Consumption of picoplankton by the bivalve larvae of Japanese pearl oysterPinctada fucata martensii

We examined grazing on bacteria and algal picoplankton (APP) by the larvae of Pinctada fucata martensii, using fluorescently labeled bacteria (FLB) an d algae (FLA). Ingestion of both FLB and FLA by the larvae indicated that b acteria and APP serve as food sources for the larvae. With natural assembla ges of bacteria and APP, the clearance rates of bacteria by the larvae (70 to 200 mu m) ranged between 0.08 and 0.12 mu l larva(-1) h(-1), and those o f APP between 0.12 and 1.5 mu l larva(-1) h(-1). Grazing pressure on natura l populations of bacteria and APP by the larvae was estimated as < 0.01% d( -1) in Uchiumi Bay, suggesting that these larvae play a minor role in the c onsumption of picoplankton.