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

CALDERON MIRIAN; CESAR ALMEIDA; MARIANA JOFRE; GONZALEZ PATRICIA

San Luis

Congreso; XXXVII Reunión Científica Anual de la SBCuyo; 2019

The expansion of urban areas is one of the most serious ecological problems the planet is facing today. Habitat degradation, thepresence of exotic species, and the modification of ecosystem processes at a basin level in many cases pose greater long-term risksthan the entry of pollutants. Hence, it is fundamental to select indicators that may reflect in a more comprehensive way these changesexperienced by the streams. The objective of this study was to evaluate the performance of multiple indicators: General WaterQuality Index (WQI), physical habitat characteristics (HMA), macroinvertebrate assemblages based metrics, and anuran amphibiancommunity metrics in three urbanized rivers of San Luis. A total of 12 sites were located along an urban gradient in the TrapicheRiver (TR), Volcan River (VR) and Potrero de los Funes River (PFR). Principal Components Analysis (PCA) was carried out usingthe following variables: WQI, HMA, macroinvertebrate taxa richness, Ephemeroptera-Plecoptera-Trichoptera richness, a BioticIndex based on macroinvertebrates (BISLS), richness and maximum relative abundance of amphibians. The two first principalcomponents (PC1 and PC2) retained 86.62 % of the variability of the data. PC1, which explained 56.79% of the variance, had strongloadings (> 0.8) of HMA, the metrics based on macroinvertebrate assemblages and the IBSSL. PC2, explaining 29.83% of thevariance, was mainly determined by WQI and amphibian metrics. The sites located upstream of the urban areas in TR and PFR weregrouped as sites with high physicochemical and biological quality in terms of macroinvertebrates metrics. On the other hand, siteslocated in or downstream of the urbanization (TR3, TR4, PFR3, PFR4, and VR4) showed a lower value of the WQI and bioticmetrics. Sites on VR showed a singular behavior with a high biological quality indicated by HMA, and macroinvertebrate andamphibians metrics; but, with low WQI values that it was due to the characteristics of the sediments where the river drains. PCAanalysis allowed us to identify that macroinvertebrates metrics were the best to reflect the physicochemical quality of water andhabitat, while amphibians accompanied this trend in a reserved way. However, this differentiation in terms of sensibility andresponses of organisms to different stressors is important to assess the effect of several impacts that natural environments sufferduring the urbanization process. The evaluation of ecological integrity by using multiple indicators is an important tool for managingwater resources around the world.