Ecotoxicology of the herbicide paraquat: effects on wildlife and knowledge gaps.

Paraquat (PQ) is an organic herbicide introduced to the commercial market in 1962 and since linked to a variety of human health effects, including lung fibrosis, liver tumors, and Parkinson's disease. Although PQ is banned in the European Union, it is still frequently used in agricultural areas of the United States and Asia. The general mechanism of PQ's toxicity is the disruption of the redox cycle in cells.

Chronic toxicity of tire crumb rubber particles to mummichog (Fundulus heteroclitus) in episodic exposures.

Microrubber (MR) encompasses all tire-related particles in the micro-scale and has recently drawn increased attention as a subclass of the broader group of microplastics. While tire particles entered the environment since the introduction of rubber tires for vehicles, the concern regarding tire wear particles (TWP) as an environmental contaminant is relatively new. Recent studies have examined physical and chemical toxicity of MR particles and leachates to a variety of organisms.

The reproductive effects of the cancer chemotherapy agent, Carmofur, on Daphnia magna are mediated by its metabolite, 5-Fluorouracil.

Carmofur is an antineoplastic agent that inhibits ceramidase, a key enzyme in the sphingolipid pathway. Previous research suggests carmofur represses reproductive maturity in Daphnia magna. The purpose of this experiment was to confirm carmofur's effects on fecundity and reproductive maturity over two generations.

20th Pollutant Responses in Marine Organisms (PRIMO 20): Global issues and fundamental mechanisms caused by pollutant stress in marine and freshwater organisms.

The 20th Pollutant Responses in Marine Organisms (PRIMO 20) conference provided a forum for scientists from around the world to communicate novel toxicological research findings specifically focused on aquatic organisms, by combining applied and basic research at the intersection of environmental and mechanistic toxicology. The work highlighted in this special issue of Aquatic Toxicology, a special issue of Marine Environmental Research, and presented through posters and presentations, encompass important and emerging topics in freshwater and marine toxicology. This includes multiple types of emerging contaminants including microplastics and UV filtering chemicals.

Effects of selective serotonin reuptake inhibitor sertraline on hybrid striped bass predatory behavior and brain chemistry.

Millions of pharmaceuticals are prescribed each year. Wastewater treatment plants fail to remove all pharmaceuticals from discharge leading to detectable concentrations entering aquatic ecosystems where the compounds can encounter nontarget organisms. Selective serotonin reuptake inhibitor (SSRI) class of antidepressants interact with transporters in the brain and peripheral nervous system to change serotonin levels in the synapse.

Competitive Adsorption of Polycyclic Aromatic Hydrocarbons to Carbon Nanotubes and the Impact on Bioavailability to Fathead Minnow (Pimephales promelas).

Recent studies investigating the influence of carbon nanotubes (CNTs) on the bioavailability of organic contaminants have mostly focused on single-solute systems; however, a more likely scenario in the natural environment is a multisolute system where chemical interactions at the surface of the CNT may alter the bioavailability of these chemicals. In the present study bisolute adsorption isotherms of pairs of chemically similar polycyclic aromatic hydrocarbons (PAHs) by multiwalled carbon nanotubes (MWCNTs) were established, in conjunction with quantifying the bioavailability of the 2 competing MWCNT-adsorbed PAHs to Pimephales promelas using bile analysis by high-performance liquid chromatography with fluorescence detection. The results showed that whereas adsorption and bioavailability of chemically similar PAHs (anthracene and phenanthrene, and fluoranthene and pyrene) were the same in a single-solute system, in bisolute systems, PAHs that could better align or flex with the MWCNT surface due to morphological characteristics would outcompete the more rigid or planar PAHs.

Toxicological effects of micronized tire crumb rubber on mummichog (Fundulus heteroclitus) and fathead minnow (Pimephales promelas).

Recent studies on the distribution of microplastics in the Charleston Harbor, SC, USA revealed that a large part of the microplastic particles that are found in the intertidal sediments are tire wear particles. These particles originate from the wear of tire treads on roadways, and wash into the estuary during rain events. The abundance of these particles has raised questions about potential toxicity to aquatic organisms that ingest these particles.

Lionfish (Pterois volitans) as biomonitoring species for oil pollution effects in coral reef ecosystems.

With oil spills, and other sources of aromatic hydrocarbons, being a continuous threat to coral reef systems, and most reef fish species being protected or difficult to collect, the use of the invasive lionfish (Pterois volitans) might be a good model species to monitor biomarkers in potentially exposed fish in the Caribbean and western Atlantic. The rapid expansion of lionfish in the Caribbean and western Atlantic, and the unregulated fishing for this species, would make the lionfish a suitable candidate as biomonitoring species for oil pollution effects. However, to date little has been published about the responses of lionfish to environmental pollutants.

Phylogenetic origins for severe acetaminophen toxicity in snake species compared to other vertebrate taxa.

While it has been known for a while that some snake species are extremely sensitive to acetaminophen, the underlying mechanism for this toxicity has not been reported. To investigate if essential detoxification enzymes are missing in snake species that are responsible for biotransformation of acetaminophen in other vertebrate species, livers were collected from a variety of snake species, together with samples from alligator, snapping turtle, cat, rat, and cattle. Subcellular fractions were analyzed for enzymatic activities of phenol-type sulfotransferase and UDP‑glucuronosyltransferase, total glutathione S‑transferase, and N‑acetyltransferase.

Bioavailability of Carbon Nanomaterial-Adsorbed Polycyclic Aromatic Hydrocarbons to Pimphales promelas: Influence of Adsorbate Molecular Size and Configuration.

Despite carbon nanomaterials' (CNMs) potential to alter the bioavailability of adsorbed contaminants, information characterizing the relationship between adsorption behavior and bioavailability of CNM-adsorbed contaminants is still limited. To investigate the influence of CNM morphology and organic contaminant (OC) physicochemical properties on this relationship, adsorption isotherms were generated for a suite of polycyclic aromatic hydrocarbons (PAHs) on multiwalled carbon nanotubes (MWCNTs) and exfoliated graphene (GN) in conjunction with determining the bioavailability of the adsorbed PAHs to Pimphales promelas using bile analysis via fluorescence spectroscopy. Although it appeared that GN adsorbed PAHs indiscriminately compared to MWCNTs, the subsequent bioavailability of GN-adsorbed PAHs was more sensitive to PAH morphology than MWCNTs.

Phylogenetic signals in detoxification pathways in Cyprinid and Centrarchid species in relation to sensitivity to environmental pollutants.

Observations in a previous study on biomarker responses in fish collected from urban creeks in Greenville, SC, indicated that there might be considerable differences in the expression of biotransformation enzymes in chub and sunfish species. To further investigate these species differences a dosing experiment was performed in which bluehead and creek chub (Nocomis leptocephalus and Semotilus atromaculatus), and redbreast sunfish, pumpkinseed, and bluegill (Lepomis auritus, L. gibbosus, and L.

Trophic transfer of microplastics in aquatic ecosystems: Identifying critical research needs.

To evaluate the process of trophic transfer of microplastics, it is important to consider various abiotic and biotic factors involved in their ingestion, egestion, bioaccumulation, and biomagnification. Toward this end, a review of the literature on microplastics has been conducted to identify factors influencing their uptake and absorption; their residence times in organisms and bioaccumulation; the physical effects of their aggregation in gastrointestinal tracts; and their potential to act as vectors for the transfer of other contaminants. Limited field evidence from higher trophic level organisms in a variety of habitats suggests that trophic transfer of microplastics may be a common phenomenon and occurs concurrently with direct ingestion.

Biochemical effects of pollutant exposure in fish from urban creeks in Greenville, SC (USA).

The city of Greenville, SC is a rapidly expanding urban area located on the Reedy River in the upstate of South Carolina. Historical and current point-source pollutants and runoff from impermeable surfaces have resulted in a contaminated river environment, which through previous studies was demonstrated to be reflected in biological effects in fish species in the river. Because it was not known how much smaller tributaries in the urbanized area were contributing to the pollution of the main stem of the Reedy River, we collected fish (bluehead chub (Nocomis leptocephalus), creek chub (Semotilus atromaculatus), bluegill (Lepomis macrochirus), and redbreast sunfish (Lepomis auritus)) from five smaller urban creeks in the Greenville area and measured several biomarkers of exposure in these animals.

Effects of an antidepressant mixture on the brain serotonin and predation behavior of hybrid striped bass.

Antidepressants have been found in measurable concentrations in final treated wastewater effluent and receiving waters throughout the world. Studies have shown that these concentrations are typically not overtly toxic, but the psychotropic mode of action of these chemicals warrants examination of their behavioral effects. Exposure of hybrid striped bass to the antidepressants fluoxetine or venlafaxine alone has been shown to cause decreased brain serotonin levels and increased time to capture prey at concentrations typically 1 to 2 orders of magnitude higher than environmentally relevant concentrations.

Influence of carbon nanotubes on the bioavailability of fluoranthene.

Concurrent with the increase in the use of carbon nanotubes (CNTs) in society is the rise of their introduction into the environment. Carbon nanotubes cause adverse effects themselves, and they have the potential to adsorb contaminants such as polycyclic aromatic hydrocarbons (PAHs). Although CNTs have a high adsorption capacity for PAHs and these contaminants can co-occur in the environment, few studies have characterized the bioavailability of CNT-adsorbed PAHs to fish.

Biomarker responses in sunfish species and largemouth bass from the Saluda River, South Carolina.

The upstate and Piedmont region of South Carolina is a rapidly urbanizing area as a result of a steadily growing population. This increase in population and development has the potential to negatively impact local aquatic systems like the Saluda River due to increased pollution from runoff, and effluents from industrial and wastewater treatment facilities. During the summer months of 2010, 159 fish from the Centrarchidae family (sunfish species (Lepomis) and largemouth bass - Micropterus salmoides) were collected from 13 sites along the Saluda River.

Seafood substitutions obscure patterns of mercury contamination in Patagonian toothfish (Dissostichus eleginoides) or "Chilean sea bass".

Seafood mislabeling distorts the true abundance of fish in the sea, defrauds consumers, and can also cause unwanted exposure to harmful pollutants. By combining genetic data with analyses of total mercury content, we have investigated how species substitutions and fishery-stock substitutions obscure mercury contamination in Patagonian toothfish (Dissostichus eleginoides), also known as "Chilean sea bass". Patagonian toothfish show wide variation in mercury concentrations such that consumers may be exposed to either acceptable or unacceptable levels of mercury depending on the geographic origins of the fish and the allowable limits of different countries.

The induction of biochemical changes in Daphnia magna by CuO and ZnO nanoparticles.

Whilst a considerable number of studies have been reported on the acute toxicity of nanoparticles (NPs) on invertebrates such as Daphnia magna, few studies have been reported on the biochemical change (biomarkers) induction on these species by NPs, especially metal oxide NPs. The aim of this study was to investigate some biomarkers in D. magna induced by copper oxide (CuO) and zinc oxide (ZnO) NPs under controlled laboratory conditions.

Assessment of heavy metal and PAH exposure in largemouth bass (Micropterus salmoides) in the Reedy River watershed, South Carolina, USA: a multi-season assessment of metallothionein and bile fluorescence.

Biomarkers can be used as tools to help determine ecological exposure in watershed assessments. In the present study, metallothionein and fixed wavelength bile fluorescence for two-, four-, and five-ring hydrocarbons were used as biomarkers of exposure in largemouth bass (Micropterus salmoides) in the Reedy River watershed located in South Carolina, USA. Fish were sampled from three impoundments and a reference site over three seasons in the same year.

Xenoestrogen exposure and effects in bluegill from the Reedy River, South Carolina, USA.

Water quality in the Reedy River basin of Greenville, South Carolina, has been impacted by diverse and highly urbanized land uses. It has been demonstrated that urban runoff and point sources, such as effluent from wastewater treatment facilities, introduce organic pollutants and potentially endocrine disrupting compounds (EDCs) into the watershed. The objective of this study was to investigate the potential toxicological effects of EDCs that may be present in the Reedy River watershed using a set of biomarkers measured in indigenous fish to characterize the exposure and biological effects of these contaminants.

Activity patterns of biotransformation enzymes in juvenile chickens after in ovo dosage of PCB126.

Little is known about the correlations between biotransformation enzymes in juvenile birds after exposure to environmental toxicants like PCBs. In this study eggs of domestic chicken (Gallus domesticus) were dosed with PCB126 in concentrations of 0.175-0.

A biomarker approach to measure biological effects of contaminant exposure in largemouth bass from Lake Conestee, South Carolina, U.S.A.

Sediments from Lake Conestee, a former reservoir now filled with pollutant-enriched sediments, located south of Greenville, South Carolina, USA, and other nearby reservoirs were collected and analyzed for lead and polycyclic aromatic hydrocarbons (PAHs). Hepatic ethoxyresorufin-O-deethylase (EROD), glutathione S-transferase (GST), UDP-glucuronosyltransferase (UGT), sulfotransferase (SULT), and erythrocyte delta-aminolevulinic acid dehydratase (ALAD) were measured in largemouth bass (Micropterus salmoides) to characterize biological effects of these contaminants over three seasons. Results showed that total PAH concentrations in Lake Conestee sediments were significantly greater than the control during each season.

Heme oxygenase induction and biliverdin excretion: implications for the bile fluorescence biomarker.

The measurement of bile fluorescence has become a popular biomarker to demonstrate the exposure of fish to polycyclic aromatic hydrocarbons. Conflicting data have been published on how to normalize bile fluorescence. To investigate if normalization to biliverdin is a suitable method, experiments were performed to study the mechanisms related to biliverdin excretion in fish.

Bile fluorescence, heme oxygenase induction, and increased biliverdin excretion by mixtures of environmental toxicants.

The measurement of bile fluorescence has become a popular biomarker to demonstrate the exposure of fish to polycyclic aromatic hydrocarbons. Conflicting data has been published on how to normalize bile fluorescence. To investigate if normalization to biliverdin is a suitable method, experiments were performed to study the mechanisms related to biliverdin excretion in fish.

Degradation and effects of the potential mosquito larvicides methazolamide and acetazolamide in sheepshead minnow (Cyprinodon variegatus).

To test for environmental persistence in order to determine the potential of carbonic anhydrase inhibitors as larvicides, the decomposition and degradation of samples containing methazolamide (MTZ) and acetazolamide (ACZ) in aqueous solution were monitored under different conditions. Additionally, nontarget species impact was assessed in an acute toxicity test using sheepshead minnow (Cyprinodon variegatus). The fish were exposed for 120 h to 10(-3) and 10(-4) M each compound in replicate seawater tanks.