Urban rivers: use of multiple indicators to assess environmental quality.

CALDERON MIRIAN; MARIANA JOFRÉ; PATRICIA GONZALEZ; CÉSAR ALMEIDA

San Luis

Congreso; XXXVII reunión Anual de la Sociedad de Biología de Cuyo; 2019

Sociedad de Biología de Cuyo

The expansion of urban areas is one of the most serious ecological problems the planet is facing today. The assessment of the environmental quality of areas in urban transformation is key for the early detection of the impacts of urbanization. Habitat degradation, the presence of exotic species, and the modification of ecosystem processes at a basin level, in many cases pose greater long-term risks than the entry of pollutants. Hence, it is fundamental to select indicators that may reflect in a more comprehensive way these changes experienced by the streams. The objective of this study was to evaluate the performance of multiple indicators: General Water Quality Index (GQI), physical habitat characteristics (HMA), macroinvertebrate assemblages based metrics, and anuran amphibian community metrics in three urbanized rivers of San Luis. A total of 12 sites were located along an urban gradient in the Trapiche River (TR), Volcan River (VR) and Potrero de los Funes River (PFR). Principal Components Analysis (PCA) was carried out using the following variables: GQI, HMA, macroinvertebrate taxa richness, Ephemeroptera-Plecoptera-Trichoptera richness, a Biotic Index based on macroinvertebrates (BISLS), richness and maximum relative abundance of amphibians. The two first principal components (PC1 and PC2) retained 86.62 % of the variability of the data, according to the eigenvalue-one criterion (variances greater than 1). PC1, which explained 56.79% of the variance, had strong loadings (> 0.8) of HMA, the metrics based on macroinvertebrate assemblages and the BISLS. PC2, explaining 29.83% of the variance, was mainly determined by GQI and amphibian metrics. The sites located upstream of the urban areas in TR and PFR were grouped as sites with high physicochemical and biological quality in terms of macroinvertebrates metrics. On the other hand, sites located in or downstream of the urbanization (TR3, TR4, PFR3, PFR4, and VR4) showed a lower value of the GQI and biotic metrics. Sites on VR showed a singular behavior with a high biological quality indicated by HMA, macroinvertebrate and amphibians metrics; but, with a low physicochemical quality (GQI), that was actually due to the characteristics of the sediments where the river drains. PCA analysis allowed us to identify that macroinvertebrate variables were the best to reflect the physicochemical quality of water and habitat, while amphibians accompanied this trend in a reserved way. However, this differentiation in terms of sensibility and responses of organisms to different stressors is important to assess the effect of multiple impacts that natural environments suffer during the urbanization process. The evaluation of ecological integrity by using multiple indicators is an important tool for managing water resources around the world.