, Palaemonetes pugio. This study examined the toxicity of chlorothalonil to three life-history stages (embryo, larvae, adult) of the grass shrimp. Also, molting frequency, growth response and metamorphosis from a larval life cycle pulsed exposure assay were examined as sub-lethal indicators of chlorothalonil exposure. Results showed embryos were the least sensitive with a 96-h Median Lethal Concentration (LC50) of 396.0 microg/L (95% Confidence Interval [CI] 331.3-472.4 microg/L). The adult 96-h LC50 was 152.9 microg/L (95% CI 120.3-194.5 microg/L). Larvae were the most sensitive to chlorothalonil exposure with a 96-h LC50 of 49.5 microg/L (95% CI 44.4-55.27 microg/L). In the life cycle pulsed exposure assay, all surviving larvae in the treatments required significantly more molts to reach postlarvae than the control. Other measured parameters showed differences between treatments and control but there was no statistical significance. This research demonstrated that chlorothalonil is highly toxic to grass shrimp and that larval grass shrimp would be the most appropriate life stage to use for chlorothalonil risk assessments since that stage is the most sensitive.     

Toxicity of the mosquito control pesticide Scourge to adult and larval grass shrimp (Palaemonetes pugio)

This study investigated the toxicity of various concentrations of technical resmethrin and Scourge on adult and larval Palaemonetes pugio, a common grass shrimp species. Two types of tests were conducted for each of the resmethrin formulations using adult and larval grass shrimp life stages, a 96-h static renewal aqueous test without sediment, and a 24-h static nonrenewal aqueous test with sediment. For resmethrin, the 96-h aqueous LC50 value for adult shrimp was 0.53 microg/L (95% confidence interval (CI): 0.46-0.60 microg/L), and for larval shrimp was 0.35 microg/L (95% CI: 0.28-0.42 microg/L). In the presence of sediment, technical resmethrin produced a 24-h LC50 value for adult shrimp of 5.44 microg/L (95% CI: 4.52-6.55 microg/L), and for larval shrimp of 2.15 microg/L (95% CI: 1.35-3.43 microg/L). For Scourge, the 96-h aqueous LC50 for adult shrimp was 2.08 microg/L (95% CI: 1.70-2.54 microg/L), and for larval shrimp was 0.36 microg/L (95% CI: 0.24-0.55 microg/L). The 24-h sediment test yielded an LC50 value of 16.12 microg/L (95% CI: 14.79-17.57 microg/L) for adult shrimp, and 14.16 microg/L (95% CI: 12.21-16.43 microg/L) for larvae. Adjusted LC50 values to reflect the 18% resmethrin concentration in Scourge are 0.37 microg/L (adult), 0.07 microg/L (larvae) for the 96-h aqueous test, and 2.90 microg/L (adult), 2.6 microg/L (larvae) for the 24-h sediment test. Larval grass shrimp were more sensitive to technical resmethrin and Scourge than the adult life stage. The results also demonstrate that synergized resmethrin is more toxic to P. pugio than the nonsynergized form, and that the presence of sediment decreases the toxicity of both resmethrin and Scourge.     

Lethal and sublethal effects of the pyrethroid, bifenthrin, on grass shrimp (Palaemonetes pugio) and sheepshead minnow (Cyprinodon variegatus)

This study investigated the lethal and sublethal effects of the pyrethroid insecticide bifenthrin on adult and larval grass shrimp, Palaemonetes pugio, and adult sheepshead minnows, Cyprinodon variegatus. The effects were determined by conducting 96-h aqueous static renewal tests and 24-h static tests with sediment. Oxidative stress biomarkers, lipid peroxidation, glutathione, and catalase were also assessed. The 96-h aqueous LC50 value for adult shrimp was 0.020 microg/L (95% CI: 0.015-0.025 microg/L) and for larval shrimp was 0.013 microg/L (95% CI: 0.011-0.016 microg/L). The 96-h aqueous LC50 for adult sheepshead minnow was 19.806 microg/L (95% CI: 11.886-47.250 microg/L). The 24-h sediment LC50 for adult shrimp was 0.339 microg/L (95% CI: 0.291-0.381 microg/L) and for larval shrimp was 0.210 microg/L (95% CI: 0.096-0.393 microg/L). The oxidative stress assays showed some increasing trends toward physiological stress with increased bifenthrin concentrations but they were largely inconclusive. Given the sensitivity of grass shrimp to this compound in laboratory bioassays, additional work will be needed to determine if these exposure levels are environmentally relevant.     

Control of common freshwater predatory fish, Channa punctatus, through Nerium indicum leaf extracts

The diethyl ether, chloroform, acetone and methanol extract of Nerium indicum leaf were evaluated for their piscicidal activity against common freshwater air breathing predatory fish Channa punctatus. The rank of order of toxicity (LC50) of the leaf extract was, diethyl ether extract (17.34 mg/l)>acetone (40.01 mg/l)>chloroform (40.61 mg/l)>and methanol (106.37 mg/l). There was a significant negative correlation between LC50 values and exposure periods. Thus increase in exposure period, LC50 decreases from 17.34 mg/l (24 h) to >13.58 mg/l (96 h) in the diethyl ether extract. Similar trends were also observed in acetone, chloroform and methanol extracts. Exposure of sub-lethal doses (40% and 80% of LC50) of the diethyl ether extract of N. indicum leaf (which has maximum piscicidal activity) for 24 or 96 h caused significant alteration in the level of total protein, total free amino acid, nucleic acid, glycogen, pyruvate, lactate and activity of enzyme protease, phosphatases, alanine aminotransferase, aspartate aminotransferase and acetylcholinesterase in liver and muscle tissue. The alterations in all the above biochemical parameters were significantly (P<0.05) time and dose dependent. There was a significant recovery in all the above biochemical parameters, in both liver and muscle tissues of fish after the seventh day of the withdrawal of treatment. Thus, the leaf extracts of N. indicum have potent piscicidal activity against fish C. punctatus and also significantly affect both aerobic and anaerobic pathway of respiration in fish.     

Ultrastructural changes in the respiratory lamellae of the catfish, Heteropneustes fossilis after sublethal exposure to malathion

Transmission electron microscopy study of the gills of Heteropneustes fossilis, exposed to 4 mg/liter of malathion (1/3 of LC50) for 24, 48, 72, and 96 h showed significant changes in its ultrastructures. Exposure to the pesticide after 24 h caused a slightly disarrayed condition in the double layered epithelial structure. Lymphatic spaces became more apparent, and a few chloride cells appeared which protruded toward the peripheral margin of the secondary lamellae. Chloride cells were exposed to the exterior by an apical pit. Pinocytosis was observed with marginal folds (MF) originating from the pillar and epithelial cells. Some vascular constrictions were also seen in the capillaries with erythrocytes. After 48 h exposure, the outer epithelial cells were stretched into a thin boundary wall and lymphatic spaces were engorged with plasma exudate. Chloride cells transversed the whole epithelium of the lamella and came into direct contact with lymphoid space and exterior to epithelial lining. Basement membrane of the capillaries became thicker. After 72 h a distorted lamellar epithelium ruptured in a few places allowing many spheroid bodies and some chloride cells come out. Marginal folds of pillar cells migrated into vascular spaces. Basement membrane of capillaries became thicker and blood channels were constricted causing vascular stasis. No erythrocytes were visible. Blood channels were filled with leukocytes and amoebocytes. After 96 h exposure to malathion narrowing of lymphatic spaces, proliferation of epithelial cells and development of pinocytotic vesicles from marginal folds of pillar cell flanges were observed. Only marginal blood channels maintained normal configuration. Vascular stasis due to thickening of the basal lamina were still evident in centrally located blood channels filled with leukocytes. Vascular stasis would likely cause a decrease in respiratory efficiency. This study has revealed that the gills of H. fossilis were affected by a sublethal dose of malathion. The ultrastructural damages to the gills were observed as early as at 24 h exposure, but the most severe damage occurred at 72 h exposure. However, signs of gill structure regeneration were seen in malathion-exposed fish after 96 h.     

Acute toxicity of alpha-cypermethrin to guppy (Poecilia reticulata, Pallas, 1859)

Alpha-cypermethrin is a synthetic pyrethroid insecticide used to control pests in domestic, industrial and agricultural situations. Adult male guppy fish (Poecilia reticulata standard test species) were selected for the bioassay experiments. The experiments were performed in four series and the 96-h LC50 value was determined for guppies. The acute toxicity experiments were carried out by static method and behavioral changes in guppies were determined for each alpha-cypermethrin (98% technical grade) concentration. Data obtained from the alpha-cypermethrin investigation were evaluated by the use of probit analysis statistical method and the 96-h LC50 value for guppy was estimated as 9.43 microg/l.     

Biochemical effects of clomazone herbicide on piava (Leporinus obtusidens)

This study aims to verify the effects of the clomazone concentration used in rice fields on acetylcholinesterase (AChE), thiobarbituric acid reactive substances (TBARS), protein carbonyl and catalase activity in tissues of piava (Leporinus obtusidens). LC(50)-96h was 5.0 mg L(-1) and the fish were exposed to 1/10 of LC(50)-96 h: 0.5 mg L(-1) of clomazone for 96 and 192h. The same parameters were also assayed after a recovery period of 192 h in clean water. AChE activity was reduced only in the brain and heart of fish exposed for 96 h. AChE activity was decreased in the brain, muscle and heart tissues after 192 h of exposure. After 192 h of recovery period, AChE activity remained diminished in brain and muscle and showed a decrease in eye. However, after 192 h of recovery, AChE activity in heart was recovered. Fish showed increased TBARS levels in brain at all experimental periods. TBARS levels decreased in liver and muscle tissues after 192 h of exposure. The increase in muscle TBARS persisted in fish transferred to clean water. Protein carbonyl in the liver was increased in all periods studied including the recovery period. Catalase activity was reduced during all periods. The present study demonstrates the occurrence of disorders in AChE, TBARS, protein carbonyl and catalase activity in piava. The results also show changes in fish after exposure to an environmentally relevant concentration of clomazone. Most effects observed persisted after the recovery period. Thus, these parameters may be used to monitor clomazone toxicity in fish.     

Impacts of quicklime (CaO) on the toxicity of copper (CuSO4, 5H2O) to fish and fish food organisms

Static bioassays of 96 h duration were conducted in the laboratory using fry of common carp (Cyprinus carpio), adult tubificid worm (Branchiura sowerbyi) and adult copepod plankton (Cyclops viridis) to determine LC50 values of Cu and CaO to these organisms and effects of interaction between Cu and CaO. Ninety-six hour LC(50) values of Cu to fry of common carp, worm and copepod were found to be 1.40 mgl(-1), 0.08 mgl(-1) and 0.03 mgl(-1) respectively. CaO up to 500 mgl(-1) did not produce any mortality of the fry of common carp up to 96 h. But 96 h LC50 values of CaO to worm and copepod were 83.00 mgl(-1) and 27.80 mgl(-1) respectively. When common carp fry, worm and the copepod were exposed to respective LC50 dose of Cu in presence of varying concentration of CaO, mortality of the organisms significantly reduced and was found inversely correlated with the doses of CaO [y = 48.36-0.807x, r = -0.99 (n = 7) for fish; y = 44.46-0.146x, r = -0.97 (n = 7) for worm; y = 49.46-0.66x, r = -0.99 (n = 7) for the copepod]. The present results indicate that CaO is non-toxic to fish and is capable of reducing the toxicity of Cu to fish while CaO and Cu are antagonistic to each other for the worm and the copepod. Potential of using CaO as antitoxic agent for Cu in water is discussed.     

Acute toxicity, uptake and clearance of diazinon by the European eel, Anguilla anguilla (L.).

The toxicity, accumulation, and elimination of diazinon were investigated for the european eel, Anguilla anguilla. The 24, 48, 72 and 96-h median lethal concentrations (LC50) were 0.16, 0.11, 0.09 and 0.08 mg/L, respectively. Fish exposed to sublethal concentration (0.042 mg/L) accumulated diazinon in liver and muscle tissues. Bioconcentration factors (BCF) of diazinon were 1850 in liver, and 775 in muscle over the 96-h exposure period. Upon removal from diazinon containing water the contaminated fish rapidly eliminated diazinon. The excretion rate constants of this insecticide were 0.108 h-1 for liver and 0.016 h-1 for muscle. Diazinon half-lives were 16.6 and 33.2 hours for liver and muscle, respectively.     

Developmental effects in Japanese medaka (Oryzias latipes) exposed to nonylphenol ethoxylates and their degradation products

The endocrine modulating potency of five alkylphenol compounds to fish, including nonylphenol (NP), three nonylphenol ethoxylate mixtures (NP1EO, NP4EO, NP9EO) and one nonylphenol ethoxycarboxylate (NP1EC) was assessed using in vivo tests conducted with Japanese medaka (Oryzias latipes). Medaka exposed to test materials from 1 day to 100 days post-hatch were monitored for alterations to sex ratios and secondary sex characteristics and development of gonadal intersex (i.e., testis-ova). The treatment with 100 microg l-1 NP (measured 29 microg l-1) induced gonadal intersex in over 80% of exposed males, mixed secondary sex characteristics in over 40% of exposed fish and suppression of the development of papillae on the anal fin of 100% of males. The 30 microg l-1 NP (measured 8.7 microg l-1) treatment induced gonadal intersex in only one of the 22 exposed males and mixed secondary sex characteristics in approximately 20% of the exposed fish. An elevated incidence of fish with mixed secondary sex characteristics and suppression of papillae development was also observed in the treatment with NP1EO at the highest test concentration of 300 microg l-1 (measured 105 microg l-1). There was no evidence of mixed secondary sex characteristics or gonadal intersex in treatments with the remaining test mixtures. This study confirms that NP is an estrogenic compound that could affect gonadal development in fish chronically exposed to concentrations in the range of 10 microg l-1. NP1EO is very weakly estrogenic at concentrations that are an order of magnitude higher than the lowest observed effect concentration for nonylphenol.     

Metal accumulation in the smooth toadfish, Tetractenos glaber, in estuaries around Sydney, Australia

This study determined the metal levels in sediments and tissues of a common estuarine fish, Tetractenos glaber (smooth toadfish), from two metal contaminated and two reference estuaries near Sydney, Australia. Metal levels were highest in sediments and fish from contaminated estuaries. Gonads contained the highest metal levels followed by muscle, gill and liver. Metal accumulation was gender-dependant (e.g. male gonads were >20 times higher in As than females; female gills were >30 times higher than males for Pb). Cadmium, Pb and Ni levels in fish tissues reflected sediment levels, indicating sediment and/or dietary metal uptake. Levels of As, Co, Cd & Pb in gills showed similar patterns to other tissues, suggesting that metals may have been taken up by gills through contaminated water. Similar metal patterns in tissues and sediments suggest more than one uptake pathway. This study indicates that multiple factors influence metal accumulation in fish.     

Aquatic ecological risks due to cyanide releases from biomass burning

Aquatic toxicity due to the creation and mobilization of chemical constituents by fire has been little studied, despite reports of post-fire fish kills attributed to unspecified pyrogenic toxicants. We examined releases of cyanides from biomass burning and their effect on surface runoff water. In laboratory test burns, available cyanide concentrations in leachate from residual ash were much higher than in leachate from partially burned and unburned fuel and were similar to or higher than the 96-h median lethal concentration (LC50) for rainbow trout (45 microg/l). Free cyanide concentrations in stormwater runoff collected after a wildfire in North Carolina averaged 49 microg/l, again similar to the rainbow trout LC50 and an order of magnitude higher than in samples from an adjacent unburned area. Pyrogenic cyanide inputs, together with other fire-related stressors, may contribute to post-fire fish mortalities, particularly those affecting salmonids.