ROLE OF THE ALGA CHLAMYDOMONAS MUNDANA IN ANAEROBIC WASTE STABILIZATION LAGOONS

The alga Chlamydomonas mundana Gerloff appears in great numbers in waste stabilization lagoons of the Mojave Desert during periods of anaerobic operation. The alga perpetuates anaerobiosis, since its feeble photosynthetic oxygen production is not sufficient to compensate for its own oxygen consumption in the presence of acetate. Growth of Chlamydomonas mundana is encouraged by anaerobic conditions that favor acetate production by anaerobic bacteria. Most of the acetate used by the alga is directly assimilated by a photosynthetic mechanism involving photosynthetic production of ATP and reducing power. This process resembles that of photosynthetic bacteria more closely than that of common sewage algae, such as Chlorella and Scenedesmus, which rapidly assimilate carbon dioxide and release oxygen. The possibility that the photometabolism of organic substrates by phytoplankton may be more widespread than the limited environment represented by an anaerobic lagoon is discussed.