No feeding on Phaeocystis sp as solitary cells (post-bloom period) by the copepod Temora longicornis in the coastal waters of the English Channel

A Phaeocystis sp. (Prymnesiophyceae) bloom regularly occurs in April-May in the Eastern English Channel. In the literature, views are divided about the in situ appetence of copepods for this alga. In a study carried out in the coastal waters off the bay of Somme, at the end of the bloom, from 29 of April to 1 of May 1996, HPLC pigment analysis on both gut algal pigments and algal pigments from the water column shows that Temora longicornis adults did not feed on single cells of Phaeocystis sp.. Alternatively, T. longicornis ingested diatoms and the gut content was correlated with the diatom biomass in the water. More, T. longicornis fed selectively on Dinophyceae and Cryptophyceae, which were scarcely present in the food environment. An inverse relationship was found between the concentration of Phaeocystis sp. in seawater and both gut content and abundance of young stages (CI-CIII copepodites) of T. longicornis. These results suggest an unfavourable impact of Phaeocystis sp. post-bloom on both feeding activity and distribution of T. longicornis.