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

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 examine combined effects of habitat degradation and water quality on amphibian assemblages in rivers affected by urban impacts. Twelve sites along three rivers were characterized in regard to urbanization and habitat condition using the calculation of a Habitat Model Affinity (HMA) score. Fifteen water quality parameters were assessed at each site. 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. Species richness and abundance were negatively correlated with phosphate, nitrate concentrations and total coliforms, and positively correlated with HMA, electrical conductivity and dissolved oxygen. Species richness was also affected negatively by turbidity. Principal component analysis showed that sites with higher amphibian community metrics were also the ones with lower nutrient levels and better habitat conditions. 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.