Do submersed plants enhance microbial activity in sediment?

The effects of three submersed plant species (Elodea canadensis Mixch., Myr iophyllum alterniflorum L. and Lobelia dortmanna L.) on bacterial activity and microbial biomass in ambient sediment were measured under laboratory co nditions with special reference to organic carbon release through the plant roots. The effect of Lobelia on denitrification potential in sediment was also assessed. Organic carbon was released into the sediment by all the thr ee plant species: of the photosynthetically fixed C-14-carbon, Elodea relea sed 14%, Myriophyllum 4% and Lobelia 2% during the 7-day experiment. Howeve r, regardless of the carbon supply, Elodea and Myriophyllum did neither enh ance the bacterial activity nor the microbial biomass in the sediment, wher eas Lobelia had a positive influence on both the variables, as well as on d enitrification potential within deeper root zone. (C) 2001 Elsevier Science B.V. All rights reserved.