Constructing an Unprecedented Time Series to Explore the Major Factors Impacting Methylmercury Bioaccumulation in Coastal Plankton

Abstract:

Methylmercury (MeHg) is a neurotoxin which humans are exposed to primarily through the consumption of seafood. It predominantly enters the marine food chain through active and passive uptake into plankton. This uptake is affected by multiple chemical, physical, and biological parameters which vary seasonally. We hypothesized that plankton abundance and community structure strongly influence plankton MeHg concentrations. We also hypothesized that seasonally-varied physical factors (temperature, salinity, dissolved organic matter) strongly drive the MeHg concentration in plankton biomass. To explore these theories, bulk seawater was collected bi-weekly to monthly from Narragansett Bay, Rhode Island. Seawater was sequentially filtered, splitting plankton into three size classes (0.2-3.0, 3.0-20 and >20.0 µm). Both filters and filtrate were analyzed for MeHg. Temperature, salinity, chromophoric dissolved organic matter, phytoplankton taxa and abundances are continuously monitored using a flow-through system at the sampling location at the University of Rhode Island. Various statistical analyses, including Principal Component Analysis, will be used to parse out the different variables influencing the patterns of dissolved and planktonic MeHg concentrations. Results will be presented in terms of the impacts of the seasonal variations on plankton MeHg concentrations.