Balance disturbance of aquatic microbial microcosm as a method to evaluate the contamination by toxic substances

Izabel Adelina Ribeiro


Toxicity tests are useful to assess relative toxicities of chemicals in the aquatic environment. Although, they have the advantages of standardized protocols, the test organisms are isolated from the context of the natural conditions. This experimental research challenges the development of an aquatic microbial microcosm with an ecological structure, to evaluate the effects of contamination by toxic substances in the aquatic environment. Two morphological groups were observed in typical ecological succession, according to the modification of the medium. The laboratorial set-up consisted of keeping an organic substrate of 350 mg L-1 of BOD, placed in glass containers maintained in continuous aeration. Growth of filamentous bacteria was observed after 24h, followed by significant exponential growth of free swimming ciliates protozoa, reaching its maximum rate on the 4th day. Disturbances were caused by the introduction of copper sulphate and insecticide dichlorvos. Complete inhibitory effect of growth was observed to ciliates at concentrations of 12.28 mg L-1 Cu and 500 mg L-1 DDVP-20. Easy to be assembled, the method suggested information about theoretical aspects of self-organization. To greater precision, we mention the study of ecological interactions, opened system development, biodiversity molecular approach and application of ecological models.

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