Fish researchers from the Vancouver Aquarium capture footage of cloud sponges in Howe Sound, just north of West Vancouver
On April 24, the Vancouver Aquarium fish research dive team visited a large cluster of cloud (glass) sponges – vital habitat for marine life – in Howe Sound that has been monitored for a half decade.
The same area had been visited earlier this year on March 22 and everything had been intact at that time but, on April 24, it was evident that two large chunks had been sliced off by fishing gear. There are also other factors that may have contributed to damaged cloud sponge, which we’ll go into more detail below. Aquarium fish researcher Donna Gibbs obtained various photos and videos illustrating the damage.
One potential cause of damage to cloud sponge could be climate patterns. Cloud sponges normally exist at considerable depth in the ocean, below the warmed surface waters of the sea. However, in Howe Sound there are specific areas where the configuration of the seabed forces deep, cold seawater upward toward the surface. At such sites, cloud sponges sometime survive for considerable periods of time and reach a large size because they thrive in cold water.
However, if an El Nino winter and spring bring warmer waters to coastal British Columbia, that could cause damage on the sponges. In recent years, a strong (and warmer) El Nino during 2009-2010 contrasted to the two previous years, which were cold. It appears that tissue death occurred in cloud sponges in shallower seas from Howe Sound to Texada Island during the late summer and fall of 2009, the season of El Nino.
In addition to climate effects, fishing gear can seriously damage these cloud sponges. The Aquarium dive team observed and documented the damage of various portions of the once-complete sponge, pictured in photos above. This added damage may affect future survival of remaining sponge structure, as the dead tissue supports living tissue. Dr. Bill Austin, cloud sponge researcher, has documented ultimate death of cloud sponges damaged by fishing gear in Saanich Inlet; see his web page for details.
Visitors to the Aquarium can get a close view of a sponge fragment in the B.C. Treasures Gallery in the Defence Island habitat. The fragment on display was returned to the Aquarium after it was cut loose by fishing downrigger gear at the Howe Sound site in the above photos.