LABORATORY STUDIES ON THE INFLUENCE OF LIVING AND DECOMPOSING FILAMENTOUS ALGAE ON THE GROWTH OF ELODEA-CANADENSIS MICHX

Elodea canadensis was cultivated in the laboratory in presence and abs ence of living and decomposing littoral filamentous algae (Cladophora glomerata) for 14 days. In treatment without algae no significant diff erences in biomass were observed in all cases. In presence of living a lgae, biomass of Elodea increased (19%) or no significant differences were observed. Decomposing algae at 20% loss of initial weight did not changed significantly the biomass of Elodea whereas the presence of d ecomposing algae at 50% loss of initial weight resulted in significant increase of biomass (27%). The effect of decomposing algae also depen ds on algae-macrophyte ratio. Twice and four times as high algae bioma ss with unfiltrated water medium may strongly reduce the biomass of El odea (44%, 37%). Addition of filtered (Whatman GF/C) water medium sepa rated from decomposing algae resulted in an increase of Elodea biomass (30%).