Lake Vedlozero is an accumulating system of a variety of anthropogenic impacts. Since the 1970s, significant changes have occurred in the landscape structure of stream catchments in the southeastern and western parts of the lake’s drainage basin. Deforestation, conversion to arable land and drainage have enriched the lake water with nutrients and organic matter. The northeastern bay of the lake receives substantial amounts of wastewater from the village of Vedlozero and water from the River Vokhtozerka, affected by agriculture in the catchment. High average annual concentrations of total phosphorus (47–173 μg/l) in the water of the bay cause continuous blooming during the open water period. Blooming intensively in the bay, blue-green algae (cyanobacteria) release toxic substances (neuro-, hepato-, and dermatotoxins) dangerous for humans and animals. Massive development of cyanobacteria in the northeastern bay of Lake Vedlozero in summer now causes skin disorders, specifically allergic dermatitis, in Vedlozero village inhabitants (especially children) who swim in the lake.