MEPS 256:301-304 (2003)  -  doi:10.3354/meps256301

Grazing of Calanus helgolandicus on Dinophysis norvegica during bloom conditions in the North Sea: evidence from investigations of faecal pellets

C. Wexels Riser1,*, S. Jansen2, U. Bathmann2 , P. Wassmann1

1Norwegian College of Fishery Science, University of Tromsø, 9037 Tromsø, Norway
2Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany

ABSTRACT: Toxic dinoflagellate blooms are a common phenomenon in the North Sea, but the fate of the toxins in the food web is largely unknown. Herbivorous copepods may play a key role in the transport of toxins through the food web, but it is still uncertain to what extent toxic algae are grazed. The present experiment was carried out during an autumn bloom of Dinophysis norvegica in the North Sea, to study whether Calanus helgolandicus feed on Dinophysis spp. under natural conditions. The experiment showed that C. helgolandicus fed very efficiently on D. norvegica at high algal concentrations (>9000 cells l-1), as 98% of the faecal pellets (FP) produced contained Dinophysis spp. cells (up to 32 cells FP-1). Therefore, C. helgolandicus feeds on D. norvegica under natural conditions, and its FP may be an important vehicle transferring toxins within the pelagic and to the benthic community.

KEY WORDS: Zooplankton · Dinophysis spp. · Calanus helgolandicus · Grazing · Faecal pellet

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