Mercury in trophic webs of estuaries in the southwest Atlantic Ocean

Highlights: • Hg in trophic webs of three Brazilian estuaries reflect anthropic pressures. • Hg bioconcentration occurred primarily in cetaceans, polychaetes and molluscs. • The highest Hg values was observed in the trophic web of the Paranaguá estuary. • Hg biodiluition was observed in the trophic web of the Santos and Cananéia estuaries. Anthropogenic activities have impacted the coastal region of Brazil. In the Paranaguá estuarine complex (PEC), Cananéia-Iguape estuarine-lagoon complex (CIELC), and Santos-São Vicente estuarine complex (SSVEC), such activities occur across differing scales. In these estuaries, the concentrations of mercury (Hg) and stable nitrogen isotopes (δ¹⁵N) were investigated in sediments and marine organisms including benthic macrofauna, fish and cetaceans. Hg bioconcentration occurred primarily in cetaceans, polychaetes and molluscs, and reflects the impact of anthropogenic activities in the regions studied (PEC and SSVEC > CIELC). Bioaccumulation occurred in most of the studied specimens, but biodilution of Hg was observed in the trophic webs of SSVEC and CIELC. Despite measuring lower Hg levels than in studies carried out in the northern hemisphere, the results highlight potential concerns for public and environmental health in these highly productive coastal regions in the southwestern Atlantic which are important for fishing and various economic activities.