Save Our Sodus, the local advocacy group that monitors the health of Sodus Bay, has issued an alert on it website.
The organization says a SUNY ESF sampling crew found a large blue green algae bloom in Oak Park Marina, a small one in Katylnn Marina, and other small sightings in the bay.
The samples were taken on Friday and results will be available on Monday.
Boaters, swimmers, and animals are asked to avoid contact with the bloom.
The organization says current water levels and warm temperatures are perfect conditions.