Density and biomass of Campsurus sp. (Ephemeroptera) and other macroinvertebrates in an Amazonian lake impacted by bauxite tailings (Lago Batata, Pará, Brazil)

For 10 years (1979 to 1989) the Lake Batata received about 18 million cubic meters per year of effluent from the washing of bauxite. About 30 % of its area was impacted. The main goal of this study has been the to evaluation of the effects of the bauxite tailing dumping on the density and biomass of the benthic macroinvertebrates community and, especially, on the population of Campsurus sp. Three sampling sites has been determined in each of the three lake regions (impacted, transition and natural); periodicity of samples has been chosen throughout the four periods of the flood pulse (high water, drawdown, low water and flood) between June 1996 and March 1997. The limnological variables measured were temperature, depth, dissolved oxygen and transparency (of water column), available phosphorus, total nitrogen and organic matter (in the sediment). Variables were organized by Pincipal Components Analysis (PCA). Density results for community of benthic macroinvertebrates were significantly lower (Kruskal-Wallis, p < 0,05) in the impacted region; the highest values were found in the natural and transition regions. Ostracoda, Chaoboridae, Oligochaeta and Chironomidae were the predominant taxonomic groups in the natural and transition regions; in the impacted region Campsurus sp. was the group with the highest relative importance with regard to density and biomass

Relationship between antropogenically caused turbidity and phytoplankton production in a clear Amazonian floodplain lake

The present study was performed in Lake Batata, a clear water Amazonian floodplain ecosystem, located on the right bank of the Trombetas river (Pará State, Brazil). For a period of 10 years (1979-1989), the lake received a large quantity of bauxite tailings from a nearby mine. These tailings originally covered about 30 % of the lake sediments, but resuspension and redeposition have resulted in an even wider distribution of the tailings. Phytoplankton production was measured at dìfferent sites in natural and impacted areas at different hydrological phases. Incubations were exposed at 5 light depths using (14)C as tracer. All vertical profiles of primary production exhibited ca. 13 % light inhibition in the surface. The maximum primary production rates (Pmax) were always found near the surface at approximately 30 cm. Production rates ranged from 9 to 664 mgC m^(-3) d^(-1), being the higher rates found during low water and lower rates during high water periods. Transparency measurements were good predictors of phytoplankton attributes. A strong predictive capacity of the turbidity effect was shown. An increase in turbidity of 3.6 times could reduce the carbon production in the lake by 51 %. In areal terms, it was estimated that Lake Batata produces ca. 122 g C m^(-2) per year. Our data reveal that although being poorer in nutrients, clear water systems are as productive as decanted white water systems. The results suggest that phytoplankton production is regulated by solar radiation and not nutrient. Despite the turbidity increase caused by resuspension of tailings, phytoplankton production remains relatively high and still plays a central role to the carbon flux in Lake Batata, especially during low water hydrological periods

INTESTINAL AND PULMONARY INFECTION BY Cryptosporidium parvum IN TWO PATIENTS WITH HIV/AIDS

We describe two patients with HIV/AIDS who presented pulmonary and intestinal infection caused by Cryptosporidium parvum, with a fatal outcome. The lack of available description of changes in clinical signs and radiographic characteristics of this disease when it is located in the extra-intestinal region causes low prevalence of early diagnosis and a subsequent lack of treatment