COMPETITION AND COEXISTENCE IN SUBMERGED AQUATIC PLANT-COMMUNITIES - THE EFFECTS OF SPECIES INTERACTIONS VERSUS ABIOTIC FACTORS

SUMMARY. 1. Aquatic plant biomass and species composition were studied at three sites in Long Lake, Alberta, Canada, to examine the role of biotic and abiotic factors in determining species diversity. 2. Results of controlled in situ experiments to test for interspecific competition showed that biomass of plants in four different mixed communities did not increase in response to selected species removals (P>0.1,n=16). 3. In contrast, biomass of the dominant taxa (Myriophyllum exalbescens, Ceratophyllum demersum and Chara sp.) were correlated (P<0.05) with abiotic factors (i.e. distance from shore, water depth, sediment exchangeable phosphorus concentration and/or sediment organic content). 4. These results suggest that interspecific competition between naturally coexisting species of submerged aquatic plants is slight and that spatial heterogeneity or differential utilization of abiotic resources promotes species diversity in submerged plant communities. Copyright © 1990, Wiley Blackwell. All rights reserved