For the first time, from the Black Sea water samples taken from the waters of three bays of the Sevastopol city, strains of the new to science algal virus of the microalgae Prorocentrum cordatum (PcV), were isolated by the author's patented methods. Using the methods and means available in the laboratory of the Institute of Natural and Technical Systems (Sevastopol, RF), some characteristics of this algal virus were studied. A short incubation period (24 h) and a relatively high infectious titer in the viral suspension (107 IE / ml) were established; the sensitivity of the algal virus to freezing (-180 C) and chloroform was revealed, which indicates a complex morphology of the virion (the presence of a supercapsid). The long-term survival of the virus under indoor conditions (up to 6 months) was also recorded, the spring-autumn seasonality and narrow species specificity in relation to the closely related host Prorocentrum pusilla were determined. Our results of monitoring during 6 months this new for science algal virus of the microalgae Prorocentrum cordatum in different in ecological status bays testified, that it can be used as an ecological indicator.