British Columbia’s Sea of Glass


 |  Biodiversity/Conservation

Photo of a glass sponge (Source: Dr. Sally Leys, researcher at Fisheries & Oceans Canada)

Photo from the documentary, Moonless Oasis by Perpetuum Films

You’ve heard of the Great Barrier Reef in Australia, but have you ever heard of the glass sponge reefs in BC? 

The Howe Sound glass sponge reefs may be considered BC’s unofficial Great Barrier Reef upon their discovery in 1987, which surprised many marine scientists because they were thought to have gone extinct 44 million years ago. As such, they are sometimes referred to as ‘living dinosaurs’

What are glass sponge reefs? 

Glass sponges are deep water-dwelling animals. The name derives from their glass-like skeletal structures, which are made from silica. The existence of glass sponges isn’t new, but glass sponge reefs—a network of glass sponges—are incredibly rare. These reefs develop as sponges and settle atop the dead skeletons from previous generations. Overtime, they can span kilometres in width and grow to the height of an 8-storey building

As filter feeders, glass sponges feed on bacteria to improve water quality. Altogether, the Howe Sound glass sponge reefs filter up to 6800 Olympic-sized swimming pools per day. 

Glass sponge reefs also cycle nutrients in the water. Nutrients such as carbon and nitrogen are essential for ocean productivity. The reefs help distribute these nutrients, making them bioavailable to other marine creatures. They are biodiversity hotspots; along with their ecological functions, the reefs create an underwater oasis for many marine creatures to thrive. 

While glass sponge reefs are typically found in depths below 70 m, a portion of the Howe Sound reefs occur at depths around 20 m. These shallow reefs are unique to Howe Sound, though they face the biggest threat of destruction.

Threats to glass sponge reefs

Marine activities like bottom-contact fishing and anchoring pose dangerous threats to glass sponge reefs—especially the shallow reefs—because they can shatter the reef structures. Human negligence quickly destroys the reefs, but it takes a disproportionately long time for regrowth since the damage inhibits their reef-building capabilities. 

Unfortunately, losses in reef coverage are inevitable in the long term. Continuous warming from climate change weakens glass sponge tissue. From interviewing marine scientist Dr. Angela Stevenson, I learned that the glass sponge tissue withdraws in extreme cases, turning from its original creamy white colour into clear white, and dies from the bottom up. 

Ongoing marine conservation strategies 

Fisheries and Oceans Canada (DFO) has established marine refuge areas in Howe Sound, where fishing activities are prohibited. Currently, DFO is exploring opportunities to engage with the Howe Sound community and environmental non-profit organizations, placing focus on education around glass sponge reefs and marine conservation. 

The Marine Life Sanctuaries Society (MLSS) has been at the forefront of glass sponge reef conservation since its discovery in 1987. MLSS has collaborated with the government to enhance regulatory efforts toward glass sponge reef protection. Moreover, MLSS also supports marine scientists in glass sponge reefs’ research. 

The Howe Sound Community Forum (HSCF) is applying for the UNESCO designation, using the glass sponge reefs as a representative species. By designating Howe Sound as a world heritage site, the HSCF strives to raise awareness regarding the diverse marine ecosystem in our local waters. 


As a “Canadian national treasure”, the Howe Sound glass sponge reefs deserve recognition. Education could help increase the effectiveness of regulatory protection by bridging the gap between the local community and the regulatory body through knowledge-sharing. Additionally, strong public awareness would aid marine conservation efforts, potentially reducing vessel activities that could destroy the reefs. 

If you’re interested in learning more about glass sponge reefs, you can visit the MLSS website for more information.