What’s Growing Beneath the Surface? Understanding widgeon grass in Chilmark Pond
- Jul 27
- 2 min read
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, occasionally interfering with boating and other recreational activities.
A common question being asked: Why has widgeon grass become so abundant this year? Like many aquatic plants, widgeon grass can experience "boom" years when environmental conditions are especially favorable. It tolerates a wide range of salinities, from freshwater to highly saline conditions, making it well adapted to the naturally fluctuating conditions of Chilmark Pond. It also thrives in warm, calm, shallow waters and can photosynthesize at higher temperatures than eelgrass. When water clarity is high enough for sunlight to reach the bottom, widgeon grass can grow rapidly, forming the dense underwater meadows now visible throughout the pond.
Importance of widgeon grass: Widgeon grass is a protected seagrass species under the Wetland Protection Act. Its presence supports ecosystem health by improving water quality, stabilizing sediments, absorbing excess nutrients, and providing habitat and food for fish, shellfish, invertebrates, and waterfowl. Although dense growth in Chilmark Pond can be inconvenient for boating, having submerged aquatic vegetation present is better for the pond ecosystem than having none at all.
Removing or disturbing intact widgeon grass would likely do more harm than good. Although dense growth may require boaters to adjust how they use certain areas of the Pond, the plant plays an important role in supporting habitat, water quality, and overall ecosystem health. Pond health exists on a spectrum from toxic cyanobacteria to clear healthy seagrass dominated waters. As Chilmark Pond begins its journey of restorations there might be some bumps in the road, but we are headed in the right direction.
Our thanks to Peter Bruce for his in-depth analysis and research on widgeon grass in Chilmark Pond!
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