Sampling
Phytoplankton samples were collected with vertical net hauls (mesh size – 25 µm and net diameter – 30 cm) in multiple locations along Vietnamese coastal waters (Fig. 1a). The samples were fixed with formaldehyde to a final concentration of approximately 5% and then stored in 25 ml dark glass bottles at the Institute of Oceanography (Nha Trang, Viet Nam). Additionally, dinoflagellate samples collected in waters surrounding Hormuz Island in the Strait of Hormuz (Persian Gulf) were examined during the study. In total, ten samples were collected with a plankton net (mesh size – 55 μm) from five sites (Fig. 1b). At first, the material was studied in vivo at the laboratory of the Department of Marine Biology of Tarbiat Modares University (Iran), and then it was preserved in formaldehyde (4% final concentration). Subsequent study of the material was carried out at the Institute for Evolutionary Ecology of the National Academy of Sciences of Ukraine (Kiev, Ukraine).