MEPS 253:209-216 (2003)  -  doi:10.3354/meps253209

ABSTRACT: Nanoplankton (2 to 20 µm) are a substantial fraction of the plankton in the sea, where they form a potential food source for zooplankton. Monocultures of 12 nanoplankton taxa of different cell size and 1 species of Thalassiosira (microplankton) were offered to Nyctiphanes australis to determine whether they would be consumed and, if so, determine rates of clearance and ingestion by the euphausiid. N. australis ingested very small cells (3.5 to 5.4 µm equivalent spherical diameter) at rates ≤5 x 10⁵ cells h^-1. A total of 8 nanoplankton taxa were consumed at rates that provided N. australis with its minimum food requirement of 2% body carbon d^-1, and so could maintain it when microplankton abundance is low. Our results suggest that N. australis can detect and avoid unpalatable food such as the chlorophytes Dunaliella and Nannochloris, but is susceptible to the toxic dinoflagellate Alexandrium minutum.

KEY WORDS: Zooplankton · Nanoplankton · Ingestion rate