Salinization Enhances Mobilization of Nutrients from Sediments to Streams

Abstract:

Many regions of the U.S. and elsewhere are experiencing increased salinization of freshwater due to the widespread application of road salts. Increased salinization has the potential to release stored nutrients from sediments, decrease biodiversity, and perturb water quality. We conducted laboratory experiments to investigate the potential effects of road salt (NaCl) on nutrient mobilization from sediments to stream water. Sediments and stream water were incubated from 2 urbanizing watersheds of the Chesapeake Bay in the Baltimore-Washington Metropolitan area. Stream sediment was incubated from 11 routinely monitored streams exhibiting a land use gradient within the Baltimore Ecosystem Study Long-Term Ecological Research (BES LTER) site and Anacostia River watershed. Our results indicate that salinization increased the release of soluble reactive phosphorus and total dissolved nitrogen at all sites. The release of dissolved organic carbon and dissolved inorganic carbon varied between sites, and these differential responses may be due to: stream sediment composition, organic matter content, and ambient water quality. The magnitude and frequency of road salt application may be amplified in the near future due to the interactive effects of climate variability and urbanization, and our research suggests this can have water quality and ecological implications for freshwater ecosystems. Further research is necessary to elucidate driving mechanisms of changes in sediment biogeochemical cycles in response to salinization and the temporal response of freshwater ecosystems.