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At least 73 records · Page 4Linked to original sources
USGS2019

In vivo effects of 17α-ethinylestradiol, 17B-estradiol and 4-nonylphenol on insulin-like growth-factor binding proteins (igfbps) in Atlantic salmon

Feminizing endocrine disrupting compounds (EDCs) affect the growth and development of teleost fishes. The major regulator of growth performance, the growth hormone (Gh)/insulin-like growth-factor (Igf) system, is sensitive to estrogenic compounds and mediates certain physiological and potentially behavioral consequences of EDC exposure. Igf binding proteins (Igfbps) are key modulators of Igf activity, but their alteration by EDCs has not been examined. We investigated two life-stages (fry and smolts) of Atlantic salmon ( Salmo salar ), and characterized how the Gh/Igf/Igfbp system responded to waterborne 17α-ethinylestradiol (EE 2 ), 17β-estradiol (E 2 ) and 4-nonylphenol (NP). Fry exposed to EE 2 and NP for 21 days had increased hepatic vitellogenin ( vtg ) mRNA levels while hepatic estrogen receptor α ( erα ), gh receptor (ghr) , igf1 and igf2 mRNA levels were decreased. NP-exposed fry had reduced body mass and total length compared to controls. EE 2 and NP reduced hepatic igfbp1b1 , -2a , -2b1 , -4 , -5b2 and -6b1 , and stimulated igfbp5a . In smolts, hepatic vtg mRNA levels were induced following 4-day exposures to all three EDCs, while erα only responded to EE 2 and E 2 . EDC exposures did not affect body mass or fork length; however, EE 2 diminished plasma Gh and Igf1 levels in parallel with reductions in hepatic ghr and igf1 . In smolts, EE 2 and E 2 diminished hepatic igfbp1b1 , -4 and -6b1 , and stimulated igfbp5a . There were no signs of compromised ionoregulation in smolts, as indicated by unchanged branchial ion pump/transporter mRNA levels. We conclude that hepatic igfbps respond (directly and/or indirectly) to environmental estrogens during two key life-stages of Atlantic salmon, and thus may modulate the growth and development of exposed individuals.

Aquatic Toxicology↗
USGS2019

Bisphenol A and 17 alpha-ethinylestradiol-induced transgenerational differences in expression of osmoregulatory genes in the gill of medaka (Oryzias latipes)

Embryonic bisphenol A (BPA) and 17α-ethinylestradiol (EE2) exposure can have far reaching health effects in fish, including adult onset transgenerational reproductive abnormalities, anxiety, and cardiac disorders. It is unknown whether these two environmental estrogens can induce transgenerational abnormalities in the gill. The present study examined transgenerational effects of BPA or EE2 exposure on genes that are critical for osmoregulation in fish. Medaka ( Oryzias latipes ) embryos were exposed to either BPA (100 μg/L) or EE2 (0.05 μg/L) for the first 7 days of embryonic development and never thereafter for the remainder of that generation (F0) and in subsequent generations of this study (F1, F2, and F3). Expression of osmoregulatory genes ( NKAα1a , NKAα1b , NKAα1c , NKAα3a , NKAα3b , NKCC1a, and CFTR ) were examined in gills of the first-generation (F0) adults which were directly exposed as embryo and in the fourth-generation adults (F3), which were never exposed to either of these environmental estrogens. Significant alterations in expression of osmoregulatory genes were observed in both F0 and F3 generations. Within the F0 generation, a sex-specific expression pattern was observed with a downregulation of osmoregulatory genes in males and an upregulation of osmoregulatory genes in females. At the F3 generation, this pattern reversed with the majority of the osmoregulatory genes upregulated in males and downregulated in females, suggesting that exposure to BPA and EE2 during embryonic development induced transgenerational impairment in molecular events associated with osmoregulatory functions in subsequent generations. These adverse outcomes may have impacts on physiological functions related to osmoregulation of fish inhabiting contaminated aquatic environments.

Aquatic Toxicology↗
USGS2020

Acute toxicity and clotting times of anticoagulant rodenticides to red-toothed (Odonus niger) and black (Melichthys niger) triggerfish, fathead minnow (Pimephales promelas), and largemouth bass (Micropterus salmoides)

Anticoagulant rodenticides (ARs) areused in rateradication efforts on island wildlife refuges. ARbait pellets can get into coralreefareasduring broadcasting and leadto exposure ofnon-target organisms, such as marine fishes. The objective of this study was to determine the sensitivity of representative saltwater fishes, Red-toothed triggerfish (Odonus niger) and Black triggerfish (Melichthys niger), and common freshwater fishes, fathead minnow (Pimephales promelas), and largemouth bass (Micropterus salmoides) to first generation ARs, diphacinone (DPN) and chlorophacinone (CPN), as well as a second-generation AR, brodifacoum (BROD). Acute toxicity of ARs was evaluated by single dose, intraperitoneal injections. The median lethal dose (LD50) ranges were 137−175μg DPN/g, 155−182μg CPN/g, and 36−48μg BROD/g for Red-toothed triggerfish and 90−122μg DPN/g, 125−164μg CPN/g, and 50−75μg BROD/g for black triggerfish. Laboratory surrogate test fish species fathead minnow and largemouth bass were of similar sensitivity toward AR-induced toxicity compared to triggerfish based on LD50 values. Sublethal effects on elevated clotting time occurred in dose-dependent fashion in all fish tested. Fish appear to have low sensitivity to AR chemicals as compared to other taxa, in particular mammals and birds, based on across-taxa comparisons of species sensitivity distributions of whole body, single dose acute lethality (LD50 values). The sensitivity of fish to waterborne exposures of ARs has yet to be fully evaluated and indeed may prove more hazardous to fish.

Aquatic Toxicology↗
USGS2020

Transcriptome analysis of testis reveals the effects of developmental exposure to bisphenol a or 17α-ethinylestradiol in medaka (Oryzias latipes)

Endocrine disrupting chemicals (EDCs) can induce abnormalities in organisms via alteration of molecular pathways and subsequent disruption of endocrine functions. Bisphenol A (BPA) and 17α-ethinylestradiol (EE2) are ubiquitous EDCs in the environment. Many aquatic organisms, including fish, are often exposed to varying concentrations of BPA and EE2 throughout their lifespan. Both BPA and EE2 can activate estrogenic signaling pathways and cause adverse effects on reproduction via alteration of pathways associated with steroidogenesis. However, transcriptional pathways that are affected by chronic exposure to these two ubiquitous environmental estrogens during embryonic, larval, and juvenile stages are not clearly understood. In the present study, we examined transcriptional alterations in the testis of medaka fish ( Oryzias latipes ) chronically exposed to a low concentration of BPA or EE2. Medaka were exposed to BPA (10 μg/L) or EE2 (0.01 μg/L) from 8 h post-fertilization (as embryos) to adulthood 50 days post fertilization (dpf), and transcriptional alterations in the testis were examined by RNA sequencing (RNA-seq). Transcriptomic profiling revealed 651 differentially expressed genes (DEGs) between BPA-exposed and control testes, while 1475 DEGs were found between EE2-exposed and control testes. Gene ontology (GO) analysis showed a significant enrichment of “intracellular receptor signaling pathway”, “response to steroid hormone” and “hormone-mediated signaling pathway” in the BPA-induced DEGs, and of “cilium organization”, “microtubule-based process” and “organelle assembly” in the EE2-induced DEGs. Pathway analysis showed significant enrichment of “integrin signaling pathway” in both treatment groups, and of “cadherin signaling pathway”, “Alzheimer disease-presenilin pathway” in EE2-induced DEGs. Single nucleotide polymorphism (SNP) and insertion-deletion (Indel) analysis found no significant differences in mutation rates with either BPA or EE2 treatments. Taken together, global gene expression differences in testes of medaka during early stages of gametogenesis were responsive to chronic BPA and EE2 exposure.

Aquatic Toxicology↗
USGS2020

Relative toxicity and sublethal effects of NaCl and energy-related saline wastewaters on prairie amphibians

Increasing salinity in freshwater environments is a growing problem due both to the negative influences of salts on ecosystems and their accumulation and persistence in environments. Two major sources of increased salinity from sodium chloride salts (NaCl) are saline wastewaters co-produced during energy production (herein, wastewaters) and road salts. Effects of road salts have received more attention, but legacy contamination from wastewaters is widespread in some regions and spills still occur. Amphibians are sensitive to contaminants, including NaCl, because of their porous skin and osmoregulatory adaptations to freshwater. However, similarities and differences between effects of wastewaters and road salts have not been investigated. Therefore, we investigated the relative influence of wastewaters and NaCl at equivalent concentrations of chloride on three larval amphibian species that occur in areas with increased salinity. We determined acute toxicity and growth effects on Boreal Chorus Frogs ( Pseudacris maculata ), Northern Leopard Frogs ( Rana pipiens ), and Barred Tiger Salamanders ( Ambystoma mavortium ). We posited that wastewaters would have additive effects on amphibians compared to NaCl because wastewaters often have additional toxic heavy metals and other contaminants. For NaCl, toxicity was higher for frogs than the salamander. Toxicity of wastewaters was also similar between chorus and leopard frogs. Only chorus frog survival was lower when exposed to wastewater compared to NaCl. Mass and length of leopard and chorus frog larvae decreased with increasing salinity after only 96 hours of exposure but did not for tiger salamanders. Size of leopard frogs was lower when exposed to NaCl compared to wastewater. However, growth effects were similar between wastewater and NaCl for chorus frogs. Taken together, our results suggest that previous studies on effects of road salt could inform future studies and management of wastewater-contaminated ecosystems, and vice versa. Nevertheless, effects of road salts and wastewaters may be context-, species-, and trait-specific and require further investigations. The negative influence of salts on imperiled amphibians underscores the need to restore landscapes with increased salinity and reduce future salinization of freshwater ecosystems.

Aquatic Toxicology↗
USGS2021

Concentration addition and independent action assessments of the binary mixtures of four toxicants on zebra mussel (Dreissena polymorpha) mortality

Researchers most often focus on individual toxicants when identifying effective chemical control agents for aquatic invasive species; however, toxicant mixtures may elicit synergistic effects. Synergistic effects may decrease required concentrations and shorten exposure durations for treatments. We investigated four toxicants (EarthTec QZ, Clam-Trol CT-2, niclosamide, and potassium chloride) that have been considered to control invasive zebra mussels ( Dreissena polymorpha Pallas, 1771). We determined the toxicity of binary mixtures for five different mixture ratios to adult mussels. We compared our observations to predictions made with concentration addition and independent action paradigms, as based on the dose-response relationships of each individual toxicant. We calculated the model deviation ratio for each combination at the LC 50 and LC 90 and identified three possible interactions: synergy, antagonism, and additivity. We found that mixtures of niclosamide and Clam-Trol CT-2 were the most synergistic while mixtures that included potassium chloride were largely additive to antagonistic. The use of synergistic combinations has potential to decrease the overall volume and concentration of individual toxicants required for dreissenid mussel treatments, thereby decreasing cost.

Aquatic Toxicology↗
USGS2021

Exposure to Deepwater Horizon crude oil increases free cholesterol in larval red drum (Sciaenops ocellatus)

The 2010 Deepwater Horizon oil spill impacted over 2100 km of shoreline along the northern Gulf of Mexico, which coincided with the spawning season of many coastal species, including red drum ( Sciaenops ocellatus ). Red drum develop rapidly and are sensitive to crude oil exposure during the embryonic and larval periods. This study investigates the predictions from recent transcriptomic studies that cholesterol biosynthetic processes are impacted by oil exposure in fish early life stages. We found that red drum larvae exposed for 72-hours to ΣPAH 50 3.55 - 15.45 µg L −1 exhibited significantly increased pericardial area, a cardiotoxicity metric, but the expression of several genes targeted in the cholesterol synthesis pathway was not affected. However, whole-mount staining revealed significant increases in free cholesterol throughout the larval body (ΣPAH 50 4.71 – 16.15 µg L −1 ), and total cholesterol followed an increasing trend (ΣPAH 50 3.55 - 15.45 µg L −1 ). Cholesterol plays a critical role in fish embryo development and ion channel function. Therefore, the disruption of cholesterol homeostasis, as observed here, could play a role in the oil toxicity phenotype observed across many fish species.

Aquatic Toxicology↗
USGS2025

Influence of cardiotoxicity on visual function in developing zebrafish ( Danio rerio ) exposed to Deepwater Horizon crude oil

Polycyclic aromatic hydrocarbons (PAHs) are toxic constituents of crude oil that can induce cardiac dysfunction and vision impairment in early life stage (ELS) fishes. However, it is currently unknown whether visual impairments are independent effects or if they result from underlying PAH cardiotoxicity. To better understand this mechanism, microinjection of microRNA 133b (miR133b) was used to impair cardiac development in ELS zebrafish (injected at <1.25 hpf). Vision and cardiac endpoints were compared between miR133b-injected and oil-exposed zebrafish (4–72 hpf, 54.68–60.41 µg/L tPAH 50 ) to determine the influence of cardiac dysfunction and oil exposure on visual function. At 7 dpf, pericardial area and eye area were measured, and visual function was assessed by optokinetic response (OKR). Over 94 % of miR133b larvae and 45 % of oil-exposed larvae exhibited pericardial edema. Across treatments, there was a strong negative linear correlation between pericardial area and eye area ( r =-0.839, p < 0.0001). All miR133b larvae that exhibited pericardial edema and 18 % of the oil-exposed larvae that exhibited pericardial edema also exhibited reduced eye area (microphthalmia). In both the miR133b and oil groups, OKR was significantly reduced in larvae exhibiting pericardial edema ( p < 0.0001) and in larvae exhibiting reduced eye area ( p < 0.0001). A negative binomial generalized linear model (GLM) indicated that reduced eye area ( p < 0.0001), rather than pericardial edema ( p = 0.76), was a significant predictor of OKR. However, pericardial edema was strongly correlated with reduced eye area across treatments. These results suggest that visual effects may result from an interaction of cardiotoxicity as well as direct impacts to the visual system.

Aquatic Toxicology↗
USGS2025

Occurrence and tissue distribution of per- and polyfluoroalkyl substances (PFAS) in fishes from waterbodies with point and non-point sources in Massachusetts, USA

Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants with known bioaccumulative and toxic effects in aquatic ecosystems. This study assessed site-specific differences in PFAS contamination in fish from Ashumet Pond, Sudbury River, and Great Herring Pond (reference site) in Massachusetts. Fish from Ashumet Pond exhibited the highest PFAS concentrations, particularly perfluorooctane sulfonate (PFOS), which exceeded levels in plasma almost 650 times those at the reference site. Principal component analysis identified distinct PFAS profiles at each site, reflecting localized contamination sources. Temporal analysis at Ashumet Pond revealed a substantial increase in plasma PFOS and perfluorodecanoic acid (PFDA) from 2020 to 2022. Tissue distribution analyses showed the highest PFAS concentrations in plasma, followed by liver and muscle, consistent with PFAS binding affinity for blood proteins. Species-specific differences in PFAS bioaccumulation were observed, with largemouth bass ( Micropterus nigricans ) exhibiting higher body burdens than banded killifish ( Diaphanus fundulus ), likely due to trophic position and dietary exposure. Histopathological assessments and gene transcript analyses revealed associations between PFAS exposure and inflammatory responses, oxidative stress, endocrine disruption, and immune-related pathways, with the most pronounced molecular effects observed at the downstream site of the Sudbury River. This study underscores the importance of understanding site-specific contamination sources, exposure pathways, and biological effects of PFAS in fish. These findings would benefit from additional research on sediment contamination, temporal analyses at each site, trophic transfer, and transcriptomic analyses across multiple organs to further elucidate PFAS toxicity mechanisms and guide remediation efforts.

Massachusetts↗
USGS2026

PFAS exposure suppresses leaf litter decomposition in a stream ecosystem

Decomposition of organic matter is critical to the biogeochemical cycling of carbon and nutrients in all ecosystems. In streams, decomposition can be influenced by anthropogenic impacts, including contaminants. Per- and polyfluoroalkyl substances (PFAS) are resistant to degradation and widespread in freshwater ecosystems, yet little is known about their influence on organic matter processing in streams. We paired an observational field study of a PFAS-impacted stream via food processing wastewater with a 28-day laboratory experiment to investigate PFAS effects on leaf litter processing using multiple lines of evidence. Leaf litter decomposition rates and microbial respiration were significantly lower downstream of the PFAS point-source compared to the paired upstream site. We hypothesized that PFAS suppressed microbial activity thereby resulting in slower decomposition rates. To investigate further and better isolate PFAS, we dosed aquatic mesocosms containing leaf packs with differing concentrations of perfluorooctane sulfonate (PFOS). Over the 28-day incubation, decomposition rates did not differ, but we observed lower respiration rates on day 28 and higher dissolved organic carbon (DOC) in PFOS-dosed mesocosms, suggesting that PFAS may suppress microbial activity and inhibit carbon processing. These results underscore that concerns regarding PFAS contamination extend beyond organismal toxicity to ecosystem-level effects. Further research is needed to understand the scale, implications, and mechanisms responsible for these changes.

Upper Mississippi River Basin↗
USGS2001

Decreased glutathione S-transferase expression and activity and altered sex steroids in Lake Apopka brown bullheads (Ameriurus nebulosus)

A number of freshwater lakes and reclaimed agricultural sites in Central Florida have been the receiving waters for agrochemical and municipal runoff. One of these sites, Lake Apopka, is also a eutrophic system that has been the focus of several case studies reporting altered reproductive activity linked to bioaccumulation of persistent organochlorine chemicals in aquatic species. The present study was initiated to determine if brown bullheads (Ameriurus nebulosus) from the north marsh of Lake Apopka (Lake Apopka Marsh) exhibit an altered capacity to detoxify environmental chemicals through hepatic glutathione S-transferase (GST)-mediated conjugation as compared with bullheads from a nearby reference site (Lake Woodruff). We also compared plasma sex hormone concentrations (testosterone, 17-?? estradiol, and 11 keto-testosterone) in bullheads from the two sites. Female bullheads from Lake Apopka had 40% lower initial rate GST conjugative activity toward 1-chloro-2,4-dinitrobenzene (CDNB), 50% lower activity towards p-nitrobutyl chloride (NBC), 33% lower activity toward ethacrynic acid (ECA), and 43% lower activity toward ??5-androstene-3,17-dione (??5-ADI), as compared with female bullheads from Lake Woodruff. Enzyme kinetic analyses demonstrated that female bullheads from Lake Apopka had lower GST-catalyzed CDNB clearance than did female Lake Woodruff bullheads. Western blotting studies of bullhead liver cytosolic proteins demonstrated that the reduced GST catalytic activities in female Lake Apopka bullheads were accompanied by lower expression of hepatic GST protein. No site differences were observed with respect to GST activities or GST protein expression in male bullheads. Female Lake Apopka bullheads also had elevated concentrations of plasma androgens (testosterone and 11-ketotestosterone) as compared with females from Lake Woodruff. In contrast, male Lake Apopka bullheads had elevated levels of plasma estrogen but similar levels of androgens as compared with male bullheads from Lake Woodruff. Collectively, our studies indicate the presence of reduced GST protein expression, reduced GST conjugative capacity and altered sex steroid homeostasis in female bullheads from a contaminated field site in Central Florida. The implications of these physiological alterations in terms of pollutant biotransformation and reproduction are discussed. ?? 2001 Elsevier Science B.V. All rights reserved.

Aquatic Toxicology↗
USGS2002

Effects of chronic dietary exposure to environmentally relevant concentrations to 2,3,7,8-tetrachlorodibenzo-p-dioxin on survival, growth, reproduction and biochemical responses of female rainbow trout (Oncorhynchus mykiss)

Adult female rainbow trout were exposed to dietary 2,3,7,8-tetrachlorodibenzo- p -dioxin (TCDD) at concentrations of 1.8, 18 and 90 ng TCDD/kg (ww) food for up to 300 day. At the end of the exposure fish were spawned and the reproductive outcomes were assessed. TCDD was accumulated into tissues and eggs in a dose-dependent manner with steady state being achieved after 50–100 day of exposure. Biochemical and hematological parameters were monitored at 50, 100, 150, and 200 day after the beginning of exposure. The survival of adult female trout was reduced in a dose-dependent manner by exposure to TCDD in the diet. Fish fed 1.8 ng TCDD/kg, moist weight of diet, showed significantly reduced survival compared with those fed the control diet. TCDD also affected survival of fry from females fed 1.8 ng TCDD/kg. Observed adverse effects in adult fish were as sensitive as early life-stage endpoints. Liver EROD activity was only moderately increased in all exposure groups after 250+ day of exposure. Low rates of edema and deformities were observed in fry from all treatment groups including controls. This study has demonstrated adverse effects of TCDD to both adults and fry at concentrations comparable to current environmental concentrations. This suggests that direct adult toxicity as well as reproductive endpoints need to be incorporated in the current risk assessment paradigm for these compounds.

Aquatic Toxicology↗
USGS2002

Toxicity of selenium and other elements in food organisms to razorback sucker larvae

Elevated selenium concentrations documented in water, sediment, and biota in irrigation drain water studies by U.S. Department of the Interior agencies and academia have raised concerns that selenium may be adversely affecting endangered fish in the upper Colorado River basin. The objective of the study was to determine the effects on endangered razorback sucker ( Xyrauchen texanus ) larvae from exposure to selenium and other trace elements in water and zooplankton collected from sites adjacent to the Colorado River near Grand Junction, CO. A 30-day study was initiated with 5-day-old larvae exposed in a 4×4 factor experiment with four food and four water treatments, and the biological endpoints measured were survival, growth, development, and whole-body residues of selenium. Mean selenium concentration in reference water (24-Road) was <0.7 μg/l, in reference food (brine shrimp) was 3.2 μg/g, at Horsethief was 1.6 μg/l in water and 6.0 μg/g in zooplankton, at Adobe Creek was 3.4 μg/l in water and 32 μg/g in zooplankton, and at Walter Walker was 13 μg/l in water and 52 μg/g in zooplankton. Although there were differences in concentrations of inorganic elements in water and biota among the three sites, selenium was apparently the only element elevated to concentrations of concern. Effects on survival were more prominent from dietary exposure compared to waterborne exposure. Selenium concentrations of ≥4.6 μg/g in food organisms adversely affected the survival of razorback sucker larvae. The onset of mortality in larvae exposed to food and water from Walter Walker seemed delayed compared to mortality in larvae exposed to food and water from Horsethief, which has been observed in two other studies. Elevated arsenic in one food source seemed to interact with selenium to reduce the toxic effects of selenium.

Colorado↗
USGS2002

Role of selenium toxicity and oxidative stress in aquatic birds

Adverse effects of selenium (Se) in wild aquatic birds have been documented as a consequence of pollution of the aquatic environment by subsurface agricultural drainwater and other sources. These effects include mortality, impaired reproduction with teratogenesis, reduced growth, histopathological lesions and alterations in hepatic glutathione metabolism. A review is provided, relating adverse biological effects of Se in aquatic birds to altered glutathione metabolism and oxidative stress. Laboratory studies, mainly with an organic form of Se, selenomethionine, have revealed oxidative stress in different stages of the mallard (Anas platyrhynchos) life cycle. As dietary and tissue concentrations of Se increase, increases in plasma and hepatic GSH peroxidase activities occur, followed by dose-dependent increases in the ratio of hepatic oxidized to reduced glutathione (GSSG:GSH) and ultimately hepatic lipid peroxidation measured as an increase in thiobarbituric acid reactive substances (TBARS). One or more of these oxidative effects were associated with teratogenesis (4.6 ppm wet weight Se in eggs), reduced growth in ducklings (15 ppm Se in liver), diminished immune function (5 ppm Se in liver) and histopathological lesions (29 ppm Se in liver) in adults. Manifestations of Serelated effects on glutathione metabolism were also apparent in field studies in seven species of aquatic birds. Reduced growth and possibly immune function but increased liver:body weight and hepatic GSSG:GSH ratios were apparent in American avocet (Recurvirostra americana) hatchlings from eggs containing 9 ppm Se. In blacknecked stilts (Himantopus mexicanus), which contained somewhat lower Se concentrations, a decrease in hepatic GSH was apparent with few other effects. In adult American coots (Fulica americana), signs of Se toxicosis included emaciation, abnormal feather loss and histopathological lesions. Mean liver concentrations of 28 ppm Se (ww) in the coots were associated with elevated hepatic GSH peroxidase, depletion of hepatic protein bound thiols and total thiols, but a small increase in GSH. Diving ducks in the San Francisco Bay area exhibited a positive correlation between hepatic Se concentration and GSH peroxidase activity (r=0.63, P<0.05), but a negative correlation between hepatic Se and GSH concentration (r=0.740, P<0.05). In willets (Catoptrophorus semipalmatus) from the San Diego area, positive correlations occurred between hepatic Se concentration and GSSG (r=0.70, P<0.001), GSSG:GSH ratio, and TBARS. In emperor geese (Chen canagica) from western Alaska, blood levels of up to 9.4 ppm occurred and were associated with increased plasma GSH peroxidase activity (r=0.62, P<0.001), but with decreased plasma GSSG reductase activity. When evaluating Se toxicity, interactive nutritional factors, including other elements and dietary protein, should also be taken into consideration. Further studies are needed to examine the relationship between different forms of environmentally occurring selenium, arsenic and mercury on reproduction, hepatotoxicity and immune function of aquatic birds. Further selenium nutritional interaction studies may also help to illucidate the mechanism of selenium induced teratogenesis, by optimizing GSH and other antioxidant defense mechanisms in a manner that would stabilize or raise the cell's threshold for susceptibility to toxic attack from excess selenium. It is concluded that Se-related manifestations of oxidative stress may serve as useful bioindicators of Se exposure and toxicity in wild aquatic birds.

Aquatic Toxicology↗
USGS2002

Selenium toxicity: cause and effects in aquatic birds

There are several manners in which selenium may express its toxicity: (1) an important mechanism appears to involve the formation of CH3Se- which either enters a redox cycle and generates superoxide and oxidative stress, or forms free radicals that bind to and inhibit important enzymes and proteins. (2) Excess selenium as selenocysteine results in inhibition of selenium methylation metabolism. As a consequence, concentrations of hydrogen selenide, an intermediate metabolite, accumulate in animals and are hepatotoxic, possibly causing other selenium-related adverse effects. (3) It is also possible that the presence of excess selenium analogs of sulfur-containing enzymes and structural proteins play a role in avian teratogenesis. l-selenomethionine is the most likely major dietary form of selenium encountered by aquatic birds, with lesser amounts of l-selenocysteine ingested from aquatic animal foods. The literature is suggestive that l-selenomethionine is not any more toxic to adult birds than other animals. l-Selenomethionine accumulates in tissue protein of adult birds and in the protein of egg white as would be expected to occur in animals. There is no suggestion from the literature that the levels of l-selenomethionine that would be expected to accumulate in eggs in the absence of environmental concentration of selenium pose harm to the developing embryo. For several species of aquatic birds, levels of Se as selenomethionine in the egg above 3 ppm on a wet weight basis result in reduced hatchability and deformed embryos. The toxicity of l-selenomethionine injected directly into eggs is greater than that found from the entry of l-selenomethionine into the egg from the normal adult diet. This suggests that there is unusual if not abnormal metabolism of l-selenomethionine in the embryo not seen when l-selenomethionine is present in egg white protein where it likely serves as a source of selenium for glutathione peroxidase synthesis in the developing aquatic chick.

Aquatic Toxicology↗
USGS1999

Embryotoxicity of Great Lakes lake trout extracts to developing rainbow trout

Planar halogenated hydrocarbons (PHHs), such as polychlorinated dibenzo- p -dioxins, dibenzofurans, and biphenyls are present in aquatic systems, and are known to produce adverse effects in fish. This study investigated the embryotoxicity of PHH mixtures through the nanoinjection of environmental extracts into newly fertilized eggs from two strains of rainbow trout. Organic extracts were obtained from whole adult lake trout collected from Lake Michigan in 1988 and Lake Superior in 1994. The graded doses of the final extracts used for injection were quantified as 2,3,7,8-tetrachlorodibenzo- p -dioxin toxic-equivalents (TEQs) based on the concentrations of dioxins, furans and non- o -PCBs in each, and as equivalent amounts found in the eggs of the original lake trout (eggEQ). Total TEQs in the lake trout were 14.7 pg TEQ/g in the Lake Michigan sample and 7.3 pg TEQ/g in the Lake Superior sample. The extract of the Lake Michigan lake trout was embryotoxic to rainbow trout; LD 50 values were 35 eggEQ (15–90, 95% F.L.) in the Arlee strain and 14 eggEQ (5–99, 95% F.L.) in the Erwin strain of rainbow trout. The LD 50 values of the Lake Michigan extract in either of these strains of rainbow trout fall within the actual range of TCDD LD 50 values based on TEQs. This indicates that an additive model of toxicity is appropriate to quantify PHHs in relation to early life stage mortality in fish. Gross lesions characteristic of exposure to PHHs (i.e. yolk-sac edema, craniofacial deformities, and hemorrhaging) increased in a dose-related manner. The lowest observable adverse effect concentrations (LOAEC) for these gross lesions and cumulative mortalities suggests that current concentrations of PHHs in lake trout from Lake Michigan are above a threshold for adverse effects and these compounds may have implications on the lack of recruitment in certain Great Lakes lake trout populations.

Great Lakes↗
USGS2000

Photoenhanced toxicity of weathered oil to Mysidopsis bahia

The toxicity of a water-accommodated fraction (WAF) prepared from weathered oil was assessed in a 7-day static renewal test with Mysidopsis bahia. Weathered oil was collected from the 5 x monitoring well at the Guadalupe oil field. Solar ultraviolet and visible light intensities were measured in various habitats in the vicinity of the weathered oil sample collection site, and the resultant measurements were used to produce laboratory light treatments that were representative of the on-site quality and intensity of natural solar radiation. Each of five WAF dilutions and a control without WAF was tested under three different simulated solar radiation intensities. During the test, survival and growth of the mysids, irradiance, and total petroleum hydrocarbon (TPH) concentrations in the test treatments were measured. Significant increases (P ??? 0.05) in mortality occurred among mysids exposed to 0.57 and 1.30 mg TPH/l and the effects were potentiated as irradiance increased. Seven-day LC50 (0.92-0.42 mg TPH/l) and LC20 (0.58-0.15 mg TPH/l) values decreased as the simulated solar irradiance increased. Calculated EC20 and EC50 values for mysid growth indicate that surviving mysids exposed to 0.1-1.0 mg TPH/l would incur significant reductions (P ??? 0.05) in productivity (biomass). Results of the present study indicate that effects elicited through the interaction of WAF of weathered oil and solar radiation will substantially increase the toxicity of weathered oil. Further, the photomediated effects of petroleum compounds measured as TPH on mysid survival and growth demonstrate a need to consider the interactions of ultraviolet light and contaminant to avoid under estimating toxicity that might occur in the environment. (C) 2000 Elsevier Science B.V.

Aquatic Toxicology↗
USGS2014

Mercury exposure associated with altered plasma thyroid hormones in the declining western pond turtle (Emys marmorata) from California mountain streams

Mercury (Hg) is a global threat to wildlife health that can impair many physiological processes. Mercury has well-documented endocrine activity; however, little work on the effects of Hg on the thyroid hormones triiodothyronine (T3) and thyroxine (T4) in aquatic wildlife exists despite the fact that it is a sensitive endpoint of contaminant exposure. An emerging body of evidence points to the toxicological susceptibility of aquatic reptiles to Hg exposure. We examined the endocrine disrupting potential of Hg in the western pond turtle (Emys marmorata), a long-lived reptile that is in decline throughout California and the Pacific Northwest. We measured total Hg (THg) concentrations in red blood cells (RBCs) and plasma T3 and T4 of turtles from several locations in California that have been impacted by historic gold mining. Across all turtles from all sites, the geometric mean and standard error THg concentration was 0.805 ± 0.025 μg/g dry weight. Sampling region and mass were the strongest determinants of RBC THg. Relationships between RBC THg and T3 and T4 were consistent with Hg-induced disruption of T4 deiodination, a mechanism of toxicity that may cause excess T4 levels and depressed concentrations of biologically active T3.

California↗