Start Date
3-1-2021 4:30 PM
End Date
3-1-2021 4:40 PM
Abstract
Field surveys show that frogs and salamanders are attracted to urban stormwater ponds, but the relative survival of eggs and tadpoles in these ponds was unknown. This study is the first of its kind to conduct a field-based reciprocal transplant experiment to directly examine the effects of urban stormwater ponds on growth and survival of a sensitive species. We collected red-legged frog eggs from existing populations in Portland and Gresham and transplanted them to outdoor cages in various types of ponds throughout the area. We collected water quality data from each pond throughout the experiment and tracked the growth and survival of the eggs and tadpoles. We found no substantial difference in survival rates among ponds where wild red-legged frogs were breeding. This indicates that eggs and tadpoles raised in urban stormwater ponds did not experience reduced survival, as long as the ponds were places where wild frogs already exist. However, we did find decreased survival in some stormwater ponds where we do not find wild frogs breeding. The elevated mortality appears associated with sediment, dissolved oxygen, and water levels rather than chemical pollutants. This indicates that some stormwater ponds are poor habitat for these frogs, but that wild frogs are generally absent from these sites anyway, so chemical pollutants do not appear to be creating ecological traps for these frogs. This study demonstrates that urban stormwater ponds can provide habitat of similar quality to natural ponds for a species of conservation concern when designs account for habitat needs.
Subjects
Conservation biology, Sustainable development, Water quality
Persistent Identifier
https://archives.pdx.edu/ds/psu/35499
Tadpoles Survive Urban Pollutants and Cages to Show Conservation Value of Altered Landscapes
Field surveys show that frogs and salamanders are attracted to urban stormwater ponds, but the relative survival of eggs and tadpoles in these ponds was unknown. This study is the first of its kind to conduct a field-based reciprocal transplant experiment to directly examine the effects of urban stormwater ponds on growth and survival of a sensitive species. We collected red-legged frog eggs from existing populations in Portland and Gresham and transplanted them to outdoor cages in various types of ponds throughout the area. We collected water quality data from each pond throughout the experiment and tracked the growth and survival of the eggs and tadpoles. We found no substantial difference in survival rates among ponds where wild red-legged frogs were breeding. This indicates that eggs and tadpoles raised in urban stormwater ponds did not experience reduced survival, as long as the ponds were places where wild frogs already exist. However, we did find decreased survival in some stormwater ponds where we do not find wild frogs breeding. The elevated mortality appears associated with sediment, dissolved oxygen, and water levels rather than chemical pollutants. This indicates that some stormwater ponds are poor habitat for these frogs, but that wild frogs are generally absent from these sites anyway, so chemical pollutants do not appear to be creating ecological traps for these frogs. This study demonstrates that urban stormwater ponds can provide habitat of similar quality to natural ponds for a species of conservation concern when designs account for habitat needs.
