Short-term changes in sedimentary microbial communities from coastal aquaculture areas

In this study, regional and short-term changes in microbial biomass and com munity structure in mariculture and non-mariculture areas were studied usin g phospholipid ester-linked fatty acid (PLFA) analysis. Sediment samples we re collected fortnightly from fish farms of Japanese flounder, and yellowta il, and ambient area (200 m away from these fish culture areas), coastal an d oyster culture areas in Hiroshima Bay. The samples were analyzed for sedi ment parameters, lipid-bound phosphate, and biomarker fatty acids. Microbia l biomass, as indicated by lipid-bound phosphate gradually increased in fis h culture areas while intermittent increases were observed in other areas. Levels of lipid-bound phosphate in sediments were in the following order: o yster<ambient<flounder<coastal<yellowtail. Results of principal component a nalysis of PLFA composition revealed short-term changes in microbial commun ity structure occurring in the study area. Marked changes in the compositio n of microbial communities were observed in fish culture impacted sediments with increased proportions of the group including sulfate reducing bacteri a. In ambient and oyster areas, no such changes in the composition of micro bial groups were evident. Microorganisms in sediments may be subjected to s tress due to the highly reduced condition of the sediments and high levels of acid volatile sulphide.