Reports of Algal Blooms

Lakes are considered to be experiencing an algal bloom when Secchi Disk Transparency is observed to be less than 2 meters by DEP staff or a trained volunteer. Transparency is measured by using a Secchi Disk and a view scope. The Secchi disk is about 8 inches in diameter and painted black and white. The disk is lowered into the lake with a measured line. The view scope is used to look into the water at the disk as it is lowered. The scope reduces the glare of the sun and wave action which could both interfere with the reading. The depth at which the disk disappears from view is measured and recorded as the Secchi Disk Transparency.

Alga growing in the lake will reduce the depth to which the disk can be seen. Lakes with a Secchi disk reading of less than 2 meters caused by alga are considered impaired. The lake is still considered safe to swim in, but you might not want to. 

The Maine Volunteer Lake Monitoring Program will soon be posting annual records of algae blooms in Maine. We will provide a link to that information when it is available.