Magazine article Natural History

Glass Castles in the Sea

Magazine article Natural History

Glass Castles in the Sea

Article excerpt

Reef-building sponges are giving up their long-held secrets.

Autumn arrived on a night wind along the Strait of Georgia, the Pacific Ocean waters between Vancouver Island and the mainland of British Columbia. The next day, a cold snap whipped waves into whitecaps as a research vessel maneuvered into position in a fjord known as Howe Sound. On deck, a crewmember closed the vaultlike hatch of the Aquarius, a fourteenfoot-long submersible.

In the sub's bubble-like chamber were a pilot and two biologists. They were about to descend hundreds of feet beneath the water's surface, beyond the world of sunlight and plants, to the realm of darkness. Called "Journey to the Sea of Glass," the October 2013 research cruise was sponsored by Nuytco Research, Ltd., owner of the Aquarius, and the Canadian Parks and Wilderness Society (CPAWS).

Swaying like a Ferris-wheel chair, Aquarius was lowered to the ocean surface on a cable above the ship's stern. Waves splashed against the bubble, and the craft gently sloshed back and forth. From inside, the view changed to the light blue-green of the sea.

The natural light faded as Aquarius slowly descended to the seafloor. Illuminated by the sub's light beams, creatures as bizarre as those in the works of Jules Verne came in sight. They loomed through the sub's lens like forests of white, yellow, and orange bushes: glass sponges, organisms with surprisingly successful adaptations to the deep's harsh conditions. Some had gaping openings known as oscula, while others beckoned with undulating fingers. Still others were masses of snow-white frills.

"At one time, however, we didn't think we'd spot something long believed extinct: glass sponge reefs," says Sally P. Leys, a marine ecologist at the University of Alberta, Canada. "We now know that these fragile reefs-of-glass thrive in the depths off the Pacific Northwest."

Indeed, not long before the Howe Sound dive, researchers had discovered glass sponge reefs in Portland Canal, an arm of Portland Inlet, part of the border between southeastern Alaska and British Columbia. Despite its name, the "canal" is a fjord. It extends seventy-one miles northward from Pearse Island, British Columbia, to Hyder, Alaska. Glass sponge reefs have now been documented along the Pacific Coast from the southernmost major fjord, Howe Sound, to the northernmost Alaskan fjord at Lynn Canal, a distance of 800 miles.

"Journey to the Sea of Glass" was the first submersible expedition to the bottom of Howe Sound. Leys found her quarry everywhere she looked.

"The deep was alive," she says, "with glass sponges."

II the fer distance, their long-dead relatives looked on.

"Mummies," they're called, these strange shapes that form one of the largest structures ever to exist on Earth.

Stretching overland some 1,800 miles from Spain to Romania is a fossil reef, a sinuous curve of millions of mummies that were once living, vase-shaped animals. In its heyday during the Jurassic Period, from 200 million to 145 million years ago, the reef was larger than today's Great Barrier Reef off Australia's northeast coast. Now it's visible only in outcrops dotted across southern and central Spain, southeastern France, Switzerland, southwest Germany, central Poland, and eastern Romania near the Black Sea.

The ancient reef was made up not of corals, but of deep-sea sponges called hexactinellids. Unlike corals, which build a skeletal structure of calcium carbonate, glass sponges use silica dissolved in seawater to manufacture a skeleton of spicules-tiny four- or six-pointed siliceous "stars."

Individual glass sponges, such as the beautiful Venus' flower basket sponge (Euplectella aspergillum), are still found in the deep sea, but those species belong to a different order from the Jurassic reef builders. The reef-building glass sponges, scientists reasoned, went extinct 100 million years ago, driven out by competition from newly arrived diatoms, single-celled algae that use the silica in seawater to build cell walls. …

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