Features of the bioecological state of water bodies in the Leningrad region and de-eutrophication measuresViktor Sboichakov, Dmitriy Kulev, Olga Reshetnikova, Tatiana Osipova and Ludmila KovalevaE3S Web Conf., 273 (2021) 04016DOI: https://doi.org/10.1051/e3sconf/202127304016