By Judith Lavoie, April 2014
By the end of this century, local marine ecosystems are likely to have shifted beyond recognition due to ocean acidification and temperature rise.
For those who did not have ocean acidification on their radar, news last month of a massive die-off of scallops at Nanaimo-based Island Scallops came as a surprise. But the shellfish industry has been aware of the problem for almost a decade.
In 2005 billions of baby oysters died along the Washington coast and low pH, a measure of acidity, was suspected as the culprit. It wasn’t until 2012 that scientists believed they had proof that was the case.
Over the last five years, Island Scallops lost more than 10-million scallop larvae and, like most shellfish farms, the company is now buffering seawater in hatcheries with calcium carbonate to make it less acidic. “Since 2009 it has become obvious that the ocean is getting more acidic and over the last several months it has increased faster than anyone expected,” said Island Scallops CEO Rob Saunders.
Even scientists have been taken by surprise, believing, until recently, that the capability of oceans to absorb carbon dioxide was almost infinite because of buffering by dissolved chemicals. “Some 50 years ago, scientists thought the buffering capacity of the ocean was so great, we would never have a problem,” said Ken Denman, professor in the School of Earth and Ocean Sciences at the University of Victoria and chief scientist with Ocean Networks Canada. Atmospheric carbon dioxide absorption by the oceans even had a positive spin as it could help slow global warming.
With tonnes of carbon dioxide from burning fossil fuels dissolving daily in seawater, however, the chemistry of the water is changing, making it more corrosive. In the past 200 years, the ocean has become 30 percent more acidic—faster than any known change in ocean pH in the last 50 million years. Already, as recent news attests, larvae of sensitive creatures such as scallops are unable to form properly in the more acidic seawater, while in other parts of the world the shells of animals, such as scallops, oysters and corals, are dissolving.
“Organisms that produce shells and skeletons are having a hard time because they can’t get enough carbonate to produce those shells,” Richard Feely, of the US National Oceanic and Atmospheric Administration’s Pacific Marine Environmental Laboratory, told a recent Metcalf Institute seminar in Seattle.
Marine scientists, Denman explained, had hoped that with the growing realization that human activities are affecting the oceans, the amount of carbon dioxide being pumped into the atmosphere would decrease, allowing the ocean chemistry to stabilize.
But that optimistic view underestimated human attachment to oil, gas and coal and an overriding reluctance to change lifestyles. “We never imagined that the rate of burning of fossil fuels would keep accelerating to the levels they have been for the last few years. We didn’t imagine that, collectively, we wouldn’t take action,” Denman admitted.
Now the ocean around Vancouver Island and Washington State is facing a triple threat and, by the end of this century, local marine ecosystems are likely to have shifted beyond recognition. Fisheries will change as some species go extinct and others thrive, inevitably altering the type of seafood we eat.
The prime culprit is ocean acidification, but exacerbating the problem around this coast is the upwelling of low-oxygen, low pH water, from depths of 200 to 300 metres, which mix with surface water and further raise the acidity. “You get a lot of tidal mixing and you get big plankton blooms and the combination of low oxygen and low pH makes it worse,” Denman said.
The final piece of the triple trouble is warming water, which makes some marine animals more susceptible to acidity. That means creatures now commonly seen around our coast are moving north and their places are being taken by southerners. As Denman explained, “Naturally you are going to have different species because most marine animals are drifting pole-ward. They end up surviving best in temperatures to which they are best suited and that temperature is moving north, but they are not all moving at the same speed.”
Already salmon in rivers in Washington and Oregon are at the tip of their southern range and Pacific salmon have been found in Arctic rivers. Meanwhile, species usually found in warmer latitudes, such as Pacific sardine and jumbo squid, are expanding their range northward.
“We expect the ecosystem is going to look quite different,” Denman said. “When you add these three stressors together, we are not sure what is going to happen, but we are pretty sure it is not good.”
Similar chemical changes in the ocean took place millions of years ago, but took much longer, giving creatures time to adjust. “There have been major die-offs in ocean acidification events, but they took place over millions of years,” Richard Feely noted in his seminar. “The species afterwards were different from the species before, and we are moving towards an event like that.”
A Smithsonian Institute paper says that although some marine species will be able to adapt, others will suffer and there will likely be extinctions. “We can’t know this for sure, but, during the last great acidification event 55 million years ago, there were mass extinctions in some creatures, including deep sea invertebrates,” the Smithsonian paper notes.
Instead of ocean acidity levelling out (or decreasing), scientific modelling now predicts it will increase by between 100 percent and 150 percent by 2100, said Feely. In 2007 he tracked the water from Canada to Mexico. His study showed that, because of the way the water circulates, acidic water now surfacing on the West Coast comes from carbon dioxide that was absorbed by the ocean decades ago. That means that even if emissions were halted immediately, local acidification would continue to worsen for several decades before flattening out.
Such a realization means those in the shellfish industry are hoping to adjust in ways that allow them to survive. More research, they feel, would help.
BC Shellfish Grower’s Association executive director Roberta Stevenson is hoping the Department of Fisheries and Oceans and Genome BC will help with gathering information as the group does not have the funds to do extensive research on its own.
“The problem is that there’s so little known about [ocean acidification] even though it’s an ongoing, long-term problem,” said Stevenson, whose organization hopes to put out some monitoring stations this summer. Oysters in BC appear to be doing well, once they are beyond the seed stage, but scallops are more sensitive, she noted.
Island Scallops CEO Rob Saunders noted that Manila clams, geoducks and mussels around Vancouver Island also seem to be coping. He believes other factors, beyond acidification, are also at play, and would like to see more research into pH levels, especially as there is limited historic information.
Saunders appears to be pinning his hopes for the future on changing farm practices. As an example, he said, instead of choosing scallop breeding stock for meat and colour, they are now selected for their ability to survive acidity. The company is also looking at harvesting after one year, instead of two years, as is being done in China. Saunders said, “The unfortunate thing is that people like the size of our scallops,” but he hopes customers adjust their tastes to the smaller, sweeter scallops.
Stevenson is hoping solutions can be found to the many problems facing Vancouver Island shellfish farmers, including ocean acidification. “It will be a sad day when we can’t eat shellfish. How do you feel about eating jellyfish?” she asked.
Award-winning journalist Judith Lavoie was an environment and First Nations reporter for the Times Colonist for many years. Twitter @LavoieJudith