Resumo

GUALDONI, Cristina M; DUARTE, Claudia A  e  MEDEOT, Erica A. Ecological status of two mountain streams of the south of Córdoba, Argentina. Ecol. austral [online]. 2011, vol.21, n.2, pp.149-162. ISSN 1667-782X.

The development of methodology that allows us to assess the environmental deterioration of fluvial systems from the biotic components has been of high attention in the last time. With the aim to evaluate the ecological state of two mountains streams in sections that cross communes of tourist interest, indexes of water and riparian forest quality were combined. In each stream, two stations were selected, one downstream and the other upstream of the recreation areas. Environmental data were registered and benthos samples were collected in the main geomorphological units, during high and low water periods. Metric indexes and Índice Biótico Carcarañá (IBC) based on benthic macroinvertebrates were calculated, and the marginal forest quality was determined by the Riparian Quality Index (QBR). The results were integrated by a modification of index ECOSTRIMED to evaluate the ecological status of the fluvial system. In both streams, the physico-chemical variables showed normal values and the metric indexes determined that the water quality vary between "moderately deteriorated" and "little deteriorated", whereas the IBC revealed a "unpolluted environment" in all sampling situations. Application of QBR showed that the riparial forest with important alterations and extreme degradation were located close to urban areas, while in the other reaches the alteration degree was translated in judgments of acceptable and good quality. When combining the results of the metric indexes with those of the QBR, in both streams were obtained quality judgments that indicated "good" and "intermediate" ecological status in the stretches located upstream of urban areas and "intermediate" in the stretches downstream of recreation areas. The results of this study contribute to corroborate that, from a biological perspective; the application of a set of metric is the most efficient and economic methodology, to evaluate the quality of the water since they integrate information derived from diverse aspects of the benthonic community. Although in the studied streams the water didn't have very good biological quality, in urban reaches, the degradation or elimination of the marginal vegetation was the main determinant of the altered ecological quality.

Palavras-chave : Water quality; Biotic indices; Benthic macroinvertebrates; Metric indices; QBR.

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