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AN ECOSYSTEM MODEL OF A RIVER-DOMINATED PACIFIC NORTHWEST ESTUARY: ROLES OF SALT MARSH-, RIVER- AND OCEAN-DERIVED MATERIALS
Citation:
Eldridge, P M., S T. Larned, AND C. L. Folger. AN ECOSYSTEM MODEL OF A RIVER-DOMINATED PACIFIC NORTHWEST ESTUARY: ROLES OF SALT MARSH-, RIVER- AND OCEAN-DERIVED MATERIALS. Presented at American Society of Limnology & Oceanography, Victoria, B.C., Columbia, June 10-14, 2002.
Description:
The Salmon River estuary on the central Oregon coast is river-dominated, with hydraulic residence times ranging from <1 day during winter high flows to a week during low flows. The estuary receives organic matter and nutrients from the river, the coastal ocean, and a bordering salt marsh. Anadromous salmonids migrate through the estuary to natal streams in the Salmon River watershed, and the estuary is an important nursery for juvenile salmonids. We developed an ecosystem model of the estuary that 1) traces the transport and utilization of C and N derived from the salt marsh, ocean, estuary and river; and 2), predicts how changes in nutrient and organic carbon loading to the estuary affects the food web. Biomass, areal coverage, and stable isotope ratios of salt marsh, benthic and water column organisms were determined, and nutrient concentrations, water flow, salinity and temperature were continuously or semi-continuously monitored. The resulting datasets were used to parameterize the ecosystem model. The model was developed using an inverse optimization procedure that combines site-specific data with general ecological and physiological relationships. The study has shown that the Salmon River ecosystem is sensitive to both the amount and location of nutrient inputs with allochthonous nutrients from the ocean, marsh, and river stimulating very different levels of autotrophic and heterotrophic production.