Abstract
In this study, regional and short-term changes in microbial biomass and community structure in mariculture and non-mariculture areas were studied using phospholipid ester-linked fatty acid (PLFA) analysis. Sediment samples were collected fortnightly from fish farms of Japanese flounder, and yellowtail, and ambient area (200m away from these fish culture areas), coastal and oyster culture areas in Hiroshima Bay. The samples were analyzed for sediment parameters, lipid-bound phosphate, and biomarker fatty acids. Microbial biomass, as indicated by lipid-bound phosphate gradually increased in fish culture areas while intermittent increases were observed in other areas. Levels of lipid-bound phosphate in sediments were in the following order: oyster<ambient<flounder<coastal<yellowtail.Results of principal component analysis of PLFA composition revealed short-term changes in microbial community structure occurring in the study area. Marked changes in the composition of microbial communities were observed in fish culture impacted sediments with increased proportions of the group including sulfate reducing bacteria. In ambient and oyster areas, no such changes in the composition of microbial groups were evident. Microorganisms in sediments may be subjected to stress due to the highly reduced condition of the sediments and high levels of acid volatile sulphide.
