If you've been boating on Chilmark Pond recently, you've probably noticed an increase in submerged plants, especially if it found its way around your propeller. This dominant species in the Pond is widgeon grass (Ruppia maritima), a submerged aquatic vegetation (SAV) commonly found in brackish waters. It has narrow, threadlike leaves and slender branching stems that can grow up to three feet long. This summer, dense patches of widgeon grass have become widespread throughout the Pond,...

The recent cyanobacteria bloom throughout Chilmark Pond is revealing different patterns across the Middle and Lower Pond showing how this complex ecosystem changes from place to place. Red Advisory Issued for Chilmark Pond Over the past week, MV CYANO detected a cyanobacteria bloom across much of the Chilmark Pond ecosystem, including both the Middle and Lower basins. In response, the Chilmark Board of Health (BOH) issued a red “Bloom Advisory” on July 21, 2026, for all regular monitoring...

Summer is just around the corner, and there’s no better way to enjoy the season than spending time in and around the Island’s ponds and waterways. As we head into warmer months, it’s important to stay informed about cyanobacteria (also known as blue-green algae) and know how to recognize potential blooms. MV CYANO helps keep the community updated with weekly pond monitoring reports and cyanobacteria risk levels determined by the Island Boards of Health. Each risk level includes...