Marine plants are the unsung heroes of ocean habitats, providing food, shelter, and substrate to the varied and wonderful animals we love to watch, photograph, or hook on the end of a line. One such plant, eelgrass, or Zostera marina, grows on sandy substrates or in estuaries along the coast and in the sounds of New England. Growing together in long green ribbons, a bed of eelgrass resembles an underwater meadow, swaying in the current.
Eelgrass serves a greater purpose than its beauty, however. Eelgrass beds aid sediment deposition and stabilize the substrate, preventing erosion. They also serve as a home and nursery for both micro-invertebrates and economically important fish and shellfish; a recent NOAA report on the importance of shallow water bottom habitat identified eelgrass as important habitat for juvenile cod, pollock, flounder, and hake, among other species. Eelgrass is also a major food source for several species of marine birds and waterfowl, including brants, redheads, widgeons, black ducks, and Canada geese, and for the endangered green sea turtle.
Although eelgrass is found throughout the Northern Hemisphere, this essential marine plant is in danger of disappearing from much of its habitat. Several factors are contributing to the decline of eelgrass. Pollution from sewage and fertilizers is a major culprit—it creates an excess of nitrogen in the water, causing algal blooms that block sunlight from reaching the eelgrass and preventing its photosynthesis. Invasive green crabs also harm eelgrass beds by dislodging and shredding stalks of grass as they dig for softshell clams, and green crab populations are growing rapidly in New England. Shellfish rakes, dredges, and boat anchors also destroy eelgrass. In the future, eelgrass faces increased stress from rising ocean temperatures and water levels.
As a result, eelgrass is disappearing rapidly from many of the places it used to thrive, in turn endangering the myriad species that rely on eelgrass for food and shelter, and leading to sediment pollution due to the loss of this important anchor for the marine substrate. Narragansett Bay is one example—once filled with eelgrass, today it has lost 90% of its eelgrass beds.
Yet all hope may not be lost. Since 2001, volunteers and divers working through Save the Bay have participated in eelgrass transplanting efforts. Eelgrass is harvested from healthy beds in the southern end of Narragansett Bay, sorted, and then hand planted by divers, who attach shoots of eelgrass to bamboo skewers and secure the sewers in the substrate. While some of the transplanted beds have failed, others have flourished and spread.
Similar restoration projects are underway in other locations, including Boston Harbor. Efforts to map the current and historical distribution of eelgrass beds are also ongoing in several states and will provide a valuable baseline for future restoration and conservation.
If efforts to mitigate the stresses on eelgrass and restore its original range continue, there is hope for this marine hero—and the abundance of life it supports—to thrive once more.