Temporal changes of subsurface chlorophyll maximum layer in the Southeastern Black Sea

Subsurface chlorophyll maxima layer (SCML), its tickness ans relation with environmental factors were investigated between May 2015 and April 2016 in river mouth and coastal waters of Southeastern Black Sea. The contribution of phytoplankton size groups to SCML were also assessed. Chlorophyll-a values tended to decrease from river mouth to coastal waters. Maximum Chlorophyll-a values were always recorded at subsurface layers and pronounce SCML were observed during thermal startification. In river mouth, chlorophyll-a at surface and subsurface chlorophyll maximum layer ranged between 0,50 (August) -3,96 (October) µg l-1, and 1,13 (February) -4,70 (October) µg l-1, respectively. In coastal waters, chlorophyll-a at surface and SCML ranged between 0,27 (March, June) -3,43 (May) µg l-1, and 1,12 (February) -4,17 (May) µg l-1, respectively. SCML were observed at 3- 26 m depths, and its tickness varied from 3 to 38 m in river mouth. In coastal waters, SCML were detected at 3 and 31 m depths and its tickness varied from 6 to 48 m in coastal waters. During study period, surface phytoplankton biomass ranged between 0,3-60,8 µg C l-1 and 0,5 to 65,4 µg C l-1 in river mouth and coastal waters, respectively. At SCML, phytoplankton biomass ranged between 0,3-60,8 µg C l-1 and 0,5-65,4 µg C l-1 in river mouth and coastal waters, respectively. Microphytoplankton (72%) dominated phytoplankton biomass follwed by nano- (16%) and picophytoplankton (12%) at surface and SCML in both stations. Subsurface chlorophyll maximum values showed statistically significant correlation with phytoplankton biomass (p<0,05).