PARENT SESSION
PS6 - Contaminant Effects on Amphibians & Reptiles
Sunday, 17 November 2002
8:00 AM to 6:30 PM
Exhibit Hall

(P083) Nitrate concentrations of stormwater retention basins in Maryland.

Massal, Laura^*,1, Casey, Ryan¹, Snodgrass, Joel¹, ¹ Towson University, Towson, MD, USA

ABSTRACT- Alteration of the landscape due to urbanization often includes the addition of stormwater retention basins to alleviate the impact of increased runoff on receiving streams. The quality of habitat these basins provide for aquatic and semi-aquatic organisms is still relatively unclear. One concern is the exposure of wildlife to toxicants that are trapped in basins. Due to reported effects of nitrate on amphibians, we chose to assess potential toxic effects of nitrate on resident amphibian populations. Each of the 11 basins in this study contained between 1-6 amphibian species. We collected water samples from basins in Owings Mills, Maryland, a developing suburb of Baltimore, during non-storm event periods (11 basins) and following storm events (3 basins). Nitrate was quantified using ion chromatography. Of all the seasonal samples, 67% were <0.05 mg/L NO₃-N. Of the remaining 33%, mean seasonal nitrate concentrations ranged from 2.0 mg/L NO₃-N in the summer to 2.7 mg/L NO₃-N in the spring, however there was no significant difference among seasons. Following storm events, nitrate levels varied both spatially and temporally within each basin. In basins with higher levels of nitrate immediately following storm events, there was a decline in nitrate levels with time. However, in basins in which the nitrate level was low immediately following a storm, there was often no decline in nitrate levels. When considered individually, some basins consistently had nitrate concentrations that exceed the lowest concentration known to induce sublethal effects in amphibians.

Key words: amphibians, nitrate, stormwater, urbanization