Seasonal distribution and species composition of zooplankton in the Eastern Marmara sea

In this study, which was conducted in February, May, July and December of 2016 at 30 stations in the upper layer and 14 stations in the lower layer, the abundance and distribution of the species composition of zooplankton in the East Marmara Sea was evaluated temporally and spatially. Environmental parameters affecting distribution are examined. In this study which make seasonally, zooplankton samples were taken vertically. During in our study, the highest abundance value of zooplankton was 2822 ind/m3 at MD6 station in December and the lowest abundance value was measured as 299 ind/m3 at İZ2 station in December. In seasonal samples, a total of 36 species / groups were identified in the upper layer including Copepoda, Cladocera, Chaetognatha, Appendicularia, Meroplankton and other groups (gelatinous organisms). The most significant species were Penilia avirostris, Acartia clausi, Oithona nana and Polchaeta larvae during summer months according to their abundance, while Acartia clausi, Calanus euxinus, Paracalanus parvus and O. nana were the most abundant in the winter months. Oithona davisae which an invasive alien species, continued to exist in the Marmara Sea. The highest zooplankton abundance was recorded in the MD8 station (2282 ind/m3) in July and the lowest in May in the MD7 station (9 ind/m3). A total of 43 species / groups were identified in the lower layer. 5 species were found in lower layer which not found in upper layer ( Aetideus spp., Clausocalanus spp., Oncaea minuta, Goniopsyllus rostratus, Ctenocalanus vanus, Euchaeta marina and Siphonophora species ).It is observed that the eastern Marmara Sea has an eutrophic structure, zooplankton abundance and distribution changes seasonally and physical parameters are important for this changes.