PEER-REVIEWED PUBLICATIONS
KEISLING, C., HARRIS, R. D., BLAZE, J., COFFIN, J., BYERS, J. E. (2020): LOW CONCENTRATIONS AND LOW SPATIAL VARIABILITY OF MARINE MICROPLASTICS IN OYSTERS (CRASSOSTREA VIRGINICA) IN A RURAL GEORGIA ESTUARY. MARINE POLLUTION BULLETIN 150 (110672).
ABSTRACT: Microplastics are an emerging concern for the health of marine ecosystems. In the southeastern US, the filter-feeding Eastern oyster, Crassostrea virginica, is susceptible to microplastic ingestion. We quantified the distribution of microplastics within adult oysters (harvestable size > 7.5cm) from 28 reefs throughout a rural estuary with limited riverine inputs (St. Catherines Sound, Georgia). To determine which variables best predict microplastic concentration in oysters, we also quantified oyster recruitment, distance to ocean, fetch, and water body width. Oysters averaged 0.72 microplastic particles per individual (0.18 particles per gram wet mass); microfragments and microplastics were equally abundant. Although microplastic concentrations were low, multivariate models identified a positive effect of water body width on the site-level concentration of plastic microfibers; average microfragment length was affected by fetch. Our work informs a growing understanding of microplastic distribution in coastal estuaries, providing an important rural contrast to the urbanized estuaries that have been examined.
COFFIN, J. L., KELLEY, J. L., JEYASINGH, P. D., TOBLER, M. (IN PREP): IMPACTS OF HEAVY METAL POLLUTION ON THE IONOMES AND TRANSCRIPTOMES OF WESTERN MOSQUITOFISH (GAMBUSIA AFFINIS).
ABSTRACT: Human-caused environmental change has affected ecosystems worldwide, and our understanding of the mechanisms mediating the resiliency of organisms to these changes remains lacking. Heavy metals from mining activities are common contaminants that negatively affect processes at all levels of biological organization, yet organisms inhabiting contaminated environments must maintain homeostasis to survive. Tar Creek in Oklahoma, USA is characterized by high concentrations of heavy metals and an abundance of Western mosquitofish (Gambusia affinis), though several species are present at lower frequency. To understand the numerical dominance of mosquitofish in Tar Creek, we used ionomic and transcriptomic data to test our predictions about the mechanisms mediating their persistence in Tar Creek. Specifically, we predicted that mosquitofish minimize uptake of heavy metals from the environment and induce transcriptional responses to detoxify metals that enter the body, allowing them to persist in Tar Creek at higher density than other species that lack these responses. We found that Tar Creek populations of all species experienced accumulation of heavy metals, suggesting mosquitofish cannot block uptake from the environment more efficiently than other species. We also found significant changes in gene expression between mosquitofish in Tar Creek and unpolluted sites. The vast majority of gene expression differences occurred in the gill, where we found evidence of upregulation of genes involved with lowering uptake of metal ions from the blood and mitigating free radicals. However, many differentially expressed genes did not appear to be involved in heavy metal detoxification, suggesting that abiotic or biotic factors other than heavy metals may impact this system and/or that previously undocumented pathways could be involved in the response to heavy metal stress in mosquitofish. Our systems level study identified well characterized as well as several putatively new mechanisms that enable mosquitofish to live in heavy metal-contaminated environments.