No abstract

SUMMARY To elucidate cause and effect relationships operating within cyanophycean water blooms, preliminary laboratory and field studies were made to discern physiologically active metabolites affecting the growth of various algal species in 3 ponds of different nutritional types. Blue‐green algal blooms in Missouri ponds were composed of relatively few species. Microcystis aeruginosa, the most prevalent species, was a major constituent of most of the blooms in which it occurred. Dense cyanophycean blooms occurred only in ponds having a high organic content. Growth inhibitors apparently were produced by blue‐green algae in nature as well as in the laboratory. The results suggest that these active metabolites may be important in controlling species succession and species dominance within a given phytoplankton population.