FIELD OBSERVATIONS OF THE TRANSPORT OF PHYTOPLANKTONS IN THE DEEP AREA OF HAKATA BAY

The concentrations of chlorophyll-a and the tidal current velocities have been measured in the head of Hakata Bay over the one tidal period under the phase that the times of the high tide and the meridian passage are about 12 o'clock. It is hyper-eutrophic sea area enclosed by the man-made island and faces to Wajiro intertidal sand-flat. The concentration of Chl.a on the tidal flat increases in the onshore direction during the high tide because of the production of phytoplanktons and the suspension of benthic microalgal, and decreases in the same direction during the ebb tide because of their settlement. The spatial distributions of the Chl. a-concentration in the sea area have been compared in the flood tide and ebb tide periods. The primary production increases uniformly the Chl.a-concentration over the whole sea area, but the difference at the edge of the tidal flat is very small. The obtained results suggest that a large amount of phytoplanktons settle down on the tidal flat or taken by benthos.