Production ecology of eelgrass (Zostera marina L.) in a cape cod salt marsh-estuarine system, Massachusetts

Primary production and biomass loss of Zostera marina L. were estimated at two sites within the Nauset Marsh system, Cape Cod, Massachusetts. Maximum live leaf-blade biomass at the Nauset Harbor (305 g dry weight (DW) m^-2) and Town Cove (199 g DW m^-2) sites peaked in mid-August. Maximum leaf-blade productivities, estimated by a leaf-marking technique, were 10.8 g DW m^-2 day^-1 and 5.5 g DW m^-2 day^-1, respectively. Leaf-blade production occurred throughout winter, but at much reduced rates (<0.2 g DW m^-2 day^-1, both sites). Net annual aboveground (leaf blades, reproductive shoots, sheaths) primary production was estimated at 987 g DW m^-2 year^-1 and 444 g DW m^-2 year^-1, respectively. Peak rates of leaf-blade biomass loss occurred in early September (Nauset Harbor, 8.5 g DW m^-2 day^-1; Town Cove, 4.7 g DW m^-2 day^-1), corresponding to a period of high eelgrass-wrack accumulation on New England shorelines. Annual leaf-blade biomass loss was 577 g DW m^-2 year^-1 and 303 g DW m^-2 year^-1, respectively. These loss rates, coupled with leaf-crop turnover rates of 6 crops year^-1, stress the role of eelgrass meadows in the support of estuarine detritus-based food webs.