Phytoplankton pigment profiles and phytoplankton size classes along the South-Eastern Black Sea

In the present study, spatio-temporal pattern of phytoplankton pigment profiles and phytoplankton size classes from December 2015 to August 2016 were seasonally investigated along the south-eastern coasts (Giresun-Artvin) of the Black Sea. Along the 12 stations, seasonal samplings were conducted from surface to 40 m depths with 10 m intervals. Contribution of phytoplankton size classes to total phytoplankton in the study area revealed significant changes and ranged from 2 to 60%; 3 to 77%; 5 and 90% for picophytoplankton, nanophytoplankton and microphytoplankton, respectively. The highest contribution to pigment pool was made by diagnostic pigments (41.35-55.49%) while the least contribution was made by photoprotectant pigments (2.98-11.68%). Regression analysis revealed that the total pigment could be used as an indicator for the region, whereas photoprotectant pigments were the last pigment to be considered. Large celled phytoplanktonic groups (microphytoplankton) are characterized by high chlorophyll-a content and small celled groups (nano- and picophytoplankton) characterized by low chlorophyll-a content in autumn and spring seasons. The relationships between chlorophyll-a and pigment indices also showed how effective seasonal dynamics are in the region.