Ingestion, faecal pellet and egg production rates of Calanus helgolandicusfeeding coccolithophorid versus non-coccolithophorid diets

Ingestion rates, faecal pellet and egg production were obtained in laborato ry experiments with females of the copepod Calanus helgolandicus collected from the English Channel in November 1994. Five different algal monoculture s were used as food: Prorocentrum micans (30 mu m ESD), Thalassiosira weiss flogii (13 mu m ESD), Dunaliella tertiolecta (7 mu m ESD), Emiliania huxley i (5 mu m ESD) and Coccolithus pelagicus (14 mu m ESD). Results obtained su ggest the low ingestion efficiency of the copepod when feeding on coccolith ophorids during late autumn-early winter. From the five species offered, on ly the largest non coccolithophorid Prorocentrum micans and Thalassiosira w eissflogii supported efficient feeding and calculated respiratory demand fo r C. helgolandicus. Both coccolithophorids, irrespective of cell size, were ingested at very low rates even when offered at high concentrations (233-4 68 mu g C l(-1)). Besides low ingestion, no egg production was found in the copepods fed with Emiliania huxleyi, although unusual high gross efficienc y (reaching 72%) was obtained in experiments performed with Coccolithus pel agicus. The late seasonal timing of the experiments (November) could explai n the low ingestion and egg production rates. (C) 2000 Elsevier Science B.V . All rights reserved.