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Microbial communities in an oligotrophic reservoir influenced by high levels of ionizing radiation
Published online by Cambridge University Press: 09 January 2012
Abstract
In this study, we investigated the microbial community (bacteria and protozooplankton) of a Brazilian reservoir that receives neutralized acid mine drainage flowing from piles of earth produced during uranium extraction. Thus, this research represents an attempt to fill a gap in the information on the ecology of freshwater microorganisms in tropical oligotrophic habitats, in particular in systems affected by high levels of the uranium. During the study, we observed very low chlorophyll a contents and protozooplankton cell densities and biomass. These cell densities were between 0 and 89 cells L−1 and were lower than those frequently reported for oligotrophic freshwater lakes. In contrast, bacterial densities were normal or even slightly high, between 1.85 to 6.0 × 109 cells L−1. The present study has demonstrated very low protozooplankton cell densities and biomass in oligotrophic reservoir under the influence of acidic mining effuents and of high levels of ionizing radiation. It is likely that the ciliate cell densities and biomasses recorded in this study, which fall significantly below the previously published values, can be explained by the chronic fractionated exposure of these protozoa to the high levels of uranium to this system.
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