September 11, 2012 — At a hatchery sitting near Qualicum Beach on Vancouver Island, Robert Saunders harvests scallops, oysters and mussels. During his 21 years of raising shellfish larvae in water pumped out of the Georgia Strait, mortality levels would rear up periodically for reasons unbeknownst to the aquaculture farmer. But nothing came close to matching his abysmal yield at Island Scallops Ltd. in 2010 when Saunders set out to grow 12 billion larvae and only seven million survived.
“I was tearing my hair out. I didn’t know what was going on,” he recalls.
“We had continuous failures in the hatchery… but never to this extent where batch after batch, spawn group after spawn group died.”
Saunders usually produces 40 to 50 million shellfish from a stock of less than one billion larvae, but attempted to raise significantly more that year because they kept dying.
Hunting for an explanation, he screened his hatchery for bacterial disease and was stumped when results came back normal.
He finally hit a break after reading a paper linking the death of a small mid-water fish to high concentrations of carbon dioxide in ocean water.
“It was the same thing we were seeing in our scallop larvae,” he says. “The fish didn’t swim very well, wouldn’t eat and died very easily.”
That’s when Saunders decided to artificially lower the carbon dioxide levels in the water used to raise his stock.
“It wasn’t until we actually started to degas the CO2 that we saw, it was miraculous, suddenly everything was living and growing,” he says.
Rising amounts of carbon dioxide in the waters in and around Baynes Sound, a channel regarded as the heart of British Columbia’s shellfish industry, have farmers like Saunders fearful about the future of their businesses.
“Basically, if you are harvesting shellfish with a shell, so clams, geoducks, urchins, scallops, muscles, then you should be worried,” Chris Harley reaffirms from his office at the University of British Columbia’s zoology department.
As an associate professor, Harley researches how creatures on the province’s coast are affected by ocean acidification – a term used to describe the continual decrease in the pH level of oceans worldwide that many scientists believe is caused by human emissions.
For shellfish, the resulting shift in ocean chemistry makes it a struggle for them to form their outer layer as a crucial ingredient to the process slips away.
“As you add carbon dioxide to seawater, the pH drops and carbonate ion availability goes down,” Harley explains.
“It’s just so energetically expensive to get those last few carbonate ions, or they just can’t find enough, that they can’t build their shells at the same rate they used to.”
In Saunders’s case, his larvae will perish when carbon dioxide levels are above 500 parts per million (ppm), although he says growing them below 400ppm is ideal. But lately, his work has been cut out for him as he is seeing water with concentrations as high as 750 and 800ppm.
While he can alter the pH levels of the water in the tanks and nursery where he raises larvae and juvenile-stage shellfish, he’s unnerved by his lack of control once the larger animals must be transferred into Baynes Sound.
“We can manage around the problem onshore, but of course in the ocean we can’t,” Saunders says.
“We’ll never be able to grow (shellfish) in tanks; we couldn’t produce enough food. So it is conceivable that we will not be able to grow it in the ocean.”
Read the full story on CTV News