Seasonal Variations of the Zooplankton Composition and Abundance in the Istanbul Strait

Composition and variation of zooplankton of the Istanbul Strait were studiedto obtain information on the distribution, abundance and biomass of dominantzooplankton species in the both layers of Black Sea and Mediterranean Sea ofIstanbul Strait and to determine the exchange of these species between thoselayers. Samples were collected vertically, using WP2 nets. In winter samplingperiod, the copepod Acartia clausi took part in the first place inabundance and meroplankton of bivalves occupied the second place. In the samplescollected during spring period, diversity and abundance of different specieswere higher than other seasonal periods. Noctiluca scintillans with anabundance value of 2380 ind./m^-3 was the dominant species, which wasfollowed by A. clausi with 2156 ind./m^-3 in the samplescollected from the upper layer, while A. clausi showed the highestabundance with 924 ind./m^-3, followed by the meroplankton of bivalveswith 840 ind./m^-3 in the samples collected from the lower layer. Insummer period, A. clausi with 952 ind./m^-3 and Peniliaavirostris with 840 ind./m³ were collected intensively. In theBlack Sea water average zooplankton abundance in winter period were 3485 ind./m^-3and during this time A. clausi was found to be the dominant species (976ind./m^-3). A second increase in the population of zooplankton wasobserved in the autumn period with a total abundance of 5969 ind./m^-3.This study carried out seasonally through the year was important in determiningdominant species of Istanbul Strait, towards understanding the ecology of theregion.