Comparative description of microbial community structure in surface sediments of eutrophic bays

Comparisons of microbial community structure in sediments of eutrophic areas such as Hiroshima Bay, Etauchi Bay, Osaka Bay and Kojima Lake in Japan were undertaken by analysing the phospholipid fatty acid (PLFA) composition in sediments. In addition, the PLFA composition of aerobic bacteria, anaerobic bacteria and sulphate reducing bacteria (SRB) were analysed to assess their contribution to sedimentary lipid. The monounsaturated PLFA and branched PLFA were predominantly present in aerobic bacteria, and anaerobic bacteria and SRB, respectively. The PLFA composition of sediments showed significant regional differences among the four study areas, indicating the significant difference in microbial community structure. The aerobic prokaryotes and eukaryotes were predominantly present in all the study areas except in Osaka Bay where the gram-positive bacteria and anaerobic bacteria were predominant. The characteristic PLFA of aerobic prokaryotes and eukaryotes were significantly higher in Kojima Lake than other areas whereas the biomarker PLFA of gram-positive bacteria were predominantly present in Osaka Bay than that in other areas. These significant variations in microbial community structure can be attributed to the differences in environmental perturbation.