MESOZOOPLANKTON DISTRIBUTION FROM SICILY TO CYPRUS (EASTERN MEDITERRANEAN) .1. GENERAL-ASPECTS

The first synoptic basin-wide oceanographic survey in the Eastern Medi terranean Sea was carried out in October-November 1991 within the fram ework of the international programme POEM-BC (Physical Oceanography of the Eastern Mediterranean - Biology, Chemistry). Mesozooplankton samp les were collected at 32 stations in the Sicily Channel, Ionian Sea, C retan Sea, Cretan Passage, Rhodes area and central Levantine Sea. Vert ical hauls were taken from four discrete depth layers in the upper 300 m water column. The gross features of the mesozooplankton communities , at the phyla, class or order level, are described. Depth-integrated abundances showed high homogeneity within each region, with the highes t and lowest values recorded in the Sicily Channel (mean: 200 ind. m(- 3)) and in the Cretan Sea (mean: 45 ind. m(-3)), respectively. Strong vertical gradients in zooplankton distribution were evident at all sta tions, the 0-50 m layer being the richest in numbers, whereas numbers sharply decreased at 100 m depth. Copepod relative abundances accounte d for approximately 80% of the total zooplankton numbers, while ostrac ods (6.4%), chaetognaths (4.2%), appendicularians (4%) and pteropods ( 1.7%) followed in rank order. It seems that the zooplankton distributi on is not always influenced by local meso-scale dynamics, but only whe n the physical forcing is strong and persistent over time, as in the R hodes gyre area.