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LINKING HABITAT CHANGE AND NUTRIENT DYNAMICS: COMPARISON OF FOOD WEBS AND NITROGEN FLUXES IN BURROWING SHRIMP- AND OYSTER-DOMINATED HABITATS
Citation:
DeWitt, T H. AND P M. Eldridge. LINKING HABITAT CHANGE AND NUTRIENT DYNAMICS: COMPARISON OF FOOD WEBS AND NITROGEN FLUXES IN BURROWING SHRIMP- AND OYSTER-DOMINATED HABITATS. Presented at Benthic Ecology Meetings, Orlando, FL, March 21-24, 2002.
Description:
Endemic thalassinid burrowing shrimps are simultaneously dominant ecosystem engineering species and economic pests within Pacific estuaries. Dense populations of two shrimps (Neotrypaea californiensis and Upogebia pugettensis) commonly occupy >75% of intertidal and shallow subtidal tideflats. As a result of their burrowing, feeding, and burrow-irrigation, the shrimps modify the physical, chemical, and biotic structure of benthic habitats and aspects of overlying waters. These activities bring burrowing shrimp into conflict with oyster culture (Crassostrea gigas) because sediment excavated by the shrimps buries or smothers the oysters, and U. pugettensis may compete with C. gigas for food. Pesticide used to control burrowing shrimp on commercial oyster beds in Washington state creates a patchwork of shrimp-dominated and oyster-dominated habitats. Many impacts of pesticide and oyster culture on estuarine fauna have been characterized, but impacts to ecosystem functions have not been investigated. We used inverse-analysis-based food web models to examine how Upogebia- or oyster-dominated tideflats affect the flux of nitrogen between the tideflat and overlying water column. The food web models were parameterized using new and existing data on community structure, physiology, and feeding ecology of species found on un-farmed tideflats dominated by U. pugettensis and on commercial oyster beds. Separate food web models were constructed for four scenarios: Upogebia-dominated tideflats, and oyster beds sprayed with pesticide 1, 12, and 36-48 months before sampling. Two predictions generated by these models are that 1) Upogebia-dominated tideflats may have greater fluxes of nitrogen between the benthos and water column than oyster-dominated tideflats, and 2) Upogebia-dominated tideflats may sustain greater rates of in-situ primary production than oyster-dominated tideflats because of greater nutrient recycling.