Lurking in Earth’s oceans is a silent and insidious threat with the capability to collapse entire ocean ecosystems. Is this some kind of sea monster, a recently discovered giant of the deep? Is this a futuristic weapon with the potential for inflicting unfathomable damage? Political conspiracy? Aliens? Nope, this is chemistry, in the form of ocean acidification. Ocean acidification is the serious but lesser-known environmental threat frequently hidden behind the limelight of its infamous companion, climate change, both of which are borne from the emissions of greenhouse gases—specifically, carbon dioxide (CO2).
|Is there danger lurking in the waters?|
The oceans are presently helping to mitigate the effects of our society’s out-of-control carbon dioxide emissions by absorbing 25% of these emissions annually, which would otherwise end up in the atmosphere and accelerate climate change even more than we’re currently experiencing. However, this helping hand comes at a steep price. Seawater naturally absorbs carbon dioxide from the atmosphere, but increasing levels of atmospheric CO2 means that the oceans are in turn absorbing more CO2 than they have historically, which is causing big problems for ocean ecosystems and the creatures that inhabit them.
When seawater absorbs CO2, the two react to form carbonic acid and free hydrogen ions, which increase the acidity of the water. This reaction “steals” carbonate from the water that otherwise would have reacted with free calcium ions to form calcium carbonate—the building block for shells of ocean inhabitants such as crustaceans, mollusks, corals and zooplankton. With calcium carbonate in short supply, these creatures expend more energy in the juvenile stage searching for these scarce but crucial building blocks than they do searching for food, and ultimately many will end up starving to death. The increasingly acidic water dissolves the shells of these creatures as well.
|Images of a shell dissolving in acidic seawater|
Losing tiny ocean creatures such as zooplankton doesn’t seem like a big deal—until you recall their place in the ocean food web. The creatures most seriously threatened by the direct effects of ocean acidification form the very bottom of the food web. If they disappear, then so do all of the fish, whales, sharks, etc. that are above them on the food web. Can you imagine losing Washington State’s famous salmon or orca whales? If ocean acidification gets out of control, our oceans could be looking pretty desolate, and the billion people that rely on their bounty for survival could find themselves in a desperate struggle to survive.
|What happens if you remove the base of the food chain? Everything above it disappears.|
In a more immediate sense, ocean acidification is posing an economic threat as crab, oyster, and other fisheries struggle with the changing ocean chemistry. In the series of articles entitled “Sea Change—The Pacific’s Perilous Turn” published last September in the Seattle Times, author Craig Welch provides a detailed look at how ocean acidification is harming commercially harvested ocean creatures and the industries that depend on them. For instance, a family oyster farm located in Willapa Bay was forced to move their hatchery to Hawaii after the water in Willapa Bay became so acidic that the juvenile oysters were unable to survive. Juvenile king crab are also struggling to survive, jeopardizing the future of the $100 million king crab industry in Alaska. Researchers have even found odd behavior in fish exposed to acidic seawater—behaviors that caused the fish to lose their sense of self-preservation and get eaten by predators, as well as displaying affected senses of smell, sight, and hearing—all of which could have a grave effect on commercial fisheries.
As always, when writing about environmental issues, I wonder “what about Washington”? Well, when it comes to ocean acidification, things aren’t looking too great for the Evergreen State. As outlined in the “Sea Change” articles, Washington is especially at risk of suffering ill effects due to our location in relation to ocean currents. Ocean currents carry cold, CO2-rich water toward the coastline, where upwelling brings the acidic seawater to the surface and into our coastal habitats. As Welch explains, the really bad news for Washington is that due to the way ocean currents circulate, the waters that are absorbing CO2 today will not reach Washington State until 30-50 years from now. So the negative effects we’re currently experiencing are not even the worst of it… we won’t see those effects for several more decades.
So what can be done to deal with ocean acidification? We can hope that adaptation will get us through: fisheries can switch to fishing species that are more CO2-tolerant, shellfish farmers can move their hatchery operations to locales with better conditions, and, although a long shot, species themselves may evolve somewhat in order to better survive in their new environment. However, the only way for us to have any chance of slowing ocean acidification and saving as much of our ocean ecosystems as possible is to get CO2 emissions under control. If our global society continues spewing CO2 into the atmosphere, the oceans will continue to absorb it, and will continue to grow into a more acidic and hostile environment.
We need to continue pushing our government leaders to implement and enforce CO2-emissions limits, to combat both climate change and ocean acidification. We also need to push for development of renewable energy sources such as wind and solar that do not emit CO2. In the meantime, you can take matters into your own hands and check out the Going Green page on this blog for ideas on lowering your personal carbon footprint.