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Results for “Aquatic Toxicology”

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At least 73 records · Page 4Linked to original sources
USGS2015

Sublethal red tide toxin exposure in free-ranging manatees (Trichechus manatus) affects the immune system through reduced lymphocyte proliferation responses, inflammation, and oxidative stress

The health of many Florida manatees (Trichechus manatus latirostris) is adversely affected by exposure to blooms of the toxic dinoflagellate, Karenia brevis. K. brevis blooms are common in manatee habitats of Florida's southwestern coast and produce a group of cyclic polyether toxins collectively referred to as red tide toxins, or brevetoxins. Although a large number of manatees exposed to significant levels of red tide toxins die, several manatees are rescued from sublethal exposure and are successfully treated and returned to the wild. Sublethal brevetoxin exposure may potentially impact the manatee immune system. Lymphocyte proliferative responses and a suite of immune function parameters in the plasma were used to evaluate effects of brevetoxin exposure on health of manatees rescued from natural exposure to red tide toxins in their habitat. Blood samples were collected from rescued manatees at Lowry Park Zoo in Tampa, FL and from healthy, unexposed manatees in Crystal River, FL. Peripheral blood leukocytes (PBL) isolated from whole blood were stimulated with T-cell mitogens, ConA and PHA. A suite of plasma parameters, including plasma protein electrophoresis profiles, lysozyme activity, superoxide dismutase (SOD) activity, and reactive oxygen/nitrogen (ROS/RNS) species, was also used to assess manatee health. Significant decreases (p<0.05) in lymphocyte proliferation were observed in ConA and PHA stimulated lymphocytes from rescued animals compared to non-exposed animals. Significant correlations were observed between oxidative stress markers (SOD, ROS/RNS) and plasma brevetoxin concentrations. Sublethal exposure to brevetoxins in the wild impacts some immune function components, and thus, overall health, in the Florida manatee.

Florida↗
USGS2015

Biokinetics of different-shaped copper oxide nanoparticles in the freshwater gastropod, Potamopyrgus antipodarum

Sediment is recognized as a major environmental sink for contaminants, including engineered nanoparticles (NPs). Consequently, sediment-living organisms are likely to be exposed to NPs. There is evidence that both accumulation and toxicity of metal NPs to sediment-dwellers increase with decreasing particle size, although NP size does not always predict effects. In contrast, not much is known about the influence of particle shape on bioaccumulation and toxicity. Here, we examined the influence of copper oxide (CuO) NP shape (rods, spheres, and platelets) on their bioaccumulation kinetics and toxicity to the sediment-dwelling gastropod, Potamopyrgus antipodarum . The influence of Cu added as CuCl 2 (i.e., aqueous Cu treatment) was also examined. Exposure to sediment mixed with aqueous Cu or with different-shaped CuO NPs at an average measured exposure concentration of 207 &mu;g Cu per g dry weight sediment for 14 days did not significantly affect snail mortality. However, growth decreased for snails exposed to sediment amended with CuO NP spheres and platelets. P. antipodarum accumulated Cu from all Cu forms/shapes in significant amounts compared to control snails. In addition, once accumulated, Cu was efficiently retained (i.e., elimination rate constants were generally not significantly different from zero). Consequently, snails are likely to concentrate Cu over time, from both aqueous and NP sources, resulting in a high potential for toxicity.

Aquatic Toxicology↗
USGS2015

Biodynamics of copper oxide nanoparticles and copper ions in an oligochaete: Part I: relative importance of water and sediment as exposure routes

Copper oxide (CuO) nanoparticles (NPs) are widely used, and likely released into the aquatic environment. Both aqueous (i.e., dissolved Cu) and particulate Cu can be taken up by organisms. However, how exposure routes influence the bioavailability and subsequent toxicity of Cu remains largely unknown. Here, we assess the importance of exposure routes (water and sediment) and Cu forms (aqueous and nanoparticulate) on Cu bioavailability and toxicity to the freshwater oligochaete, Lumbriculus variegatus , a head-down deposit-feeder. We characterize the bioaccumulation dynamics of Cu in L. variegatus across a range of exposure concentrations, covering both realistic and worst-case levels of Cu contamination in the environment. Both aqueous Cu (Cu-Aq; administered as Cu(NO 3 ) 2 ) and nanoparticulate Cu (CuO NPs), whether dispersed in artificial moderately hard freshwater or mixed into sediment, were weakly accumulated by L. variegatus . Once incorporated into tissues, Cu elimination was negligible, i.e., elimination rate constants were in general not different from zero for either exposure route or either Cu form. Toxicity was only observed after waterborne exposure to Cu-Aq at very high concentration (305 &micro;gL -1 ), where all worms died. There was no relationship between exposure route, Cu form or Cu exposure concentration on either worm survival or growth. Slow feeding rates and low Cu assimilation efficiency (approximately 30%) characterized the uptake of Cu from the sediment for both Cu forms. In nature, L. variegatus is potentially exposed to Cu via both water and sediment. However, sediment progressively becomes the predominant exposure route for Cu in L. variegatus as Cu partitioning to sediment increases.

Aquatic Toxicology↗
USGS2016

Biodynamics of copper oxide nanoparticles and copper ions in an oligochaete - Part II: Subcellular distribution following sediment exposure

The use and likely incidental release of metal nanoparticles (NPs) is steadily increasing. Despite the increasing amount of published literature on metal NP toxicity in the aquatic environment, very little is known about the biological fate of NPs after sediment exposures. Here, we compare the bioavailability and subcellular distribution of copper oxide (CuO) NPs and aqueous Cu (Cu-Aq) in the sediment-dwelling worm Lumbriculus variegatus. Ten days (d) sediment exposure resulted in marginal Cu bioaccumulation in L. variegatus for both forms of Cu. Bioaccumulation was detected because isotopically enriched 65 Cu was used as a tracer. Neither burrowing behavior or survival was affected by the exposure. Once incorporated into tissue, Cu loss was negligible over 10 d of elimination in clean sediment (Cu elimination rate constants were not different from zero). With the exception of day 10, differences in bioaccumulation and subcellular distribution between Cu forms were either not detectable or marginal. After 10 d of exposure to Cu-Aq, the accumulated Cu was primarily partitioned in the subcellular fraction containing metallothionein-like proteins (MTLP, ≈40%) and cellular debris (CD, ≈30%). Cu concentrations in these fractions were significantly higher than in controls. For worms exposed to CuO NPs for 10 d, most of the accumulated Cu was partitioned in the CD fraction (≈40%), which was the only subcellular fraction where the Cu concentration was significantly higher than for the control group. Our results indicate that L. variegatus handle the two Cu forms differently. However, longer-term exposures are suggested in order to clearly highlight differences in the subcellular distribution of these two Cu forms.

Aquatic Toxicology↗
USGS2017

The effects of fipronil and the photodegradation product fipronil desulfinyl on growth and gene expression in juvenile blue crabs, Callinectes sapidus , at different salinities

Endocrine disrupting compounds (EDCs) are now widely established to be present in the environment at concentrations capable of affecting wild organisms. Although many studies have been conducted in fish, less is known about effects in invertebrates such as decapod crustaceans. Decapods are exposed to low concentrations of EDCs that may cause infertility, decreased growth, and developmental abnormalities. The objective herein was to evaluate effects of fipronil and its photodegradation product fipronil desulfinyl. Fipronil desulfinyl was detected in the eggs of the decapod Callinectes sapidus sampled off the coast of South Carolina. As such, to examine specific effects on C. sapidus exposed in early life, we exposed laboratory-reared juveniles to fipronil and fipronil desulfinyl for 96 hours at three nominal concentrations (0.01, 0.1, 0.5 μg/L) and two different salinities (10, 30 ppt) . The size of individual crabs (weight, carapace width) and the expression of several genes critical to growth and reproduction were evaluated. Exposure to fipronil and fipronil desulfinyl resulted in significant size increases in all treatments compared to controls. Levels of expression for vitellogenin (Vtg), an egg yolk precursor, and the ecdysone receptor (EcR), which binds to ecdysteroids that control molting, were inversely correlated with increasing fipronil and fipronil desulfinyl concentrations. Effects on overall growth and on the expression of EcR and Vtg differ depending on the exposure salinity. The solubility of fipronil is demonstrated to decrease considerably at higher salinities. This suggests that fipronil and its photodegradation products may be more bioavailable to benthic organisms as salinity increases, as more chemical would partition to tissues. Our findings suggest that endocrine disruption is occurring through alterations to gene expression in C. sapidus populations exposed to environmental levels of fipronil, and that effects may be dependent upon the salinity at which exposure occurs.

Aquatic Toxicology↗
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

2,3,7,8-Tetrachlorodibenzo-p-dioxin induces apoptotic cell death and cytochrome P4501A expression in developing Fundulus heteroclitus embryos

Fundulus heteroclitus embryos were exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) during early development using nanoinjection or water bath exposure. TCDD caused developmental abnormalities that included hemorrhaging, loss of vascular integrity, edema, stunted development and death. The LC50 and LD50 of TCDD for Fundulus embryos were ???19.7??9.5 pg TCDD/??l (water bath) and 0.25??0.09 ng TCDD/g embryo (nanoinjection). To identify a possible cause for these developmental abnormalities we analyzed the effects of TCDD on apoptotic cell death and cytochrome P4501A (CYP1A) expression in the embryos. TCDD exposure increased apoptotic cell death in several tissues including brain, eye, gill, kidney, tail, intestine, heart, and vascular tissue. CYP1A expression was also increased in the TCDD-exposed embryos predominantly in liver, kidney, gill, heart, intestine, and in vascular tissues throughout the embryo. There was co-occurrence of TCDD-induced apoptosis and CYP1A expression in some, but not all, cell types. In addition the dose response relationships for apoptosis and mortality were similar, while CYP1A expression appeared more sensitive to TCDD induction. Copyright ?? 2001 Elsevier Science B.V.

Aquatic Toxicology↗
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↗