By Harold Hedelman
I’m sitting on a rustic table at Drakes Bay Oyster Co. (in Point Reyes National Seashore). I can’t decide which is more delicious: the sun-warmed fresh sea air coming from Drakes Estero, or the half dozen oysters I’ve just consumed. I just feel lucky to be here.
But thanks to Homo sapiens, both fresh air and oysters are getting more rare by the day. The story that connects oysters with pollution of Earth’s atmosphere began over 500 million years ago, when the first marine creature evolved to use calcium carbonate (also the main ingredient of concrete) in the ocean to build its body.
Today, over a hundred thousand marine species, including the oysters we eat, use the same ancient process to build their shells and skeletons. They require a delicately balanced ocean chemistry that, sadly, is rapidly becoming unbalanced due mainly to the burning of fossil fuels.
This problem is called ocean acidification and yet another evil brother of global warming. The facts are simple, the outcomes dire.
- Burning fossil fuel (coal, petroleum, and natural gas) releases carbon dioxide (CO2). In 2007, 8,365 million metric tons of carbon dioxide were released this way.
- It’s happening on a massive global scale: About 1/3 of the CO2 is absorbed by the ocean.
- When CO2 reacts with seawater, hydrogen ions are released, making the water more acidic (lowering the pH).
- The hydrogen binds up the carbonate, reducing the amount available to marine animals.
- It’s happening fast. While atmospheric CO2 stayed at or below 280 ppm for 400,000 years, since the industrial revolution (in the last 250 years) it has spiked to over 390 parts per million.
- The effects are with us now, worsening, and will last for a long time.
In the worst case, the sea’s carbonated creatures won’t be able to build their shells; they may even go extinct. This would be a disaster for all of us because the smallest calciferous ocean organisms are foundations of ocean ecosystems. If they dissolve in an acid ocean, the food webs that rely on them dissolve too!
Researchers from UC Davis studied the native Olympia oysters, Ostrea lurida (AKA Olys), that live right in our backyard, in Tomales Bay. To find out how Olys will fare as the ocean acidifies, they built tanks to simulate future levels of CO2 in the ocean. They placed microscopic native oyster larvae inside and watched them grow.
What they discovered was large impacts on the oysters’ shells during early life history stages. Under a microscope, these samples are smaller and less hearty. And as these stunted larvae make the transition to adulthood, they never recover to become full-sized or vigorous. The ecosystem services they provide are reduced proportionally.
Ocean acidification is already harming life in the sea, and the problem has been felt locally. Local oyster farmers, including Drakes Bay Oyster Company–where I’m sitting right now–procure larval ‘seed’ from hatcheries in the Pacific Northwest. In 2006, these hatcheries experienced widespread larval mortality. By 2008, scientists determined the cause: acidic ocean water prevents the larvae from forming shells. That knowledge helped the hatchery operators design methods, at least for the time being, to change their operations and avoid the die offs.
Acidification levels aren’t yet at the code red crisis stage, but they could double in 100 years. For the calciferous creatures of the ocean, there would be no escape, not even in an area as remote and pristine as Drake’s Estero.
There are myriad actions each of us can take to make a difference; most boil down to reducing consumption and our own carbon footprint. Let your government representatives know that it’s time to take action on climate change.
It’s impossible to predict the precise trajectory of the impacts of ocean acidification. It could reduce the long-term effectiveness of The Watershed Project’s native oyster restoration work. And, down the road, it could certainly mean, I realize with a sigh, no oysters on a picnic bench on a beautiful spring day for my children, or anyone else.
To support our native oyster restoration work financially (we need your help!), DONATE NOW.
To find out more about it, or to sign up for a future viewing of “Shell Shocked: Saving Oysters to Save Ourselves,” contact firstname.lastname@example.org.
Image credits (from top): Shawn Zimmerman, www.inn-california.com, www.oceanpowermagazine.net