HYDROGEN and OXYGEN PHOTOPRODUCTION BY MARINE ALGAE*

The first measurements of the simultaneous photoproduction of hydrogen and oxygen in marine green algae are reported. Eight species in the genera Chlamydomonas, Chlorella and Halochlorocococcum were tested in CO2‐free seawater. Four of the five species of Chlamydomonas were able to produce hydrogen in the light after a period of 3 ‐ 4 h of dark anaerobic adaptation. Only one of the two Chlorella species tested was able to photoproduce hydrogen, in trace amounts. Halochlorocococcum fla–9 gave positive results and Chlamydomonas species (clone f‐9) had a steady‐state rate of hydrogen and oxygen production during irradiation with a stoichiometric ratio near 2:1. The integrated yields of hydrogen and oxygen produced by this species corresponds to about 450 turnovers of the photochemical reaction centers. This number exceeds (by about a factor of 20) the electron‐carrying capacity of the electron transport chain linking Photosystems I and II. These data suggest that Chlamydomonas f‐9 makes seawater a potential substrate for solar hydrogen and oxygen production.