Watch: Underwater treasures threatened by giant anchor chains

As part of our ongoing efforts to understand what kinds of marine life are being be affected by freighters parking in the Southern Gulf Islands, a group of local volunteers raised enough money for a dive team. They explored an area adjacent to Gabriola Island, where Transport Canada is considering five new anchorage sites.

The resulting video showed an impressive number of species, and brought with it the alarming realization of just what’s at stake.

Anchor Chains

Did you know that an anchor chain from one bulk cargo ship can disturb and even destroy as much as one square kilometre of rich marine habitat on the ocean floor?

When a two to three hundred metre long cargo ship drops anchor, it deploys hundreds of metres of heavy chain. The majority of that chain lies on the sea floor to help ensure a horizontal force on the anchor, which is what holds the vessel in place. As the ship surges and sways with winds, currents and tides, it swings around its anchor, causing the heavy chain to drag around the anchor in a circular pattern. This disturbs and in some cases destroys any marine life in its path.

There has been very little study of the environmental impacts of anchor chains on the ocean floor on Canada’s west coast. However, we know from research in other parts of the world, that anchor chain scouring can do incredible damage to the marine environment.

What’s it like down there?

When Transport Canada looks for “suitable” places for anchoring giant, ocean going vessels, they look mostly at 4 factors:

  • good holding ground
  • appropriate ocean depth
  • shelter from high winds
  • proximity to ports

Unfortunately some of those same conditions are essential to support an extraordinary diversity of marine life.  As any experience local diver will tell you, the area around the Southern Gulf Islands is considered to be among the most productive marine ecosystems in the world.

To be more precise, the local waterways are host to a complex food chain that includes untold numbers of living organisms and leads right up to foundation fish species, salmon, and ultimately marine mammals like the critically endangered Southern Resident Killer Whales.

Glass Sponges

One of the first things that stood out as residents reviewed the video samples, were images of cloud, vase and boot sponges. These are all types of rare and ecologically valuable glass sponges.  While the presence of individual glass sponges is not cause for immediate alarm, it is known that, left undisturbed, they can lead to glass sponge gardens, which can form the basis for glass sponge reefs.

Up until recently, glass sponge reefs were thought to have gone extinct 40 million years ago. All of that changed in 1987 when living glass sponge reefs were found in Hecate Strait. At the time, scientists likened the discovery to finding a herd of dinosaurs.  

Since then, smaller reefs have been found in other locations off the Pacific Coast of Canada and the United States, including Howe Sound and in locations around the Southern Gulf Islands, including Mayne, Samuel and Galiano Islands and just off the northeastern tip of Gabriola Island.

According to BC’s Canadian Parks and Wildlife Service, “BC’s prehistoric glass sponge reefs are an international treasure.” They provide vital habitat to a wide range of marine animals including spot prawns and sharks. They are also important habitat for endangered rockfish, which feature prominently in the video.

Threats to Rockfish

Speaking of Rockfish, did know there are 27 species of rockfish, some of which can live to be over 100 years old?

In the Gabriola video alone several varieties of Rockfish including many Yelloweye Rockfish appear in terrain where anchorages are being proposed. “Yelloweyes” are listed as a species of concern under Canada’s Species At Risk Act and are one of the reasons there are over a dozen Rockfish Conservations Zones throughout the Southern Gulf Islands. Unfortunately this has not stopped the practice of allowing cargo ships to anchor in the vicinity.

It is well accepted in science that habitat size is directly linked to population size and to the nature of species interactions. All species require a minimum number and density of individuals to persist, which means they also require a minimum amount of suitable habitat. Rockfish already face a number of threats including overfishing, global warming and loss of habitat, too much of which is being taken up with industrial activity such as freighter anchoring.

So what does this all mean?

In this article, we’ve chosen to focus on just two of the important species that are impacted and just one of the many harmful impacts of anchorages – namely anchor scour.

We know this environment supports countless marine organisms from tiny species hidden to most on the ocean floor, to fish, marine mammals, endless populations of bird species, and the list goes on.

According to current statistics, close to 17% of fish, 34% of birds and 43% of mammal species that live in the Salish Sea are listed as either threatened, endangered or are candidates for that listing.  Many of them can be found in and around the Southern Gulf Islands.

Transport Canada is currently reviewing the system that allows foreign cargo ships to anchor without fees for as long as they want, outside of federally regulated Ports.  In the case of BC’s Southern Gulf Islands, we think the practice must be stopped and Canada must put the protection of our valued ecosystems ahead of the interests of foreign shipping companies.

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