Island boards of health, working in conjunction with the Great Pond Foundation, issued the summer’s first cyanobacteria bloom watch notices last week.

More than half the nitrogen polluting Great Ponds along the south shore is coming from wastewater, a newly released report has found.

Wastewater discharge from urbanization to the north and east of Edgartown Great Pond has been identified as the primary source of increased nitrogen loading in the pond, according to a new study by a Woods Hole scientist.