To investigate environmental factors affecting the species composition of benthic diatoms, surveys of the surface sediment and overlying water were conducted at three intertidal flats in Tokyo Bay: Marine Park, Edogawa, and Kasai. Species were identified by light microscopy and classified into two growth form types: gliding and adhesive. In total, 67 taxa were identified. Seasonal variations of dominant growth forms differed between the intertidal flats; dominant species were Catenula adhaerens, Cocconeis sp. 1, and Fallacia sp. (adhesive type) on the Marine Park; Fallacia forcipata (gliding type) on the Edogawa; and Amphora copulata, A. laevissima (adhesive type), Gyrosigma fasciola, and Navicula cf. mollis (gliding type) on the Kasai. Cluster analysis based on the similarity of major species differentiated the three sites, while the Kasai cluster was further subdivided by season. Redundancy analysis revealed that (1) the correlative environmental factors differed between growth forms and only the gliding type was positively related to mud content, and (2) diatom species composition on the Kasai was related to salinity. These results indicate that tide and wave disturbance and also salinity strongly affect benthic diatom species composition in Tokyo Bay.

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Clogging of water intake pipes by sessile bivalves is a serious problem hindering the safe operation of industrial and power plants. We developed a system to monitor such clogging by means of an acoustic emission (AE) technique. A sheet-type optical fiber sensor developed in our laboratory was used to monitor AE signals produced by single individuals or colonies of mussel Mytilus galloprovincialis attached by their byssus inside a PMMA pipe. No relation was found between mussel size and peak frequency of AE signal; However, the mussels each had a characteristics frequency, and the scattering of AE signals frequencies corresponded to the number of mussels in a colony. In addition, the AE signal generation rate increased with increasing numbers of mussels in the pipe, but continuous monitoring showed that the signal genera- tion rate also increased when mussels were removed. Continuous monitoring is thus needed if pipe clogging is to be monitored effectively by this AE technique.

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