Feeding strategy as a key driver of the bioaccumulation of MeHg in megabenthos

Abstract. The bioaccumulation of methylmercury (MeHg) in the marine food chain poses a neurotoxic risk to human health, especially through the consumption of seafood. Although MeHg bioaccumulation at higher trophic levels is relatively well understood, MeHg bioaccumulation at the base of the food web remains underexplored. Given the neurotoxic effects of MeHg on human health, it is essential to understand the drivers of bioaccumulation at every level of the food chain. We coupled six megabenthos functional groups in the ECOSMO end-to-end ecosystem model to the MERCY v2.0 Hg cycling model. We investigated how various feeding strategies influence the bioaccumulation of both inorganic Hg (iHg) and MeHg in marine ecosystems. We show that feeding strategy significantly influences bioaccumulation and correlates more strongly with iHg than does trophic level. In particular, suspension feeders have elevated iHg levels, while filter feeders have elevated MeHg levels compared to other megabenthos. Additionally, we show that feeding strategies alone allow us to accurately model the bioaccumulation of both iHg and MeHg in low-trophic-level megabenthos. However, when modeling higher trophic levels, incorporating the allometric scaling law substantially improves model performance. These results demonstrate the need for a holistic approach in which iHg, MeHg, and the trophic level of organisms are evaluated at both high and low trophic levels to identify what food web structures drive high MeHg concentrations in seafood.