Zooplankton feeding ecology: Grazing on phytoplankton and predation on protozoans by copepod and barnacle nauplii in Disko Bay, West Greenland

Abstract

Grazing experiments were conducted with Calanus spp. and Balanus cf. crenatus nauplii incubated with natural plankton from Disko Bay, West Greenland during the post-spring-bloom period. Both copepod and barnacle nauplii were feeding on different types of protists although at different rates. Calanus spp. nauplii preferred large ciliates and dinoflagellates whereas flagellates ∼5 pm in diameter and Myrionecta rubra were hardly ingested at all. B. cf. crenatus nauplii preferred diatoms and also consumed the small flagellates at relatively high rates. Compared to Calanus spp. nauplii, B. cf. crenatus nauplii ingested ciliates and dinoflagellates at low rates suggesting a more herbivorous feeding mode than the more predaceous copepod nauplii. The daily grazing impact of the nauplii community in Disko Bay was estimated using the weight-specific mean clearances from the grazing experiments and field biomass values of different categories of prey and nauplii. These calculations showed that the grazing impact by the nauplii community on all prey categories was generally modest (1.3 to 9.2 %). However, the dominant part of the total food intake by Calanus spp. nauplii in the surface water was composed of ciliates and dinofiagellates, most of which were phagotrophic.