Beneath the surface of the sea along B.C.’s coast lies a city of living, growing glass. Towering up to 20 metres above the murky darkness of the sea floor, glass-sponge reefs are delicate twisting structures of silica. Their shapes vary from maze-like branches to billowing, cauliflower-like clouds.
Until recently, nobody had been able to keep glass sponges alive long enough for meaningful study. However, Angela Stevenson, a biologist at the University of British Columbia, has pioneered research on glass sponges that flourished in her lab for a record length of time — apart from those she subjected to heat and acid to test their resilience. That impressed other researchers.
“I got an email and they were like, ‘It’s amazing that you’ve kept them two months’… I was like, ‘It’s actually five,’” Stevenson said. “They were like WOW!”
Individual sponge gardens can be found across the world, but B.C.’s expansive glass-sponge reefs are the only known ones on Earth.
Until 1986 when scientists discovered the reefs in Hecate Strait, which sits between Haida Gwaii and the northern B.C. mainland, glass-sponge reefs were thought to have disappeared 40 million years ago.
“If we re-discovered a T. Rex, people would go crazy,” said Stevenson. “This is what happened with the sponge reefs.”
As more glass sponge reefs continue to be discovered, scientists are becoming increasingly aware of the threat human activity poses to these living fossils. One recent reef discovery in the Broughton Archipelago was found smothered under a layer of waste from a salmon farm.
Broader concerns include warming sea temperatures and ocean acidification.
Stevenson’s research raises serious questions about how climate change will affect sponges’ essential role in B.C.’s marine ecosystems. Warmer ocean temperatures appear to be dramatically weakening their filter-feeding abilities, which are essential element in maintaining local food chains.
“When you change the balance, that’s when you get problems,” Stevenson said. “I don’t know how the system will be impacted, but we are likely to see cascading effects.”
Glass sponges constantly pump water through their glassy structures, taking bacteria and other small particles out of the water to use for growth.
These chimney-like tubes start by drawing in water through the pores lining their walls. Cells fixed to the inner walls then shuffle the water and food up to the top using protein whips.
Other cells grab and eat the micro-organisms floating through the water and, finally, clean water is pumped out of the top.
They’re filtering the water for the entire ecosystem. Even Stevenson’s little laboratory sponges are ravenous filtration machines.
“Imagine drinking 72 one-litre cartons of milk in one hour. That’s one little sponge,” Stevenson said.
Stevenson said this feeding process is key to B.C.’s marine environment. “They’ll filter the Howe Sound in one year – the entire body of water,” Stevenson said. The reefs also provide habitat for other sea life.
Based on Stevenson’s lab results, all the animals in the food chain could be affected as sea temperatures and composition change.