UCBC Exploratory Dive Series
Dive 2 - Lost Reef Bioherm
March 22, 2015
The Lost Reef area of Howe Sound, British Columbia, lies between Pam Rocks and the Christie Islet Bird Sanctuary.
Although there is no indication at the surface of anything unusual, sonar has revealed that an underwater mountain rises up between these two small spits of land, to a minimum depth of around 34m at mid-tide.
Drop camera footage has shown that this pinnacle is home to a Glass Sponge Bioherm, a massive cluster of slow-growing sponges that have built themselves up into reefs over long periods of time.
The frameworks of these sponges are composed of silica, so when they die they don't decompose, but are instead flattened into a durable substrate by the weight of successive generations of sponges growing atop them.
Their growth rate is estimated at 0-7cm per year, and their lifespan can be measured in centuries. Slowly accumulating over many generations, sponge reefs can potentially reach sizes up to 19m high and kilometers wide.
Glass Sponge Bioherms are very rare, found only in the Strait of Georgia and Howe Sound.
In addition to filtering bacteria from the water for food, they also provide excellent habitat for rockfish, spot prawns and other marine species.
On March 22, 2015, expert technical divers Hamish Tweed and Chris Straub descended into the Lost Reef Bioherm for a preliminary look.
The scope of what they found astounded them.
Up until this point, the only observations we have of the Lost Reef Bioherm have been obtained through the use of drop cameras, which gave us an idea of what was down there, but failed to convey the panoramic scope of this rarely-seen environment.
"You don't understand it," said Hamish Tweed, "You just don't get it until you're almost literally standing next to it... I just wasn't expecting it at all."
The divers descended onto the top of the pinnacle and swam down a slope that was thickly covered with sponges, some of which were up to two meters in height. In between clusters of sponges were trenches of dead sponge large enough that the divers could swim along them between the clusters, with sponges hedging them in on either side. The dead sponge did not appear to have been damaged by human activity, which is presently a problem for other sponge habitats in Howe Sound, notably the Kelvin Grove Sea-mounts.
The Lost Reef Exploratory Bioherm Dive video footage has revealed up to two sponge species that may have been undiscovered prior to the Lost Reef's exploration. In among the sponges the divers saw a large number of crabs and fish, including rockfish. Further study on this site will include an attempt to establish a count of gravid rockfish, and the collection of water samples at depth.
After spending about 20 minutes at and around their maximum depth of 69m, the divers left the pinnacle and began the long series of decompression stops and gas switches that would bring them safely back to the surface. 17 stops and 80 minutes later, they reached the surface and were assisted onto the dive boat.
Having successfully conducted this preliminary dive, they were now forearmed with knowledge of the Lost Reef Bioherm site.
Subsequent expeditions planned for the UCBC Exploratory Dive Series will be more focused on studying the inhabitants of the reef in order to better understand and protect this rarely-seen niche of British Columbia's ecosystem.