Relation between tide and phytopigment, suspended solid concentration of Manila clam, Ruditapes philippinarum, farming ground

Phytopigment and suspended solid concentrations in bottom seawater with tid al rhythm at estuary of a Manila clam Ruditapes philippinarum farming groun d were investigated. Chlorophyll a in the bottom seawater increased at floo d and high tide, and decreased at ebb and low tide. Fine particles in the b ottom seawater had a high ratio of chlorophyll a and phaeo-pigments. Chloro phyll a in the sediment flux increased from flood to high tide, and decreas ed from ebb to low tide. Fine particles in the sediment flux had a high rat io of chlorophyll a and phaeo-pigments. These results suggest that phytopla nkton and sediment are supplied mainly from offshore to the estuary with th e tide during flood to high tide periods. Phytopigment contents in tile digestive diverticula of Manila clams increas ed rapidly from flood to high tide. These results indicate that algal diet of Manila clam may be supplied mostly during the flood to high tide period and Manila clam actively digest algal diets during these periods.