Eelgrass

There’s one PEI plant that most people are very familiar with, but few have seen growing in its natural habitat: Eelgrass (Zostera marina).

This is how most of us know Eelgrass: washed up along the shore. Eelgrass actually grows in extensive beds offshore as well as in our bays and estuaries, and – despite what you may think – it’s a true flowering plant and not a seaweed. Eelgrass has roots, stems, leaves, flowers, and vascular tissue (structures that move water and nutrients through the plant); seaweeds are algae that lack all of these parts and reproduce through spores. 

When it washes ashore, Eelgrass brings organic matter and nutrients (especially nitrogen and phosphorus) that are important to coastal plants and fungi. Offshore, Eelgrass is essential habitat for marine animals and provides nursery areas for commercially-important species. This plant also helps filter and oxygenate water, keeps marine sediment in place, sequesters carbon, and reduces the coastal impacts of storms by slowing currents and lowering wave energy. Eelgrass beds are among the most productive habitats we have and are indicators of a healthy environment. 

Eelgrass is also an important food for the Brant Goose – a small (duck-sized) waterbird, similar in colour to the Canada Goose but with a white necklace rather than a cheek patch. Brant can sometimes be seen on the Island, especially during spring migration. 

In the early 1930s, about 90% of the Eelgrass on both sides of the Atlantic died suddenly – within a few years – resulting in a comparable drop in numbers of Brant Geese, as well as declines in lobster, scallops, clams, crabs, cod, and halibut. The catastrophe was attributed to ‘seagrass wasting disease’, caused by a sudden over-population of a native microorganism (Labyrinthula zosterae). 

The reason for the increase in Labyrinthula still isn’t fully understood, but theories include changes in water temperature or salinity, reduced light due to sedimentation or the growth of other algae, and pollution from land. Whatever the cause, Eelgrass took more than a decade to recover; recovery of the geese, shellfish, and fin-fish that rely on the plant took even longer. 

Today, Eelgrass is considered common and healthy in the waters around the Island, but it is vulnerable to climate and land use. When you see Eelgrass washed up on shore, take a moment to appreciate the many roles of this important part of PEI Untamed!