Mercury Bioaccumulation in the Longnose Gar: A Model Species for Examining Patterns of MeHg Uptake

Though mercury (Hg) occurs naturally, anthropogenic emissions have increased atmospheric Hg levels by an estimated factor of three since the Industrial Revolution. This increase has caused corresponding increases in Hg levels in terrestrial and aquatic ecosystems. Wetlands contain anaerobic sulfur-reducing bacteria which contribute to transformation of elemental mercury into its most toxic form, methylmercury (MeHg).  As a result, wetlands serve as a pathway for Hg from freshwater to the marine environment, along which it is taken up by organisms.  Concentrations in fishes vary based on a suite of biological and environmental factors.  Longnose gar (Lepisosteus osseus) are an excellent model species to study Hg uptake due to their extensive range, high abundance, top predator status, and tolerance for a range of salinities. The present study examines patterns of Hg accumulation along a salinity and temporal gradient within muscle tissue of longnose gar in two South Carolina river systems.  Preliminary results show an increase in Hg concentration with increasing fish size, decreasing salinity, and Hg fluctuations throughout the year. A better understanding of Hg uptake and retention patterns in fishes will aid managers in making decisions regarding consumption advisories of commercial fishes in light of potential human health risks.