MEASUREMENT OF MEIOFAUNA GRAZING RATES ON MICROPHYTOBENTHOS - IS PRIMARY PRODUCTION A LIMITING FACTOR

Nematode and harpacticoid copepod grazing rates on microphytobenthos were measured in an oyster pond on the French Atlantic coast using a three-compartment model (sediment, microalgae and meiofauna). Undisturbed natural sediments were used in simulated in situ conditions. Total meiofauna grazing pressure (33.94-mu-g C . 10 cm-2 . h-1) slightly exceeded primary production (29.53-mu-g C . 10 cm-2 . h-1). Microbiota-meiofauna interactions (e.g., feeding preference and the assimilation: ingestion ratio) might explain such results and could be an alternative to the meiofaunal food limitation hypothesis. Despite a lower biomass, the grazing rate of nematodes (4.6 x 10(-3) . h-1) was almost twice as high as copepods (2.43 x 10(-3) . h-1). Other food sources are probably involved in C fluxes to meiofauna, particularly in copepod nutrition.