Assessing legacy and endocrine disrupting pollutants in Boston Harbor with transcriptomic biomarkers

Within monitoring frameworks, biomarkers provide several benefits because they serve as intermediates between pollutant exposure and effects, and integrate the responses of contaminants that operate through the same mechanism of action. This study was designed to verify the use of transcriptomic biomarkers developed in our prior work (i.e., Coastal Biosensor of Endocrine Disruption; C-BED assay) on Mytilus edulis and identify additional biomarkers for legacy pollutants. M. edulis were collected from a reference site in Pemaquid, ME, USA and deployed by the Massachusetts Water Resources Authority (MWRA) at locations in and outside Boston Harbor, MA, USA: including (1) Boston Inner Harbor (IH), (2) the current outfall (OS), (3) 1 km away from the current outfall (LNB), and (4) Deer Island (DI), the site where untreated wastewater was formerly discharged into the bay. Differential gene expression was quantified with a high density microarray. Seven genes significantly correlated with whole tissue concentration of PAHs, and six genes significantly correlated with whole body concentrations of PCBs, two groups of legacy contaminants that were elevated at stations IH, OS, and DI. Enrichment analysis indicated that IH mussels had the highest induction of stress response genes, which correlated with the higher levels of contaminants measured at this site. Based on the C-BED assay gene analysis, stations IH and OS exhibited signs of endocrine disruption, which were further confirmed by incorporating the results for the C-BED assay within the Integrated Biomarker Response (IBR) approach. This study successfully demonstrated the potential use of transcriptomic biomarkers within a monitoring program to identify the presence and organismal responses to endocrine disrupting and legacy contaminant classes.