In this study, benthic dinoflagellates, which are one of the key primary producers of the oceans and seas but have not been sufficiently researched in our coastal waters, were examined. Benthic and epiphytic dinoflagellate sampling was carried out in 4 different seasons at 16 stations determined especially in areas where mussel farms are located in the Western Black Sea, Marmara Sea and northern Aegean Sea. Dinoflagellates attract attention with their ability to play a role in harmful algal blooms and produce toxins. These organisms are an important component of phytoplankton due to their ability to adapt to very different environmental conditions, their habitat diversity, and their ecology based on broad niche preferences. However, approximately 10% of the 2000 described dinoflagellate species are benthic forms, and the species compositions of benthic habitats are quite different from those of planktonic habitats. Benthic forms of dinoflagellates, such as planktonic members, can also cause harmful algal blooms, but most studies emphasize planktonic species. Benthic and epiphytic dinoflagellate communities have been studied and described in detail mostly in tropical and subtropical waters, but their presence is also known in temperate and subarctic waters globally. Benthic and epiphytic toxic dinoflagellate species, whose distribution has expanded from tropical and subtropical waters to more temperate coastal areas, emerge as a potentially expanding global problem that needs to be seriously addressed. With the increase in sea water temperature resulting from global climate change and the "tropicalization" of the Mediterranean climate, which is known as temperate, tropical creatures spread and settled in the Mediterranean via the Suez Canal and the Strait of Gibraltar, and similarly, it is known that the Black Sea is becoming Mediterranean with the influx of species from the Mediterranean to the Black Sea. Gaps in regional knowledge regarding benthic dinoflagellates in Mediterranean coastal waters make it difficult to make predictions about future trends in BHAB formation in this region. The gaps in knowledge regarding the possible existence of benthic dinoflagellates in the coastal waters of the Black Sea are much greater than in the Mediterranean. In this study conducted in the Turkish coastal waters of the Western Black Sea, Marmara Sea and Northern Aegean Sea, Amphidinium, Coolia and Prorocentrum were the most common benthic dinoflagellates. As a result of the study conducted in four seasons, the lowest abundance level was recorded in Balıklıova (Urla/İzmir) with 7 cells/g dry weight Prorocentrum in November 2022, and the highest was recorded in Çandarlı (Dikili/İzmir) with 232971 cells/g dry weight Coolia. . During the study, only in August 2022 sampling, the benthic dinoflagellate group recorded at Bandırma, Erdek and Kepez sampling points with the highest 3284 cells/g dry weight and the lowest 67 cells/g dry weight was Amphidinium. Significant increases in benthic dinoflagellates are noteworthy, especially in the May 2022 period in the north of the Aegean Sea and in the August-November 2022 samples in the Western Black Sea samples. This study will provide information on the presence and distribution of these important benthic dinoflagellates in the coastal waters of Turkey and will form a basis for future research. Especially the Mediterranean and Black Sea regions being affected by climate change requires further research to understand the behavior of benthic dinoflagellates in these regions.