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.

"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.

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.