Ecosystem-scale rates of primary production within wetland habitats of the northern San Francisco Estuary

Salt marsh restoration is hypothesized to provide shoreline stabilization, increased fish habitat, and organic carbon subsidies for estuarine food webs. Organic carbon comes from diverse primary producers that differ in carbon fixation rates and areal extent within wetland systems. This study was designed to obtain some of the first estimates of the relative contribution of different primary producers to total organic carbon production within open water and tidally flooded wetlands of the northern San Francisco Estuary (SFE). Carbon fixation rates of phytoplankton, microphytobenthos, and low marsh emergent vegetation were measured in two natural and four restoring wetlands in 2004. Areal (m²) rates of carbon fixation were greatest for low marsh vegetation, while phytoplankton and microphytobenthos rates were one and two orders of magnitude lower, respectively. However, when areal production rates were scaled to the amount of habitat available for each primary producer group, the relative importance of each group varied by location. Given that each primary producer group supports a different subset of estuarine consumers, the type of food subsidy desired should influence the amount open water channel, mudflat and low marsh area restored. Large-scale wetland restoration activities should consider the types of primary producers likely to occupy restored habitats when estimating future food web impacts.