DETERMINATION OF MICROBIAL BIOMASS AND ITS COMMUNITY STRUCTURE FROM THE DISTRIBUTION OF PHOSPHOLIPID ESTER-LINKED FATTY-ACIDS IN SEDIMENTS OF HIROSHIMA BAY AND ITS ADJACENT BAYS

Phospholipid ester-linked fatty acid (PLFA) composition in sediment samples collected from 20 sampling stations of Hiroshima Bay and its adjacent bays are reported. Thirty-one individual fatty acids were identified in the sediments which comprised of saturated, monounsaturated, polyunsaturated and branched fatty acids. A majority of these fatty acids are characteristic of aerobic and anaerobic bacteria especially sulphate-reducing bacteria. PLFA profiles in the sediments varied among the stations indicating the differences in the contributing microbial communities. The calculated biomass also varied from 0·3 × 107 to 2·6 × 107 cells g-1 dry weight sediment. The shift in microbial community structure within the study area is understood from the seven clusters obtained by the similarity analysis of PLFA composition. The results of environmental parameters revealed the existence of both oxic and anoxic conditions in the study area and the PLFA composition in sediments is discussed in relation to these environmental parameters. Low concentrations of polyunsaturated fatty acids (PUFA) determined in sediments, characteristic of microeukaryotes, could be attributed to the existing environmental conditions and pollution in the study area. Small quantities of long chain fatty acids in sediments indicated that the terrestrial input is low. © 1992 Academic Press Limited.