Dynamics of Sediment-Water Interface

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"Benthic-pelagic coupling" is a key aspect of both material cycles and ecology in oligotrophic deep-sea floor environments, However, it remains unclear whether "bentho-pelagic coupling" exists in eutrophic deep-sea environments. Eutrophic deep-sea environments are mainly located along ocean margins. Interdisciplinary research was carried out to understand seasonal carbon cycling in a eutrophic deep-sea environment along the western margin of the Pacific, in Sagami Bay, central Japan. We collected data from surface water samples, satellite photographs, sediment trap moorings and multiple core samplings at the permanent station in the central part of Sagami Bay between 1997 and 1998. Bottom nepheloid layers were also observed through video images, which were recorded at a real-time deep-sea floor observatory off Hatsushima in Sagami Bay.Distinct spring blooms were observed during mid-February through May in 1997. Mass fluxes deposited in sediment traps did not show distinct signals of spring blooms because of the influence of resuspended materials. However, dense clouds of suspended particles were observed only in the spring in benthic nepheloid layer. This phenomena corresponds well to the increase of phytodetrital matters after the spring bloom. A phytodetrital layer started to form on the sediment surface about two weeks after the start of the spring bloom. Chlorophyll-alpha was detected in the top 2 cm of the sediment only during presence of a phytodetritus layer. Protozoan and metazoan meiobenthos increased in densities after phytodetritus deposition. "Benthic-pelagic coupling" was certainly observed even in a eutrophic marginal ocean environment.