Location of the Reefs
The Glass Sponge reefs we are focusing on are in the waters of Saanich Inlet near Senanus Island. Senanus island is part of the Tsartlip reserve, and encompasses sacred burial sites as well as being central to the ancestral history of the Tsartlip Nation.
The reefs lie in the deep (30M+) waters surrounding the island, and are most prevalent and vulnerable surrounding a pinnacle lying approximately 370 meters off Senanus Island at a bearing of 300d from the northernmost marker on the island.
What They Are and Why They Are Important
Glass sponge reefs are ancient, globally unique deep-sea ecosystems constructed by silica-based (glass) sponges. Thought to be extinct for millions of years, they were discovered alive off the Pacific coast of Canada. These incredibly fragile structures act as vital nurseries and habitats for numerous marine species.
Key Characteristics
Unique Skeleton: Unlike regular bath sponges that are protein-based, these sponges extract silica from the water to build intricate, rigid glass skeletons.
Massive Scale: They grow like coral reefs by piling on top of previous generations. They can form vast complexes covering hundreds of square kilometres, with some reefs soaring 25 metres tall—about the height of an 8-story building.
"Living Fossils": These reefs were thought to have gone extinct alongside the dinosaurs roughly 40 million years ago, but 9,000-year-old living reefs were discovered in British Columbia waters in 1987.
Extreme Fragility: They are highly susceptible to damage. Their glass skeletons break easily upon impact, and the fragile reefs grow very slowly, at a rate of only 1 to 2 centimetres per year.
Ecological Importance
Biodiversity Hotspots: The reefs provide a vital structural habitat, refuge, and nursery ground for many commercially and ecologically important species, including rockfish, prawns, halibut, and sharks.
Ecosystem Services: They act as important "filters" in the ocean. They trap fine sediments, play a significant role in carbon and nitrogen processing, and act as silica sinks.
Conservation & Threats
Fragile Recovery: Because of their slow growth and reliance on unbroken skeletal frameworks for new sponges to settle, destroyed sections can take hundreds of years to recover.
Human Impact: The reefs are highly vulnerable to bottom-contact fishing (like trawling) and industrial development (such as pipelines or shipping), which can crush the structures or smother the filter-feeding sponges with sediment. While other Glass Sponge Reefs in BC are currently specifically protected by DFO mandate (ie Howe Sound), the reefs at Senanus Island are not. The reasoning apparently is that the area is already designated as an RPA (Rockfish Protection Area) as well as other potentially overlapping designations. Therefor it falls to the local community to ensure that this entire ecosystem is better protected through information and education.
The Goal
As the interested parties in the preservation of the Senanus Island Glass Sponge Reefs are not a formally organised society or government agency, the goal at this point is simply public awareness, education and physical demarcation of the sensitive area (informational buoy). This has been accomplished so far through the use of Diver Training, Social Media, physical presentations (schools), media releases and TV documentaries.
Up to this point, the most sensitive area has been marked by an informal float secured to the bottom with an anchoring point located near the reefs, yet within reasonable distance so as to access the reefs by a short swim by divers. This anchor point is semi-permanent, and is there to ensure that boats do not attempt to anchor anywhere in the area and potentially damaging the reefs. This system has worked reasonably well for many years, but sadly has been the target of theft numerous times. As private individuals, new buoys and line and chain have been purchased multiple times and installed, only to have the marker buoy 'disappear' again and again. The most recent buoy was clearly marked as "PROTECTED AREA" and "DIVE SITE", yet was removed by parties unknown within a month of installation. We have learned that the most effective way to garner public support and respect for sensitive underwater habitats is through education. By photographing and documenting the reefs divers have the tools needed to inform the public - simply talking about it or describing it doesn't seem to garner the needed attention to promote awareness and care.
The Interested Parties
The primary source of information thus far has been recreational divers who have a passion for all things underwater, but with a particular focus on preserving and protecting the fragile underwater habitat we are fortunate to be able to visit. The mantra of "Take only pictures and leave only bubbles" is shared by all and is reflective of these values. No spearfishing, no picking up crabs, and no touching of anything are the rules. The only exception to this is when man made items are found littering the seabed - cannonballs, old prawn or crab traps, garbage that has been thrown overboard by careless boaters, etc. When safe to do so, these types of items are carefully removed and brought to the surface for proper disposal.
There have been numerous efforts to inform the public about this specific ecosystem - many of them ongoing. Below are just a few examples of the public outreach specific to the Saanich Inlet Glass Sponges and is shared to underline the widespread support amongst the environmental community for continued work to protect the reefs.
APTN (Aboriginal Peoples Television Network)
Television Series "Web of Life"
Season 1 | Episode 7 "The Sea of Glass"
Aired 13 December 2025
This episode focuses specifically on the Glass Sponge Reefs of BC and specifically the interests of the aboriginal peoples in their preservation and the conservation of the surrounding ecosystem.
CPAWS (Canadian Parks and Wilderness Society)
"Saving the Sea of Glass"
Visit CPAWS Website
Watch Video
Sponges of the Northeast Pacific Ocean
This website sadly no longer updated due to lack of funding. It is likely available for continued support if it was offered. Information below is from the current website:
Are You A Prawn Fisher? In Saanich Inlet sponges occur only shallower than 230 ft. Here prawn fishers can avoid damaging sponges by keeping their traps below 250 ft. as long as the water has oxygen. However, in other inlets sponges may be destroyed at depths down to 400 feet. On an Easter weekend, biologists mapped the locations of 64 prawn traps (red dots) in the recreational fishery in Saanich Inlet, BC. Commercial fishermen can each deploy 150 to 300 traps at a time.
Are You a Crab Fisher? Please keep traps shallower than 100 ft. and on soft bottoms.
Are You A Line Fisher? Please lift up cannonballs and lines to shallower than 100 ft. when near known sponge gardens such as in Saanich Inlet.
Are You a Scuba Diver? Practice outside the sponge beds, avoid flailing kicks, adjust your buoyancy to stay off bottom and photograph but don't touch.
This sponge was tom in two by a cannonball or a prawn trap. It subsequently died and became covered with silt. It is likely the plumbing of the pumping system had become too disrupted. Most sponges breakdown when they die, however, the mainframe skeleton of a Cloud Sponge remains intact for at least decades.
Examples of common things that cause damage to glass sponge gardens: fishing cannonball prawn trap, scuba diver.
Be Sea Adventures
Of particular note is the video taken by local diver Ryan Swan on the Saanich Inlet Glass Sponges. This documentary has been widely shared via social media and has proven to be an excellent outreach to the broader community. The video was also picked up by Global News and broadcast nationally in April of this year providing education and information about this fragile resource to the entire country.
UASBC
The Underwater Archaeological Society of British Columbia (UASBC) actively explores and documents marine ecosystems, including encounters with ancient deep-water glass sponges (such as cloud sponges) during their technical and wreck diving expeditions in local Pacific Northwest waters like Saanich Inlet and off Port Hardy
Here is an overview of these fascinating deep-sea creatures and their relationship with the local diving community:
- What They Are: Glass sponges are ancient, fragile sea creatures that construct their skeletons entirely out of silica (glass). They form globally unique reefs and bioherms that provide vital habitats for various marine species, including young rockfish.
Project Baseline
Visit Website
Project Baseline is a global grassroots conservation initiative and citizen-science project that mobilizes divers to document and track environmental changes in aquatic ecosystems. By logging dive data, photos, and videos, volunteers help build a long-term catalog of underwater conditions. There is a specific local chapter that documents the health and changes of the Glass Sponge ecosystem in Saanich Inlet.
New Partners Welcome!
It is our collective wish to have all interested parties join us in the informative efforts and protection of the Senanus Island Glass Sponge Reefs. THIS IS NOT A SOLICITION FOR FUNDS. It is simply hoped that as resources develop, that sharing of information via posters, pamphlets and other means would be possible.
New Marker Buoy
Through private funding a new (proper) white informational buoy has been obtained.
It is slated to have decals installed as follows:
- Reflective tape around the uppermost part of the vertical cylinder.
- "GLASS SPONGE REEF MARINE REFUGE" around the perimeter.
- DIVE FLAGS in 3 locations around the lower perimeter.
- With the Tsartlip First Nation's permission, their band LOGO on one side of the upright cylinder.
- On the other side of the upright cylinder, symbols indicating NO ANCHORING NO PRAWNING NO FISHING
This buoy will be installed by qualified volunteer divers when it is complete. It will be attached to a mid-line float at approximately 7M depth. The midline float will then be secured to the existing anchoring point. An attachment point at the surface will be installed to allow for safe diver access to the reefs without endangering any of the surrounding ecosystem.
Conclusion
This overview has been put together as a first step in hopefully gathering support for all efforts to promote education and information surrounding the Glass Sponge Reefs in Saanich Inlet - particularly around Senanus Island. The hope is that through community involvement and cooperation we will work together to ensure this fragile ecosystem in our own backyard is preserved for generations to come. The sharing of information, photos and videos between all parties as desired as well as with the general public will go a long ways to increasing public awareness and ultimately the conservation of these ecosystems.
If further information is desired or a willingness to help and become involved in this effort, please feel free to contact Keith Karlsson via email at thekarlssons@shaw.ca.
Keith Karlsson
Project leader
Been on the water all my life
2000+ dives in BC and WA state waters. Hundreds of those in Saanich Inlet.
Divemaster and TC ticketed small boat captain.
Recently retired from life career at Sherwood marine.
