Eelgrass Beds | Oceana Canada

Marine Ecosystems

Eelgrass Beds

Distribution

Worldwide in temperate latitudes

Physical Ocean Characteristics

Clear, shallow, low-nutrient waters in protected bays and inlets

Keystone Species

Eelgrass (zostera spp.), juvenile fish including salmon & herring, waterfowl

Ecosystem Services

Fish nurseries, carbon storage, coastal protection, water quality

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Eelgrass (Zostera marina) is a common species of seagrass that can form expansive, underwater meadows, also known as eelgrass beds. These eelgrass beds are considered important ecosystem engineers, creating complex 3D structure with their leaves that benefit marine species and coastal ecosystems as a whole. Marine animals like fish, invertebrates and even waterfowl will use these beds as nursery, refuge and foraging habitats. Although eelgrass is often mistaken for seaweed, it is actually a species of aquatic, flowering plant that can be found in tidelands and shallow, calm inlets, bays and estuaries. Like all plants, eelgrass relies on sunlight to convert carbon dioxide into energy by photosynthesis. Eelgrass is also unique when compared to seaweed and algae in that it can sequester carbon dioxide in it’s roots, making eelgrass beds an important consideration for climate change mitigation.

Eelgrass looks much like the grass that may grow on your lawn - except that it’s found underwater in brackish and salty environments. The blades, or leaves, of eelgrass are green, about one centimetre wide and can grow to almost a metre long. They grow in clumps in shallow, clear water and are great ecosystem health indicators for estuaries and similar coastal habitats. Because eelgrass relies on clear water, low disturbance and low nutrient levels, a change in any of these indicators can destroy entire eelgrass beds.

Eelgrass and other seagrass beds are some of the most productive ecosystems in the world, meaning they produce significant amounts of oxygen and new plant matter, by harvesting the sun’s energy, every year. In both ecological and economic value, they rival tropical rainforests and the world’s most productive farmland. The importance of eelgrass beds became truly apparent after a widespread wasting disease, caused by an infectious marine “slime mould”, outbreak in the 1930’s that killed off 90 per cent of eelgrass along the Atlantic coast of North America. After the loss of eelgrass habitat, declines of clams, lobsters, crabs, scallops, cod and flounder were recorded. There was also a documented 90 per cent decline in migratory populations of Brant geese that rely heavily on eelgrass meadows for foraging.

It is clear that eelgrass provides important habitat and nursery grounds for marine species and waterfowl, but they also provide numerous ecosystem services to humankind. Eelgrass meadows reduce erosion of coastlines by providing a physical barrier, act as a carbon sink and improve water quality by filtering polluted runoff, stabilizing sediments and absorbing excess nutrients. Their ability to sequester carbon in marine sediments, which is also called “blue carbon”, positions eelgrass beds as one of the most important blue carbon ecosystems in the fight against climate change, alongside salt marshes and mangrove forests. Unfortunately, human activities like dredging, shoreline development and upstream activities like industrial agriculture and sewage dumping can all negatively affect eelgrass beds and destroy these important coastal marine habitats. And while human activity and development along coastlines has destroyed much of the world’s eelgrass beds, over the past few decades there have been many eelgrass restoration efforts along the coast of North America.

 

FUN FACTS

 

  • Eelgrass beds can be found along Canada’s Pacific and Atlantic coasts, as well as along the coast of James Bay in the Arctic.
  • Historically, eelgrass was harvested and eaten by First Nations communities and used to smoke meats. Dried eelgrass was used to stuff mattresses, upholstery and even used as housing insulation.
  • In British Columbia, up to 80 per cent of commercially important fish and invertebrate species rely on eelgrass at some point in their life cycle.
  • There is a town in Haida Gwaii, off the coast of British Columbia, called T’anuu ‘llnagaay (Eelgrass Town). Its name alone conveys the importance of eelgrass to coastal, Haida communities. Tending the meadows of the sea: Traditional Kwakwaka’wakw harvesting of Ts’áts’ayem (Zostera marina) is a great resource to learn more about the uses and harvesting of eelgrass by local First Nations.

 

FURTHER READING

 

Fisheries and Oceans Canada - Eelgrass in Canada

NOAA - The importance of eelgrass

Ocean Watch - Eelgrass

USDA - Plant fact sheet

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