I happen to like oysters, in the way that a bear likes honey, and so it caught my eye last week when Oregon researchers published what they call the first research definitively linking the ocean’s rising acidity to big problems in the oyster beds.
You, on the other hand, might not care for oysters at all – but even so, this bad news should concern you for reasons that have nothing to do with appetite.
Oysters clean up the brackish waters where they live, provide essential habitat for other animals and plants, and otherwise deliver “ecological services” that qualify them as a keystone species in their communities. Their contributions are prodigious.
Filtering 50 gallons a day, each
Some years ago I went out with a group of oystermen, scientists and resource managers into Chesapeake Bay, which is both the nation’s largest estuary and one of its most befouled. Two unforgettable statistics from that day:
- An adult oyster of the bay’s native species can filter the man-made crud from as much as 50 gallons of water per day.
- If the Chesapeake’s oyster populations could be restored to their natural levels, they could in turn restore the bay to near-pristine conditions in about a week.
Now, back to Oregon: According to a summary by the National Science Foundation, the scientists there
found that increased seawater carbon dioxide (CO2) levels, resulting in more corrosive ocean water, inhibited the larval oysters from developing their shells and growing at a pace that would make commercial production cost-effective.
As atmospheric CO2 levels continue to rise, this may serve as the proverbial canary in the coal mine for other ocean acidification impacts on shellfish.
The study took place at the Whiskey Creek Shellfish Hatchery at Netarts Bay, near Tillamook, a fourth-generation operation that is among the West Coast’s largest suppliers of seed to oyster farms.
Starting in 2006, the operators noticed unusually high mortality among oyster “spat,” as the larval stage is known, that couldn’t be traced to a virus or other typical pathogen.
Rising acidity disrupts shell formation
They sent seawater samples to a lab at Oregon State University, which found them to be abnormally acidic because “ridiculously high” levels of dissolved CO2 – and further linked those levels to absorption of carbon dioxide from the atmosphere.
A good backgrounder on Whiskey Creek’s problems and ocean acidification generally is at Yale Environment 360. In it, Elizabeth Grossman explains that higher acidity impairs the oysters’ ability to take up shell-building calcium in a form called aragonite:
In the first 24 to 48 hours of an oyster’s life, as it forms its first shell, the larvae go from being almost 0 percent shell to at least 70 percent shell before they begin to grow more tissue, explains George Waldbusser, assistant professor of ocean ecology and biochemistry at Oregon State University’s College of Oceanic and Atmospheric Sciences. Lower aragonite saturation means the tiny larvae — much smaller than a poppy seed — need to expend more energy to make their shells.
“If too much energy is used at one stage, they may not be able to survive to a subsequent stage or overcome the stress,” says Waldbusser.
Acidic water sometimes kills oyster larvae outright, so that they fail to survive past the egg stage. At other times, the eggs hatch, but larvae fail after a week or two.
The new research has brought some pushback from people who point out that ocean acidity at the surface is also increased by wind-driven “upwelling” of acidic water from the ocean depths, where dead and decomposing material releases CO2.
Nobody really disputes that, just as nobody really disputes that the ocean is absorbing an awful lot of CO2 from the atmosphere. Indeed, the global-warming deniers have seized on this “buffering” effect as another reason we don’t need to worry about how our fundamental reformulation of earth’s atmosphere is changing everything else, too. Some think oysters have the evolutionary capability to adapt to the new conditions.
In the short run, operations like Whiskey Creek can cope because their oysters are hatched and raised in confinement, which means the rising acidity can be countered — at considerable expense — by filtering organic matter out of the water or treating it with baking soda.
How much baking soda would be needed to keep the Chesapeake and other U.S. estuaries habitable for oysters is a statistic I’ve not been able to find.
The carbon cost of newsprint
Two more interesting numbers from last week’s news stream: subscribing to a home-delivered daily newspaper adds 208 pounds, on average, to a person’s annual greenhouse-gas contributions. Reading the paper online adds only 54.
I read it in The New York Times: The RAND Corporation, under contract to the U.S. Department of Energy, made the calculations to illustrate its approach to “energy services analysis.”
The number in either case is a mere rounding error in the overall problem of greenhouse gases, with the average American emitting something like 20 short tons a year. But newspaper subscriptions are only a convenient example – RAND sees opportunities to rethink our habits in relation to clothing, food, waste disposal, transportation, health care and other aspects of life …
The idea is that focusing on the human wants and needs that energy is used to satisfy, and working backward from there, would free people to see the gross inefficiencies that may be lurking within our old habits.
I happen to like newspapers, too, almost as much as oysters, and I’m among those who thought he could never get used to life without a fresh one on the doorstep every morning. But then came the day I realized that I was taking each day’s copy of the Strib straight from my doorstep to the recycling bin and reading it online instead.
The sheer amount of wasted wood pulp was the main motivator for going newsprint-free; the CO2 savings is a nice added benefit – and an interesting example to counter the buzz about how much “invisible” energy we consume with our digital devices.
Yes, it’s a lot of juice and, yes, most of it still comes from coal, but every alternative has its costs. And surely any reduction in greenhouse gases is worth consideration.
The full RAND study is available here as a PDF – it runs to 82 pages and discusses a wide range of other applications for its analytic method. Please try not to print it out.