Wastewater discharge, a potential stressor to estuarine species and ecosystems, frequently contains contaminants of emerging concern. These compounds, such as pharmaceutical and personal care products, some polybrominated diphenyl ethers, steroid hormones, and some newer pesticides, are increasingly identified at low levels in U.S. water bodies, posing unknown risks to ecological communities and human consumers. While many studies have examined acute effects on individual species, few studies address potential ecological effects under chronic exposure and environmentally relevant conditions to a suite of contaminants. This project assesses the presence of wastewater contaminants in estuaries and their effects on Pacific oysters, a commercially important species in the Pacific Northwest, under real environmental conditions. In July 2016, we initiated a field transplant study in Coos Bay, OR, Netarts Bay, OR, and Grays Harbor, WA. Juvenile oysters (settled on nonliving oyster shells) were transplanted to sites along a hypothesized pollution gradient, with one site adjacent to a wastewater treatment plant outfall and the others at increasing distances from the outfall. Oysters were left for nine months and collected in April 2017. At study completion, settlement, oyster shell size, weight, and condition index will be measured and composite samples analyzed for representative contaminants.
Preliminary observations during mid-study site visits indicate differences in settlement of organisms other than oysters on nonliving shells. At Netarts Bay, barnacles were highly abundant on oyster shells. At North Bend (site within Coos Bay) barnacles and macroalgae were abundant. At Coos Bay, the most degraded site, we found an abundance of settled tunicates, which are common in areas with higher nutrients. Combined with other endpoints to be measured in April 2017, this research will fill important data gaps on community composition, oyster health and contaminant accumulation at sites exposed to wastewater. This information is relevant to coastal water quality regulations in Oregon and Washington and may inform future selection of bivalve aquaculture sites.