GROWTH OF BLUE-GREEN-ALGAE IN THE MANUKAU (NEW-ZEALAND) OXIDATION PONDS .2. EXPERIMENTAL STUDIES ON ALGAL INTERACTION

An experimental approach was made to the interaction between the blue-green algae Anahaena and Microcystis and the normal oxidation pond dominant Chlorella. Methods employed were dialysis tubing, mixed culture with assay by in vivo absorbance, and by interaction tubes in which the algae were separated by a filter membrane. No dialysable inhibitor material in the oxidation ponds was detected with in situ experiments. In mixed culture Chlorella inhibits Anabaena only when starting concentration of Chlorella is high and that of Anabaena is low. On the other hand at all concentrations Anabaena quickly dominated Chlorella. These results were confirmed in interaction tubes where the algae were separated and the results extended to show Microcystis also inhibits Chlorella growth. Filtrate experiments indicate that both Microcystis and Anabaena produce a filterable substance capable of suppressing Chlorella growth but that Chlorella does not exert any influence on blue-green algae by way of soluble materials. © 1979.