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USGS1981

Effects of industrial effluents, heavy metals, and organic solvents on mallard embryo development

Mallard eggs were externally exposed at 3 and 8 days of incubation to 7 different industrial effluents and to 7 different heavy metal, organic solvent, and petroleum solutions to screen for potential embryo-toxic effects. This route of exposure was chosen in order to simulate the transfer of pollutant from the plumage of aquatic birds to their eggs. Five of the effluents including mineral pigment, scouring effluent, sludge, and tannery effluent resulted in small but significant reductions in embryonic growth. Treatment with methyl mercury chloride solution of 50 ppm (Hg) impaired embryonic growth but much higher concentrations were required to affect survival and cause teratogenic effects. Oil used to suppress road dust was the most toxic of the pollutants tested and only 0.5 microliter/egg caused 60% mortality by 18 days of development. These findings, in combination with other studies suggest that petroleum pollutants, or effluents in combination with petroleum, may pose a hazard to birds' eggs when exposure is by this route.

Toxicology Letters↗

USGS1985

Organophosphorus insecticide induced decrease in plasma luteinizing hormone concentration in white-footed mice

Oral intubation of 50 and 100 mg/kg acephate inhibited brain acetylcholinesterase (AChE) activity by 45% and 56%, and reduced basal luteinizing hormone (LH) concentration by 29% and 25% after 4 h in white-footed mice ( Peromyscus leucopus noveboracensis ). Dietary exposure to 25, 100, and 400 ppm acephate for 5 days substantially inhibited brain AChE activity, but did not affect plasma LH concentration. These preliminary findings suggest that acute exposure to organophosphorus insecticides may affect LH secretion and possibly reproductive function.

Toxicology Letters↗

USGS1985

Effects of fluoride on screech owl reproduction: Teratological evaluation, growth, and blood chemistry in hatchlings

The effects on reproduction in screech owls ( Otus asio ) of chronic dietary sodium fluoride administration at 0, 40, and 200 ppm were examined. Fluoride at 40 ppm resulted in a significantly smaller egg volume, while 200 ppm also resulted in lower egg weights and lengths. Day-one hatchlings in the 200 ppm group weighed almost 10% less than controls and had shorter crown-rump lengths. No gross abnormalities were apparent. Skeletal clearing and staining revealed significantly shorter tibiotarsus lengths in the 40 ppm and 200 ppm groups and a shorter radius-ulna length in the 200 ppm group. By 7 days of age, body weights and lengths did not differ from controls, but the tibiotarsus in the 200 ppm group remained shorter. No significant differences were detected in hematocrit, hemoglobin, plasma calcium or alkaline phosphatase. Plasma phosphorus levels were higher in the 40 ppm group than in controls. These results, in combination with the findings of Pattee et al. [25], revealed significant impairment of overall reproduction, suggesting that sodium fluoride could cause slight to moderate reproduction disorders in owls in fluoride-polluted areas.

Toxicology Letters↗

USGS1994

A review of lead poisoning in swans

Nearly 10,000 swans of six species or subspecies from 14 countries have died from poisoning caused by lead that originated from ingestion of fishing weights, shotgun pellets (shot), or contaminated vegetation or sediments associated with mining and smelting wastes. Lead contamination in mute swans in England caused local population declines during the late 1970s and 1980s. More tundra swans died from lead poisoning than any other species. The extreme record involved an estimated 7200 tundra swans that died over five winters at one locality in North Carolina. The recent legislation to ban lead fishing weights in most of England and Wales and recent replacement of lead shot with steel shot for waterfowl hunting in the United States and a few areas of Europe, including Denmark, are expected to reduce the incidence of lead poisoning in swans.

Comparative Biochemistry and Physiology, Part C: P↗

USGS1996

Regional cholinesterase activity in white-throated sparrow brain is differentially affected by acephate (Orthene®)

Effects of a 14-day dietary exposure to an organophosphorus pesticide, acephate (acetylphosphoramidothioic acid O,S-dimethyl ester), were determined on cholinesterase activity in three regions (basal ganglia, hippocampus, and hypothalamus) of the white-throated sparrow, Zonotrichia albicollis , brain. All three regions experienced depressed cholinesterase activity between 0.5–2 ppm acephate. The regions exhibited cholinesterase recovery at 2–16 ppm acephate; however, cholinesterase activity dropped and showed no recovery at higher dietary levels (>16 ppm acephate). Evidence indicates that the recovery is initiated by the magnitude of depression, not the duration. In general, as acephate concentration increased, differences in ChE activity among brain regions decreased. Three terms are introduced to describe ChE response to acephate exposure: 1) ChE resistance threshold, 2) ChE compensation threshold, and 3) ChE depression threshold. It is hypothesized that adverse effects to birds in the field may occur at pesticide exposure levels customarily considered negligible.

Comparative Biochemistry and Physiology, Part C: P↗

USGS2004

Roles of uptake, biotransformation, and target site sensitivity in determining the differential toxicity of chlorpyrifos to second to fourth instar Chironomous riparius (Meigen)

Early life stages of aquatic organisms tend to be more sensitive to various chemical contaminants than later life stages. This research attempted to identify the key biological factors that determined sensitivity differences among life stages of the aquatic insect Chironomous riparius. Specifically, second to fourth instar larvae were exposed in vivo to both low and high waterborne concentrations of chlorpyrifos to examine differences in accumulation rates, chlorpyrifos biotransformation, and overall sensitivity among instars. In vitro acetylcholinesterase (AChE) assays were performed with chlorpyrifos and the metabolite, chlorpyrifos-oxon, to investigate potential target site sensitivity differences among instars. Earlier instars accumulated chlorpyrifos more rapidly than later instars. There were no major differences among instars in the biotransformation rates of chlorpyrifos to the more polar metabolites, chlorpyrifos-oxon, and chlorpyridinol (TCP). Homogenate AChE activities from second to fourth instar larvae were refractory to chlorpyrifos, even at high concentrations. In contrast, homogenate AChE activities were responsive in a dose-dependent manner to chlorpyrifos-oxon. In general, it appeared that chlorpyrifos sensitivity differences among second to fourth instar C. riparius were largely determined by differences in uptake rates. In terms of AChE depression, fourth instar homogenates were more sensitive to chlorpyrifos and chlorpyrifos-oxon than earlier instars. However, basal AChE activity in fourth instar larvae was significantly higher than basal AChE activity in second to third instar larvae, which could potentially offset the apparent increased sensitivity to the oxon. ?? 2003 Elsevier B.V. All rights reserved.

Aquatic Toxicology↗

USGS2005

Aqueous exposure to Aroclor 1254 modulates the mitogenic response of Atlantic salmon anterior kidney T-cells: Indications of short- and long-term immunomodulation

Polychlorinated biphenyls (PCBs) exist as persistent organic pollutants in numerous river systems in the United States. Unfortunately, some of these rivers are sites of active Atlantic salmon restoration programs, and polychlorinated biphenyls have been implicated as ancillary factors contributing to failed salmon restoration. Here, we investigate the immediate and chronic effects of intermediate duration aqueous PCB exposure (1 or 10 ??g L-1 Aroclor 1254) on the mitogen-stimulated lymphoproliferative response of Atlantic salmon anterior kidney leukocytes (AKLs). A short-term study was designed to examine immunomodulation in Atlantic salmon smolts immediately following 21 days of aqueous exposure, while a long-term study evaluated chronic impacts in the mitogen response in parr 15 months post-exposure as larvae. The proliferative response of AKLs to the mitogens concanavalin A (CON A), phytohemaglutinnin-P (PHA-P), pokeweed mitogen (PWM), and lipopolysaccharide were used as an indice of immunomodulation. The proliferative response to the T-cell mitogens CON A and PHA-P was significantly increased in the 10 ??g L-1 group (n = 10; P = 0.043 and 0.002, respectively) immediately following exposure of smolts. Additionally, The PHA-P response was significantly increased in the 1 ??g L-1 exposure group (n = 10, P = 0.036). In fish treated as larvae and tested 15 months later, the PHA-P sensitive populations exhibited elevated proliferation in the 1 and 10 ??g L-1 groups (n = 12, P < 0.04) relative to the vehicle control while the PWM response was significantly increased (n = 12, P = 0.036) only in the 10 ??g L-1 treated groups. These results demonstrate an immunomodulatory effect of PCBs on T-cell mitogen sensitive populations of lymphocytes in Atlantic salmon as well as long-term immunomodulation in PHA-P and PWM sensitive populations. ?? 2005 Elsevier B.V. All rights reserved.

Aquatic Toxicology↗

USGS2005

Individual variability in esterase activity and CYP1A levels in Chinook salmon (Oncorhynchus tshawytscha) exposed to esfenvalerate and chlorpyrifos

Acetylcholinesterase (AChE) activity has traditionally been monitored as a biomarker of organophosphate (OP) and/or carbamate exposure. However, AChE activity may not be the most sensitive endpoint for these agrochemicals, because OPs can cause adverse physiological effects at concentrations that do not affect AChE activity. Carboxylesterases are a related family of enzymes that have higher affinity than AChE for some OPs and carbamates and may be more sensitive indicators of environmental exposure to these pesticides. In this study, carboxylesterase and AChE activity, cytochrome P4501A (CYP1A) protein levels, and mortality were measured in individual juvenile Chinook salmon (Oncorhynchus tshawytscha) following exposure to an OP (chlorpyrifos) and a pyrethroid (esfenvalerate). As expected, high doses of chlorpyrifos and esfenvalerate were acutely toxic, with nominal concentrations (100 and 1 ??g/l, respectively) causing 100% mortality within 96 h. Exposure to chlorpyrifos at a high dose (7.3 ??g/l), but not a low dose (1.2 ??g/l), significantly inhibited AChE activity in both brain and muscle tissue (85% and 92% inhibition, respectively), while esfenvalerate exposure had no effect. In contrast, liver carboxylesterase activity was significantly inhibited at both the low and high chlorpyrifos dose exposure (56% and 79% inhibition, respectively), while esfenvalerate exposure still had little effect. The inhibition of carboxylesterase activity at levels of chlorpyrifos that did not affect AChE activity suggests that some salmon carboxylesterase isozymes may be more sensitive than AChE to inhibition by OPs. CYP1A protein levels were ???30% suppressed by chlorpyrifos exposure at the high dose, but esfenvalerate had no effect. Three teleost species, Chinook salmon, medaka (Oryzias latipes) and Sacramento splittail (Pogonichthys macrolepidotus), were examined for their ability to hydrolyze a series of pyrethroid surrogate substrates and in all cases hydrolysis activity was undetectable. Together these data suggest that (1) carboxylesterase activity inhibition may be a more sensitive biomarker for OP exposure than AChE activity, (2) neither AChE nor carboxylesterase activity are biomarkers for pyrethroid exposure, (3) CYP1A protein is not a sensitive marker for these agrochemicals and (4) slow hydrolysis rates may be partly responsible for acute pyrethroid toxicity in fish. ?? 2005 Elsevier B.V. All rights reserved.

Aquatic Toxicology↗

USGS2006

The chlorinated AHR ligand 3,3′,4,4′,5-pentachlorobiphenyl (PCB126) promotes reactive oxygen species (ROS) production during embryonic development in the killifish ( Fundulus heteroclitus )

Exposure to dioxin-like chemicals that activate the aryl hydrocarbon receptor (AHR) can result in increased cellular and tissue production of reactive oxygen species (ROS). Little is known of these effects during early fish development. We used the fish model, Fundulus heteroclitus , to determine if the AHR ligand and pro-oxidant 3,3′,4,4′,5-pentachlorobiphenyl (PCB126) can increase ROS production during killifish development, and to test a novel method for measuring ROS non-invasively in a living organism. The superoxide-sensitive fluorescent dye, dihydroethidium (DHE), was used to detect in ovo ROS production microscopically in developing killifish exposed to PCB126 or vehicle. Both in ovo CYP1A activity (ethoxyresorufin- o -deethylase, EROD) and in ovo ROS were induced by PCB126. In ovo CYP1A activity was inducible by PCB126 concentrations as low as 0.003 nM, with maximal induction occurring at 0.3 nM PCB126. These PCB126 concentrations also significantly increased in ovo ROS production in embryonic liver, ROS being detectable as early as 5 days post-fertilization. These data demonstrate that the pro-oxidant and CYP1A inducer, PCB126, increases both CYP1A activity and ROS production in developing killifish embryos. The superoxide detection assay (SoDA) described in this paper provides a semi-quantitative, easily measured, early indicator of altered ROS production that can be used in conjunction with simultaneous in ovo measurements of CYP1A activity and embryo development to explore functional relationships among biochemical, physiological and developmental responses to AHR ligands.

Aquatic Toxicology↗

USGS2006

The effect of chronic chromium exposure on the health of Chinook salmon (Oncorhynchus tshawytscha)

This study was designed to determine fish health impairment of Chinook salmon ( Oncorhynchus tshawytscha ) exposed to chromium. Juvenile Chinook salmon were exposed to aqueous chromium concentrations (0–266 μg l −1 ) that have been documented in porewater from bottom sediments and in well waters near salmon spawning areas in the Columbia River in the northwestern United States. After Chinook salmon parr were exposed to 24 and 54 μg Cr l −1 for 105 days, neither growth nor survival of parr was affected. On day 105, concentrations were increased from 24 to 120 μg Cr l −1 and from 54 to 266 μg Cr l −1 until the end of the experiment on day 134. Weight of parr was decreased in the 24/120 μg Cr l −1 treatment, and survival was decreased in the 54/266 μg Cr l −1 treatment. Fish health was significantly impaired in both the 24/120 and 54/266 μg Cr l −1 treatments. The kidney is the target organ during chromium exposures through the water column. The kidneys of fish exposed to the greatest concentrations of chromium had gross and microscopic lesions (e.g. necrosis of cells lining kidney tububules) and products of lipid peroxidation were elevated. These changes were associated with elevated concentrations of chromium in the kidney, and reduced growth and survival. Also, variations in DNA in the blood were associated with pathological changes in the kidney and spleen. These changes suggest that chromium accumulates and enters the lipid peroxidation pathway where fatty acid damage and DNA damage (expressed as chromosome changes) occur to cause cell death and tissue damage. While most of the physiological malfunctions occurred following parr exposures to concentrations ≥120 μg Cr l −1 , nuclear DNA damage followed exposures to 24 μg Cr l −1 , which was the smallest concentration tested. The abnormalities measured during this study are particularly important because they are associated with impaired growth and reduced survival at concentrations ≥120 μg Cr l −1 . Therefore, these changes can be used to investigate the health of resident fish in natural waters with high chromium concentrations as well as provide insight into the mechanisms of chromium toxicity.

Aquatic Toxicology↗

USGS2006

Dietary exposure of largemouth bass to OCPs changes expression of genes important for reproduction

Dieldrin and p,p???-DDE are ubiquitous contaminants known to act as endocrine disruptors, causing impaired development and reproduction in fish and wildlife. In order to elucidate the mechanisms by which dieldrin and p,p???-DDE cause endocrine disruption in largemouth bass (Micropterus salmoides), fish were exposed subchronically through the diet to both contaminants. Following 120 days of exposure, p,p???-DDE decreased estradiol in females, but increased 11-ketotestosterone in both sexes. Dieldrin on the other hand, decreased estradiol and 11-ketotestosterone in both sexes. Both pesticides also altered steady state mRNA expression levels of a set of genes chosen to represent three possible mechanisms of endocrine disruption: (1) direct interaction with soluble sex steroid receptors, (2) biosynthesis of endogenous sex hormones, and (3) metabolism of endogenous hormones. p,p???-DDE acted as a weak estrogen, increasing the expression of vitellogenin and estrogen receptor ?? in the liver. p,p???-DDE also altered the expression of genes involved in the synthesis of endogenous hormones as well as their metabolism. Dieldrin, on the other hand, only altered expression of vitellogenin and not estrogen receptor ??. Dieldrin also altered the expression of genes involved in hormone synthesis and metabolism, and it dramatically lowered plasma hormone levels. Both pesticides targeted expression of genes involved in all three modes of action, suggesting that they each have multiple modes of action. ?? 2006 Elsevier B.V. All rights reserved.

Aquatic Toxicology↗

USGS2006

Larval exposure to environmentally relevant mixtures of alkylphenolethoxylates reduces reproductive competence in male fathead minnows

The ubiquitous presence of nonylphenolethoxylate/octylphenolethoxylate (NPE/OPE) compounds in aquatic environments adjacent to wastewater treatment plants (WWTP) warrants an assessment of the endocrine disrupting potential of these complex mixtures on aquatic vertebrates. In this study, fathead minnow larvae were exposed for 64 days to a mixture of NPE/OPE, which closely models the NPE/OPE composition of a major metropolitan WWTP effluent. Target exposure concentrations included a total NPE/OPE mixture load of 200% of the WWTP effluent concentration (148 μg/L), 100% of the WWTP effluent concentration (74 μg/L) and 50% of the WWTP effluent concentration (38 μg/L). The NPE/OPE mixture contained 0.2% 4- t -octylphenol, 2.8% 4-nonylphenol, 5.1% 4-nonylphenolmonoethoxylate, 9.3% 4-nonylphenoldiethoxylate, 0.9% 4- t -octylphenolmonoethoxylate, 3.1% 4- t -octylphenoldiethoxylate, 33.8% 4-nonylphenolmonoethoxycarboxylate, and 44.8% 4-nonylphenoldiethoxycarboxylate. An additional exposure of 5 μg/L 4-nonylphenol (nominal) was conducted. The exposure utilized a flow-through system supplied by ground water and designed to deliver consistent concentrations of applied chemicals. Following exposure, larvae were raised to maturity. Upon sexual maturation, exposed male fish were allowed to compete with control males in a competitive spawning assay. Nest holding ability of control and exposed fish was carefully monitored for 7 days. All male fish were then sacrificed and analyzed for plasma vitellogenin, developmental changes in gonadal tissues, alterations in the development of secondary sexual characters, morphometric changes, and changes to reproductive behavior. When exposed to the 200% NPE/OPE treatment most larvae died within the first 4 weeks of exposure. Both the 100% and 50% NPE/OPE exposures caused a significant decrease in reproductive behavior, as indicated by an inability of many of the previously exposed males to acquire and hold a nest site required for reproduction. In contrast, the 5 μg/L 4-nonylphenol exposure resulted in significantly enhanced reproductive behavior compared to that of control males and a majority of the nesting sites were held by previously exposed males. No significant change in the development of gonadal tissues was observed. The 100% NPE/OPE exposure resulted in a significant reduction in the gonadal somatic index and in the prominence of secondary sexual characteristics of exposed larvae. This study indicates that NPE/OPE mixtures have an effect on the reproductive competence of previously exposed male fathead minnows. In addition, 4-nonylphenol concentrations utilized in all exposures were below regulatory guidelines, suggesting that evaluation of 4-nonylphenol alone may not be sufficient for identifying potentially adverse effects of this suite of compounds usually found as mixtures in the aquatic environment.

Aquatic Toxicology↗

USGS2007

Effects of aqueous exposure to polychlorinated biphenyls (Aroclor 1254) on physiology and behavior of smolt development of Atlantic salmon

Polychlorinated biphenyls (PCBs) are a widespread aquatic contaminant and are present in both wild and hatchery raised Atlantic salmon, Salmo salar. The possible sub-lethal alterations in smolt physiology and behavior due to PCB exposure of salmon have not been widely examined. In this study, we examined the effects of the PCB mixture Aroclor 1254 on survival and smolt development of Atlantic salmon. In separate experiments, fish were exposed as yolk-sac larvae or as juveniles just prior to the parr-smolt transformation in April to 1 ??g l-1 (PCB-1) or 10 ??g l-1 (PCB-10) aqueous Aroclor 1254 (A1254), or vehicle for 21 days. After exposure, yolk-sac larvae were reared at ambient conditions for 1 year, until the peak of smolting the following May. Juveniles were sampled immediately after exposure. Both groups were assessed for behavioral, osmoregulatory, and endocrine disruption of smolt development at the peak of smolting. PCB-1 and PCB-10 treated yolk-sac larvae exhibited significant increases in the rate of opercular movement after 14 and 21 days of exposure. At the peak of smolting, prior exposure as yolk-sac larvae to PCB-1 did not affect behavior, while PCB-10 dramatically decreased volitional preference for seawater. Neither concentration of A1254 had long-term effects on the osmoregulatory or endocrine parameters measured in animals exposed as yolk-sac larvae. Juvenile fish exposed to PCB-1 or PCB-10 during smolting exhibited a dose-dependent reduction in preference for seawater. Fish treated with the higher dose of A1254 also exhibited a 50% decrease in gill Na+,K+-ATPase activity and a 10% decrease in plasma chloride levels in freshwater. In addition, plasma triiodothyronine was reduced 35-50% and plasma cortisol 58% in response to exposure to either concentration; whereas plasma thyroxine, growth hormone, and insulin-like growth factor I levels were unaffected. These results indicate that the effects of exposure to A1254 may vary according to developmental stage. Exposure to A1254 in the freshwater environment can inhibit preparatory adaptations that occur during smolting, thereby reducing marine survival and sustainability of salmon populations. ?? 2007 Elsevier B.V. All rights reserved.

Aquatic Toxicology↗

USGS2007

Reproductive responses of male fathead minnows exposed to wastewater treatment plant effluent, effluent treated with XAD8 resin, and an environmentally relevant mixture of alkylphenol compounds

On-site, continuous-flow experiments were conducted during August and October 2002 at a major metropolitan wastewater treatment plant (WWTP) to determine if effluent exposure induced endocrine disruption as manifested in the reproductive competence of sexually mature male fathead minnows ( Pimephales promelas ). The fathead minnows were exposed in parallel experiments to WWTP effluent and WWTP effluent treated with XAD8 macroreticular resin to remove the hydrophobic-neutral fraction which contained steroidal hormones, alkylphenolethoxylates (APEs), and other potential endocrine disrupting compounds (EDCs). The effluent composition varied on a temporal scale and the continuous-flow experiments captured the range of chemical variability that occurred during normal WWTP operations. Exposure to WWTP effluent resulted in vitellogenin induction in male fathead minnows, with greater response in October than in August. Concentrations of ammonia, APEs, 17β-estradiol, and other EDCs also were greater in October than in August, reflecting a change in effluent composition. In the October experiment, XAD8 treatment significantly reduced vitellogenin induction in the male fathead minnows relative to the untreated effluent, whereas in August, XAD8 treatment had little effect. During both experiments, XAD8 treatment removed greater than 90% of the APEs. Exposure of fish to a mixture of APEs similar in composition and concentration to the WWTP effluent, but prepared in groundwater and conducted at a separate facility, elicited vitellogenin induction during both experiments. There was a positive relation between vitellogenin induction and hepatosomatic index (HSI), but not gonadosomatic index (GSI), secondary sexual characteristics index (SSCI), or reproductive competency. In contrast to expectations, the GSI and SSCI increased in males exposed to WWTP effluent compared to groundwater controls. The GSI, SSCI, and reproductive competency were positively affected by XAD8 treatment of the WWTP effluent.

Aquatic Toxicology↗

USGS2007

Determining metal assimilation efficiency in aquatic invertebrates using enriched stable metal isotope tracers

We employ a novel approach that combines pulse-chase feeding and multi-labelled stable isotopes to determine gut passage time (GPT), gut retention time (GRT), food ingestion rate (IR) and assimilation efficiency (AE) of three trace elements for a freshwater gastropod. Lettuce isotopically enriched in 53 Cr, 65 Cu and 106 Cd was fed for 2 h to Lymnaea stagnalis . The release of tracers in feces and water was monitored for 48 h, during which unlabelled lettuce was provided ad libidum . The first defecation of 53 Cr occurred after 5 h of depuration (GPT), whereas 90% of the ingested 53 Cr was recovered in the feces after 22.5 h of depuration (GRT). 53 Chromium was not significantly accumulated in the soft tissues upon exposure. In contrast, 65 Cu and 106 Cd assimilation was detectable for most experimental snails, i.e., 65/63 Cu and 106/114 Cd ratios in exposed snails were higher than those for controls. Food IR during the labelled feeding phase was 0.16 ± 0.07 g g −1 d −1 . IR was inferred from the amount of 53 Cr egested in the feces during depuration and the concentration of 53 Cr in the labelled lettuce. Assimilation efficiencies (±95% CI) determined using mass balance calculations were 84 ± 4% for Cu and 85 ± 3% for Cd. The ratio method yields similar AE estimates. Expanding the application of this novel stable isotope tracer technique to other metals in a wide variety of species will provide unique opportunities to evaluate the interplay between digestive processes and dietary influx of metals. Understanding the biological processes that modulate dietborne metal uptake is crucial to assess the toxicity of dietborne metals.

Aquatic Toxicology↗

USGS2007

Effects of hexazinone and atrazine on the physiology and endocrinology of smolt development in Atlantic salmon

Exposure to hexazinone (HEX) and atrazine (ATZ), highly mobile and widely used herbicides along rivers in the United States, is potentially harmful to Atlantic salmon, which have been listed as an endangered species. To determine the effects of these contaminants on smolt development, juvenile Atlantic salmon were exposed under flow-through conditions to 100 μg l −1 HEX, 10 and 100 μg l −1 ATZ in fresh water (FW) for 21 days at 10 °C beginning in mid-April. Twelve fish per treatment were sampled in FW, following a 24 h seawater (SW) challenge and after growth for 3 months in SW. Exposure to 100 μg l −1 HEX or 10 μg l −1 ATZ caused no mortalities of smolts in FW or after SW challenge, while 9% of the fish exposed to 100 μg l −1 ATZ died during exposure. Fish exposed to 100 μg l −1 ATZ reduced feeding after 10 days of exposure and had an impaired growth rate in FW and during the first month in SW; compensatory growth occurred in the second and third month in SW. HEX and ATZ at 10 μg l −1 exposure had no effect on plasma levels of cortisol, growth hormone (GH), insulin growth factor I (IGF-I), thyroxine (T 4 ) and plasma 3,5,3′-triiodo- l -thyronine (T 3 ), Cl − , Mg 2+ , Na + , Ca 2+ in FW or after SW challenge. FW smolts exposed to 100 μg l −1 ATZ had decreased plasma Cl − , Mg 2+ , Na + and Ca 2+ ions and increased cortisol. No effect on plasma levels of GH, IGF-I, T 4 or T 3 was found in FW smolts exposed to 100 μg l −1 ATZ. Following SW challenge, fish previously exposed to 100 μg l −1 ATZ had significant increases in hematocrit, plasma cortisol, Cl − , Mg 2+ , Na + , Ca 2+ and a decrease in T 4 and T 3 . It is concluded that under the conditions imposed in this study, HEX does not affect salinity tolerance of Atlantic salmon smolts, while ATZ causes ionoregulatory, growth and endocrine disturbance.

Aquatic Toxicology↗

USGS2008

Impairment of the reproductive potential of male fathead minnows by environmentally relevant exposures to 4-nonylphenolf

The synthetic organic compound 4-nonylphenol (NP) has been detected in many human-impacted surface waters in North America. In this study, we examined the ability of NP to alter reproductive competence in male fathead minnows after a 28 day flow-through exposure in a range of environmentally relevant concentrations bracketing the U.S. Environmental Protection Agency toxicity-based NP chronic exposure criterion of 6.1 μg NP/L. Exposure to NP at and above the EPA chronic exposure criterion resulted in an induction of plasma vitellogenin (VTG) within 14 days. However, 7 days after the cessation of exposure, VTG concentrations had dropped more than 50% and few males expressed VTG above the detection threshold. All of the morphological endpoints, including gonadosomatic index, hepatosomatic index, secondary sexual characters, and histopathology, were unaltered by all NP treatments. However, when NP-exposed male fish were allowed to compete with control males for access to nest sites and females, most treatments altered the reproductive competence of exposed males. At lower NP concentrations, exposed males out-competed control males, possibly by being primed through the estrogenic NP exposure in a fashion similar to priming by pheromones released from female fathead minnows. At higher NP exposure concentrations, this priming effect was negated by the adverse effects of the exposure and control males out-competed treated males. Results of this study indicate the complexity of endocrine disrupting effects and the need for multiple analysis levels to assess the effects of these compounds on aquatic organisms.

Aquatic Toxicology↗

USGS2008

Impacts of short-term acid and aluminum exposure on Atlantic salmon (Salmo salar) physiology: A direct comparison of parr and smolts

Episodic acidification resulting in increased acidity and inorganic aluminum (Al i ) is known to impact anadromous salmonids and has been identified as a possible cause of Atlantic salmon population decline. Sensitive life-stages such as smolts may be particularly vulnerable to impacts of short-term (days–week) acid/Al exposure, however the extent and mechanism(s) of this remain unknown. To determine if Atlantic salmon smolts are more sensitive than parr to short-term acid/Al, parr and smolts held in the same experimental tanks were exposed to control (pH 6.3–6.6, 11–37 μg l −1 Al i ) and acid/Al (pH 5.0–5.4, 43–68 μg l −1 Al i ) conditions in the lab, and impacts on ion regulation, stress response and gill Al accumulation were examined after 2 and 6 days. Parr and smolts were also held in cages for 2 and 6 days in a reference (Rock River, RR) and an acid/Al-impacted tributary (Ball Mountain Brook, BMB) of the West River in Southern Vermont. In the lab, losses in plasma Cl − levels occurred in both control parr and smolts as compared to fish sampled prior to the start of the study, however smolts exposed to acid/Al experienced additional losses in plasma Cl − levels (9–14 mM) after 2 and 6 days, and increases in plasma cortisol (4.3-fold) and glucose (2.9-fold) levels after 6 days, whereas these parameters were not significantly affected by acid/Al in parr. Gill Na + ,K + -ATPase (NKA) activity was not affected by acid/Al in either life-stage. Both parr and smolts held at BMB (but not RR) exhibited declines in plasma Cl − , and increases in plasma cortisol and glucose levels; these differences were significantly greater in smolts after 2 days but similar in parr and smolts after 6 days. Gill NKA activity was reduced 45–54% in both life-stages held at BMB for 6 days compared to reference fish at RR. In both studies, exposure to acid/Al resulted in gill Al accumulation in parr and smolts, with parr exhibiting two-fold greater gill Al than smolts after 6 days. Our results indicate that smolts are more sensitive than parr to short-term acid/Al. Increased sensitivity of smolts appears to be independent of a reduction in gill NKA activity and greater gill Al accumulation. Instead, increased sensitivity of smolts is likely a result of both the acquisition of seawater tolerance while still in freshwater and heightened stress responsiveness in preparation for seawater entry and residence.

Aquatic Toxicology↗