Acid stress evaluation using multimetric indices in the Carolina stream (San Luis –Argentina)

TRIPOLE¹, E.S. & CORIGLIANO², M. del C.

¹ Universidad Nacional de San Luis, Facultad de Química, Bioquímica y Farmacia, Area de Zoología, Chacabuco y Pedernera (5700) San Luis. Argentina. stripole@unsl.edu.ar

² Universidad Nacional de Río Cuarto, Departamento de Ciencias Naturales, AP 3, 5800. Río Cuarto. Argentina. mcorigliano@exa.unrc.edu.ar.

ABSTRACT: The effect of water acidity on benthic macroinvertebrates using multimetric indices was evaluated. Biological integrity indices were adjusted for a stream reach affected by acid drainage from an abandoned mine. This permitted to demonstrate changes in the community of benthic macroinvertebrates subject to acid stress. Five sampling sites were established, in Grande river and in Carolina stream; four of them represented the reference condition. The latter were contrasted with the affected site to establish its degree of impairment. The sampling program was carried out between May 1997 and December 1998. The metric indices that discriminated between the reference situation and the problem site were selected while those that provided redundant information were eliminated. The range of metric values was divided into four categories and then translated in water quality judgments. After the selection, 13 metrics were considered reliable for the analysis and were used for the aggregation in the index and later evaluation of the biological quality of the water. The final evaluation of the multimetric index for the problem site was the sum of the scores of the selected metric indices. The biological condition of problem site was determined as moderately deteriorated environment. Biological monitoring by means of multimetric methods is sensitive to biological degradation in mining areas and effective when it is developed from the database of a regional reference condition.