Source - sink dynamics of anurans in stormwater basins of New Jersey's coastal plain:

Stormwater basins are a commonly employed Best Management Practice designed to deal with the negative effects of runoff from impervious surfaces. They are ubiquitous in the landscape; yet the effect of these basins on faunal assemblages has not been investigated. Stormwater basins have the potential to influence the breeding distribution of anurans by being sources for some species and sinks for others. This study aims to determine which anuran species benefit from the existence of stormwater basins, which species are negatively impacted, and what local and landscape variables are the best predictors of these effects. Thirty-six permanently ponded stormwater basins in southern New Jersey’s outer coastal plain were monitored in 2008 for the presence of mating adults and anuran larvae by aural surveys, dip-netting and trapping. Interviews, visual encounters, dip-netting, and traps assessed fish presence. Water temperature, conductivity, and pH were measured throughout the growing season. A 100 foot buffer area surrounding the basins was divided into managed and unmanaged grass and woody vegetation as well as impervious surface. Two connectivity metrics, distance to a canopied corridor and percent of undeveloped upland within 500 meters, were analyzed in ArcGIS. Fish were detected in 92% of the basins. Resistance to fish predation distinguished successful species, those with larvae present, from unsuccessful species, those with calling activity but no larval presence. Permanently ponded basins were sources for Bufo woodhousii fowleri, and Rana catesbeiana, and sinks for Pseudacris crucifer crucifer, Hyla versicolor, and Rana clamitans. Connectivity to and availability of terrestrial habitat were significant predictors of how many species mated at the basins. The number of species increased as access to and amount of quality terrestrial habitat increased. This suggests that placement of permanently ponded basins near populations of threatened or endangered amphibians susceptible to fish predation is unadvisable. Additionally, as permanent stormwater ponds are sources for Rana catesbeiana, in areas where bullfrogs are invasive, basins will likely increase propagule pressure.M.S.Includes bibliographical references (p. 41-47)by Kathleen McCarth