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IMPACTS OF NITROGEN LOADING ON SALT MARSH INTEGRITY IN NEW ENGLAND, USA
Citation:
Wigand, C, R A. McKinney, M Chintala, AND P. M. Groffman. IMPACTS OF NITROGEN LOADING ON SALT MARSH INTEGRITY IN NEW ENGLAND, USA. Presented at Estuarine Research Federation Conference, Seattle, WA, September 14-18, 2003.
Description:
Salt marsh habitat integrity is linked with the ability to provide good water quality and high biodiversity. We measured high denitrification enzyme activity (DEA) in ten coastal salt marshes in Narragansett Bay, Rhode Island (seasonal means ranging from 7,476 - 53,494 kg N-1ha-1y-1), which supports the hypothesis that these habitats are important natural buffers between the land and the sea. The findings that the fall DEA in the high marsh significantly increased with watershed nitrogen (N) load, and likewise, that DEA significantly increased in N-amended treatments in a fertilization experiment, suggests that marsh denitrification could represent a responsive negative feedback on N loading to the estuary. The bay-wide survey also suggested that the reduction of plant species richness, the extent and density of Spartina patens, and the increase of tall S. alterniflora, could be a response to elevated N loads due to residential development. Additionally, physical characteristics such as tidal flooding, marsh slope and width also influence plant structure in Narragansett Bay. This field survey supports the hypothesis of competitive displacement of dominant marsh plant species under elevated N. Changes in marsh plant structure could result in a reduction of the available niches for salt marsh biota.