To water oxidation. Acaryochloris ecotypes have been found in marine environments in close association with other oxygenic phototrophs such as Prochloron (associate with colonial ascidians) (3, 5, 10), eukaryotic macroalgae (11, 12), and in a microbial mat in the Salton Sea, a saline and highly eutrophic California lake (13). In each environment, the photosynthetically available radiation is likel