In September, after months of reporting from the South Pacific to Alaska, The Seattle Times published Sea Change, a series of stories that detailed the threat posed by ocean acidification.
Earlier this week, local weather expert Cliff Mass, a professor of atmospheric sciences at the University of Washington, posted a lengthy critique of one of the stories on his weather blog. Then, on Friday, he went on the radio to talk about it. Mass suggested a major tenet of that story – that ocean acidification already has killed billions of oysters in the Pacific Northwest – was not true.
His rationale for his post was this: “Trying to scare folks by blaming current problems on atmospheric CO2, without strong evidence, ruins the credibility of the scientific community. And credibility is a precious thing.”
Mass could not be more correct about the importance of credibility.
Unfortunately, his conclusions are wrong, because his critique ignored the actual science.
Here is how Mass characterized his central thesis: “The Seattle Times minces no words: Damage to the shellfish industry during the last few years is the clear result of increasing CO2 in the atmosphere. This conclusion is probably not true, for reasons described below.”
Here’s the key problem with Mass’ statement: Ocean acidification actually is to blame for current problems with Northwest oysters. And that fact is supported by strong evidence. Suggesting otherwise is a misreading of the science.
Readers need not take our word for it.
Mass neglected to mention that it wasn’t The Seattle Times that reached this conclusion. It was some of the world’s foremost experts in chemical oceanography – the scientific community that actually understands the role of carbon in the ocean. We interviewed these scientists over and over – some more than a dozen times – and reported their findings, which are backed by a combination of several studies. The key ones are here, here, here, here, here and here. (Mass did not reference any of them.)
Many of the experts – Richard Feely, Chris Sabine, Simone Alin, Jeremy Mathis, all with the National Oceanic and Atmospheric Administration in Seattle – have been furloughed by the government shutdown and aren’t available to respond. But several have spoken publicly in the past about the link between atmospheric CO2 and shellfish deaths.
Here, starting at about 2:45, Feely describes to a European reporter ocean acidification’s role in the deaths of oysters in the Pacific Northwest: http://www.youtube.com/watch?v=eUG21s-6sFs.
Here, during a lecture earlier this year at a conference sponsored by the International Council for the Exploration of the Sea, Feely goes into more detail. His discussion of the oyster phenomenon begins at 24:20: http://www.youtube.com/watch?v=etFob9Wy45E
Sabine takes an even more thorough look here, at about 38:00: http://www.youtube.com/watch?v=vaRgGpRS8dI
Mass is not a chemical oceanographer, but he is a scientist with some familiarity with these issues. So, to be absolutely certain we did not make a mistake, The Seattle Times asked another of the region’s leaders in chemical oceanography, Burke Hales, at Oregon State University, to review his critique and our story.
Hales’ pioneering research in ocean carbon chemistry underlies much of what we know about the role carbon dioxide from fossil fuel emissions plays in changing the chemistry of Northwest seas.
After reading Mass’ critique, here is Hales’ response: “The Seattle Times got the oyster story right.”
We asked Hales what he thought of Mass’ contention that “atmospheric CO2 is probably not” the cause of recent oyster problems.
Hales was blunt. “This is not true.”
Here’s why: Waters welling up from the deep along the coast during certain wind events are naturally rich in carbon dioxide and bring that CO2-rich water right to the surface. That CO2 reduces the availability of certain chemicals in the marine water that young oysters draw upon to form their shells.
“This has been known for a long time and been thoroughly published and vetted in the published scientific literature for a couple of decades,” said Hales.
Under normal conditions, Pacific oysters, a nonnative species here, do OK, but live right at the edge of their tolerance.
But just a little extra CO2 can push larval oysters over a threshold so that they have trouble making shells. This, too, “has been covered extensively in the recent scientific literature and the cause of the sensitivity is known,” Hales said.
These changes in ocean CO2 were the leading cause of death for billions of larval oysters at Whiskey Creek, a major shellfish hatchery along the Oregon coast that supplies young oysters to many of the shellfish growers in Washington. Scientists know this through their own research. Even more telling, Hales said, is that when hatchery workers found ways to reduce the CO2, oysters stopped dying.
“When steps were taken to address ocean CO2 levels (artificial chemical buffering, monitoring to avoid the worst conditions), the problems greatly decreased,” Hales said.
So the question is: Where did that extra bit of CO2 come from?
This is what Mass takes issue with.
He pointed out that natural variability in CO2 – from upwelling and factors such as plant and animal respiration and decay – is high along the coast and in Puget Sound. He argued that this variability is so great that it dwarfed any change in CO2 caused by absorption of human-caused emissions. Mass wrote: “The clear implication: the Seattle Times has gotten this story fundamentally wrong.”
Not so, said Hales.
“The existence of natural variability in no way implies that the story is fundamentally wrong,” Hales said. “Natural variability has never been swept under the rug. It is prominently featured in each of the scientific publications that provide the basis for the Times article, and explicitly addressed.”
Instead, Hales said, Mass seemed to miss that this natural variation is what, under normal circumstances, already can bring young oysters so close to their tolerance. The rising baseline of CO2 from fossil fuel emissions just pushes them over the cliff.
“The rising baseline means that the ‘bad’ intervals caused by natural variability will be worse, more frequent, and more persistent,” Hales said. “The existence of natural variability probably makes things a little worse – if the coastal waters were always constant at today’s atmospheric CO2 levels, there would be no instances of harmful conditions until 2040 or so when the atmosphere reaches the break-even point we identified for oysters.
“The fact that natural variability sometimes puts the system close to bad conditions means that the rising baseline will put those close encounters into dangerous territory.”
Hales agreed that wide swings in the natural variability of ocean CO2 would have created harmful conditions in the past on occasion, “but they would have been fewer, less intense, and shorter in duration than was observed.”
Today, the CO2 content of these upwelling waters is higher than it has been in the past, “because of the addition of anthropogenic (human-made) CO2,” Hales said. “This has been published in the scientific literature on two occasions, once in 2008 and again in 2013, using well-established methods for doing the calculations.”
The result: “The most recent publication suggests that harmful conditions (for oysters) are three times as likely to occur now as in pre-industrial times,” Hales said.
The idea, as Mass suggested, that other sources of CO2 – from decaying organic matter to pollution – are the more likely cause of increased CO2 is just not supported by science, Hales said.
Since 2007, Hales said, “the possible natural causes like intensified upwelling and increasing hypoxia” have not been particularly remarkable. “Yet the CO2-induced oyster failures have increased.”
Meanwhile, “there is no evidence that any other factor like logging practices or sewage treatment pollution discharge has gotten worse over time,” Hales said.
The Oregon coast, for example, where the biggest hatchery draws water from the sea, is relatively pristine.
“First, the global signal of these other pollutants is miniscule compared to the CO2 effect, and none of these factors are at work in the open-coast and Netarts Bay (the site of the Whiskey Creek hatchery, along the Oregon coast) setting where we documented the influence of anthropogenic CO2 in coastal waters and the CO2 effect on larval oysters,” Hales said.
“Second, there is the issue of timing,” Hales said. “The effects we documented and explained for the larval oysters occurred in summer, when the influence of river discharge is minimal on the open coasts and the ocean input dominates the chemistry of the source waters. Winter 2006 and 2007 flooding events had nothing to do with summer 2009 ocean or bay chemistry, or the response of larval oysters to that chemistry.
“The relative importance of local factors in Puget Sound and Hood Canal has also been studied and addressed in a scientific publication,” Hales said. “This is not my work, but these other potential drivers have been addressed.”
Lastly, Mass pointed to another blogger’s contention that perhaps the real cause of shellfish deaths was that oyster growers had employed bad practices at their hatcheries.
Again, Hales dismissed the suggestion.
“I’ll take special exception to the ‘poor practices at oyster hatcheries’ comment,” Hales said. “The suggestion that oyster hatchery operators were doing all the right things until recently, and then just suddenly started doing things that somehow made their production sensitive to CO2 is absurd.”
In fact, the only factor Mass seemed unwilling to contemplate as a cause of oyster deaths is the one best-documented in the scientific literature:
Rising anthropogenic CO2. In other words, more CO2 from the burning of coal and other fossil fuels.
“The ocean carbonate community has spent the last couple of decades determining how to estimate the amount of the total carbon dioxide in the water that came from absorption of anthropogenic CO2 from the atmosphere,” Hales said. “It’s not an easy calculation, but it has been done and done with high certainty.”
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