EFFECTS OF FILAMENTOUS ALGAE ON SUBMERGED MACROPHYTE GROWTH - A LABORATORY EXPERIMENT

Elodea canadensis Michx. and Potamogeton pectinatus L. were cultivated in the laboratory in the presence and absence of filamentous algae (Cladophora glomerata (L.) Kutz.) for 20 or 30 days. In treatments without algae, macrophyte biomass increased in all cases (from 17 to 76% of initial fresh weight). In the presence of algae, Elodea lost weight (35-57% of initial weight), no significant differences in biomass were observed in the case of Potamogeton. Algae decreased growth of new shoots and accelerated decay of old shoots. Chlorophyll a was significantly lower in macrophytes growing with algae than in plants grown alone.