Glass sponges may be one of the most peculiar creatures on the planet. These animals were one of the first complex lifeforms on the planet and individuals may live for more than 200 years.
They create complex and beautiful skeletons made of silica (the same compound that windows are made of) that look like they’ve been woven out of lace.
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Found around the world, usually in deep waters, these filter-feeders are typically solitary or scattered across the seabed.
But in 1987, researchers from the Geological Survey of Canada discovered something incredible: they found four glass sponge reefs in the Hecate Strait and Queen Charlotte Sound in British Columbia, Canada.
Two hundred million years ago, glass sponge reefs could be found across the Tethys Sea: a prehistoric ocean located where central Europe is found today.
“Glass sponge reefs were thought to have gone extinct about 40 million years ago,” explains NOAA on its website. “To date, these are the only such reefs known to exist.”
Glass sponge reefs comprise just three different species – Heterochone calyx, Farrea occa, and Aphrocallistes vastus – which can merge their bodies together to form a reef.
According to UNESCO World Heritage Centre, “rather than just building on top of one another, reef-building glass sponges fuse their silica skeletons together to build a rigid but delicate framework.” When the sponges die, new individuals settle on top of the framework created by the remaining skeletons, a little like an oyster reef.
This natural marvel in British Columbia is believed to be around 9,000 years old – that’s older than Stonehenge.
The remarkable reef holds the Guinness World Record for the largest concentration of glass sponge reefs on the planet. It covers more than 270 square miles in waters between 140m and 240m deep. At some points, the reef grows to an impressive 21 metres – that’s taller than three giraffes balanced on top of one another.
Like coral reefs, glass sponge reefs are important habitats that provide a home for many animals, including crabs,prawns, starfish, and fish such as rockfish, herring, halibut and even sharks.
Perhaps surprisingly for something that has survived for thousands of years, the world’s biggest glass sponge reef is not particularly resilient.
“These sponges are exceptionally fragile, with skeletons made of silica, or glass,” says the Government of Canada on its website. “The ocean conditions necessary to allow such large reefs to develop are rare, and the fragility of the reefs makes them vulnerable to damage from human activity.”
These incredibly delicate creatures can shatter easily, which can be catastrophic for the reef. “The slow growth and vulnerability of the sponges suggests that recovery from damage may take tens to several hundreds of years,” says the Government of Canada.
Much of the reef has already been damaged by human activities, such as bottom trawling. As well as physically damaging the sponges, this type of fishing can have other negative impacts. For example, being smothered by sediment can prevent these filter-feeders from getting the nutrients they need from the water.
The reefs are protected but, sadly, they had already been harmed by fishing activities. “Over half of the large reefs in Hecate Strait were destroyed by trawlers before fishing closures were put in place by the federal government in 2002,” according to the IUCN. Protections were later increased to forbid all types of fishing that put or drag nets on the seafloor from taking place within 200 metres of the reefs.
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Top image: Hecate Strait and Queen Charlotte Sound by DoraDalton / Getty Images
