Determination of the seasonal phytoplankton composition inside and outside of the Mersin marina

The determination of phytoplankton composition of inside and outside water of Mersin Marina in period of November 2022, April and June 2023 was aimed. The phytoplankton species distribution, abundance and biomass were comparatively investigated. A total of 110 taxa belonging to Bacillariophyceae, Coscinodiscophyceae, Mediophyceae, Dinophyceae, Prymnesiophyceae, Cyanophyceae, and Thecofilosea classes were determined. In the taxonomic distribution of phytoplankton classes, the contribution of Dinophyceae to the phytoplankton composition was determined as 49% in November 2022, 48% in April 2023, and 70% in June 2023. The Dinophyceae class was followed by the Mediophyceae > Bacillariophyceae > Coscinodiscophyceae classes, respectively, and Prymnesiophyceae, Cyanophyceae, and Thecofilosea contributed less than 1% to the taxonomic distribution. The total phytoplankton abundance determined in the water column at the stations was found to be 521496 cells/l in the November, 543200 cells/l in the April and 103668 cells/l in the June. Phytoplankton biomass was found to be 134.05 µg/l in November, 117.23 µg/l in April, and 42.10 µg/l in June. The phytoplankton biomass was found to be 134.05 µg/l in November, 117.23 µg/l in April, and 42.10 µg/l in June. The variation of phytoplankton abundance and biomass in selected stations inside and outside the marina, depending on season and depth, was comparatively examined. While Mediophyceae made the highest contribution to phytoplankton abundance and biomass in November 2022, and Dinophyceae in June 2023, Premniophyceae made the highest contribution to abundance and Mediophyceae to biomass in April 2023. It was determined that, the dominant phytoplankton species were Chaetoceros gracilis, Asterionellopsis glacialis, Chaetoceros curvisetus and Bacteriastrum comosum in November, Chaetoceros didymus and Chaetoceros lauderi in April and Pseudonitzschia delicatissima, Gyrodinium fusiforme, Pselidinum fusus and Heterocaopsa pygmea in June. Emiliana huxleyi has been dominant species in all season. Species diversity was analyzed statistically, Shannon (H ') value was determined as 1.87 in June, 1.67 in November and 1.10 in April. Evenness (J) value was found to be 0.78 in June, 0.65 in November and 0.59 in June. Richness (d) value was found to be 1.23 in June, 1.38 in November an 0.64 in April.