Biomagnification of Mercury in Fish from Two Gold Mining-Impacted Tropical Marshes in Northern Colombia.

Total mercury concentrations (T-Hg) and stable isotope ratios (δ15 N and δ13 C) were analyzed in the muscle of fish, collected at two marshes impacted by gold mining in Northern Colombia, to evaluate the seasonal and spatial behavior of these variables and mercury biomagnification based on their relationship with δ15 N ratios in the fish. There was not significant (p > 0.05) seasonal differences (dry and rainy season) in δ15 N and δ13 C values in none marsh, suggesting that these fish species keep a similar feed pattern within each marsh along the year. However, there were significant differences (p < 0.05) between marshes in δ15 N, δ13 C, and T-Hg, as well as significant seasonal differences (p < 0.05) in T-Hg values for some species, suggesting the possible influence of factors, such as differences in length of food chains between marshes and different degree of anthropogenic impact in relation to human settlements, farmland, livestock (higher in Ayapel marsh), and gold mining activity (higher in La Raya marsh). Correlations analysis showed significant (p < 0.05) relationships between T-Hg concentrations and δ15 N values, as well as trophic level, evidencing a T-Hg biomagnification process in the fish food chain from both marshes and consequently a potential health risk for human riverside inhabitants who eat these fish.