This study represents a new statistical mapping approach in surface ecological mapping on the basis of environmental and phytoplankton data of the Sasyk Reservoir, formerly an estuary of the Black Sea coast. Ecological maps were constructed with the help of new tools in Statistica 12.0 Program. Bioindication groups and environmental variables in data mapping helped us to characterize the studied reservoir in summer 2013 as moderate temperature, fresh water, low acid and low alkaline, standing–low-streaming water, with medium amounts of oxygen, medium pollution, Class III of water quality, eutrophic, mainly with moderate concentrations of organic bounded nitrogen. The impact of coming elements affecting the reservoir ecosystem were revealed as the Sarata and Kogylnik rivers for water pH and organic pollution, and the Danube canal as the source of water salinity and available nitrogen. The central part of the reservoir was indicated as having the most unstable community with a large phytoplankton biomass and the lowest Shannon index. A new approach to surface mapping is so easy that we can recommend it for monitoring the Sasyk Reservoir ecosystem in combination with bioindication.