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Measuring nutrient flux in Pacific Coast salt marshes using fluctuating water-level chambers
Citation:
White, C., T. H. DEWITT, AND H. A. STECHER, III. Measuring nutrient flux in Pacific Coast salt marshes using fluctuating water-level chambers. Presented at Coastal and Estuarine Research Federation (CERF) Biennial Meeting, Daytona Beach, FL, November 06 - 10, 2011.
Impact/Purpose:
We have identified a method that will help to quantify nutrient flux for multiple tidal wetland habitat types, which when coupled with areal cover of the habitats and estimates of inundation duration, can be used to estimate landscape-level nutrient removal rates.
Description:
Nutrient removal from the water column is an important ecosystem function that contributes to the production of clean water, a final valued ecosystem service of wetlands. However, little data is currently available for nutrient exchange in Pacific Northwest tidal ecosystems. We have identified a method that will help to quantify nutrient flux for multiple tidal wetland habitat types, which when coupled with areal cover of the habitats and estimates of inundation duration, can be used to estimate landscape-level nutrient removal rates. This technique, a modification of the method developed by Chambers (1992), utilizes fluctuating water-level nutrient flux chambers that inundate enclosed patches of marsh habitat with artificial seawater at the same rate and water depth as occur in the surrounding wetland. Water of known nutrient concentration is delivered to the chamber as the incoming tide increases pressure on an external collapsible reservoir and is drawn back out as the tide recedes and reduces pressure. We demonstrate that the hydraulic head pressure created by the incoming and outgoing tide will successfully equilibrate chamber water levels to within about 3 cm of ambient levels and that water losses/gains from the system are minimal, typically less than 0.01% of the initial reservoir volume. Preliminary results from experimental chambers deployed in vegetated low marsh sites of Yaquina Bay, OR in early spring indicate uptake rates of about 5 umol/m2/hr for PO4, 20 for NO2+NO3, and 10 for NH4, though considerable within- and between-site variability exists.