Determination of the communities of pico, nano and microplankton in the Aegean sea

Aegean Sea, in terms of its primary production and nutrients, is one of the most oligotrophic sea in the world. Like in most oligotrophic and subtropical oceanographic regions, low biomass values in the Aegean Sea are generally associated with the dominance of Nanoplankton, Synechococcus, prochlorophytes and tiny flagellates. On the other hand, the diversity of microplanktonic species is very high in the Aegean Sea, although their importance in terms of abundance is rather low. The aim of this study is to determine the spring community structure of phytoplankton size classes (pico-, nano-, microplankton) and their relationship with physico-chemical variables, and to evaluate phytoplankton (pico-, nano-, microplankton) organic carbon biomass with particulate organic carbon in the open waters of the Aegean Sea. A total of 220 phytoplankton taxa, 160 of them identified as the species level, were observed during the cruise at 10 stations in March 2012. Total microplankton abundance ranged between 31.148 and 2.887.824 cells/l; nanoplankton abundance ranged between 4.639 and 1.081.020 cells/l and picoplankton abundance ranged between 2.57x107 and 8.81x107 cells/l in the whole sampling area. Four species belong to Bacillariophyceae and Prymnesiophyceae, identified with scanning electron microscope, have found for the first time in the Aegean Sea. All parameters measured have been varied from the North to the South of the Aegean Sea. Their values have been varied from North to South in terms of phytoplankton abundance, biomass and other physicochemical parameters. The findings of this study have shown that phytoplankton showed large spatial changes even small differences in physico-chemical variables. In the euphotic zone about the first 50 m depth of the first five stations were clearly seperated from the other stations according to the results of principal component analysis (PCA). SIMPER analysis revealed that diatoms and dinoflagellates direct the phytoplankton community in the north and south, respectively. According to the results of spatial autocorrelation analysis, stations had high spatial autocorrelation in the North Aegean and they showed significant clusters in terms of phytoplankton size classes and physicochemical variables. In the South Aegean, although there was a positive spatial autocorrelation between stations, no significant clusters have been observed.