Seasonal variation and taxonomic composition of mesozooplankton in the southern Black Sea (off Sinop) between 2005 and 2009

Abstract

The monthly and long-term fluctuations of mesozooplankton abundance, biomass, and taxonomic composition in the Sinop inner harbor (southern Black Sea) between 2005 and 2009 are presented in the present study. In total, 31 mesozooplankton taxa were identified during the study. The recorded average mesozooplankton abundance and biomass were 34,323 ± 7580 ind. m$^{-2}$ and 1208 ± 460 mg m$^{-2}$ in 2005, 95,063 ± 31,434 ind m$^{-2}$ and 1787 ± 604 mg m$^{-2}$ in 2006, 97,626 ± 12,141 ind m$^{-2}$ and 1034 ± 20 mg m$^{-2}$ in 2007, 91,918 ± 10,476 ind m$^{-2}$ and 775 ± 121 mg m$^{-2}$ in 2008, and 146,918 ± 19,671 ind m$^{-2}$ and 1955 ± 437 mg m$^{-2}$ in 2009, respectively. The highest abundance values of mesozooplankton were encountered in March 2006 (299,110 ind m$^{-2}$) with the contribution of Copepoda nauplii (167,000 ind m$^{-2}$) particularly. Meanwhile, the mesozooplankton biomass was highest in October 2005 (5852 mg m$^{-2}$), due to Parasagitta setosa (3695 mg m$^{-2}$). The heterotrophic dinoflagellate Noctiluca scintillans was a major component of plankton samples in the Sinop region, presenting its highest values in April 2005. Mesozooplankton abundance values showed significant differences (except 2007-2009 and 2008-2009) during the 5-year sampling period. Since the middle of 2006, an increase in abundance, biomass, and biodiversity of mesozooplankton has been detected. Many mesozooplanktonic species/groups showed seasonality in the study (especially Cladocera species). This seasonality was determined to be based on temperature changes.