Do submersed plants enhance microbial activity in sediment?

The effects of three submersed plant species (Elodea canadensis Mixch., Myriophyllum alterniflorum L. and Lobelia dortmanna L.) on bacterial activity and microbial biomass in ambient sediment were measured under laboratory conditions 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 three plant species: of the photosynthetically fixed C-14-carbon, Elodea released 14%, Myriophyllum 4% and Lobelia 2% during the 7-day experiment. However, regardless of the carbon supply, Elodea and Myriophyllum did neither enhance the bacterial activity nor the microbial biomass in the sediment, whereas Lobelia had a positive influence on both the variables, as well as on denitrification potential within deeper root zone. (C) 2001 Elsevier Science B.V. All rights reserved.