Weekly Sea Discovery: the Rare Glass Sponge Reefs of British Columbia

For our first Weekly Sea Discovery we are showcasing the incredible glass sponge reefs discovered off the coast of British Columbia which were thought to be extinct from the entire globe.

Following the first discovery of these reefs in Hecate Strait in 1987, scientists widened their search and found multiple reefs in the Strait of Georgia and Howe Sound—and, amazingly, right off the shores of Mayne Island! Our local reef is made up of two glass sponge (Hexactinellida) species: the Cloud Sponge (pictured below) and Fingered Goblet Sponge. These sponges can grow large and in all sorts of shapes, providing a complex structure that is important habitat for many organisms in the surrounding communities such as rockfish, spot prawns and other invertebrates.

Cloud Sponge. Photo: Dan Hershman

What exactly is a sponge? Sponges are invertebrates made up of porous skeletons that have cells which pump water from the outside-in. Through this process they filter all the tiny bacteria and microbes from the water for food.

While you may never see these mysterious glass sponges with your own eyes, these reefs have a very important role in the filtration of our ocean. Just one kilometre of reef can filter 80,000 litres of water in a second! Even with this massive pumping power, glass sponges are as fragile as their name suggests because their structures are made up of needles of glass known as “spicules”. These glass skeletons can shatter from a sudden disturbance.

Diver Observing Hecate Strait Glass Sponge Reef. Photo: Adam Taylor

Because of the fragility and importance of these ecosystems, the Department of Fisheries and Oceans has protected areas of glass sponge reef from commercial and non-commercial fisheries through the Strait of Georgia and Howe Sound Glass Sponge Reef Conservation Initiative. For example, fishing practices like bottom-trawling can destroy sections of glass sponge reef. Bottom-trawling also disturbs sediment that can smother the sponges. It is important that we continue to protect these unique ecosystems that support a wide number of species and keep our ocean clean.

A rock fish peaks out of a glass sponge reef near Gambier Island. Photo: Adam Taylor

If you’d like to learn more about these amazing creatures, check out http://glassspongereefs.com/ created by the Canadian Parks and Wilderness Society.


Brenda Webster · May 4, 2020 at 8:38 am

Just amazing and all the more reason to regulate commercial fishing methods!

    Charlotte Matthews · July 23, 2020 at 9:52 am

    Thanks Brenda. Working with fisheries in order to protect these habitats is essential.

Glen Dennison · July 22, 2020 at 9:54 pm

The marine life sanctuaries society of BC has lead the path for discovery, documention and protection of the Howe Sound reefs. Check out the MLSS web site for the most up to date information on glass sponge reefs.

    Charlotte Matthews · July 23, 2020 at 9:49 am

    Thank you so much Glen, I will check out their research on the Howe Sounds sponge reefs.

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