Aquatic Sciences Meeting, Albuquerque 2001

SS19 Revisiting Redfield: C:N:P Stoichiometry in Aquatic Ecosystems (Disciplinary Connections)

Date: Tuesday, February 13, 2001, Time: 9:45:00 AM

Location: Acoma/Zuni/Tesuque

Sundareshwar, P, V, Duke University, Durham, USA, pvs@duke.edu

Morris, J, T, University of South Carolina, Columbia, USA, morris@sc.edu

Koepfler, E, , Coastal Carolina University, Conway, USA, eric@coastal.edu

Fornwalt, B, , University of South Carolina, Columbia, USA,

PHOSPHORUS CONTROL OF NITROGEN TRANSFORMATIONS IN COASTAL WETLANDS

Denitrification rate varies widely within and among ecosystems and we do not fully understand the causes or consequences. The influence of phosphorus availability on this pathway and N cycling in general, though recognized, is seldom considered. We measured the rates of biological nitrogen fixation and nitrous oxide production after experimental addition of phosphorus in an oligotrophic salt marsh estuary. Potential rates of denitrification and nitrogen fixation were reduced upon phosphorus enrichment, indicating the existence of a complex coupling between the biogeochemical cycling of these two nutrients. It was also demonstrated that at identical nitrate loads, nitrous oxide production was sensitive to the phosphorus status of heterotrophic bacteria, with higher production occurring under conditions of phosphorus limitation. This supports the Redfield model and implies that denitrification rates in coastal ecosystems will be more sensitive to N-loading rates where heterotrophic bacteria are limited by phosphorus rather than by nitrogen.

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Aquatic Sciences Meeting, Albuquerque 2001

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