PH AND EH ON ALDABRA ATOLL .1. COMPARISON OF MARINE AND FRESHWATER ENVIRONMENTS

An account is given of the range of pH and Eh in marine and freshwater aquatic sites on one atoll (Aldabra, Indian Ocean). There is a very wide range in values of pH and Eh for both marine and freshwater environments, the range for pH in general being wider in freshwater ones and Eh in marine ones. Photosynthetic microbial communities on lagoon sediments may be arranged in an approximate order of their association with sediments of particular Eh values. These are, from high to low: Scytonema sp., pennate diatoms, Schizothrix sp., Microcoleus chthonoplastes, Hyella balani, purple phototrophic bacteria. © 1979 Dr. W. Junk b. v. Publishers.