The vertical distribution and grazing activity of copepods was studied during the summer of 1985 throughout the North Sea. In most areas, copepods did not vertically migrate and their vertical distribution followed that of the phytoplankton which was restricted to the upper 20–30
m. This behavior may be a consequence of barely sufficient or limiting food concentrations (about 200 mg·m−3). The diel grazing patterns as a function of variations in phytoplankton are described for the dominant zooplankton species: Calanus finmarchicus, Oithona
similis, Temora longicornis, Pseudocalanus elongatus, Acartia spp., Centropages hamatus, Microsetella spp.
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