B ased on short-term sampling collection in the neritic waters off Alexandria (Egypt), diatoms contributed recurrent intensive occurrence most of the time, while the microflagellates Micromonas and Pyramimonas species appeared in the transient periods (October and May). Zooplankton exhibited several peaks in early and late September, mid-January and early August, mainly copepods and protozoan species. Phylo-zooplankton abundance was affected by mxUti-factorial control with temperature and

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... ty being the majors, and nitrate at some time. Zooplankton grazing has been postulated to play at times an effective role in regulating the phytoplankton cycle, and inflects losses on its numerical standing crop. Yet, their large continuous seasonal variations had strongly influenced the phyto-zooplankton relationship. Subsequently, different patterns could be distinguished; top-bottom (inverse) relationship at intermittent periods when diatoms dominated; reduced grazing pressure connected with specific diatom species (Asterionellci glacial b\ Chaeioceros spp., Rhizosoleriia delicaiula)\ and/or with mixed community of diatom, dinoflagellate and euglenophyte species; inability of grazing to control blooms of the fast-growing diatoms (Cy/indrofheca closleriunu Thalassiosira spp.), and that of microflagellates of monospecific nature {Pyramimonas spp.); positive increasing relationship with small-sized cells {Skeletonema costatum, Thalassiosira spp.);and a time lag (massive zooplankton occurrence followed that of phytoplankton within a week during August and September). Zooplankton grazing pressure could help the change in phytoplankton dominance and composition (the possible avoidance of zooplankton consumers to take up the non-diatom, cells as long as the smaller 60 Wagdy Labib producers T. subtilis.. T. pseudonana and S. costaium were present, offering some advantage to non-diatom species to dominate).