The biological method of water quality analysis, for the first time, was applied in Russia during the examination of Neva Bay of the Gulf of Finland in the Baltic Sea by Wislouch S.M. Neva River was a source of drinking water in St. Petersburg and, at the same time, a discharge for all city drains. As a result, it became hazardous to health, being a source of various diseases, especially cholera. From August 1911 to September 1912 pollution studies of the Bay were made to solve the question - where to send the treated waste water of the future sewage system of St. Petersburg. In total, 37 trips were made during this time, 510 samples were taken, including 375 plankton samples and 35 benthic samples. Wysłouch S. M. gave an overview of objects collected at 265 stations located in the area of Neva Bay - from estuary of Bolshaya Neva to Kronstadt, along the southern coast of the Bay and partially along the Northern coast. He brought a list of algae, including 97 species: Algae Cyanophyceae (writing all taxa retained on original source) - 17 species, Flagellata - 19 species, Peridineae - 1, One - 30, Conjugatae - 2, Diatomaceae - 28 species, Fungi (1), Bacteria (17), Protozoa (28), Rotatoria (17). Taking into account the algae and other organisms saprobity indices, areas with different degrees of contamination were identified. All the data was put on map of the Gulf. The most heavily polluted area was the Sea channel, and the area between the Lisij Nos and Kronstadt was the cleanest.