265 - Spatial and Temporal Patterns in Copepod Methylmercury Bioaccumulation in Long Island Sound

Methylmercury (MeHg) in apex predators is most influenced by the efficiency of MeHg bioaccumulation at lower trophic levels. Copepods, the most abundant metazoans in the ocean and a significant link in marine food webs, accumulate over 90% MeHg from their diet, phytoplankton. Long Island Sound (LIS) is a temperate estuary with a westward gradient of increasing, temperatures, nutrients, water column mercury, phytoplankton, and copepod abundances. Therefore, LIS serves as a useful model for MeHg bioaccumulation studies. We hypothesized that MeHg concentrations in copepods follow prey abundances and seawater temperatures, both of which promote higher feeding and therefore exposure to diet-bound MeHg. Additionally, due to higher phytoplankton concentrations during the spring bloom, we hypothesized that springtime MeHg concentrations in copepods are the highest. Lastly, due to water column depth impacting dissolved MeHg concentrations, we hypothesized that copepods from shallow embayments accumulate more MeHg compared to deeper offshore locations. To test these hypotheses, we sampled copepods, and seawater to analyze them for MeHg, phytoplankton, and copepod species abundances. Sampling was performed monthly from February to October of 2018 in three embayments and offshore locations. We found no longitudinal differences in dissolved or copepod MeHg, while copepod MeHg values were significantly higher in embayments compared to offshore stations (0.18 ± 0.02 vs. 0.12 ± 0.01 pg/ind; One-Way ANOVA, p

Authors: Wesley Huffman, Robert Mason, Hans Dam, Zofia Baumann