Influence of water quality and habitat conditions on amphibian community metrics in rivers affected by urban activity

CALDERÓN, MIRIAM R; TELLO, JESICA; GUEVARA, CARLOS; ALMEIDA, CÉSAR; JOFRÉ, MARIANA; GONZÁLEZ, PATRICIA

San Luis

Congreso; VII Congreso Argentino de la Sociedad de Toxicología y Química Ambiental; 2018

SETAC

Anuran amphibians are highly dependent on aquatic ecosystems. Many amphibian species are exhibiting population declines primarily due to habitat destruction and water quality degradation as a result of urban expansion. The objective of this study was to explore the interrelationships between amphibian community metrics and water quality parameters in urban rivers. Twelve sites along three rivers were characterized regarding urbanization level and habitat condition using the calculation of a Habitat Model Affinity (HMA) score. Fifteen water quality parameters were assessed at each site in order to evaluate the degree of water degradation, and also a Simplified Index of Water Quality (SIWQ) and a general Water Quality Index (WQI) were applied. Species richness and relative abundance of amphibians were estimated from visual encounter and calling surveys during summer season between 2009 and 2013. No significative correlation was found between amphibian metrics and water quality indices. Species richness and abundance were correlated significantly (negatively) with phosphate, nitrate and total coliforms, and significantly correlated (positively) with HMA, electrical conductivity and dissolved oxygen. Species richness was also negatively and significantly affected by turbidity. Significantly correlated metrics were used to run a Principal Component Analysis (PCA). The first two principal components retained 78,51 % of the variability of the system (rivers environmental quality data and amphibians metrics), according to the eigenvalue-one criterion (variances greater than 1). PCA showed that sites with higher amphibian community metrics were also the ones with lower nutrient levels and better habitat conditions. The lack of relationship between amphibian metrics and water quality indices was not entirely unexpected since water quality indices often incur in the loss of valuable information about individual variables and their interaction. This study identified important water quality parameters affecting amphibians in rivers with increasing urban impact; and provides information that can be used in the design of strategies to minimize the impacts of urbanization on aquatic biodiversity.