Lake Menomin, often exhibits blue-green algae blooms , or cyanobacteria blooms yearly. Each year sees different degrees of blue-green " bloom" severity due to many contributing environmental factors. Some cyanobacteria may contain cyanotoxins.
https://www.epa.gov/cyanohabs/learn-about-cyanobacteria-and-cyanotoxins
The odor you experience is a combination of ammonia and hydrogen sulfide gas. It is common when large quantities of organic compounds break down. We have a relatively high pH in our lake water otherwise ammonia would become mostly ammonium and stay soluble (contained in the water). With less available hydrogen more becomes the gas. We experience the burning of the nostrils and bad smell mostly in late August and September when the cyanobacteria is breaking down.
Small bay areas typically deplete in carbon dioxide which is needed for photosynthesis. As a result scum layers form when the cyanobacteria float to the top and take the needed gases out of the atmosphere. Consequently, the dense accumulation and heat result in some of the cyanobacteria dying. They release their pigments when they die. The color in the water is phycocyanin or a blue-green- pigment creating the color you are seeing. 
Cyanobacteria bloom in 1964
Bloom in 2014
Seasonal "blue-greens" release odor upon decay
Blue-green algae has many look-a-likes and this causes confusion to water quality concerns beyond the less-desired blue-greens, or cyanobacteria.
Lake Finajajon in Sweden has been used as a comparative process towards remedying this yearly excessive out-of-balance environmental occurrence on Lake Menomin.
Local business, political, and civic groups have opposed funding and lake district creation (for funding) towards betterment of this decades long seaonal cycle.
https://dnr.wi.gov/lakes/bluegreenalgae/documents/BGAReportOct2005.pdf
https://www.uwsp.edu/cnr-ap/UWEXLakes/Documents/programs/convention/2012/JimKreitlow-What%27sThisGreenGoopInMyWater.pdf?fbclid=IwAR1wfW4imnyNUOh_rca-ayTeSxvyjKasmiXBjz_8nL-vfSPbHoKSjpitelU
