More than 97 percent of climate scientists tell us that adding greenhouse gases like carbon dioxide and methane to the atmosphere is changing our climate. As these gases accumulate, they trap heat from the sun and gradually raise the planet’s average temperature. This will lead to a plethora of inhospitable weather and a generally nasty time for those of us living on the planet’s surface.
But while the term “global warming” is simple enough to understand, how this process is transforming our ocean is slightly more complicated and much more corrosive.
The Ocean Is Acidifying
The ocean absorbs about 30 percent of the CO2 emitted from human activites. As the volume of atmospheric CO2 grows, the ocean collects its proportionate share. To give you an idea of how much that is, in 2013, countries emitted nearly 40 billion tons of carbon. According to the World Meteorological Organization, that represents the biggest surge in CO2 concentration since 1984.
That’s bad news for the climate, but it’s really bad news for the ocean. When the ocean absorbs CO2, it converts the gas into carbonic acid. Until the Industrial Revolution, there wasn’t enough carbonic acid in the water to unbalance the ecosystem. But after more than a century of unchecked carbon emissions, the ecosystem has been measurably upended. The pH level of surface waters has dropped from 8.18 to 8.07, an unprecedented shift in the last 300 million years of the fossil record.
So what does more acid in the ocean mean? For one thing, it means less calcium carbonate. This mineral is a key ingredient in the shells of several marine species, and without it fewer shellfish are surviving to adulthood. One oyster farm in Washington state reported that their oyster production declined by 42 percent in just 10 years. The tiny shellfish that feed Alaska’s salmon stocks are also in danger, to say nothing of the state’s lucrative crab fishery.
Carbonic acid not only dissolves calcium carbonate, it also dissolves limestone, which makes it more difficult for coral to grow. Combine that with the reduction of pteropods and other zooplankton at the bottom of the food chain and the impacts to marine life are potentially catastrophic.
Life above sea level will also be impacted. Investigations of carbon upwelling zones along the West Coast suggest that lower pH levels make it more difficult for certain phytoplankton to absorb nutrients, rendering them vulnerable to disease and toxins. And that’s a problem, because healthy phytoplankton produce about 60 percent of the oxygen on Earth.
Some diatoms, like Pseudo-nitzschia, actually produce more toxin at lower pH levels. According to Dr. Vera Trainer, an oceanographer with NOAA’s Fisheries Marine Biotoxins Program, ingesting toxins from Pseudo-nitzschia can cause permanent short-term memory loss and in some cases death. Studies have shown that this species of phytoplankton can be five times more toxic at levels of ocean acidification already occurring off the California coast. NOAA suspects that a string of bird and whale deaths in 2015 may be due to domoic acid poisoning, a byproduct of these toxic algae blooms.
Ocean Warming Facilitates Algae Blooms, Dead Zones and Coral Bleaching
Ocean acidification and ocean warming are two sides of the same carbon coin.
Three-quarters of the planet is covered in water, so it should be no surprise that that’s where the majority of the planet’s heat is going. The oceans absorb roughly 90 percent of the heat energy generated by global warming, and right now oceans are warming so fast they’re “breaking scientists’ charts,” according to thermal sciences professor John Abraham.
Warmer water and toxic algae are a potent mix, and together they will create larger and more frequent dead zones throughout the ocean. These are areas where decomposing algae cause bacteria to eat up all the oxygen in the water, rendering it uninhabitable for sea life.
Global warming will also make toxic algae blooms more common in non-ocean bodies of water, such as Lake Erie. Last year, Toledo declared a state of emergency after microsystin entered its water supply and forced the shutdown of the Collins Park Water Treatment Plant. The toxin was produced by an algal bloom in the area, much like the one that forced the shut down of the Carroll Township plant east of Toledo just one year previous.
Meanwhile, ocean warming is bleaching the good algae out of coral reefs, turning them ghostly white and making them more susceptible to disease and death. This past year, NOAA declared a “coral bleaching event” for the planet and said over one-third of the ocean’s corals would be affected.
“We’re in shock and awe of what’s happening,” Ove Hoegh-Guldberg, a marine scientist at the University of Queensland in Brisbane, Australia, told Nature News. “It’s a doozy of an event.”
Like the disappearance of microscopic pteropods, losing coral has a major ripple effect across the marine food chain. Though they cover less than one percent of the ocean floor, coral reefs support a quarter of all marine life.
And Here’s the Bad News
When we take a step back, the bleak picture we’ve painted here comes into focus. The ocean is acidifying, making it less hospitable to marine life and less profitable to coastal economies; as it acidifies, some phytoplankton make less oxygen and others become more poisonous; as they become more poisonous, they contaminate our water and kill more fish. And while this is going on, ocean warming is just making it all worse.
Unfortunately, that’s not the bad news. The bad news is, it could take a millennium for the ocean to recover from what we’ve done to it. Humanity does not have the power to reverse this crisis. In the best case scenario (i.e., we stop burning fossil fuels), it can only be prevented from getting worse. The fact that the planet still spends $775 billion billion on fossil fuel subsidies makes that scenario a dim prospect.
Sarah E. Myhre, a marine ecologist at UC Davis, sums up the situation like so: “We as a society and civilization have to come to terms with the things that we are going to sacrifice if we do not reduce our greenhouse gas footprint.”
It’s time to talk terms.