Ecosystem metabolism in a temporary Mediterranean marsh (Doñana National Park, SW Spain)

The metabolic balance of the open waters supporting submerged macrophytes of the Doñana marsh (SW Spain) was investigated in spring, when community production is highest. The marsh community (benthic + pelagic) was net autotrophic with net community production rates averaging 0.61 g C m -2 d-1, and gross production rates exceeding community respiration rates by, on average, 43%. Net community production increased greatly with increasing irradiance, with the threshold irradiance for communities to become net autotrophic ranging from 42 to 255 μE m -2 s-1, with net heterotrophic at lower irradiance. Examination of the contributions of the benthic and the pelagic compartments showed the pelagic compartment to be strongly heterotrophic (average P/R ratio Combining double low line 0.27), indicating that the metabolism of the pelagic compartment is highly subsidised by excess organic carbon produced in the strongly autotrophic benthic compartment (average P/R Combining double low line 1.58).This work was funded by a grant from the Spanish Ministry of Education and Researc. OGH and KSJ were supported by funds allocated from the Danish Natural Science Research council, and PG by Tour du Valat Foundation