Glass sponge reefs are unlike anything else in the world. These fragile bioherms can reach 14 meters in height and cover a square kilometer, providing an important habitat for the fish that live in them. Until about twenty-five years ago, people believed that glass sponge reefs had gone extinct during the Jurassic Period, but then they were discovered living in very deep water in Hecate Strait in northern British Columbia.
During the last fifteen years, diving biologists have discovered several of these ancient glass sponge reefs at locations in Howe Sound where the depths are shallow enough to be safe for divers using compressed air. Expert sport divers can safely get to these reefs located between 25 to 35 meters in depth, and the opinion amongst the diving community is that the public needs to become much more aware of these reefs if there is to be any chance of them being considered for protective management to ensure their future. B.C.’s commercial spot prawn fishermen have, just recently, agreed to voluntarily avoid nine prehistoric glass-sponge reefs in the Strait of Georgia to help better protect these fragile environments.
Vancouver Aquarium divers have been monitoring three of these reefs, but it turns out that the shape and size of the sponges can vary enough that a video from one year cannot be related to images from previous years since the sponges change so significantly. It is not always growth that occurs either. The warmer El Nino years appear to cause physical distress so that some of the sponge growth dies back, but re-growth occurs at a pace that surprises some experts. A great deal needs to be learned from repeated observations at precisely defined places.
In order to allow for confirmed locations to document these glass sponges, the Aquarium crew decided to install coded stakes in the mud adjacent to the outer edge of one reef, so that video or photo frames could include a code that will enable comparisons through time. The video above shows a couple of these stakes and asks for diver interest; that interest will soon be directed by a new Vancouver Aquarium web page. Stay tuned for new developments. The federal government is underway with a plan to protect many sponge reefs in the Strait of Georgia and Howe Sound in 2015, but only one of these shallow, dive-able reefs is included in that plan.
For more information or questions about the monitoring of these glass sponge reefs contact a member of the Vancouver Aquarium research team at: 604-659-3780 or via email [email protected].