Water quality assessment through biotic indices in a heterogeneous basin (Río Grande, Jujuy, Argentina)

Abstract

The aim of this work is to evaluate the ecological quality of waters along an environmentally heterogeneous basin, using macroinvertebrate biotic indices (BI). Twelve sampling sites were selected in the Río Grande basin, following an altitudinal gradient across the Puna, Monte and Yungas ecoregions. Sampling was conducted in the dry and rainy seasons, during three consecutive years (2012 to 2014). At each site, physico-chemical parameters were measured and benthic macroinvertebrates were collected. Principal component analysis (PCA) was applied to explore environmental variability in terms of physico-chemical parameters. The water quality of the basin was assessed by means of different biotic indices. Correlation analyses were performed between the biotic indices and the physicochemical parameters. Altitude, NaCl, total dissolved solids (TDS) and electrical conductivity were higher at the Puna and Monte sites, while river discharge, width and depth were higher at the Yungas sites. Biotic indices suggested good water quality. The BMWP (Biomonitoring Working Party) and family richness were the most suitable indices to simultaneously compare the rivers of the different ecoregions. The change in the composition of macroinvertebrate assemblages was observed at an altitude of 1500 m a. s. l., separating arid and humid zones and coinciding with inflection points of conductivity, NaCl and TDS.