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The relationship between agriculture and wildlife can be both synergetic and challenging, as the increased surface of agricultural land makes it increasingly important for agriculture and wildlife to coexist. This study aims to describe the use of freshly drilled dry bean fields by birds and mammals in Brazilian Cerrado and Atlantic Forest sites and their diversity and abundance within in-crop and off-crop areas (with native permanent vegetation and other surrounding crop fields) at four different farms. A comprehensive survey was conducted, using various sampling methods, including point counts, foraging counts, trail cameras, and occasional encounters. In all, contacts for 12 518 birds across 306 species and 313 mammals across 34 species were registered. The off-crop areas exhibited greater species richness, abundance, and diversity than the in-crop areas on all farms. For birds, 47 species were recorded in-crop, of which 15 were classified as insectivores, 15 as granivores, seven as omnivores, seven as carnivores, and three as frugivores. The number of in-crop observations per species was small. The abundance off-crop was greater for 31 species observed in-crop, indicating that dry bean fields are probably not a preferred habitat for those species. Species classified as granivorous are most likely to feed on dry bean seeds. However, almost all granivorous species observed in-crop areas are too small to be able to feed on dry bean seeds. For mammals, nine species were recorded in-crop, of which four were classified as carnivores, three as omnivores, one as insectivore, and one as granivore. Additionally, despite the considerable effort in this study, no evidence was found that birds and mammals feed on dry bean seeds. The results highlight the importance of off-crop areas in dry bean fields, characterized by a more diverse and abundant bird community than in-crop. Integr Environ Assess Manag 2024;20:864-874. © 2023 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

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Urbanization, agriculture, and other human activities can exert considerable influence on the health and integrity of stream ecosystems. These influences vary greatly over space, time, and scale. We investigated trends in stream biotic integrity over 19 years (1997-2016) in relation to natural and anthropogenic factors in their spatial context using data from a stream biomonitoring program in a region dominated by agricultural land use. Macroinvertebrate and fish diversity and abundance data were used to calculate four multimetric indices (MMIs) that described biotic integrity of streams from 1997 to 2016. Boosted regression trees (BRT), a machine learning technique, were used to model how stream integrity responded to catchment-level natural and anthropogenic drivers including land use, human population density, road density, runoff potential, and natural factors such as latitude and elevation. Neither natural nor anthropogenic factors were consistently more influential on the MMIs. Macroinvertebrate indices were most responsive to time, latitude, elevation, and road density. Fish indices were driven mostly by latitude and longitude, with agricultural land cover among the most influential anthropogenic factors. We concluded that 1) stream biotic integrity was mostly stable in the study region from 1997 to 2016, although macroinvertebrate MMIs had decreased approximately 10% since 2010; 2) stream biotic integrity was driven by a mix of factors including geography, human activity, and variability over yearly time intervals; 3) MMI responses to environmental drivers were nonlinear and often nonmonotonic; 4) MMI composition could influence causal inferences; and 5) although our findings were mostly consistent with the literature on drivers of stream integrity, some commonly seen patterns were not evident. Our findings highlight the utility of large-scale, publicly available spatial data for understanding drivers of stream biodiversity and illustrate some potential pitfalls of large scale, integrative analyses.

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Cyanobacteria are widely distributed in fresh, brackish, and ocean water environments, as well as in soil and on moist surfaces. Changes in the population of cyanobacteria can be an important indicator of alterations in water quality. Metabolites produced by blooms of cyanobacteria can be harmful, so cell counts are frequently monitored to assess the potential risk from cyanobacterial toxins. A frequent uncertainty in these types of assessments is the lack of strong relationships between cell count numbers and algal toxin concentrations. In an effort to use ion concentrations and other water quality parameters to determine the existence of any relationships with cyanobacterial toxin concentrations, we monitored four cyanobacterial toxins and inorganic ions in monthly water samples from a large reservoir over a 2-year period. Toxin concentrations during the study period never exceeded safety limits. In addition, toxin concentrations at levels above the limit of quantitation were infrequent during the 2-year sampling period; non-detects were common. Microcystin-LA was the least frequently detected analyte (86 of 89 samples were ND), followed by the other microcystins (microcystin-RR, microcystin-LR). Cylindrospermopsin and saxitoxin were the most frequently detected analytes. Microcystin and anatoxin concentrations were inversely correlated with Cl-, SO 4 - 2 , Na+, and NH 4 + , and directly correlated with turbidity and total P. Cylindrospermopsin and saxitoxin concentrations in water samples were inversely correlated with Mg+2 and directly correlated with water temperature. Results of our study are expected to increase the understanding of potential relationships between human activities and water quality.

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Declining bird populations across the United States have been noted in a number of studies. Although multiple explanations have been proposed as causes of these declines, agricultural intensification has often been suggested as a significant driver of bird population dynamics. Using spatially explicit USDA-NASS Cropland Data Layer, we examined this relationship by comparing bird count data from the Breeding Bird Survey collected between 1995 and 2016 across 13 states in the central United States to corresponding categorical changes in land cover within a 2-km radius of each survey transect. This approach allowed us to compare the slopes of counts for 31 species of birds between grassland- and cropland-dominated landscapes and against increasing levels of cropland (all types combined) and pooled corn and soybean land cover types. Nearly all birds demonstrated significant responses to land cover changes. In all cases, the number of species exhibiting positive or negative responses was comparable, and median differences in percent change per year ranged from -0.5 to 0.7%. Species that responded either positively or negatively did not appear to fall into any particular foraging guild. If changes in agricultural practices are a major cause of declines, we would expect to see it across the spatial scale studied and across the majority of species. While these results do not rule out potential agricultural effects, such as toxicity resulting from pesticide exposure, which may have species-specific or localized effects, a variety of factors related to habitat are likely the most significant contributor overall. Given these results over a large spatial scale basis (multistate) and across numerous bird species, there is not a broad general trend of greater decline in crop-intensive areas. Integr Environ Assess Manag 2018;14:692-702. © 2018 SETAC.

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Understanding dermal exposure is important for higher-tier avian ecological risk assessments. However, dermal exposure and toxicity are often unknown for avifauna. The US EPA's Terrestrial Investigation Model (TIM) uses a method to estimate avian dermal LD50 values (and ultimately dermal exposure) that frequently results in unusually high dermal exposure and low dermal LD50 estimates. This is primarily a result of using organophosphate and carbamate toxicity data to develop the oral-dermal relationship. An estimated dermal LD50 is necessary to generate a dermal route equivalency factor that normalizes potency relative to oral toxicity within the dermal pathway dose equation. In this study, atrazine dermal absorption experiments were conducted with mallard, northern bobwhite, and rat skin. These data were used to derive an avian-mammal dermal route equivalency factor for atrazine and introduce a new approach for estimating dermal LD50 values and ultimately predicting exposure via the TIM dermal pathway. Compared to the default TIM method, this new approach yielded TIM output with lower mean total dose, lower dermal fraction of total dose, greater oral fraction of total dose, and reduced model predicted mortality for atrazine. In addition, the new approach was compared with other methods for estimating avian dermal LD50 values such as those proposed for use with mammalian data and physico-chemical properties and a triazine-specific oral-dermal equation using mammalian LD50 data. The three alternative approaches resulted in output similar to one another and different from the default TIM methods. These results indicate that a dermal route equivalency factor derived from empirical data provides a higher avian dermal LD50 estimate that is consistent with other methods. In addition, the use of this dermal route equivalency factor results in greatly reduced modeled atrazine risk to birds than previously reported in US EPA risk assessments using TIM.

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The increase in use of nanomaterials such as multiwalled carbon nanotubes (MWCNTs) presents a need to study their interactions with the environment. Trophic transfer was measured between Daphnia magna and Pimephales promelas (fathead minnow, FHM) exposed to MWCNTs with different outer diameter (OD) sizes (MWCNT1 = 8-15 nm OD and MWCNT2 = 20-30 nm OD) in the presence and absence of copper. Pristine FHM were fed D. magna, previously exposed for 3 d to MWCNT1 or MWCNT2 (0.1 mg/L) and copper (0.01 mg/L), for 7 d. D. magna bioaccumulated less MWCNT1 (0.02 µg/g) than MWCNT2 (0.06 µg/g), whereas FHM accumulated more MWCNT1 (0.81 µg/g) than MWCNT2 (0.04 µg/g). In the presence of copper, MWCNT bioaccumulation showed an opposite trend. Mostly MWCNT1 (0.03 µg/g) bioaccumulated in D. magna, however less MWCNT1 (0.21 µg/g) than MWCNT2 (0.32 µg/g) bioaccumulated in FHM. Bioaccumulation factors were higher for MWCNT1s than MWCNT2. However, an opposite trend was observed when copper was added. Plasma metallothionein-2 was measured among treatments; however concentrations were not statistically different from the control. This study demonstrates that trophic transfer of MWCNTs is possible in the aquatic environment and further exploration with mixtures can strengthen the understanding of MWCNT environmental behavior.

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Thiamethoxam is a neonicotinoid insecticide used widely in agriculture to control a broad spectrum of chewing and sucking insect pests. Recent detection of thiamethoxam in surface waters has raised interest in characterizing the potential impacts of this insecticide to aquatic organisms. We report the results of toxicity testing (acute and chronic) conducted under good laboratory practices for more than 30 freshwater species (insects, molluscs, crustaceans, algae, macrophytes, and fish) and 4 marine species (an alga, a mollusc, a crustacean, and a fish). As would be anticipated for a neonicotinoid, aquatic primary producers and fish were the least sensitive organisms tested, with acute median lethal and effect concentrations (LC50/EC50) observed to be ≥80 mg/L in all cases, which far exceeds surface water exposure concentrations. Tested molluscs, worms, and rotifers were similarly insensitive (EC50 ≥ 100 mg/L), except for Lumbriculus sp., with an EC50 of 7.7 mg/L. In general, insects were the most sensitive group in the study, with most acute EC50 values < 1 mg/L. However, the crustaceans Asellus aquaticus and Ostracoda exhibited a sensitivity similar to that of insects (acute EC50 < 1 mg/L), and the midge larvae Chaoborus sp. were relatively insensitive compared with other insects (EC50 > 5.5 mg/L). The most sensitive chronic response was for Chironomus riparius, with a 30-d no-observed-effect concentration (NOEC; emergence) of 0.01 mg/L. Observed toxicity to the tested marine organisms was comparable to that of freshwater species. We used the reported data to construct species sensitivity distributions for thiamethoxam, to calculate 5% hazard concentrations (HC5s) for acute data (freshwater invertebrates), and compared these with measured concentrations from relevant North American surface waters. Overall, based on acute toxicity endpoints, the potential acute risk to freshwater organisms was found to be minimal (likelihood of exceeding HC5s < 1%). Environ Toxicol Chem 2017;36:2838-2848. © 2017 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.

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The use of carbon-based nanomaterials (CNMs) such as multiwalled carbon nanotubes (MWCNTs), graphene, and graphene oxide (GO) is increasing across many applications because of their unique and versatile properties. These CNMs may enter the aquatic environment through many pathways, creating the potential for organism exposure. The present study addresses the bioaccumulation and toxicity seen in Daphnia magna exposed to CNMs dispersed in sodium dodecyl benzene sulfonate (SDBS). In study I, D. magna were exposed to varying outer diameters of MWCNTs for 24 h in moderately hard or hard freshwater. Bioaccumulation of MWCNT was found in all treatments, with the highest concentrations (0.53 ± 0.27 µg/g) in D. magna exposed in hard freshwater (p < 0.005). The median lethal concentration (LC50) was determined for D. magna exposed to CNMs in moderately hard and hard freshwater. In study II, D. magna were exposed to CNMs for 72 h in moderately hard freshwater to assess swimming velocity and generation of reactive oxygen species (ROS) detected by dichlorofluorescein fluorescence. An overall decrease was seen in D. magna swimming velocity after exposure to CNMs. The generation of ROS was significantly higher (1.54 ± 0.38 dichlorofluorescein mM/mg dry wt) in D. magna exposed to MWCNTs of smaller outer diameters than in controls after 72 h (p < 0.05). These results suggest that further investigation of CNM toxicity and behavior in the aquatic environment is needed. Environ Toxicol Chem 2017;36:2199-2204. © 2017 SETAC.

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Perfluoroalkyl substances (PFAS) have recently received increased research attention, particularly concerning aquatic organisms and in regions of exposure to aqueous film forming foams (AFFFs). Air Force bases historically applied AFFFs in the interest of fire training exercises and have since expressed concern for PFAS contamination in biota from water bodies surrounding former fire training areas. Six PFAS were monitored, including perfluorooctane sulfonate (PFOS), in aquatic species from 8 bayou locations at Barksdale Air Force Base in Bossier City, Louisiana (USA) over the course of 1 yr. The focus was to evaluate temporal and spatial variability in PFAS concentrations from historic use of AFFF. The PFOS concentrations in fish peaked in early summer, and also increased significantly downstream of former fire training areas. Benthic organisms had lower PFOS concentrations than pelagic species, contrary to previous literature observations. Bioconcentration factors varied with time but were reduced compared with previously reported literature values. The highest concentration of PFOS in whole fish was 9349 ng/g dry weight, with 15% of samples exceeding what is believed to be the maximum whole fish concentration reported to date of 1500 ng/g wet weight. Further studies are ongoing, to measure PFAS in larger fish and tissue-specific partitioning data to compare with the current whole fish values. The high concentrations presently observed could have effects on higher trophic level organisms in this system or pose a potential risk to humans consuming contaminated fish. Environ Toxicol Chem 2017;36:2022-2029. © 2016 SETAC.

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Fungicides in aquatic environments can impact non-target bacterial and fungal communities and the invertebrate detritivores responsible for the decomposition of allochthonous organic matter. Additionally, in some aquatic systems daily water temperature fluctuations may influence these processes and alter contaminant toxicity, but such temperature fluctuations are rarely examined in conjunction with contaminants. In this study, the shredding amphipod Hyalella azteca was exposed to the fungicide pyraclostrobin in three experiments. Endpoints included mortality, organism growth, and leaf processing. One experiment was conducted at a constant temperature (23 °C), a fluctuating temperature regime (18-25 °C) based on field-collected data from the S. Llano River, Texas, or an adjusted fluctuating temperature regime (20-26 °C) based on possible climate change predictions. Pyraclostrobin significantly reduced leaf shredding and increased H. azteca mortality at concentrations of 40 µg/L or greater at a constant 23 °C and decreased leaf shredding at concentrations of 15 µg/L or greater in the fluctuating temperatures. There was a significant interaction between temperature treatment and pyraclostrobin concentration on H. azteca mortality, body length, and dry mass under direct aqueous exposure conditions. In an indirect exposure scenario in which only leaf material was exposed to pyraclostrobin, H. azteca did not preferentially feed on or avoid treated leaf disks compared to controls. This study describes the influence of realistic temperature variation on fungicide toxicity to shredding invertebrates, which is important for understanding how future alterations in daily temperature regimes due to climate change may influence the assessment of ecological risk of contaminants in aquatic ecosystems.

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A combination of multiple stressors may be linked to global amphibian declines. Of these, pesticides and UVB radiation co-exposures were examined on the African clawed frog (Xenopus laevis) to provide information that may be useful for amphibian conservation. The independent action model and inferential statistics were used to examine interactions between pesticides (malathion, endosulfan, α-cypermethrin, or chlorothalonil) and environmentally relevant UVB exposures. UVB radiation alone caused 35-68% mortality and nearly 100% of malformations. Pesticides and UVB had additive effects on larval mortality; however, several non-additive effects (antagonistic and synergistic interactions) were observed for total body length. Insecticides mainly affected axial development, whereas UVB radiation caused high incidence of edema, gut malformations, and abnormal tail tips. These results suggest that sublethal developmental endpoints were more sensitive for detecting joint effects. This work has implications for amphibian risk assessments for ecosystems where pesticides and high UVB radiation may co-occur.

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Metal oxide nanoparticles, such as copper oxide (CuO), are mass produced for use in a variety of products like coatings and ceramics. Acute exposure to CuO nanoparticles has caused toxicity to many aquatic organisms, yet there is no information on the effect of prolonged CuO nanomaterial exposures. This study examined effects of chronic exposure to CuO nanoparticles on Xenopus laevis growth and development. Experiments included a 14 d subchronic exposure and a 47 d chronic exposure throughout metamorphosis. The subchronic exposure caused mortality in all tested CuO concentrations, and significant growth effects occurred after exposure to 2.5 mg L(-1) CuO. Chronic exposure to 0.3 mg L(-1) CuO elicited significant mortality and affected the rate of metamorphosis. Exposure to lower concentrations of CuO stimulated metamorphosis and growth, indicating that low dose exposure can have hormetic effects.

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Reptiles have been understudied in ecotoxicology, which limits consideration in ecological risk assessments. The goals of the present study were 3-fold: to improve oral and dermal dosing methodologies for reptiles, to generate reptile toxicity data for pesticides, and to correlate reptile and avian toxicity. The authors first assessed the toxicity of different dosing vehicles: 100 µL of water, propylene glycol, and acetone were not toxic. The authors then assessed the oral and dermal toxicity of 4 pesticides following the up-and-down procedure. Neither brodifacoum nor chlorothalonil caused mortality at doses ≤ 1750 µg/g. Under the "neat pesticide" oral exposure, endosulfan (median lethal dose [LD50] = 9.8 µg/g) was more toxic than λ-cyhalothrin (LD50 = 916.5 µg/g). Neither chemical was toxic via dermal exposure. An acetone dosing vehicle increased λ-cyhalothrin toxicity (oral LD50 = 9.8 µg/g; dermal LD50 = 17.5 µg/g), but not endosulfan. Finally, changes in dosing method and husbandry significantly increased dermal λ-cyhalothrin LD50s, which highlights the importance of standardized methods. The authors combined data from the present study with other reptile LD50s to correlate with available avian data. When only definitive LD50s were used in the analysis, a strong correlation was found between avian and reptile toxicity. The results suggest it is possible to build predictive relationships between avian and reptile LD50s. More research is needed, however, to understand trends associated with chemical classes and modes of action.

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Pesticide use and ultraviolet-B (UVB) radiation have both been suggested to adversely affect amphibians; however, little is known about their interactive effects. One potential adverse interaction could involve pesticide-induced dysregulation of DNA repair pathways, resulting in greater numbers of DNA photo-adducts from UVB exposure. In the present study, we investigated the interactive effects of UVB radiation and two common pesticides (endosulfan and α-cypermethrin) on induction of DNA photo-adducts and expression of DNA damage and repair related genes in African clawed frog (Xenopus laevis) embryos. We examined 13 genes that are, collectively, involved in stress defense, cell cycle arrest, nucleotide excision repair (NER), base excision repair, mismatch repair, DNA repair regulation, and apoptosis. We exposed X. laevis embryos to 0, 25, and 50 µg/L endosulfan or 0, 2.5, and 5.0 µg/L α-cypermethrin for 96 h, with environmentally relevant exposures of UVB radiation during the last 7 h of the 96 h exposure. We measured the amount of cyclobutane pyrimidine dimers (CPDs) and mRNA abundance of the 13 genes among treatments including control, pesticide only, UVB only, and UVB and pesticide co-exposures. Each of the co-exposure scenarios resulted in elevated CPD levels compared to UVB exposure alone, suggesting an inhibitory effect of endosulfan and α-cypermethrin on CPD repair. This is attributed to results indicating that α-cypermethrin and endosulfan reduced mRNA abundance of XPA and HR23B, respectively, to levels that may affect the initial recognition of DNA lesions. In contrast, both pesticides increased transcript abundance of CSA and MUTL. In addition, mRNA abundance of HSP70 and GADD45α were increased by endosulfan and mRNA abundance of XPG was increased by α-cypermethrin. XPC, HR23B, XPG, and GADD45α exhibited elevated mRNA concentrations whereas there was a reduction in MUTL transcript concentrations in UVB-alone treatments. It appeared that even though expression of XPC and CSA were induced by exposure to UVB or pesticides, XPA was the limiting factor in the NER pathway. Our results suggest that pesticides may increase the accumulation of UVB-induced DNA photo-adducts and one likely mechanism is the alteration of critical NER gene expression. The present study provides important implications for evaluating the combined risks of pesticide usage and potentially increasing UVB radiation in aquatic ecosystems.

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Effects of contaminants on behavior may have important consequences on wildlife populations because behaviors such as predation, predator avoidance, reproduction, and social interaction can affect population dynamics. As a common environmental stressor, ultraviolet-B (UVB) radiation causes various deleterious effects and some aquatic organisms actively avoid UVB radiation in water. However, the extent to which environmental contaminants can impair UVB avoidance has not been evaluated, which may cause greater UVB exposure and toxicity. In the present study, we used Xenopus laevis tadpoles to determine if acute exposure to sublethal concentrations of agricultural chemicals can alter tadpole response to UVB radiation. We exposed tadpoles to four pesticides (malathion, endosulfan, α-cypermethrin, and chlorothalonil) for 96 h. At the end of the exposure, tadpoles were transferred to tanks divided into UVB and no-UVB areas. We observed tadpoles for 30 min and recorded time spent in the UVB area. We compared the proportion of time tadpoles spent in the UVB area among different concentrations for each pesticide. There was no significant difference between FETAX control and solvent control tadpoles. When combined, control tadpoles spent less than half of the time in the UVB area indicating that X. laevis tadpoles exhibit UVB avoidance behavior. Tadpoles exposed to 5 µg/L endosulfan spent significantly more time under UVB than control tadpoles. Other pesticides had no effect on tadpole UVB avoidance behavior. Our results suggest that some neurotoxic pesticides can affect UVB avoidance in larval amphibians, which may increase their exposure and subsequently the risk of UVB-induced damage. The present study highlights the importance of examining the interaction between two stressors that co-occur across broad spatial scales and to consider behavioral alteration when evaluating the risk of pesticides to amphibians.

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Fullerene (C(60)), with its unique physical properties and nanometer size, has been mass-produced for many applications in recent decades. The increased likelihood of direct release into the environment has raised interest in understanding both the environmental fate and corresponding biological effects of fullerenes to living organisms. Because few studies have emphasized fullerene uptake and resulting biochemical responses by living organisms, a toxicity screening test and a 28-d bioaccumulation test for Lumbriculus variegatus were performed. No mortality was observed in the range of 0.05 mg C(60) /kg dry sediment to 11.33 mg C(60) /kg dry sediment. A biota-sediment accumulation factor of micron-sized fullerene agglomerates (µ-C(60)) was 0.032 ± 0.008 at day 28, which is relatively low compared with pyrene (1.62 ± 0.22). Catalase (CAT) activity, an oxidative stress indicator, was elevated significantly on day 14 for L. variegatus exposed to µ-C(60) (p = 0.034). This peak CAT activity corresponded to the highest body residues observed in the present study, 199 ± 80 µg C(60) /kg dry weight sediment. Additionally, smaller C(60) agglomerate size increased bioaccumulation potential in L. variegatus. The relationship between C(60) body residue and the increased CAT activity followed a linear regression. All results suggest that C(60) has a lower bioaccumulation potential than pyrene but a higher potential to induce oxidative stress in L. variegatus.

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Hydrophobic organic contaminants readily partition from aqueous to organic phases in aquatic systems with past research largely focusing on sediment. However, within many aquatic systems, matrices such as leaf material and detritus are abundant and ecologically important, as they may represent a primary exposure route for aquatic invertebrates. The objectives of the present study were to examine partitioning and toxicity to Hyalella azteca among permethrin and p,p'-DDT contaminated sediment, leaf, and a sediment-leaf mixture. Log organic carbon-water partitioning coefficients ranged from 4.21 to 5.82 for both insecticides, and were greatest within sediment and lowest in coarse leaf material. H. azteca lethal concentrations for 50% of the population (LC50s) ranged from 0.5 to 111µgg(-1) organic carbon, and were dependent on the matrix composition. The variation in sorption and toxicity among matrices common within stream ecosystems suggests that the ecological niche of aquatic organisms may be important for estimating risk of hydrophobic pesticides.

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The toxicity of several agricultural chemicals to aquatic invertebrates has been shown to be temperature-dependent, but the role of daily temperature variation has rarely been examined. The authors simulated a natural daily temperature pattern (a fluctuating cycle of 21 °C to 31 °C over a 24-h period) based on field-collected data from Southern High Plains wetlands (TX, USA) and conducted a series of experiments comparing responses from this exposure scenario to a constant exposure at 24 ± 1 °C. Results indicate alterations in pesticide toxicity under the fluctuating temperature regime compared with that of the constant temperature exposure. There was a significant interaction of temperature regime and bifenthrin on Chironomus dilutus survival, and C. dilutus ash-free dry mass was lower in the fluctuating temperature treatment. The 10-d median lethal concentration (LC50) for Hyalella azteca exposed to chlorothalonil was lower under the fluctuating temperature regime compared with the constant temperature regime. For Daphnia magna exposed to malathion, the main effects of temperature regime and malathion were observed on cholinesterase activity. The present study demonstrates how environmentally relevant daily temperature variation influences contaminant effects on aquatic invertebrates.

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Chlorothalonil is a broad spectrum fungicide widely used in agricultural and urban environments, yet little is known regarding its effects on amphibians. We examined effects of chlorothalonil on growth, malformations, and mortality in embryos and larvae of Xenopus laevis and Spea multiplicata, and assessed variation in sensitivity among aquatic organisms using a species sensitivity distribution (SSD). Chlorothalonil induced gut malformations in X. laevis embryos and inhibited growth. Tail degeneration was observed in larvae of both species and reduced tail length to total length ratios occurred at environmentally relevant concentrations (5.9 and 11.0 µg/L). The mechanism of tail degeneration is unclear, but alteration in the expression of genes involved in tail resorption is a hypothesized mechanism. Larval amphibians were more sensitive than invertebrates and fish. Based on our results and the range of reported environmental concentrations, chlorothalonil may pose a risk to larval amphibians in certain habitats and scenarios.

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To avoid overestimating the risk of polycyclic aromatic hydrocarbons (PAHs), research is needed to evaluate the bioavailable portion of PAHs in the environment. However, limited PSDs were developed for a terrestrial soil system. In this study, two sorbents, octadecyl (C18) and multi-walled carbon nanotubes (MWNTs), were individually evaluated as sorbents in passive sampling devices (PSDs) as biomimetic samplers to assess the uptake of PAHs from soil. C18-PSDs were an excellent biomimetic tool for PAHs with a low molecular weight in complex exposure conditions with different soil types, types of PAHs, aging periods, and initial PAH concentrations in soil. The utility of MWNT-PSDs was limited by extraction efficiencies of PAHs from MWNTs. However, when compared to C18-PSDs, they had higher adsorption capacities and were less expensive. This study provides data regarding useful techniques that can be used in risk assessment to assess the bioavailability of PAHs in soil.

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