Environmental factors influencing the efficiency of mercury transfer from sediments to fish in the Colombian Pacific and Caribbean

Marine sediments play a key role in the biogeochemical cycle of mercury, acting as sinks that facilitate its accumulation in marine organisms and posing a risk to the food security of coastal communities and human health. This study determined the temporal dynamics and environmental variables that influence the transfer of total mercury in dry weight from sediments to fish in artisanal fishing areas of the Pacific and Caribbean coasts of Colombia. The concentrations of total mercury in dry weight were analyzed in the sediment, seston, and muscle (dry wt) of eight fish species caught using two artisanal fishing methods (net and hook), during dry and wet seasons. Biota-sediment accumulation factor (BSAF) was calculated to estimate the transfer of mercury from the sediments to fish. All fish had a BSAF of >1, indicating accumulation of total mercury in dry weight in fish tissues, and values of >2 on average, suggesting their potential as macroconcentrators. The BSAF was higher in demersal fish (family Lutjanidae; 56.7 ± 32.3), and in the Caribbean, where it was up to four times higher than that in the Pacific. The BSAF increased during the wet season, when the lowest concentrations of mercury were in the sediments, due to an increase in bioavailability associated with organic matter. The study identified three patterns of mercury transfer between species, influenced by variables such as organic matter content, total dissolved solids, and environmental mercury concentrations. These results demonstrate a complex dynamic of mercury mobilization controlled by environmental factors and highlight the importance of considering climatic conditions, habitat, and community composition in assessing mercury risks in coastal ecosystems.