Contaminant exposure effects in a changing climate: how multiple stressors can multiply exposure effects in the amphipod Hyalella azteca

Free Versus Bound Concentration: Passive Dosing from Polymer Meshes Elucidates Drivers of Toxicity in Aquatic Tests with Benthic Invertebrates

Aquatic toxicity tests with benthic organisms are used to predict the toxicity of hydrophobic organic chemicals (HOCs) in sediments, assuming that the freely dissolved concentration (Cfree) is a good surrogate of bioavailability in the exposure system. However, Cfree of HOCs is difficult to control in water-only setups. Moreover, the role of dissolved organic carbon (DOC) in the occurrence of toxicity needs clarification because DOC concentrations in sediment porewater can be substantially higher than in typical test water. We introduced biocompatible polyethylene meshes with high sorptive capacities and fast release kinetics as a novel passive dosing phase, which maintained Cfree and Cwater (i.e., free + DOC-bound) in Hyalella azteca water-only tests. Adding the supernatant fraction of peat to test water as a DOC source increased Cwater to an extent comparable to sediment porewater and significantly increased and decreased the observed toxicity of permethrin and benzo[a]pyrene, respectively, to H. azteca. This result indicates that DOC can both benefit and harm test species likely due to the increased health after ingestion of DOC and to the uptake of DOC-bound HOCs, respectively. Passive dosing in combination with the addition of sediment DOC surrogates may better reflect exposure and habitat conditions in sediment porewater than conventional aquatic tests. Environ Toxicol Chem 2024;43:1747-1756. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Effects of temperature and salinity on bioconcentration and toxicokinetics of permethrin in pyrethroid-resistant Hyalella azteca

Recent studies demonstrated pyrethroid resistance associated with voltage-gated sodium channel mutations in populations of the epibenthic amphipod, Hyalella azteca. Resistant populations were able to tolerate and bioconcentrate pyrethroids at concentrations significantly higher than toxic levels for non-resistant populations. In conjunction with elevated bioconcentration potential, environmental alteration particularly as a result of global climate change is anticipated to significantly alter abiotic parameters including temperature and salinity. These changes are expected to influence uptake and biotransformation of contaminants. Thus, the aims of the current study were a) to examine the bioconcentration potential of permethrin in two pyrethroid-resistant clades of H. azteca and b) assess the influence of temperature and salinity changes on toxicokinetic parameters. Two pyrethroid-resistant clades of H. azteca were exposed to ¹⁴C-permethrin at three salinities (0.2, 1.0 and 6.0 practical salinity units (PSU)) and temperatures (18, 23 and 28 °C). Tests were conducted for up to 36 h and uptake, elimination and biotransformation rates were calculated. Both populations demonstrated bioconcentration factors (BCFs) between five and seven times greater than published data for non-resistant H. azteca, with significant differences between clades. Calculated BCF values were comparable to field populations of resistant H. azteca, emphasizing the potential for elevated pyrethroid bioconcentration in the natural environment and increased exposure for predators consuming pyrethroid-resistant aquatic invertebrates. Alterations to temperature and salinity had no statistically significant effect on uptake or parent compound half-life in either population, though biotransformation was elevated at higher temperatures in both populations. Salinity had a variable effect between the two populations, with lower BCF values at 1.0 PSU in clade D H. azteca and greater BCFs at 6.0 PSU in clade C H. azteca. This is the first study to demonstrate the potential for future climate scenarios to influence toxicokinetics in pyrethroid-resistant aquatic organisms.

Occurrence, spatial distributions, and ecological risk of pyrethroids in coastal regions of South Yellow and East China Seas

Pyrethroids are increasingly receiving attention as aqueous micropollutants, but their presence has been reported only in a few small coastal areas. In this study, we investigated the distribution, sources, and risks of nine pyrethroids in large marine zones. The 40 seawater samples were collected from the South Yellow Sea (SYS) and East China Sea (ECS) in China, during the spring of 2020, using a high-volume, solid-phase extraction method. The total pyrethroid concentrations ranged from 0.72 to 1.82 ng L^-1 in the SYS and from 0.02 to 11.0 ng L^-1 in the ECS. We used cluster analysis to classify pollutant sources into five categories, and discussed the influence of sources on the transport and distribution of pyrethroids in each group. Ecological risk assessment indicated that pyrethroids pose a high risk to crustaceans and a negligible risk to others. These results are important for understanding the behavior of pyrethroids in marine environments.

EDCs trigger immune-neurotransmitter related gene expression, and cause histological damage in sensitive mud crab Macrophthalmus japonicus gills and hepatopancreas

Endocrine-disrupting chemicals (EDCs), distributed at various concentrations in freshwater and marine ecosystems, affect the survival, reproduction, and behavior of wide ranges organisms. Most toxicology studies on EDCs have focused on the endocrine system of invertebrates, and research on invertebrate neurotransmitters is limited. In the present study, we investigated the expression of Macrophthalmus japonicus genes encoding γ-aminobutyric acid transporter subtype 2 (GAT-2) and glutamine synthetase (GS), which play important roles as neurotransmitters at synapses. We observed differences in the mRNA expression levels of GAT-2 and GS as well as histological changes in various tissues after exposure to bisphenol-A (BPA) and di-(2-ethylhexyl) phthalate (DEHP). The amino acid sequences of M. japonicus GAT-2 and GS formed separate branches in crustaceans, fish, insects, and mammals. M. japonicus GAT-2 and GS expression levels were highest in the gills, hepatopancreas, and stomach, and showed different between DEHP or BPA treatments. In particular, hepatopancreas GS expression on Day 1, the first step in the presynaptic process, was upregulated after BPA and DEHP exposure, while GAT-2, sequential step in the presynaptic process, was significantly elevated only in DEHP. After BPA treatments, gill GS expression was increased at all concentrations, whereas GAT-2 expression was overall down regulations. In contrast, in DEHP treatment groups hepatopancreatic GS and GAT-2 expression at Day 1 was only significantly higher and all groups including gill GS and GAT-2 expression were downregulation. Histological changes in the gills and hepatopancreas were observed in a concentration-dependent manner. Accordingly, BPA and DEHP exposure in crabs could be stimulate neurotransmitter gene expression and alter the morphological structure of gill and hepatopancreas.

Interactions of Environmental Chemicals and Natural Products With ABC and SLC Transporters in the Digestive System of Aquatic Organisms

An organism’s diet is a major route of exposure to both beneficial nutrients and toxic environmental chemicals and natural products. The uptake of dietary xenobiotics in the intestine is prevented by transporters of the Solute Carrier (SLC) and ATP Binding Cassette (ABC) family. Several environmental chemicals and natural toxins have been identified to induce expression of these defense transporters in fish and aquatic invertebrates, indicating that they are substrates and can be eliminated. However, certain environmental chemicals, termed Transporter-Interfering Chemicals or TICs, have recently been shown to bind to and inhibit fish and mammalian P-glycoprotein (ABCB1), thereby sensitizing cells to toxic chemical accumulation. If and to what extent other xenobiotic defense or nutrient uptake transporters can also be inhibited by dietary TICs is still unknown. To date, most chemical-transporter interaction studies in aquatic organisms have focused on ABC-type transporters, while molecular interactions of xenobiotics with SLC-type transporters are poorly understood. In this perspective, we summarize current advances in the identification, localization, and functional analysis of protective MXR transporters and nutrient uptake systems in the digestive system of fish and aquatic invertebrates. We collate the existing literature data on chemically induced transporter gene expression and summarize the molecular interactions of xenobiotics with these transport systems. Our review emphasizes the need for standardized assays in a broader panel of commercially important fish and seafood species to better evaluate the effects of TIC and other xenobiotic interactions with physiological substrates and MXR transporters across the aquatic ecosystem and predict possible transfer to humans through consumption.

Romain SJ, Pedersen EI, Siddiqui S, Chappell PE, White JW, Armbrust KL, Brander SM. Salinity Alters Toxicity of Commonly Used Pesticides in a Model Euryhaline Fish Species (Menidia beryllina)

Changing salinity in estuaries due to sea level rise and altered rainfall patterns, as a result of climate change, has the potential to influence the interactions of aquatic pollutants as well as to alter their toxicity. From a chemical property point of view, ionic concentration can increase the octanol–water partition coefficient and thus decrease the water solubility of a compound. Biologically, organism physiology and enzyme metabolism are also altered at different salinities with implications for drug metabolism and toxic effects. This highlights the need to understand the influence of salinity on pesticide toxicity when assessing risk to estuarine and marine fishes, particularly considering that climate change is predicted to alter salinity regimes globally and many risk assessments and regulatory decisions are made using freshwater studies. Therefore, we exposed the Inland Silverside (Menidia beryllina) at an early life stage to seven commonly used pesticides at two salinities relevant to estuarine waters (5 PSU and 15 PSU). Triadimefon was the only compound to show a statistically significant increase in toxicity at the 15 PSU LC₅₀. However, all compounds showed a decrease in LC₅₀ values at the higher salinity, and all but one showed a decrease in the LC₁₀ value. Many organisms rely on estuaries as nurseries and increased toxicity at higher salinities may mean that organisms in critical life stages of development are at risk of experiencing adverse, toxic effects. The differences in toxicity demonstrated here have important implications for organisms living within estuarine and marine ecosystems in the Anthropocene as climate change alters estuarine salinity regimes globally.

Global variation in freshwater physico-chemistry and its influence on chemical toxicity in aquatic wildlife

Chemical pollution is one of the major threats to global freshwater biodiversity and will be exacerbated through changes in temperature and rainfall patterns, acid-base chemistry, and reduced freshwater availability due to climate change. In this review we show how physico-chemical features of natural fresh waters, including pH, temperature, oxygen, carbon dioxide, divalent cations, anions, carbonate alkalinity, salinity and dissolved organic matter, can affect the environmental risk to aquatic wildlife of pollutant chemicals. We evidence how these features of freshwater physico-chemistry directly and/or indirectly affect the solubility, speciation, bioavailability and uptake of chemicals [including via alterations in the trans-epithelial electric potential (TEP) across the gills or skin] as well as the internal physiology/biochemistry of the organisms, and hence ultimately toxicity. We also show how toxicity can vary with species and ontogeny. We use a new database of global freshwater chemistry (GLORICH) to demonstrate the huge variability (often >1000-fold) for these physico-chemical variables in natural fresh waters, and hence their importance to ecotoxicology. We emphasise that a better understanding of chemical toxicity and more accurate environmental risk assessment requires greater consideration of the natural water physico-chemistry in which the organisms we seek to protect live.

Trophic transfer, bioaccumulation and transcriptomic effects of permethrin in inland silversides, Menidia beryllina, under future climate scenarios

Global climate change (GCC) significantly affects aquatic ecosystems. Continual use of pyrethroid insecticides results in contamination of these ecosystems and concurrent GCC raises the potential for synergistic effects. Resistance to pyrethroids has been documented in Hyalella azteca, a common epibenthic amphipod and model organism. Resistant H. azteca can bioconcentrate elevated amounts of pyrethroids and represent a threat to consumers via trophic transfer. In the present study, a predator of H. azteca, the inland silverside (Menidia beryllina), was used to examine the impacts of GCC on pyrethroid bioaccumulation via trophic transfer from resistant prey organisms. M. beryllina were fed ¹⁴C-permethrin dosed pyrethroid-resistant H. azteca for 14 days at three salinities (6, 13 and 20 practical salinity units (PSU)) and two temperatures (18 and 23 °C). Fish were analyzed for total body residues, percent parent compound and percent metabolites. Gene expression in liver and brain tissue were evaluated to assess whether dietary bioaccumulation of permethrin would impact detoxification processes, metabolism, and general stress responses. M. beryllina bioaccumulated significant amounts of permethrin across all treatments, ranging from 39 to 557 ng g^-1 lipid. No statistically significant effect of temperature was found on total bioaccumulation. Salinity had a significant effect on total bioaccumulation, owing to greater bioaccumulation at 6 PSU compared to 13 and 20 PSU, which may be due to alterations to xenobiotic elimination. Permethrin bioaccumulation and the interaction with temperature and salinity elicited significant transcriptional responses in genes relating to detoxification, growth, development, and immune response. Given the increased prevalence of pesticide-resistant aquatic invertebrates, GCC-induced alterations to temperature and salinity, and the predicted increase in pesticide usage, these findings suggest trophic transfer may play an important role in pesticide bioaccumulation and effects in predatory fish.

Molecular mechanisms of local adaptation for salt-tolerance in a treefrog

Salinization is a global phenomenon affecting ecosystems and forcing freshwater organisms to deal with increasing levels of ionic stress. However, our understanding of mechanisms that permit salt tolerance in amphibians is limited. This study investigates mechanisms of salt tolerance in locally adapted, coastal populations of a treefrog, Hyla cinerea. Using a common garden experiment, we (i) determine the extent that environment (i.e., embryonic and larval saltwater exposure) or genotype (i.e., coastal vs. inland) affects developmental benchmarks and transcriptome expression, and (ii) identify genes that may underpin differences in saltwater tolerance. Differences in gene expression, survival, and plasma osmolality were most strongly associated with genotype. Population genetic analyses on expressed genes also delineated coastal and inland groups based on genetic similarity. Coastal populations differentially expressed osmoregulatory genes including ion transporters (atp1b1, atp6V1g2, slc26a), cellular adhesion components (cdh26, cldn1, gjb3, ocln), and cytoskeletal components (odc1-a, tgm3). Several of these genes are the same genes expressed by euryhaline fish after exposure to freshwater, which is a novel finding for North American amphibians and suggests that these genes may be associated with local salinity adaptation. Coastal populations also highly expressed glycerol-3-phosphate dehydrogenase 1 (gpd1), which indicates they use glycerol as a compatible osmolyte to reduce water loss - another mechanism of saltwater tolerance previously unknown in frogs. These data signify that Hyla cinerea inhabiting coastal, brackish wetlands have evolved a salt-tolerant ecotype, and highlights novel candidate pathways that can lead to salt tolerance in freshwater organisms facing habitat salinization.

The effect of salinity fluctuation in freshwater streams on the fecundity of post-diapause Chironomus dilutus

Much scientific research dedicated to understanding the effects of freshwater salinization caused by road de-icing salts has utilized static exposures, with many tests conducted at winter or spring temperatures. While relevant for lentic ecosystems, pulsed patterns of salinity occur in lotic environments, particularly in summer months where precipitation can decrease elevated salinity levels caused by retention of residual salts. The current study aimed to evaluate the effects of pulsed patterns of salinity on the emergence, sex ratio, and fecundity of Chironomus dilutus over two generations of laboratory exposure. Three road de-icing salt treatments, including a control, modeled after environmental monitoring data of two local streams, were used to determine the ecological effects of periodic declines in salinity on C. dilutus at summer temperatures. No significant effects were observed on emergence success or sex ratios within or across generations, but fecundity of C. dilutus in the high salt treatment was reduced regardless of generation (P < 2e-16), possibly due to increased osmoregulatory stress caused by increased salinities. The intermediate and decreasing salinities may account for the lack of negative effects on emergence success and sex ratios by protecting sensitive life stages. More research is needed on long-term effects of reduced fecundity on population viability. The current study suggests more research using a similar experimental design is needed to fully evaluate the influence of road de-icing salts in lotic environments, as static laboratory exposures may not accurately reflect environmental changes in salinity.

Salinity Changes the Dynamics of Pyrethroid Toxicity in Terms of Behavioral Effects on Newly Hatched Delta Smelt Larvae

Salinity can interact with organic compounds and modulate their toxicity. Studies have shown that the fraction of pyrethroid insecticides in the aqueous phase increases with increasing salinity, potentially increasing the risk of exposure for aquatic organisms at higher salinities. In the San Francisco Bay Delta (SFBD) estuary, pyrethroid concentrations increase during the rainy season, coinciding with the spawning season of Delta Smelt (Hypomesus transpacificus), an endangered, endemic fish. Furthermore, salinity intrusion in the SFBD is exacerbated by global climate change, which may change the dynamics of pyrethroid toxicity on aquatic animals. Therefore, examining the effect of salinity on the sublethal toxicity of pyrethroids is essential for risk assessments, especially during the early life stages of estuarine fishes. To address this, we investigated behavioral effects of permethrin and bifenthrin at three environmentally relevant concentrations across a salinity gradient (0.5, 2 and 6 PSU) on Delta Smelt yolk-sac larvae. Our results suggest that environmentally relevant concentrations of pyrethroids can perturb Delta Smelt larvae behavior even at the lowest concentrations (<1 ng/L) and that salinity can change the dynamic of pyrethroid toxicity in terms of behavioral effects, especially for bifenthrin, where salinity was positively correlated with anti-thigmotaxis at each concentration.

Fitness costs of pesticide resistance in Hyalella azteca under future climate change scenarios

Global climate change continues to cause alterations in environmental conditions which can be detrimental to aquatic ecosystem health. The development of pesticide resistance in organisms such as Hyalella azteca can lead to increased susceptibility to environmental change. This research provides a robust assessment of the effects of alterations in salinity on the fitness of H. azteca. Full-life cycle bioassays were conducted with non-resistant and pyrethroid-resistant H. azteca cultured under two salinity conditions representing a rise from freshwater control (0.2 psu) to increased salinity due to salt-water intrusion, reduced snowpack and evaporative enrichment (6.0 psu). Additionally, the upper thermal tolerance was defined for each population at each salinity. Pyrethroid-resistant H. azteca exhibited reduced thermal tolerance; however, they produced more offspring per female than non-resistant animals. Compared to the low salinity water, both non-resistant and pyrethroid-resistant H. azteca produced more offspring, grew larger (based on dry mass), and produced larger offspring in elevated salinity, although pyrethroid-resistant animals had lower survival and lipid levels. This study provides fundamental information about the fitness potential of H. azteca in a changing climate, suggesting advantages for non-resistant animals under future climate scenarios. In addition, this research further supports the need to consider the effects of global climate change when conducting risk assessment of contaminants of concern, as well as the contribution of contaminants when investigating climate change impacts on populations, as exposure may contribute to niche contraction.

Antrodia cinnamomea Extraction Waste Supplementation Promotes Thermal Stress Tolerance and Tissue Regeneration Ability of Zebrafish

Antrodia cinnamomea (AC) has been shown to have anti-inflammatory, anti-tumor, and immunomodulation activities. It is estimated that hundreds of metric tons of AC extraction waste (ACEW) are produced per year in Taiwan. This study aims to assess the feasibility of applying ACEW as feed supplement in the aquaculture industry. ACEW significantly inhibited the growth of microorganisms in the water tank, by around 39.4% reduction on the fifth day with feed supplemented of 10% ACEW. The feed conversion efficiency of zebrafish with 10% ACEW supplementation for 30 days was 1.22-fold compared to that of the control. ACEW dramatically improved the tolerances of zebrafish under the heat and cold stresses. When at water temperature extremes of 38 °C or 11 °C, compared to the 100% mortality rate in the control group, the 10% ACEW diet group still had 91.7% and 83.3% survival rates, respectively. In a caudal fin amputation test, the fin recovery of zebrafish was increased from 68.4% to 93% with 10% ACEW diet after 3-week regeneration. ACEW effectively down-regulated the gene expression of TNF-α, IL-1β, IL-6, and IL-10, and up-regulated the gene expression of IL-4/13A. Additionally, the supplement of ACEW in the feed can maintain and prevent the fish’s body weight from dropping too much under enteritis. Taken together, ACEW has beneficial potential in aquaculture.

Effects of combined stressors to cadmium and high temperature on antioxidant defense, apoptotic cell death, and DNA methylation in zebrafish (Danio rerio) embryos

Fish are frequently affected by environmental stressors, such as temperature changes and heavy metal exposure, in aquatic ecosystems. In this study, we evaluated the combined effects of cadmium (Cd) toxicity and temperature (rearing temperature of 26 °C and heat stress at 34 °C) on zebrafish (Danio rerio) embryos. The survival and heart rates of zebrafish embryos decreased at relatively high Cd concentrations of 0.07 and 0.1 mg L^-1. Abnormal morphology was induced by exposure to a combination of Cd toxicity and heat stress. The yolk sac edema size was not significantly different between the control- and Cd-treated groups. Cd exposure induced reactive oxygen species (ROS) production and cell death in the live zebrafish. High temperature (34 °C) triggered Cd-induced cell death and intracellular ROS production to a greater extent than the rearing temperature of 26 °C. Transcriptional levels of six genes-CAT, SOD, p53, BAX, Dnmt1, and Dnmt3b-were investigated. The mRNA expression of CAT and SOD, molecular indicators of oxidative stress, was increased significantly at 34 °C after Cd exposure. The mRNA expression of CAT was more sensitive to temperature than that of SOD in Cd-treated zebrafish. p53 and BAX, apoptosis-related genes, were upregulated upon combined exposure to high temperature and Cd. In addition, at 34 °C, the expression of Dnmt1 and Dnmt3b transcripts, markers of DNA methylation, was increased upon exposure of zebrafish to all concentrations of Cd. Overall, these results suggest that high temperature facilitates the potential role of Cd toxicity in the transcriptional regulation of genes involved in the antioxidant system, apoptosis, and DNA methylation.

Occurrence and Probable Sources of Urban-Use Insecticides in Marine Sediments off the Coast of Los Angeles

Insecticides such as pyrethroids and fipronil are used in large amounts in both agricultural and urban settings and have the potential to elicit toxicity to nontarget aquatic organisms. In California, like in many other regions of the world, urban centers are located along the coast, and it is documented that urban-use insecticides enter the marine environment, where little is known about their occurrence and consequences. In this study, we measured the spatial distribution of pyrethroids and fipronil (and its metabolites) on the Palos Verdes Shelf off the coast of Los Angeles. Total pyrethroid levels ranged from nd to 170 μg/kg (dry weight), and fipronil sulfide levels ranged from 1.8 to 5.6 μg/kg. Two pyrethroids were traced to wastewater effluent discharge, while two others and fipronil sulfide were traced to to surface runoff. Toxicity units (TUs) were estimated for benthic invertebrates, which ranged from no toxicity (nt) to 146 for total pyrethroids, and 0.09 to 1.6 and 4.2 to 75 for fipronil sulfide, depending on the indicator species. Therefore, near-shore deposition of urban-use insecticides due to wastewater discharge and surface runoff poses a significant risk to marine benthic invertebrates and highlights the importance of monitoring near-shore ocean environments and developing mitigation strategies to reduce seaward movement.

Toward Sustainable Environmental Quality: Priority Research Questions for North America

Anticipating, identifying, and prioritizing strategic needs represent essential activities by research organizations. Decided benefits emerge when these pursuits engage globally important environment and health goals, including the United Nations Sustainable Development Goals. To this end, horizon scanning efforts can facilitate identification of specific research needs to address grand challenges. We report and discuss 40 priority research questions following engagement of scientists and engineers in North America. These timely questions identify the importance of stimulating innovation and developing new methods, tools, and concepts in environmental chemistry and toxicology to improve assessment and management of chemical contaminants and other diverse environmental stressors. Grand challenges to achieving sustainable management of the environment are becoming increasingly complex and structured by global megatrends, which collectively challenge existing sustainable environmental quality efforts. Transdisciplinary, systems-based approaches will be required to define and avoid adverse biological effects across temporal and spatial gradients. Similarly, coordinated research activities among organizations within and among countries are necessary to address the priority research needs reported here. Acquiring answers to these 40 research questions will not be trivial, but doing so promises to advance sustainable environmental quality in the 21st century. Environ Toxicol Chem 2019;38:1606-1624. © 2019 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.