Banca de QUALIFICAÇÃO: CASSIO DA SILVA CABRAL

THE MOLAR RATIO Se:Hg IN TROPHIC GUILDS OF FISH FROM AN AMAZON LAKE (PURUZINHO, HUMAITÁ–AM)

Keywords: Amazon. Lake. Riverside Community Toxicity.

Mercury (Hg) is a heavy metal with no known physiological functions with potential toxicological capacity. The Amazon for decades was a deposit of Hg of anthropogenic origin, whether from artisanal mining or deforestation and, more recently, the large reservoirs for energy generation have collaborated with this problem. This metal has the ability to accumulate in the trophic chain because its organic form, methylmercury, has a high affinity with biological tissues, and its entry into the trophic chain is mainly through plankton, microcrustaceans and fish, the latter as the source most significant cause of human contamination by Hg. Fish is the main source of animal protein in the riverside communities of the Amazon, thus making this population vulnerable to contamination by Hg, however it is also an important source of Selenium (Se), Vitamins D and omega 3. Se has been object of studies for presenting an antagonism to Hg, modifying or minimizing its toxicity. In this work, these elements were studied, with the objective of raising the concentrations of Se and Hg in the most consumed fish species in a lake community in the Amazon. The studied area, Lake Puruzinho, has been the target of research since the early 2000s that indicate significant Hg concentrations both in humans and in other biological and non-biological samples. With the development of this work, it was identified that the top-of-chain species presented the highest concentrations of total Hg, following what is reported in the literature, as well as the highest percentage ratios of methylmercury. Regarding selenium, planktivores (0.2111 mg.kg-1) and piscivores (0.1902 mg.kg-1). It was observed that 81% of the analyzed fish had a Hg:Se molar ratio above 1, with 61% of this total composed of piscivorous species. Therefore, it is believed that the Hg:Se molar ratio is acting as a natural protection against the possible toxicological manifestations of Hg.