The possibility of submerged macrophyte recovery from a propagule bank in the eutrophic Lake Mikolajskie (North Poland)

摘要

Changes in submerged macrophyte communities in the eutrophic Lake Mikolajskie have been studied for the last 40 years. As the recent commissioning of a number of sewage treatment plants within the complex of the Mazurian Great Lakes has led to an improvement in water transparency, it was expected that species composition would start to return to the state present before intensive eutrophication. The role of seed and oospore banks in the reconstruction of submerged macrophytes is analysed on the basisof laboratory experiment. Cores of sediments (9 cm long) were collected from the littoral of Lake Mikolajskie. The cores were divided in 3 cm layers and were incubated under laboratory conditions. Five species of submerged macrophytes were germinated from the propagule banks. The richest in viable propagules was the deepest layer and poorest in active propagules was the shallowest layer of sediment. The recolonization of the littoral zone of Lake Mikolajskie by species, which occurred at a earlier period in the lake's history is possible because viable propagules have persisted in deeper sediments.