How does water clarity affect eelgrass growth. Click on the image above to see what researchers found.
Sheltering meadows of eelgrass trim southern New England’s coast like lace. Shallow bays, estuaries and lagoons once offered an ideal environment for Zostera marina, a submerged sea grass with long, narrow leaves. These lush, ocean fringes shelter important fish species, such as flounder, bay scallop and hard clams—and reduce the power of storm waves.
In 1931, the once abundant “prairies of the sea” began to disappear. They since have dwindled by as much 90 percent. Scientists have identified factors ranging from pollution to disease and brown tides, waterway impacts and lack of genetic diversity. Whatever the cause, the effect is clear and worrisome.
Regional efforts at restoration—including distributing eelgrass seeds and transplanting shoots— were costly and only occasionally successful.
Aiming to reverse this decades-long decline, the Conservancy recently sponsored a new study, funded by the National Oceanic and Atmospheric Administration and led by renowned eelgrass expert Dr. Fred Short of the University of New Hampshire. Dr. Short and his team collected and analyzed plants from 10 locations—from Cape Cod to Long Island.
They found that eelgrass throughout the region is surprisingly diverse. If not a genetic bottleneck, then what was responsible for the decline? Dr. Short’s team determined the answers were high nitrogen content—from sewage treatment plans, septic systems and polluted runoff—coupled with warming ocean temperatures.
Their recommended solution is three-fold:
- Reduce nitrogen pollution.
- Protect the region’s most resilient sea-grass populations.
- Use grasses from resilient areas as donors for future restoration to ensure the best chance of success.
“This research gives us a far better understanding of the genetics and resilience of eelgrass populations,” says Jon Kachmar, director of The Nature Conservancy’s Southeastern Massachusetts Program. “That helps us make better choices about restoring eelgrass to historic locations. It also reinforces the need to reduce nitrogen and other excess nutrients from our coastal waters.”
With strong science, practical solutions and your continued support, eelgrass may once again boast a plentiful, sheltering presence in New England’s coastal waters.
One way to protect eelgrass is through conservation moorings. See this 2013 report about conservation moorings.