Sea snot, which was seen and reported in the Adriatic and Tyrrhenian Seas in the early 1990s, had been on Turkey's agenda as an environmental massive disaster from the winter months of 2021 until the end of summer in the Sea of Marmara. Due to the magnitude and topicality of the subject, the samples collected from the coastal areas where sea snot is observed in Marmara from January until July were examined. According to the results obtained, 5 classes were determined in sea snot. Species of algae that secrete mucilage, which provides stickiness to the formation, were also been identified in sea snot. These are 1 dinoflagellate, 2 Prymnesiosides, 5 diatoms, and 2 cyanobacteria species. 8 toxic planktonic species were detected in sea snot: 1 causing PSP poisoning and 3 of dinoflagellate causing DSP poisoning; 1 of prymnesiophisid that releases ichthyotoxin to the sea environment, and 3 of diatoms that cause ASP poisoning.