Lakes become more productive as they accumulate nutrients with time and this process is called natural eutrophication which probably occurs very rarely. This natural eutrophication is generally fastened by antropogenic factors. Lake Mogan is a shallow lake with surface area 5.5 km² in the close vicinity of Ankara, Turkey. Lake is under the recreational use. Natural process of eutrophication gained a momentum due to anthropogenic effects in the last decade. Numerous studies and suggestions have been made as well as prevention, but process is continuing as represented in this study. Lake eutrophication assessment was done in order to illustrate trophic gradient changes and its impact on zooplankton and zoobenthos. Trophic state index (TSI) which consists three parameters; total phosphorus (orthophosphate), chlorophyll-a concentration and Secchi disc depth, is constructed. No possible trophic gradient change was observed in lake spatially but changes according to seasons are evaluated.