Production and decomposition of eelgrass (Zostera marina L.) in saline Lake Grevelingen

During five 28-hours measurements in 1981, the oxygen production and consumption in an eelgrass community in saline Lake Grevelingen were investigated using light plexiglass enclosures. Applying a conversion factor of 0.29 the amount of carbon fixed and the amount of organic carbon mineralized were estimated. Gross and net production were estimated over 24-hours periods. There appeared to be a good correlation between production and insolation on the water surface. For every measurement period the production as a function of light and aboveground eelgrass biomass in the enclosure were calculated. This showed a maximum of 5.10−6 mg C.J.−1 g dry weight−1 in April and minimum of 1.4.10−6 mg C.J.−1 g−1 in August. Using the calculated production coefficients, the insolation and the eelgrass biomass the gross production, net production and consumption during the growing season of 1976 were calculated. Gross production amounted to 340 gC.m−2, and net production came to 130 g C.m−2. Approximately 60 gC.m−2 was respired by the eelgrass plants while the remaining 150 gC.m−2 was consumed or mineralized by other organisms on the sampling spot. Approximately 120 g C.m−2.yr−1 was transported by wind and wave action towards the eastern part of the lake where it became anaerobically degraded. This resulted in the formation of sulfide and methane.