What Is Ocean Acidification?

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The oceans have reduced the effects of global warming for thousands of years by absorbing carbon dioxide. Now the basic chemistry of the oceans is changing because of our activities, with devastating consequences for marine life.

What Causes Ocean Acidification?

It's no secret that global warming is a major issue. A main cause of global warming is our release of carbon dioxide, primarily through the burning of fossil fuels and the burning of vegetation. Over time, the oceans have helped this problem by absorbing excess carbon dioxide. According to NOAA, the oceans have absorbed nearly half of the fossil fuel emissions we've generated over the past 200 years.

As the carbon dioxide is absorbed, it reacts with the ocean water to form carbonic acid. This process is called ocean acidification. Over time, this acid causes the pH of the oceans to decrease, making ocean water more acidic. This can have drastic consequences on corals and other marine life, with cascading impacts on the fishing and tourism industries.

More About pH and Ocean Acidification

The term pH is a measure of acidity. If you've ever had an aquarium, you know that pH is important, and pH needs to be adjusted to optimal levels for your fish to thrive. The ocean has an optimal pH, too. As the ocean becomes more acidic, it becomes more difficult for corals and organisms to build skeletons and shells using calcium carbonate.

In addition, the process of acidosis, or buildup of carbonic acid in body fluids, may affect fish and other marine life by compromising their ability to reproduce, breathe and fight diseases.

How Bad is the Ocean Acidification Problem?

On a pH scale, 7 is neutral, with 0 the most acidic and 14 the most basic. The historical pH of sea water is about 8.16, leaning on the basic side of the scale.The pH of our oceans has fallen to 8.05 since the beginning of the Industrial Revolution. While this may not seem like a big deal, this is a change greater in magnitude than any time in the 650,000 years before the Industrial Revolution. The pH scale is also logarithmic, so that slight change in pH results in a 30 percent increase in acidity.

Another problem is that once the oceans get their "fill" of carbon dioxide, scientists think the oceans could become a carbon dioxide source, rather than a sink. This means the ocean will contribute to the global warming problem by adding more carbon dioxide to the atmosphere.

Effects of Ocean Acidification on Marine Life

The effects of ocean acidification can be dramatic and far-reaching, and will affect animals such as fish, shellfish, corals, and plankton. Animals such as clams, oysters, scallops, urchins and corals that rely on calcium carbonate to build shells will have a difficult time building them, and protecting themselves as the shells will be weaker.

In addition to having weaker shells, mussels will also have a reduced ability to grip as the increased acid weakens their byssal threads.

Fish will also need to adapt to the changing pH and work harder to remove acid out of its blood, which can impact other behaviors, such as reproduction, growth and food digestion.

On the other hand, some animals such as lobsters and crabs may adapt well as their shells become stronger in more acidic water. Many of the possible effects of ocean acidification are unknown or still being studied.

What Can We Do About Ocean Acidification?

Lowering our emissions will help the ocean acidification problem, even if that just slows the impacts long enough to give species time to adapt. Read the Top 10 Things You Can Do to Reduce Global Warming for ideas on how you can help.

Scientists have acted swiftly on this issue. The response has included the Monaco Declaration, in which 155 scientists from 26 countries declared in January 2009 that:

  • Ocean acidification is accelerating and severe damages are imminent;
  • Ocean acidification will have broad socioeconomic impacts, affecting marine food webs, causing substantial changes in commercial fish stocks and threatening food security for millions of people;
  • Ocean acidification is rapid, but recovery is slow;
  • Ocean acidification can be controlled only by limiting future atmospheric carbon dioxide levels.

The scientists called for intense efforts to research the problem, evaluate its impacts and cut emissions drastically to help curb the problem.


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Kennedy, Jennifer. "What Is Ocean Acidification?" ThoughtCo, Oct. 29, 2020, thoughtco.com/what-is-ocean-acidification-2291528. Kennedy, Jennifer. (2020, October 29). What Is Ocean Acidification? Retrieved from https://www.thoughtco.com/what-is-ocean-acidification-2291528 Kennedy, Jennifer. "What Is Ocean Acidification?" ThoughtCo. https://www.thoughtco.com/what-is-ocean-acidification-2291528 (accessed January 24, 2021).