DISTRIBUTION OF THE BENTHIC MACREINVERTEBRATE COMMUNITY IN AN AMAZONIAN ECOSYSTEM IMPACTED BY BAUXITE TAILINGS - LAGO BATATA (PARA, BRAZIL)

Abstract

Lago Batata was a disposal site for 25,000 m³/d effluents from the baixite washing process for approximately 10 years; as result ecological conditions over about 30% of the total area of the lake were significantly compromised. Deposition of the tailings over the natural sediment profoundly altered the ecological conditions in the sedimentary compartment The objective of this research was to demonstrate the influence of the bauxite tailings and of the Amazonian hydrological cycle on the structure of the benthic community of Lake Batata; and in addition, to form conclusions as to the role of the zoobenthos as an indicator of ecological conditions in the lake. Discriminant function analysis was employed, where the densities of the different groups of organisms and several abiotic variables were measured: temperature, dissolved oxygen, pH, electrical conductivity, water tranparency, suspended matter, chlorophyll-a, pheophytin-a, ammonia, dissolved nitrogen and total nitrogen in the water columm; and total P, total N and organic matter in the sediment The results showed the influence off bauxite tailings on the benthic community, with a different pattern of organism distribution in the three areas studies (impacted, transition and natural). Moreover it was shouwn that the composition of the benthic organisms unerwent alteration in the four periods of the Amazonian hydrological cycle (filling phase. high water, drawdown and low water), furnishing evidence of the role of the community as an indicator of ecological conditions in Lake Batata.