Primary production in a shallow water lake with special reference to a reed swamp

Phytoplankton gross primary production (14C method) in the shallow, eutrophic Danish Lake Arresoe in 1973 was 980 g C m-2. Calculated net primary production was near zero. Macrophyte net primary production was measured by harvesting the maximum biomass, and above ground values were between 420 and 1325 g ash free dry wt m-2, while below ground values were between 2480 and 8570 g ash free dry wt m-2. The reed swamps were mapped on aerial photographs, and the composition of the macrophyte vegetation was determined. A comparison of macrophyte vegetation in 1944 and 1972 showed a reduction in species diversity, especially of submerged species. The seasonal variations in physical and chemical data indicated strong eutrophication in Arresoe. (author)