Eelgrass: Humble Protector of our Fish and Shores, by Emily LeGrand

This blog was originally posted at Small Scales, the excellent East Coast fisheries blog administered by the Marine Issues Committee of the Ecology Action Centre.  Follow Small Scales on Twitter

If you’ve ever spared a thought about eelgrass, it’s probably been when you’ve been swimming in the ocean and some eelgrass tickled your belly and feet. You may have even thought something like, ‘I wish there was no eelgrass around, so I could see the bottom and stop feeling squeamish.’

But it is time to think again! Because eelgrass does so much more than just make swimmers uneasy.

Considered a keystone species, eelgrass has many features that allow it to offer free, natural protection to some of Nova Scotia’s most unique and vital assets. And the fact that eelgrass is in decline across our coastlines is bad news for our small-scale fisheries, coastal property owners, and everyone who enjoys the benefits of coastal ecosystem health around our province.

Found along coastlines all over the world, eelgrass is a rare example of a flowering land plant that has evolved to survive underwater. The long, emerald green, flat leaves of eelgrass, which can grow up to a meter in length, billow in the waves along the coast in the sub-tidal and intertidal zones where it still gets enough light through the water column to photosynthesize. Their extensive root system anchors the eelgrass in place, while also locking in sediments and stored carbon.

Thick, waving eelgrass meadows provide vital nurseries for many of Atlantic Canada’s important fishery species. Juvenile groundfish, including haddock and cod hide between the fronds to find rest and protection from predators as they grow. Studieshave shown that these young fish choose this habitat over open water if available, and that they do not cluster in schools as they do in open water, likely because they do not need the protection of the schooling behaviour. Young fish living in eelgrass meadows have also been found to grow bigger than fish of the same species that do not live in eelgrass.

Also unsung heroes of coastal erosion protection, dense eelgrass beds of work to slow and dissipate wave energy as it moves toward the land. Indeed, many studies show that a coastline stretch with a healthy eelgrass bed just offshore experiences slower erosion rates than neighbouring stretches with otherwise similar conditions.

Eelgrass beds also support cleaner coastal waters, as slowed water flow allows sediments contained in the water to settle out onto the bottom among the eelgrass’s thick root system. From here, suspension feeders – including periwinkles and sand dollars- that live around the roots of eelgrass can then filter these particles as they eat, vitally improving water quality, which in turn helps the plant get enough light.

There are notable eelgrass beds in many coastal areas around Nova Scotia, especially in estuaries, inlets and bays, such as Antigonish Harbour, Chedabucto Bay, Petpeswick, Cole Harbour, Musquodoboit Harbour, and Chezzetcook.

Unfortunately, though,, most of Nova Scotia’s eelgrass beds are in a state of decline. For eelgrass to complete all of its good work, they need shallow, clear water to photosynthesize, and healthy, firm root systems to survive. But this humble and important plant is increasingly threatened by pollution-caused eutrophication, sedimentation, and invasive species.

Sewage effluent from coastal cottages, along with over-fertilized lawns and other managed landscapes can cause an increase in nutrients in coastal runoff. These nutrients allow algae to grow very quickly. As these algae die and decompose, this removes oxygen from the water. The algae also blocks sunlight from reaching the eelgrass, making it difficult for these sensitive plants to receive enough light to grow. When too much sediment erodes from coastal land, this also muddies the waters and limits the amount of sunlight reaching the eelgrass.

Another threat to eelgrass in Nova Scotia is the green crab, especially on the South Shore around Port Joli and Port Mouton. These crabs, introduced from areas of the Atlantic near Iceland in the 1980s, burrow deep in the mud of eelgrass beds, snipping the root systems as they dig. In some places, green crabs have completely decimated the eelgrass beds, leaving mud, young fish without food and protection, and shores and salt marshes exposed to the full impact of waves. Scientists and volunteers at Kejimkujik Seaside are trapping the green crab, mapping eelgrass beds so that we know what’s there and what we’re losing, and transplanting eelgrass to help it grow back. If you find yourself in that area this coming spring and summer, volunteering with these important initiatives is a great way to learn more, have some adventurous fun, and make a real impact on Nova Scotia’s coastal health.

So maybe eelgrass is a little icky to swim by. But if we can have a second thought, maybe it could be about doing our part to make sure eelgrass beds are healthy, so they can continue to help keep Nova Scotia’s coastal communities healthy too. On coastal properties, making sure sewage does not find its way to the ocean, using little or no lawn fertilizers, and covering bare soil with plants and plant material are all very effective ways to keep our coastal waters clean and clear for the eelgrass. And in turn, the eelgrass will offer a home for young fish to regenerate our economically important fisheries, and protect our shores from battering wave erosion.

 

Emily LeGrand coordinates the Living Shorelines project for the Ecology Action Centre’s coastal and water team, and is inspired by all the great work the humble, sensitive eelgrass meadows do for Nova Scotia.

To mark World Water Day (March 22nd, 2014), EAC is organizing Love Your Water Month. And if you love water, you’ve got to love eelgrass too! Click here for a glimpse of the water love-ins happening throughout March.