Tidal induced regulation of nitrogen fixation activity (C2H4 production) in a Georgia Salt Marsh

Abstract

Nitrogen fixation potential, determined by the acetylene reduction technique, was measured at fourteen sites across a Georgia salt marsh. The transect spanned (1) tall and short Spartina alterniflora, and natural Juncus and Salicornia monocultures and (2) small tidal creek which usually floods over a levee into a short Spartina marsh during high tides. Spring tides usually flood the entire marsh and enter the Juncus zone. Nitrogen fixation potential in the soil was related to sites of daily tidal inundation and not to interstitial salinity. We also artificially altered the salinity in cores from short and tall Spartina zones to investigate whether nitrogen-fixing populations were tolerant to fluctuations in salt concentration. Results indicate that populations in the marsh are diverse and fluctuate monthly with respect to salinity tolerance in Sapelo Island salt marsh soils.