Measurement of meiofauna grazing rates on microphytobenthos: is primary production a limiting factor?

Abstract

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 μg C·10 cm −2·h −1) slightly exceeded primary production (29.53 μg 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 × 10 −3 · h −1) was almost twice as high as copepods (2.42 × 10 −3 · h −1). Other food sources are probably involved in C fluxes to meiofauna, particularly in copepod nutrition.