April Doroski

M.S. Candidate, University of Connecticut

Conference Travel Grant Type 2 (Society of Wetland Scientists)

Effects of salinity and metals on denitrification across coastal wetlands in urban landscapes

“Coastal wetlands are located at a vulnerable interface experiencing both landward pressures of contaminated runoff and seaward pressures of saltwater intrusion. These anthropogenic stressors may threaten the capacity of wetlands to remove pollutants, such as excess nutrients and metals. We examined the effects of salinity, organic matter, and metal concentrations on potential denitrification rates in 36 tidal wetlands on the coast of the Long Island Sound. Soil cores were collected in June 2015 from saltwater, brackish, and freshwater tidal wetlands and analyzed 0-5 cm (top soil layer) and 5-10 cm (bottom soil layer) depth intervals. Results of a multiple linear regression model selection for potential denitrification rates in the top soil layer include soil organic matter, salinity, zinc, and lead in the best fit model (AIC =41.89 ; r2 =0.36 ; p<0.05). Potential denitrification rates were positively related to organic matter and zinc, and negatively related to salinity and lead. Results of a multiple linear regression model selection for potential denitrification rates in the bottom layer include manganese and zinc in the best fit model (AIC =43.69; r2 =0.33 ; p<0.05). Potential denitrification rates were positively related to manganese and negatively related to zinc. Our results suggest a potential suppression of denitrification with elevated salinity, particularly for soils at the oxic-anoxic interface, and also suggest that there may be a coupling of manganese and nitrogen cycling in deeper anoxic soils. Although some common urban metal contaminants were present in best fit models (i.e., zinc, lead), the results were not consistent for the two depth intervals. It is essential to understand the mechanisms controlling the complex interactions of physiochemical properties on ecosystem function of wetlands in order to properly manage or mitigate potential effects of saltwater intrusion on wetlands in urban areas. ”