Denitrification Enzyme Activity of Fringe Salt Marshes in New England (USA)

Abstract

Coastal salt marshes are a buffer between the uplands and adjacent coastal waters in New England (USA). With increasing N loads from developed watersheds, salt marshes could play an important role in the water quality maintenance of coastal waters. In this study we examined seasonal relationships between denitrification enzyme activity (DEA) in salt marshes of Narragansett Bay, Rhode Island, and watershed N loadings, land use, and terrestrial hydric soils. In a manipulative experiment, the effect of nutrient enrichment on DEA was examined in a saltmeadow cordgrass [Spartina patens (Aiton) Muhl.] marsh. In the high marsh, DEA significantly (p < 0.05) increased with watershed N loadings and decreased with the percent of hydric soils in a 200-m terrestrial buffer. In the low marsh, we found no significant relationships between DEA and watershed N loadings, residential land development, or terrestrial hydric soils. In the manipulation experiment, we measured increased DEA in N-amended treatments, but no effect in the P-amended treatments. The positive relationships between N loading and high marsh DEA support the hypothesis that salt marshes may be important buffers between the terrestrial landscape and estuaries, preventing the movement of land-derived N into coastal waters. The negative relationships between marsh DEA and the percent of hydric soils in the adjacent watershed illustrate the importance of natural buffers within the terrestrial landscape. Denitrification enzyme activity appears to be a useful index for comparing relative N exposure and the potential denitrification activity of coastal salt marshes.

Effect of nutrient loading on biogeochemical and microbial processes in a New England salt marsh

“…Although denitriWcation rates measured in intact cores showed no fertilization eVects, denitriWcation enzyme activity measured in soil slurries from these same plots in June in a concurrent study showed signiWcantly elevated rates in the N treatments (Wigand et al 2004b). This suggests that with suYcient nitrate and labile organic matter, added nitrogen enhances denitriWcation rates.…”

An integrated approach to assess broad-scale condition of coastal wetlands—the Gulf of Mexico Coastal Wetlands pilot survey

“…Laboratory methodologies for the analysis of sediment and pore water samples are described in detail in Heitmuller (2007). Other samples and measurements, including surface water salinity, conductivity, temperature, and pH and leave tissue samples for plant C:N:P and stable N isotope ratios (Wigand et al 2004), are collected within the Tier 2 AA.…”

No-net-loss not met for nutrient function in freshwater marshes: recommendations for wetland mitigation policies

“…Amendment rates were 0.64 mgÁg À1 for C, 0.19 mgÁg À1 for N and 0.019 mgÁg À1 for P, based on fertilization levels in similar published experiments (Groffman et al 1996, Hunter and Faulkner 2001, Allen and Schlesinger 2004, Wigand et al 2004) and a molar C:N:P ratio of 46:7:1 for bacteria (Reiners 1986). One subset was incubated for 4 d and analyzed for CO 2 and CH 4 (GC-14 Gas Chromatograph, Shimadzu Scientific Instruments); another subset was incubated for 2 h and analyzed for N 2 O (GC-14 Gas Chromatograph, Shimadzu Scientific Instruments).…”