Cyanobacteria thrive especially well where lawns are present.
Recent rains have "rinsed" large quantities of Phosphorus into the lake from upslope lawns. Alton Bay isn't as prone to this "rinsing" as Winter Harbor, where wake-surfing "visitors" ply their craft.
We shouldn't encourage Connecticut-style lawns, but strongly suggest
Blueberry sod as suggested by SAMIAM recently.