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The toxicity of petroleum can increase considerably after exposure to solar radiation, during which certain components in the mixture, including polycyclic aromatic hydrocarbons (PAHs), absorb light in ultraviolet and visible portions of the solar radiation spectrum. A phototoxic target lipid model (PTLM), previously developed to predict the phototoxicity of single PAHs, is validated for 4 species (Americamysis bahia, Rhepoxynius abronius, Daphnia magna, and Pimephales promelas) exposed to 12 compounds that are components of petroleum, including alkylated PAHs and dibenzothiophene. The PTLM is also used to predict the phototoxicity of binary and ternary mixtures of 3 PAHs, pyrene, anthracene, and fluoranthene, to A. bahia and Menidia beryllina. Finally, it is used to predict the toxicity of water accommodated fractions of neat and naturally weathered Macondo crude oil samples from the Deepwater Horizon oil spill sites. The Gulf of Mexico species, including A. bahia, M. beryllina, Cyprinodon variegatus, and Fundulus grandis were exposed to the oil samples under natural and simulated solar radiation. The results support the applicability of the PTLM for predicting the phototoxicity of petroleum. Environ Toxicol Chem 2018;37:2165-2174. © 2018 SETAC., (© 2018 SETAC.)

This study investigated the effects of gamma radiation on the early developmental stages in hermaphroditic fish embryos of Kryptolebias marmoratus. The authors measured reactive oxygen species (ROS) level and antioxidant enzyme activities with the endpoint hatching rate after gamma irradiation of different embryonic stages. Then, the transcriptional changes of antioxidant enzyme-coding genes were evaluated by quantitative real-time reverse transcription polymerase chain reaction in response to gamma radiation on embryonic stages. Gamma radiation inhibited hatching rate and caused developmental impairment in a dose-dependent manner. Embryos showed tolerances in a developmental stage-dependent manner, indicating that early embryonic stages were more sensitive to the negative effects of gamma radiation than were later stages. After 5 Gy rate of radiation, the ROS level increased significantly at embryonic stages 2, 3, and 4 with a significant induction of all antioxidant enzyme activities. The expressions of glutathione S-transferase isoforms, catalase, superoxide dismutase (Mn-SOD, Cu/Zn-SOD), glutathione reductase, and glutathione peroxidase mRNA were upregulated in a dose-and-developmental stage-dependent manner. This finding indicates that gamma radiation can induce oxidative stress and subsequently modulates the expression of antioxidant enzyme-coding genes as one of the defense mechanisms. Interestingly, embryonic stage 1 exposed to gamma radiation showed a decreased expression in most antioxidant enzyme-coding genes, suggesting that this is also related to a lower hatching rate and developmental impairment. The results of this study provide a better understanding of the molecular mode of action of gamma radiation in aquatic organisms., (Copyright © 2012 SETAC.)

The use of nanoparticulate silver (AgNP) is increasingly widespread and recently has been shown to have a plausible release route into aquatic environments. To date, relatively little research has examined the effects of AgNP on estuarine fish. The authors present data indicating that chronic exposure to low levels of AgNP induces significant adverse effects in both juvenile and adult sheepshead minnows (Cyprinodon variegarus; SHMs). Chronic exposure to low levels of AgNP produced significant increases in tissue burdens in both juvenile and adult SHMs, resulting in significant thickening of epithelia gill tissue and in dramatically altered gene expression profiles. The results do not appear to be attributable to the release of silver ions through particle dissolution. The alteration in gene expression was greatest in adult gonads, but no evidence of AgNP-related dysfunction was found at the tissue level. In contrast, the authors found a significant effect on gill morphology, but very little evidence of effect on gill transcription profiles., (Copyright © 2011 SETAC.)

Estimating long-term effects of endocrine-disrupting chemicals on a species is important to assessing the overall risk to the populations. The present study reports the results of a 42-week exposure of estuarine sheepshead minnows (Cyprinodon variegatus) to the androgen, 17beta-trenbolone (Tb) conducted to determine if partial-(F0) or single-generation (F1) fish exposures identify multigenerational (F0-F3) effects of androgens on fish. Adult F0 fish were exposed to 0.007, 0.027, 0.13, 0.87,and 4.1 microg Tb/L, the F1 generation to < or =0.87 microg Tb/L, the F2 fish to < or =0.13 microg Tb/L, and the F3 fish to < or =0.027 microg Tb/L. The highest concentrations with reproducing populations at the end of the F0, F1, and F2 generations were 4.1, 0.87, and 0.027 microg Tb/L, respectively. Reproduction in the F0, F1, and F2 generations was significantly reduced at 0.87, 0.027, and 0.027 microg Tb/L, respectively. Fish were significantly masculinized in the F1 generation exposed to 0.13 microg Tb/L or greater. Female plasma vitellogenin was significantly reduced in F0 fish exposed to > or =0.87 microg Tb/L. Gonadosomatic indices of the F0 and F1 generations were significantly increased at 0.87 and 0.13 microg Tb/L in the F0 and F1 generation, respectively, and were accompanied by ovarian histological changes. Reproduction was the most consistently sensitive measure of androgen effects and, after a life-cycle exposure, the daily reproductive rate predicted concentrations affecting successive generations. The present study provides evidence that a multiple generation exposure of fish to some endocrine-disrupting chemicals can result in developmental and reproductive changes that have a much greater impact on the success of a species than was indicated from shorter term exposures.

The vast majority of investigations into the bioavailability and toxicity of explosives to receptors in aquatic environments has focused on deriving toxicity metrics for discrete chemical exposures to single species using pure compounds at relatively high concentrations. This study assessed the environmental fate and potential for biological effects of a common military formulation, Composition B, under more realistic exposure scenarios (e.g., those that more closely simulate a breached artillery round or residual exposure following a low-order detonation). We used a novel approach incorporating multiple species and toxicity endpoints in sediment exposures over a 34-d exposure period. Composition B fragments exposed at the sediment surface rapidly released 2,4,6-trinitrotolune (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) to the overlying water column. In comparison, burial of fragments resulted in dramatically reduced exposure, bioconcentration, and toxicity. The addition of a conservative flow rate to the aquaria also reduced water and tissue concentrations by factors of two to three. Although the exposure system likely represented a worst-case scenario relative to most conditions found in coastal and estuarine environments, overlying water concentrations generally did not approach known toxicity thresholds, while porewater concentrations were sufficiently elevated above toxicity thresholds immediately adjacent to the fragments, limiting hazardous exposure only to very localized scales. Bioconcentration correlated closely with observed toxicity and was either not detectable (buried), or low (exposed), as is expected based on the low hydrophobicities of TNT and RDX., (Copyright 2010 SETAC.)

Populations exposed to environmental contaminants can undergo intense selection pressures, which in turn can lead to a loss of genetic variation. We assessed this loss of genetic variation in the least killifish Heterandria formosa for laboratory populations that had undergone eight generations of selection for an increased resistance to cadmium. Using microsatellite markers, we compared genetic variation between three selection and three control laboratory populations and between these laboratory populations and the source population. Heterozygosity was lower in each selection population than it was in its paired control population, with this difference being statistically significant in two of the three comparisons. This is evidence that adaptation to environmental contaminants can result in an overall loss of genetic variation. Furthermore, the laboratory populations had much lower heterozygosity than did the source population. The latter loss of genetic variation, probably a result of random drift, did not prevent the laboratory populations from showing a strong response to the selection for cadmium resistance. The loss of genetic variation resulting from maintaining populations in the laboratory demonstrates that it is important to maintain a large population size for such populations and that the potential for loss of genetic variation in laboratory populations is taken into consideration in ecotoxicology when extrapolating from laboratory to natural populations.

Results of laboratory and field studies have demonstrated that salinity influences the accumulation of copper. The present study is, to our knowledge, the first to examine the effect of salinity on copper accumulation in a teleost fish across a comprehensive range of salinity from freshwater to seawater. This was done in an effort to identify potential target tissues and differences in chemical interactions across salinities that will aid in the development of a seawater biotic ligand model (BLM) for copper. Killifish (Fundulus heteroclitus) were acclimated to five salinities (0, 5, 11, 22, and 28 ppt) and exposed to three copper concentrations (0 [nominal], 30, and 150 microg L(-1), yielding 15 treatment groups. Fish from each group were sampled for tissue copper analysis at 0, 4, 12, and 30 d postexposure. Whole-body and liver accumulations were highest at lower salinities. The liver accounted for 57 to 86% of the whole-body copper even though it accounted for less than 4% of the body mass. Similarly, the gill accumulated more copper at lower salinities, whereas the intestine generally accumulated more copper at higher salinities. Speciation calculations indicate that CuCO3 likely accounts for much of the accumulation, possibly with some contributions from CuOH+ and Cu(OH)2. The free ion, Cu2+, does not appear to be associated with copper accumulation. However, the differences in physiology and in the concentrations of competing cations across salinities suggest that speciation alone cannot explain accumulation. The present findings may have implications for future development of a BLM for saline environments by identifying potential target tissues.