A COMPARATIVE APPROACH USING AN AMAZONIAN NATIVE FISH (Hyphessobrycon heterohabdus) AND AN EXOTIC FISH (Danio rerio) SPECIES AS MODEL ORGANISMS ON UNDERSTANDING SULFATE TOXIC EFFECTS

The sulfate anion (SO42-) occurs naturally in Amazon rivers. Metal sulphide oxidation, and seawater intrusion are some of its natural sources. However, human actions such as the release of wastewater by mining, metallurgy, food, medicine, foundry, steel and cellulose manufacturing industries, alumina refinery wastewater and others generate enrichment of sulfate in the environment. Little is known about how sulfate high concentrations affect local organisms. Assessing antioxidant defences (antioxidant capacity against peroxyl radicals - ACAP) and possible oxidative damage (lipid peroxidation - LPO) of exposed organisms allows negative impacts to be detected even before organism mortality occurs. Therefore, this study sought to understand the biochemical and potentially lethal effects of increasing concentrations of sodium sulfate (Na2SO4), starting from the sulfate concentration defined in Brazil’s National Environment Council (CONAMA) Resolution 357/2005 (250 mg. L-1), on native (Hyphessobrycon heterorhabdus) and exotic fish (Danio rerio). Lipid peroxidation become statistically significant for D. rerio species at a concentration of 2500 mg L-1 of sulfate, which is 10 times higher than the upper limit permitted for surface waters. Individuals of the H. heterorhabdus species, however, did not suffer significant oxidative damage as their antioxidant defenses (ACAP) were activated from a dosage of 1,250 mg. L-1 of sulfate. Additionally, the estimated LC50-96h (the concentration of the substance that causes mortality of 50% of organisms during 96h of exposure) according to the probits analyses were 6,023 mg. L-1 of sulfate for D. rerio and 57,202 mg. L-1 of sulfate for H. heterorhabdus. As results revealed, an overdose of sulfate would be required to cause toxicity in the fish species evaluated in this study, since the initial impacts on organisms only began at concentrations 5 times higher than those defined as the maximum limit allowed for surface waters. In addition, the native species showed better adaptability to increasing concentrations of sodium sulphate compared to the standardized species, as the former was able to induce antioxidant defences, which reduced oxidative damage and mortality. Thus, prioritizing the use of native species as model organisms allows identifying response patterns of organisms that occur naturally in the region to be studied.