Seasonal cycle of zooplankton abundance and biomass in Hamsilos Bay,Sinop, Southern Black Sea,Turkey

In this investigation, zooplankton was studied between July 2015 and June 2016 in Hamsilos Bay to examine spatial and temporal variations in abundance, biomass and taxonomic composition. The recorded mean zooplankton abundance and biomass were 3770.35 ind. m^?3 and 25.06 mg m^?3 in the inner station, 3928.11 ind. m^?3 and 28.19 mg m^?3 in the middle station and 3948.22 ind. m^?3 and 28.74 mg m^?3 in the outer station, respectively. The high abundance and biomass values observed in September 2015 were attributed to Oithona davisae (4575 ind. m^?3 at the inner station) and Penilia avirostris (33.4 mg m^?3 at the outer station), respectively. Copepoda was the most abundant during the entire period of the survey. In terms of abundance and biomass, Copepoda was followed by meroplankton and Cladocera. Most species within the zooplankton community exhibited evident seasonality throughout the year in Hamsilos Bay. This was particularly apparent for O. davisae, Centropages ponticus, Cladocera and meroplankton, which were abundant in summer–autumn, and for Pseudocalanus elongatus, which was more abundant during winter and spring. It has been determined that O. davisae, which is a non-indigenous cyclopoid copepod species of the Black Sea, has successfully inhabited southern Black Sea and has established a permanent population in this area.