Distribution of phototrophic thionic bacteria in the anaerobic and micro-aerophilic strata of mangrove ecosystem of Cochin

Dense population of epipelic photoautotrophic bacteria were found in the surface sediments during April 1984 to October 1984 in the mangrove ecosystem of Cochin. Pigment analysis by Spectrophotometric techniques re:vealed the structure and relative abundance of the populations. Maximum bacterio-chlorophyll ' a ' was encountered in May (1650.6 mg/m-') whereas bacteriochlorophvll ‘c'and 'd' were found to be more during April 1984(1069.2mg/m-' and 510mg/m-° respectively). The bacterial pigments developed in the anoxic cultures in the present investigation showed absorp' tion maximum at 662 nm, therefore it can be classified as ' Chlorobium dilorophyll 660'. The predominant bacteria were identified as members of the genera Chloronema, Chromatium, Begggiatoa, Thiopedia an d Leucothiobacterla. Unidentified brown Chlorobiaceae were present. Maximal development of the population was found during April 1984. The distribution of oxygen, temperature salinity, pH and Eh profiles were determined. Phototrophic sulfur bacteria ranged from 4.2-19.4% of the total anaerobes isolated. The main factors determining the growth of green sulfur bacteria were light and high sulfide concentration whereas the growth of purple sulfur bacteria was mainly controlled by subdued light and low sulfide concentration during the experimental period