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NUTRIENT LOADING EFFECTS ON BIOGEOCHEMICAL AND MICROBIAL PROCESSES IN A NEW ENGLAND HIGH SALT MARCH (SPARTINA PATENS)
Citation:
Caffrey, M C. Murrell, C Wigand, AND R A. McKinney. NUTRIENT LOADING EFFECTS ON BIOGEOCHEMICAL AND MICROBIAL PROCESSES IN A NEW ENGLAND HIGH SALT MARCH (SPARTINA PATENS). Presented at Estuarine Research Federation Conference, Seattle, WA, Sep 14-18, 2003.
Description:
An ever-increasing population in the coastal zone has led to increased nutrient loading to estuaries worldwide. Marshes represent an important transitional zone between uplands and estuaries and can intercept nutrient inputs from uplands. We examined the effects of N and P fertilization on biogeochemical and microbial processes during the summer growing season in a Spartina patens marsh located in the National Estuarine Research Reserve on Prudence Island (RI). Quadruplicate 1 m2 plots were fertilized with N and P additions, N only, P only or no additions. Fertilizer had been regularly applied at a rate of 1 gN m-2 wk-1 and 0.1 gP m-2 wk-1 for about 2 years. Denitrification potentials were significantly enhanced in the N-amended over P-amended or unamended treatments. Sediment oxygen consumption and actual denitrification measured in intact cores were higher in the N+P treatment although denitrification was not statistically significant due to core-to-core variation. Most of the denitrification occurring in sediments was coupled to nitrification because overlying water NOx concentrations were low (<5 uM). P fertilization led to a DIP release from sediments while no additions or N-only treatments had significant P uptake. Fertilization treatments had no noticeable effect on bacterial production, mycorrhizal infection, NH4+, or NOx fluxes. Heterogeneity in the availability of nitrate and organics as well as the oxidation-reduction status of the sediments may mask fertilization effects on some microbial processes.