© by PSP.Abundance of picoplanktonic marine cyano-bacterium Synechococcus was monitored weekly over a year period at an oligotrophic deep shelf station in the northeastern Levantine basin (northeastern Mediterranean). In addition to abundance, ambient parameters such as; temperature, salinity, secchi disc depth, total suspended sediment, ni-trate+nitrite, phosphate, chlorophyll and phyto-plankton were also collected. Population was found most abundant during March & December (1.8 × 104 cells/ml) and June & August (1.4 × 104 cells/ml) whereas to the lowest counts were retained in October (9.6 × 103 cells/ml) and July (1.0 × 104 cells/ml). Low levels observed in July coincided with the initial phase of an extraordinary upwelling event that lasted for about 10 weeks. Average cell counts at surface (1.8 × 104 cells/ml) almost three fold that observed at 100m (6.4 × 103 cells/ml). In contrast to homogeneous temperature & salinity profiles, fluctuations in population abundance with depth was observed during winter con-vectional mixing (January & February). Abundances remained below 1.0×104 cells/ml below 50 m due to stratification observed during summer & autumn. Cell abundances ranged from a minimum of 4.9 × 103 to a maximum of 4.4 × 104 cells ml-1-1 with an annual mean level of 1.8 × 104 cells ml-1-1 at surface. At the lower part of the euphotic layer abundances ranged from a minimum of 3.0 × 102 to a maximum of 2.8 × 104 cells ml-1-1 with an annual mean level of 6.5 × 103 cells ml-1-1 at 100 m depth. Based on Spearman's rank correlation analysis, a highly significant correlation between Synechococ-cus abundance and ambient temperature was observed indicating the populations' affinity to elevated temperatures.