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HomeTechnology & ScienceConservationists worry about destruction of B.C.'s rare glass sponge reefs

Conservationists worry about destruction of B.C.’s rare glass sponge reefs


Glen Dennison worries every time he heads out on the waters in Howe Sound outside of West Vancouver. That’s because he’s concerned about the health of the prehistoric creatures he found nearby.

“I discovered them — so, you know, right away, they’re my children,” Dennison said with a laugh on his small boat, which he has filled with custom-made equipment to monitor the rare glass sponge reefs below. 

Dennison was writing a book on diving in Howe Sound in 1984 when he made a significant discovery of massive glass sponge reefs. They look like something from another world, with beige and brown tubes delicately intertwining as fish dart between them. 

While individual glass sponges are not uncommon, scientists believed that reefs of them — also known as bioherms — which can grow to 20 to 30 metres high, had gone extinct 40 million years ago.

“When I saw it, I was totally amazed. I didn’t understand what I was looking at,” said Dennison. “It’s nature’s own artwork.”

These reefs are as fragile as the most delicate crystal, given that they are made of silica, the main component of glass. They can be instantly shattered by things like crab and prawn traps, anchors, fishing line and downriggers.

Not only are these sponges rare, scientists say they contribute to the health of the Howe Sound.

Glen Dennison has been fighting to protect the glass sponge reefs since he first discovered them in Howe Sound near Vancouver in 1984. (Dillon Hodgin/CBC)

“They filter the water, roughly every 90 days, of the entire sound,” Dennison said. “They’re bacteria feeders, they’re habitat for the rock fish here. So it’s an ecosystem that is not only beautiful, it is incredibly useful.”

But their fragility leaves them susceptible to damage from commercial and recreational fishing. Dennison describes seeing large square holes in reefs where traps have been dropped, damage that can lead to the death of nearby sponges. The steel balls dropped from downriggers are another example, he says.

Mapping the reefs

Dennison’s accidental discovery launched a decades-long fight to protect the reefs, with Dennison almost single-handedly funding most of the dives to document them. He used his skills as an engineer to create a special camera that can be dropped down dozens of metres to capture live images of the reefs and map every inch of them.

His work helped push the Department of Fisheries and Oceans (DFO, now called Fisheries and Oceans Canada) to put protections in place banning bottom-contact fishing. This prohibits any activities that make contact with the bottom of the ocean, including dropping traps or downriggers. 

But Dennison, now president of the Marine Life Sanctuaries Society, says it isn’t uncommon to find new damage.

“The DFO enforcement officers are doing the best job they possibly can out there,” Dennison suggested. “But they are so short-staffed that they just cannot protect the sound properly.”

On a recent Monday, Dennison brought divers Tori Preddy and Greg McCraken out on the water to check the health of the reefs.

This is an example of a custom 3D map created by Glen Dennison to capture every glass sponge reef, which is shown here in red. (Glen Dennison/Marine Life Sanctuaries Society)

Last fall, Preddy went for a dive and discovered damage from a prawn trap that had shattered the delicate tubes of a reef.

“I honestly thought we had been dropped at the wrong place,” she said. “I was like, what is this? Where is the reef? What is going on? So, it was really disheartening.”

Greg McCraken owns a dive shop and offers a course on diving the reefs. He teaches the technical skills required, as some reefs are 60 metres below the surface and require advanced deep-water diving skills. He also tries to teach divers the importance of protecting the reefs.

“To see how the reefs looked even 10 years ago,” he said. “It is really sad to see the images we are witnessing when we go down there [now].”

Punishments have increased

The Department of Fisheries and Oceans says it patrols regularly, adding that after the initial protections were put in place, infractions dropped dramatically. But Fisheries officer Eric Jean says the pandemic brought a whole new group of people on the water, and infractions jumped.

“There was a whole new cohort of individuals that are playing and recreating in these areas and perhaps under the guise they don’t know reefs are there,” Jean said.

He said new legislation from April of 2021 created higher fines and potential bans for recreational and commercial fishers.

“These new tickets are hundreds of dollars more than the tickets we had to utilize only a year ago,” Jean said. Officers also encourage people to report infractions and to reach out for information before heading out on the water.

But Dennison says more enforcement and education is needed.

“We cannot enforce on destruction,” he said. “That means that you can’t wait till someone drops a trap down there and hope that you’re going to give them a ticket or take away their gear. The reefs will be gone.”

While bottom-contact fishing is banned, many of the reefs do not ban dropping anchor, an issue DFO said was up to Transport Canada.

A rockfish is seen taking refuge inside the glass sponge reef. (Greg McCraken)

In statements to CBC, Transport Canada said, “Anchoring has long been recognized as accessory to the common law public right of navigation. While Transport Canada has not legally prohibited anchoring in these areas, in practice there are no commercial anchorage sites.”

A statement also said, “Operators of recreational boats who may be laying anchor over reefs should seek local information found in marinas on the area in which they will be navigating.”

Another threat

Another kind of human activity is also threatening the reefs’ survival: warming and more acidic waters due to climate change can also damage and kill the glass sponge.

Researcher Angela Stevenson was one of the only people who has been able to maintain small sponges in an aquarium to study the effects. 

She said warmer and more acidic water reduces their ability to filter water and ultimately damages them. 

WATCH | Scientists say glass sponge reefs are like living dinosaurs: 

Unique glass reefs off B.C. coast under threat

Glass sponge reefs are believed to only exist off British Columbia’s coast, but some say they are disappearing at an alarming rate despite recent new protections from fishing activities.

“It means they’re filtering a lot less of the microbes and the particles in the water,” she said. In her research she found that in warmer water “they could withstand less pressure. So they broke more easily.”

On this day’s dive, the news is not all bad. There does not appear to be a lot of new damage, at least at this one reef.

“There’s still lots of good sponges, but I definitely saw the damaged sponges as well,” McCraken said. “Pretty similar to what it was last time I was here.” 

But Dennison worries next time, this might not be the case.

“If it’s damaged or destroyed, it may not come back,” he said. “We don’t have the science yet to prove that these things are going to regenerate again. They may actually disappear off the planet.”


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