A Preliminary Study on the Intense Pelagic and Benthic Mucilage Phenomenon Observed in the Sea of Marmara

In the intense mucilage formation observed in the Sea of Marmara in 2021, Phaeocystis pouchetii (Prymnesiophyceae) together with Skeletonema costatum, Cylindrotheca closterium, Thalassiosira rotula (Bacillariophyceae), and Gonyaulax fragilis (Dinophyceae) were detected in the foamy mucilage in the surface layer, and Chrysoreinhardia giraudii and Nematochrysopsis marina (Chrysophyceae), which are known to produce filamentous mucilage in benthic habitat. In addition, with the contribution of these groups, a higher cell abundance (2.1×10^7 cells/L) and chlorophyll-a value (15.9 µg/L) was reached than the mucilage event experienced in previous years. In the microscopic observations, typical dominant genera of the Sea of Marmara such as Protoperidinium and Tripos were observed very little in terms of species composition, and the fact that three previously unobserved species became dominant and the Cyanophyceae group was represented by different species indicated that phytoplankton composition changed in the mucilage formation in this period. The changing species composition with these 3 species that are known to make mucilage and which are new records for the Sea of Marmara point to the transportation by ship ballast waters or the inflow of brackish water with heavy rains. It is recommended to take the necessary measures to control domestic and industrial wastes and terrestrial inputs, which cause these species to reach numerical abundance and form mucilage, to carry out fisheries in a controlled manner, and to prevent the discharge of ship ballast waters and bilge waters