A Mesocosm Assessment of the Effect of Bioturbation by the Ghost Shrimp (Lepidophthalmus louisianensis) on the Fate of Petroleum Hydrocarbons in the Intertidal Zone.

To fully assess the long-term impacts of oil spills like the 2010 Deepwater Horizon incident in the northern Gulf of Mexico, the potential for organisms other than microbes to affect the fate and distribution of the oil may have to be considered. This influence could be substantial for abundant bioturbating benthic animals like the ghost shrimp Lepidophthalmus louisianensis. An assessment of the influence of these ghost shrimp on petroleum hydrocarbons was conducted in laboratory micro- and mesocosms containing coastal Gulf of Mexico sediment, seawater, and oil or the polynuclear aromatic hydrocarbon (PAH) pyrene. In an experiment with pyrene added to the water column, the ghost shrimp presence lowered water-column pyrene concentrations. In an experiment with oil added to the sediment surface, the ghost shrimp presence decreased PAH concentrations in the sediment surface layer but increased these in the water column and subsurface sediment. A companion study and a mass-balance analysis indicated a net loss of PAHs through an enhancement of microbial degradation. In an experiment in which oil was added as a narrow subsurface layer in the sediment, the ghost shrimp presence appeared to broaden the oil's depth distribution. Taken together, these results demonstrate that ghost shrimp can significantly influence the biodegradation and distribution of spilled oil in coastal ecosystems. Environ Toxicol Chem 2020;39:637-647. © 2019 SETAC.

Crude oil toxicity to fiddler crabs (Uca longisignalis and Uca panacea) from the northern Gulf of Mexico: Impacts on bioturbation, oxidative stress, and histology of the hepatopancreas.

The intensive drilling and extraction of fossil fuels in the Gulf of Mexico result in a considerable risk of oil spills impacting its coastal ecosystems. Impacts are more likely to be far-reaching if the oil affects ecosystem engineers like fiddler crabs, whose activities modify biogeochemical processes in the sediment. The present study investigated effects of oil on the fiddler crabs Uca longisignalis and Uca panacea, which are important as ecosystem engineers and as prey for a wide variety of species. The present study used mesocosms and microcosms to investigate the effects of crude oil on fiddler crab burrowing and to assess cellular and tissue damage by the oil. Fiddler crabs were exposed for periods of 5 or 10 d to oil concentrations up to 55 mg/cm2 on the sediment surface. Their burrowing was delayed, their burrows were smaller, and they transported less sediment in the presence of oil. The hepatopancreas had elevated levels of oxidative stress and a higher abundance of blister cells, which play a role in secretory processes. Interspecific differences were observed; most effects were strongest in U. panacea, though burrowing was more strongly affected in U. longisignalis. The present study demonstrates that crude oil is likely to impact fiddler crabs and many species that depend on them for their diet or for the ecological changes that result from their burrowing. Environ Toxicol Chem 2018;37:491-500. © 2017 SETAC.

The bioaccumulation and effects of selenium in the oligochaete Lumbriculus variegatus via dissolved and dietary exposure routes.

Aquatic organisms take up selenium from solution and from their diets. Many questions remain regarding the relative importance of selenium accumulation from these sources and resulting effects in benthic invertebrates. The present study addressed the toxicity and accumulation of Se via dissolved and dietary exposures to three different Se species, in the freshwater oligochaete Lumbriculus variegatus. Worms were exposed to 20µg/g dry weight of selenite (Se(IV)), selenate (Se(VI)), or seleno-l-methionine (Se-Met) in their diet (sediment) or to 15µg/L dissolved Se in water-only exposures. While the dissolved and sediment Se levels differed greatly, such levels may co-occur at a Se-contaminated site. Se accumulation, worm population growth, lipid peroxidation (as TBARS), and Na(+)/K(+)-ATPase activity were quantified at the end of the 2-week exposure. The sediment Se-Met exposure caused 100% mortality, while worm densities were reduced by the other exposures except the Se(VI) one. Se bioaccumulation was generally higher for the sediment-Se exposure than the dissolved-Se ones, and was higher for Se(IV) than Se(VI) in the dissolved-Se exposure but not the sediment-Se one. The Se accumulation was highest for Se-Met. The oligochaetes that accumulated Se had higher levels of lipid peroxidation and reduced Na(+)/K(+)-ATPase activity. The present study's findings of differences in Se accumulation and toxicity for the three Se species, with effects generally but not exclusively a function of Se body burdens, underscore the need for research on these issues in invertebrates. Moreover, the results imply that the dietary uptake route is the predominant one for Se accumulation in L. variegatus.

Accumulation and effects of Cr(VI) in Japanese medaka (Oryzias latipes) during chronic dissolved and dietary exposures.

Chromium (Cr) is an essential metal and a nutritional supplement for both human and agricultural uses. It is also a pollutant from a variety of industrial uses. These uses can lead to elevated Cr levels in aquatic environments, where it can enter and affect aquatic organisms. Its accumulation and subsequent effects in fish have received relatively little attention, especially for chronic exposure. In the present study, Japanese medaka were chronically exposed to dissolved or dietary Cr(VI) for 3 months. Cr accumulation in liver, gills, intestine, and brain was evaluated. Effects on the antioxidant system, nervous system (acetylcholinesterase, AChE), digestive system (α-glucosidase, α-Glu), and tissue histology (liver and gills) were also assessed. Cr accumulation was observed in the intestine and liver of fish exposed to Cr-contaminated brine shrimp. However, chronic dissolved Cr exposure led to significant Cr accumulation in all organs tested. Analysis of the subcellular distribution of Cr in medaka livers revealed that 37% of the Cr was present in the heat stable protein fraction. The dissolved Cr exposure had pronounced effects on the antioxidant system in the liver, with an elevated ratio of reduced glutathione/oxidized glutathione (GSH/GSSG) and decreases in GSH and glutathione S-transferase (GST). The α-Glu activity in the intestine was significantly inhibited. In addition, Cr exposure caused histopathological alterations in the gills and liver. In general, the effects of dietary Cr were relatively minor, possible due to the much lower accumulation in the fish. Our results imply that Japanese medaka accumulate Cr mainly via uptake of dissolved Cr(VI).

Relationship between hydrocarbon measurements and toxicity to a chironomid, fish larva and daphnid for oils and oil spill chemical treatments in laboratory freshwater marsh microcosms.

This research investigated the extent to which various common hydrocarbon measures can be used to predict toxicity to freshwater aquatic organisms due to fouling by oil. Actual toxicity results, on laboratory freshwater marsh microcosms using two water-column species and a benthic species, were described earlier. The hydrocarbon measures used were TPH(g), TPH(FID), TPH(MS), TTAH (sum of 41 target aromatic hydrocarbons), principal components of 41 TAHs, and each individual TAH. In general, toxicity was more closely related to TPH(MS) levels than to TPH(FID) and (especially) TPH(g) levels. The strongest relationships were found for TTAH levels and for the principal components of the TAHs. Regressions of toxicity on many individual TAHs were also strong, with a single group of compounds explaining as much as 59% of the variation in survival. While the various regressions were highly significant statistically and at times able to accurately predict broad differences in toxicity, the high variation in survival at a specific hydrocarbon concentration indicates that these hydrocarbon measures can not substitute for actual toxicity determinations in accurately ranking the toxicity of samples from oiled freshwater marshes.