Superfund Research Program
Methylmercury Production and Fate in Response to Multiple Environmental Factors
Project Leader: Celia Y. Chen
Grant Number: P42ES007373
Funding Period: 2000-2020
The goal of Project 2 is to use experimental approaches, field studies, and modeling to investigate the combined and interactive effects of environmental changes in temperature, salinity, and organic carbon (OC) associated with climate change on the fate of methylmercury (MeHg) in marine ecosystems. MeHg is the bioavailable and toxic form of mercury found in fish that humans consume. The research focuses on different biogeochemical and ecological processes and compartments: MeHg production in sediments, input to the water column, bioaccumulation in estuarine primary producers and consumers, and ultimately the impact of these processes on human exposure to MeHg.
During the first year of the study, the researchers used experimental mesocosms to link biogeochemical processes to bioaccumulation in amphipods (Leptocheirus plumulosis) and oysters (Crassostrea virginica), amphipod bioaccumulation experiments for parameterizing modified chemical mixture models, and phytoplankton experiments to investigate effects of temperature and carbon on MeHg bioaccumulation. In the month long mesocosm experiment, they examined the individual and combined effects of sediment organic carbon (low OC, high OC) and temperature (low: 15°C, high: 25°C) on bioaccumulation of THg and MeHg. Mesocosm samples are still being analyzed but their single factor experiments with amphipods indicated that bioavailability increased with temperature and decreased with increased organic carbon with the temperature effects being greater. In phytoplankton experiments, they also found that higher temperature and light increased uptake in phytoplankton but that the resulting increased phytoplankton densities decreased cellular concentrations. Thus, the processes controlling the pathways of MeHg to fish that humans consume are influenced by environmentally relevant changes in temperature and organic carbon that are predicted to occur with climate change but the effects differ between compartments. These different responses will be included in their future bioaccumulation and human exposure models.