Rare glass sponge reefs are at risk of starvation with increasing temperatures in the waters of Howe Sound and the Strait of Georgia off B.C.’s South Coast, new research shows.
Researcher Angela Stevenson produced the study over three years while at the University of British Columbia’s department of zoology. She says warm waters can severely hinder the reefs’ ability to filter water.
“Their ability to filter is reduced by two to … 5.5 times,” said Stevenson whose findings were published in Scientific Reports.
The reefs, some of which can grow as tall as 20 to 30 metres, play an important role in maintaining water quality in B.C.’s oceans by filtering microparticles and passing nutrients down to creatures deeper in the ocean.
They also provide habitat for lobsters, crabs, rock fish and prawns, among other species.
“It’s feeding ground, it’s a nursery ground, it’s a place where different species seek shelter,” said Stevenson.
“It’s like a metropolis at the bottom of the ocean.”
Stevenson said they measured the water in Howe Sound during the summer months of their research period, then emulated those temperatures in their lab and found it had adverse effects on their sponge samples.
“We increased the temperature … by 1.5 degrees Celsius, which is pretty conservative and it’s within the near future projections,” said Stevenson.
“We saw stress in which they stopped feeding… Once you stop feeding, you’re starving your tissue,” she added.
This species of glass sponge was thought to have died off 40 million years ago, until fragile living reefs were discovered near Haida Gwaii off B.C.’s North Coast in the mid-1980s.
The reefs are easily damaged by fish nets, bottom trawling and any industrial activity that stirs up sediment and clogs the sponges’ filters.
In early 2017, the federal government restricted commercial fishing in a 2,410-square-kilometre marine conservation area to protect the sponges, comprising three sites between Vancouver Island and the archipelago of Haida Gwaii which are in addition to the smaller protected areas to the south.