Inefficient feeding by Calanus helgolandicus and Temora longicornis on Coscinodiscus wailesii: quantitative estimation using chlorophyll-type pigments and effects on dissolved free amino acids

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Abstract
Inefficient or ''sloppy'' feeding behavior by copepods results in algal cell fragmentation and ingestion of only a fraction of the debris produced. In this work, 2 copepod species, Calanus helgolandicus and Temora longicornis were fed the large diatom Coscindiscus wailesii to investigate this process in the laboratory. Conditions favoring sloppy feeding (large prey size and high food concentration) were used to set the upper limits of such effects. Chlorophyll-type pigments tracked particulate debris production. Influence of food cell breakage upon dissolve free amino acids (DFAA) was also assessed. Serial filtrations following foold and grazer removal after short grazing sessions showed that, for C. helgolandicus and T. longicornis respectively, 26% and 35% of the pigments contained in the cells removed during feeding were recovered as > 0.7 .mu.m particulate debris (most debris were < 10 .mu.m). Debris were composed only of cell fragments as feces were absent due to the short grazing session. DFAA total concentration and extracellular composition were not modified significantly by copepod grazing action, suggesting a rapid and selective uptake of amino acids by bacteria and cells. Analysis of pigments in the experimental specimens indicated low levels (5 to 20%) compared to levels of chlorophyll ingested (estimated on the basis of cell disappearance), suggesting further losses in debris smaller than 0.7 .mu.m or pigment transformations in the copepods.