Eelgrass meadows: nurseries and carbon storage all in one

Eelgrass meadows: nurseries  and carbon storage all in one

Eelgrass (Zostera marina) meadows provide food and protection for over 80% of commercially important fish, crabs and shellfish, serving as spawning grounds, nurseries and habitats. Instead of finding soggy diapers in these nurseries, you may only see slimy greenish brown thin strands waving in the water or lying on the sand at low tide; however, they are as vital as rainforests to halt climate change. In fact, they capture and store carbon even more than terrestrial forests. Salt marshes and eelgrass meadows of B.C. sequester the equivalent of the emissions of 200,000 passenger cars (Island Trust Conservancy 2014). Although eelgrass and seaweeds make up only 0.05% of the biomass available on the earth, they can provide 50-71% of the world’s storage of carbon (Chung et al., 2011).

eelgrass Gabriola

Mapping Eelgrass Meadows on Gabriola Island

Luckily, there are many resources to help protect these sensitive habitats. For one, Islands Trust Conservancy mapped eelgrass meadows extensively until 2014 on almost every shoreline of Gabriola Island and other southern Gulf Islands of B.C. From their website http://www.islandstrustconservancy.ca/initiatives/marineconservation/eelgrass-mapping.aspx, one can see continuous, patchy, sparse and potential restoration areas around Gabriola (see Figure 1). Subsequently, Sea Change Marine Conservation Society reported the following about Gabriola in their 2017-2018 Gulf Islands Habitat Survey Report: Degnen Bay required removal of underwater debris, and along with Descanso Bay and Sandwell Bay, require designated boat moorage with signage about eelgrass habitat both on shore and in the bay on floats.

Eelgrass Gabriola Island west
Eelgrass Gabriola East
Figure 1 Gabriola Island eelgrass meadow maps (Courtesy Islands Trust Conservancy, 2013).

Attention Boaters and Beachcombers

Furthermore, Sea Change Marine Conservancy Society’s website, https://seachangesociety.com/resources/ state that boat anchors and their lines scour eelgrass meadows and leave large swaths of barren tracks. For boaters who fish, essentially, their anchors are destroying the valuable fish stocks they seek. Also, mooring buoys and swimming docks can cause the same damage. Moreover, Mayne Island Conservancy Society website, http://conservancyonmayne.com/shoreline.php, provides information for boaters such as anchoring at depths greater than 6 metres (20 ft.) and avoiding dropping anchor  in the same area if the anchor or prop pulls up eelgrass. Most responsible boaters use a conservation buoy consisting of a helical screw anchor, buoyant anchor line, or a float to keep the line from dragging on the bottom. Likewise, beach combers should control their dogs and resist trampling the eelgrass.

Sea Change Marine Conservancy Society video on protecting and restoring eelgrass meadows

Unfortunately, other pressures such as water pollution, shoreline erosion and global warming also contribute to loss of eelgrass meadows.

Now, the next time you scan an eelgrass meadow at low tide, reflect that you are witnessing a nursery, spawning ground, and one of the most efficient biological processes to halt climate change. Learn to recognize and protect these sensitive yet vital ecosystems.

References

Chung, I.K., Beardall, J., Mehta, S., Sahoo, D., Stojkovic, S., (2011). Using marine macroalgae for carbon sequestration: a critical appraisal. J. Appl. Phycol. 23 (5), 877–886.