La comunidad bentónica como indicadora de zonas de degradación y recuperación en el arroyo Toledo (Uruguay)

Abstract

Macrozoobenthos composition and abundance of an organie polluted stream (A. Toledo, Uruguay) are compared among sites of control (C ), degradation (D ) and recuperation (R), which were seasonally sampled. Water ionie composition, conductivity, pH, temperature and COD were not different among sites, while oxygen, and BOD did show significant differences. Benthos was more abundant in R main1y due to Heleobia spp. Oligochaetes were dominant in C and D, with Branchiura sowerbyi only in C and Limnodrilus hoffmeisteri in D. Hirudinea, main1y Gloiobdella michaelseni, occured almost only in R. The richness of taxa was higher in R, but its high abundance of Heleobia spp. and Sphaeridae leads to the lowest diversity, which was higher in C than in D, and in warm than in cold seasons for these two sites. The logarithmic distribution model shows cornmunities of low evenness in all sites