Surface water mitigates the anti-metamorphic effects of elevated perchlorate concentrations in New Mexico spadefoot toad larvae (Spea multiplicata).

Perchlorate (ClO4-) has potential to negatively impact amphibian populations by inhibiting thyroid hormone production, and thus metamorphosis in developing larvae. However, variability exists in species sensitivity, and there is evidence suggesting that natural surface waters can mitigate the anti-metamorphic potential of perchlorate. New Mexico spadefoot toad tadpoles, Spea multiplicata, were exposed to natural surface waters spiked with nominal concentrations of 0, 1000, 1350, 1710, 3000, 5110, and 8000 µg/L perchlorate ion for up to 42 days. No consistent dose-response trends were observed in mortality, rate of metamorphosis, Gosner stage, mass, or length. This study suggests that perchlorate exposure to concentrations as high as 8000 µg/L in natural surface waters does not result in adverse effects on New Mexico spadefoot tadpoles and emphasizes the importance of using site-specific conditions and species when evaluating ecological risks in perchlorate-impacted areas.

Inorganic elements in green sea turtles (Chelonia mydas): relationships among external and internal tissues.

Inorganic elements from anthropogenic sources have entered marine environments worldwide and are detectable in marine organisms, including sea turtles. Threatened and endangered classifications of sea turtles have heretofore made assessments of contaminant concentrations difficult because of regulatory restrictions on obtaining samples using nonlethal techniques. In the present study, claw and skin biopsy samples were examined as potential indicators of internal tissue burdens in green sea turtles (Chelonia mydas). Significant relationships were observed between claw and liver, and claw and muscle concentrations of mercury, nickel, arsenic, and selenium (p < 0.05). Similarly, significant relationships were observed between skin biopsy concentrations and those in liver, kidney, and muscle tissues for mercury, arsenic, selenium, and vanadium (p < 0.05). Concentrations of arsenic, barium, chromium, nickel, strontium, vanadium, and zinc in claws and skin biopsies were substantially elevated when compared with all other tissues, indicating that these highly keratinized tissues may represent sequestration or excretion pathways. Correlations between standard carapace length and cobalt, lead, and manganese concentrations were observed (p < 0.05), indicating that tissue concentrations of these elements may be related to age and size. Results suggest that claws may indeed be useful indicators of mercury and nickel concentrations in liver and muscle tissues, whereas skin biopsy inorganic element concentrations may be better suited as indicators of mercury, selenium, and vanadium concentrations in liver, kidney, and muscle tissues of green sea turtles.

Embryotoxicity of mixtures of weathered crude oil collected from the Gulf of Mexico and Corexit 9500 in mallard ducks (Anas platyrhynchos).

Dispersants are applied to marine crude oil spills to enhance microbial degradation and reduce impacts of crude oils on ecosystems. In summer 2010, the dispersant Corexit 9500 was applied to crude oil in the Gulf of Mexico. The co-occurrence of the Deepwater Horizon oil spill with nesting efforts of birds in the Gulf region may have resulted in exposure of adult birds, and subsequently bird eggs, to combinations of crude oil and Corexit 9500. The objective of this study was to examine the embryotoxicity of 50:1 and 10:1 mixtures of weathered crude oil collected from the Gulf of Mexico and Corexit 9500 applied to mallard duck eggs. Combinations of weathered crude oil and Corexit 9500 were applied to eggshells of mallard ducks via paintbrush in varying masses ranging from 0.1 to 59.9 mg and 0.1 to 44.9 mg for 50:1 and 10:1 mixtures, respectively. Conservatively derived median lethal applications for 50:1 and 10:1 mixtures of weathered crude oil and Corexit 9500 were 21.3±4.9 mg/egg (321.8 µg/g egg) and 33.1±11.8 mg/egg (517.0 µg/g egg), respectively. Spleen mass of hatchlings exposed to the 50:1 mixture was the only physiological measure significantly different from controls of both mixtures. Results indicated that decreasing ratios of dispersant relative to weathered crude oil decreased toxicity to mallard embryos. In comparison to treatments of eggs with weathered crude oil alone, toxicity increased when the oil to dispersant ratio was 50:1, but decreased with the mixture that contained more dispersant (10:1).

Embryotoxicity of weathered crude oil from the Gulf of Mexico in mallard ducks (Anas platyrhynchos).

Weathered crude oil in the Gulf of Mexico can result from oil spills such as the Deepwater Horizon incident that occurred on April 20, 2010 or from natural seeps. Adult waterbirds of the Gulf Coast region may become exposed to weathered crude oil while foraging, wading, or resting, and residues can then be transferred to nests, eggs, and hatchlings. Although the toxicity of many types of crude oil to avian embryos has been thoroughly studied, the effects of weathered crude oil on developing avian embryos are not well characterized. The objective of the present study was to examine embryotoxicity of weathered crude oil collected from the Gulf of Mexico in June 2010 using mallard ducks (Anas platyrhynchos) as a model species. Weathered crude oil was applied to fertilized mallard duck eggs by paintbrush in masses ranging from 0.1 to 99.9 mg on day 3 of incubation. Mortality occurred as early as day 7 and the conservatively derived median lethal application of weathered crude oil was 30.8 mg/egg (0.5 mg/g egg) or 30.7 µl/egg (0.5 µl/g egg). Body mass, liver and spleen mass, crown-rump and bill lengths, and frequency of deformities were not significantly different among hatchlings from oiled and control eggs. In comparison to published reports of fresh crude oil embryotoxicity, weathered crude oil was considerably less toxic. We conclude that avian toxicity varies according to the degree of crude oil weathering and the stage of embryonic development at the time of exposure. Results indicate bird eggs exposed to weathered crude oil from the Gulf of Mexico during summer 2010 may have had reduced hatching success.

Environmental exposure to polychlorinated biphenyls among raccoons (Procyon lotor) at the paducah gaseous diffusion plant, Western Kentucky, USA.

An investigation involving raccoons (Procyon lotor) as a sentinel species at the Paducah Gaseous Diffusion Plant (PGDP) in Western Kentucky (USA) delineated the extent of exposure to polychlorinated biphenyls (PCBs) and PCB spatial distribution. Raccoon exposure to PCBs was demonstrated through analysis of subcutaneous fat, abdominal fat, liver, and brain tissues from raccoons collected at the PGDP but also was clearly evident in raccoons from a reference area situated along the Ohio River (USA). Raccoons with the highest tissue PCB concentrations appeared to be those inhabiting areas nearest the plant itself and most likely those that ventured into the plants interior. Male raccoons at the PGDP had similar concentrations of total PCBs in subcutaneous fat (1.86 +/- 0.64 microg/g) as males from the reference site (1.41 +/- 0.35 microg/g), but females had higher PCB body burdens than those at the reference site (9.90 +/- 6.13 microg/g vs 0.75 +/- 0.40 microg/g). Gross measurements of exposure to radiation-producing materials revealed that counts per minute exceeded background in 61% of PGDP raccoons compared with 27% at the reference site and five raccoons at the PGDP had beta counts that were more than twice the background. Differences among trapping success, growth rates, and serum chemistry parameters were noted but may have been related to habitat and other environmental and population density factors.