Eelgrass | OtterKnow Kids Encyclopedia

What Is Eelgrass?

Eelgrass is a true flowering plant that lives entirely underwater in the shallow, salty waters of the ocean. Its scientific name is Zostera marina, and unlike seaweed or kelp, eelgrass has real roots, stems, leaves, and even tiny flowers — just like plants on land. Scientists believe that eelgrass ancestors once lived on dry ground millions of years ago and gradually moved back into the sea over time. The long, ribbon-like leaves sway gently with the ocean currents and can grow up to four feet long. Eelgrass is found along coastlines throughout the Northern Hemisphere, from the chilly shores of Alaska to the warm waters of the Mediterranean Sea.

Underwater Meadows

Divers collecting eelgrass samples from an underwater meadow

Eelgrass grows in dense underwater meadows that look like waving green fields on the ocean floor. These meadows are among the most productive ecosystems on the planet, supporting hundreds of species of fish, invertebrates, and marine mammals. Baby fish and shellfish use the thick beds of eelgrass as nurseries, hiding among the leaves until they are big enough to survive in open water. Seahorses wrap their tails around eelgrass blades to anchor themselves in the current, and manatees graze on the leaves in warmer waters. The meadows also slow down wave energy, which helps protect shorelines from erosion during storms.

Fighting Climate Change from the Sea Floor

One of the most important things about eelgrass is its ability to capture and store carbon dioxide, the greenhouse gas that contributes to climate change. Seagrass meadows like eelgrass can store carbon in their roots and the surrounding sediment up to 35 times faster than tropical rainforests of the same size. Scientists call this “blue carbon” because it is stored in ocean ecosystems rather than on land. A healthy eelgrass meadow locks away carbon for hundreds or even thousands of years in the mud beneath it. This makes protecting and restoring eelgrass meadows one of the most powerful natural tools we have for fighting climate change.

Threats and Conservation

A tiny seahorse holding onto seaweed with its curly tail

Sadly, eelgrass meadows around the world are shrinking due to pollution, coastal development, and warming ocean temperatures. When too many nutrients from farm runoff and sewage enter the water, they cause algae blooms that block the sunlight eelgrass needs to survive. Rising ocean temperatures stress the plants and make them more vulnerable to disease. Scientists estimate that the world has lost about 30 percent of its seagrass meadows since the 1870s. Conservation groups and researchers are now working hard to replant eelgrass in damaged areas, sometimes by scattering seeds from boats or transplanting healthy plants from thriving meadows.