Sensitivity of Embryos of Southern Appalachian Amphibians to Ambient Solar UV‐B Radiation

Abstract

Abstract: Studies suggest that increased ground‐level UV‐B radiation due to stratospheric ozone depletion is adversely affecting many aquatic organisms. In particular, ambient UV‐B radiation can kill or deform amphibian embryos and may be contributing to global amphibian declines. Sensitivity tests have been conducted primarily at northern latitudes (>42° N), where ozone thinning is most prevalent. Studies in southern California and Spain, however, suggest that some amphibians are vulnerable to ambient UV‐B at these lower latitudes. We tested the sensitivity of pond‐breeding amphibians to UV‐B radiation in the southern Appalachian Mountains (35° N; 660 m) of the United States, where stratospheric ozone has declined during the last two decades. We exposed eggs of frogs ( Hyla chrysoscelis, Pseudacris triseriata, Rana sylvatica) and a salamander (Ambystoma maculatum) to three treatments under field conditions that provided maximum exposure to solar radiation: (1) a polycarbonate filter that blocks> 98% of UV‐B (2) an acrylic filter that transmits 80% of UV‐B, and (3) unfiltered sunlight. Survivorship to hatching ( grand mean = 91%) and the percentage of embryos deformed ( grand mean = 4.4%) did not differ significantly among treatments for any species, but differences in the percentage of embryos deformed approached statistical significance for Hyla (p = 0.06) and Pseudacris (p = 0.10). More refined analyses using orthogonal contrasts revealed that deformity rates for both species were significantly lower in embryos that were shielded from UV‐B than in unshielded controls. A pooled analysis of all anurans also indicated that deformity rates were higher in treatments with UV‐B transmitting plates than in those with blocking plates. Collectively, our data suggest that pond‐breeding amphibians in the southern Appalachians currently incur only slight risk from exposure to ambient UV‐B radiation. If ground‐level radiation increases in the future, the risk for certain species could increase significantly.