Stunning Glass Sponge Reefs Discovered Near Washington Coast

Habitat May Be Vital Breeding Ground For Regional Fisheries

By Emily Marshall

Plastic bottles. Torn fishing nets. Crab claws. All items you might expect to find in the by-catch of commercial fishing trawlers. But the presence of creamy white and yellow glass sponges believed to have gone extinct millions of years ago was not anticipated.

The presence of these fragments of glass sponges spurred University of Washington professor Paul Johnson to organize a reef-hunting expedition off the Washington coast. This past June, his team discovered massive reefs harboring all three known species of reef-building glass sponges. These newly revealed reefs are located 30 miles west of Grays Harbor, Wash. and are similar in size and composition to glass sponge reefs found off the coast of British Columbia in the 1990s.

Glass sponges are among the most primitive animals. They are white to yellow-orange cup-shaped filter feeders that siphon silica from the sea water to produce their namesake glass skeletons. Until they were discovered in British Columbia's Georgia and Hecate Straits, reef-forming glass sponge species had been thought to have gone extinct 150 million years ago when more efficient silica scavengers, the algae, evolved.

The deep water reefs off the Washington and British Columbian coasts suggest that the reef species adapted by moving deeper into the ocean. At 600-foot depths, silica and oxygen levels are high enough for sponge survival, but light levels are too low for their algae competitors, which must use sunlight to produce energy.

Johnson sought Washington Sea Grant funding to look for glass sponge reefs off the Washington coast after joining a 2005 University of Victoria expedition to the Georgia Strait reefs. He was intrigued by the undersea oases he saw, and realized that similar environmental conditions were present in Washington. Johnson had seen previous sonar images from the Washington coast showing apparent reef structures and was aware that fishing trawlers had long been bringing back shards of glass sponges. A seven-day cruise on the University of Washington research vessel Thomas G. Thompson confirmed his suspicion. Johnson's team found several reefs at depths of up to 650 feet on the edge of the continental shelf. The reefs are hundreds of feet in length and width and rise 6-15 feet off the sea floor.

The Washington reefs are in a much less sheltered region of ocean than those in British Columbia, and their discovery expands the known range of reef-building glass sponges to the open seas. A large methane seep is located near the Washington reefs and the sponges appear to be feeding on methane-consuming bacteria, or methanotrophs. A similar methane seep was recently detected near the Hecate Strait reef, but no connection to methanotropic bacteria has been made. The methane-based Washington ecosystem may therefore be unique among glass sponge reefs.

Johnson says that in an otherwise sparsely populated area of ocean, the sponge reefs housing zooplankton, sardines, crabs, prawns, and rockfish stand out as an important link in the ocean food chain. Similar to their coral reef cousins, the sponge reefs provide protection for pregnant and young fish, as well as refuge for many other species. The region of Washington coast surrounding the glass sponge reefs is a bustling fishery, and the reefs likely function as a nursery for the young of many species.

Scientists and conservationists are lobbying to expand the areas of seafloor protected from trawling to include the newly discovered sponge reefs. The reefs are thousands of years old, but one pass by a trawler can destroy centuries of growth and severely damage the ecosystem, much like chopping down a rainforest. Johnson says fishermen get agitated when asked not to fish such rich areas, but that this is short-sighted: "You could fish the area around a reef forever, but if you trawl it you're destroying the nursery and shooting yourself in the foot.”

Emily Marshall is a graduate student in microbiology at the University of Washington/Fred Hutchinson Cancer Research Center.

Images

Top: A rockfish explores the glass sponge reefs off the coast of British Columbia. Similar reefs recently discovered off the Washington coast may serve as a vital nursery for young rockfish and many other species. Photo: University of Victoria

Bottom: The box frames an approximately 2-square-mile region 30 miles west of Grays Harbor where University of Washington researchers recently detected large glass sponge reefs on the edge of the continental shelf. Map: University of Washington