PARENT SESSION
Oral Session # 27: Wetland Ecology II: Amphibians, Chemical Cycling, and Tidal Forests.
Presiding: D Jenkins
Tuesday, August 5. 1:30 PM to 5:00 PM, SITCC Meeting Room 101.
Nutrient controls on oligohaline marsh macrophyte community zonation and production (Plum Island Ecosystem LTER).
Daoust, Robert*,1, Morris, James1, 1 Department of Biological Sciences, Columbia, SC, USA
ABSTRACT- Distinct zonation of marsh macrophyte communities is a prominent feature of estuarine wetlands. These zonal patterns exist along strong gradients of salinity stress which co-occur with ecosystem-wide nutrient limitation of macrophyte production. Past research has explicitly sought to delineate the relative importance of nutrient availability and salinity stress as factors in controlling these zonation patterns. This research, however, has been focused within saltmarshes. Macrophyte community zonation also occurs in upstream, oligohaline marshes but little research has been done in these systems. Macrophyte dynamics within oligohaline marshes is, however, inherently more complex than in downstream systems since nutrient availability varies in response to fluctuations in freshwater discharge and marine inputs. We utilized in situ reciprocal transplants of Typha angustifolia and Spartina patens (two co-occurring dominant macrophytes in an oligohaline New England marsh), nested within a factorial nitrogen and phosphorus fertilization experiment, to elucidate mechanisms which control the zonation patterns observed within oligohaline marshes. Species-specific responses to nutrient additions exist with T. angustifolia responding to phosphorus and S. patens to nitrogen, indicating that both of these nutrients are local determinants of macrophyte production. The reciprocal transplants further show that while both species are able to survive within their neigbouring community, when nutrient availability is manipulated T. angustifolia outperforms S. patens. These results imply that changes in nutrient loading to estuaries will directly affect the distribution and zonation patterns of macrophyte communities within oligohaline marshes. Furthermore, this study indicates that the role of phosphorus in estuarine systems may be more important than has previously been suggested.
Key words: Typha angustifolia, nutrient competition, marsh zonation, Spartina patens