Metal contamination in omnivores, carnivores and detritivores fish along the Tramandaí River Basin, RS, Brazil

Abstract

Heavy metals are different from other toxic agents because they are not metabolized, destroyed and excreted. They reach water resources mainly through anthropic action, be it agricultural, industrial, occupational, among others. Fish, often exposed to such contamination, are an important source of food in the Tramandaí River Basin (TRB) and stand out for their commercial importance. Increased action and anthropic occupation in this region, and studies that demonstrate the contamination of water and sediments in the coastal lagoons of the region, it is important to quantify these metals in fish of different trophic levels. Thus, the study was carried out in nine lagoons of the TRB with monthly sampling between May 2011 and April 2012, using waiting nets of 5 to 9 mm to collect juvenile specimens of Geophagus brasiliensis, Oligosarcus spp., Hoplias malabaricus and Loricariichthys anus. Heavy metals were transported in the suppliers' liver by AAS obtaining distribution with non-normal distribution, with medians for cadmium, chromium, mercury and lead of 0.356; 0.752; 0.437; 0.000 µg/g, respectively. There was no correlation between the indications of metals from different sources. The correlation between eating habits and differentiated metals differed only for cadmium, greater among detritivores. Based on Anvisa, 100% exceeded the limits for cadmium and chromium, 40% for mercury and 3% for lead. The accumulated mean was higher in detritivore and lower in carnivore. The average accumulation prevailed in freshwater fish, however with no significant difference between sub-basins, which is unrelated to the population issue.The results showed regional fish with heavy metal accumulation exceeding the established limits and unrelated to biomagnification by trophic levels, as well as a preferential accumulation in fish of the freshwater systems.