What Is Ocean Acidification?

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.

The Causes and Impact of Acid Rain

Examining the Impact of Acid Rain Forests and Wildlife Worldwide

Acid rain is a very real phenomenon worldwide, and it's been documented since the 1800s, as the Industrial Revolution caused the burning of fossil fuels like coal, gas, and oil. When these fuels or any other organic material like wood or paper are burned, they release compounds like sulfur dioxide (SO2) and nitrous oxides (NOx) into the air.

The Causes of Acid Rain

Are SO2 and NOx the causes of acid rain?

Indirectly, yes. When SO2 and NOx enter the atmosphere, they react with water vapor, oxygen, and other compounds to form sulfuric acid and nitric acid. This process may take place locally, or -- when winds blow emissions hundreds of miles away -- across international or state boundaries. These acids lower the pH of water condensation in the atmosphere, and when that condensation falls as rain, fog or snow, the resulting acids can wreak havoc on plant and animal life.

(Note: The more acids found in rain, the lower the pH. The pH scale goes from 0 to 14. Values from 0 to 6 are considered acid, 7 is considered neutral, and values from 8 to 14 are considered alkaline. A pH of 1, for example, is far more acidic than a pH of 6.)

The Effects of Acid Rain on Wildlife

The effects of acid rain can vary depending on where it falls and what the local rock and soil are composed of. An alkaline soil can help buffer the effects of acid rain and reduce its impact on local lakes.

However, when acid rain falls on some soils, the acids can wipe out important microbes and insects that live in soil and leaf litter. When acids from rain and snow enter rivers and lakes, it can kill fish and their eggs -- many fish eggs can't survive at pH lower than 5.

This has caused the disappearance of some fish like brook trout from streams in the eastern U.S., where acid rain is more prevalent than in western states.

Crayfish, clams, amphibians and other aquatic wildlife are also killed off by acid rain.

The Effects of Acid Rain on Forests

Trees are among the most visible victims of acid rain. When acid rain or snow falls on forest floors, it leaches out valuable nutrients that are found in the soil, leaving behind aluminum and other elements that can be toxic to plant life. Thus, the trees slowly die from lack of food and from soil toxins -- eventually, an entire forest can be killed off by acid rain.

Trees are especially vulnerable at higher altitude, since they receive more rain and snow, and are often surrounded by acid fog and clouds. The effects of acid rain and snow have been widely seen throughout the Appalachian Mountains, including the Great Smoky Mountains, the Adirondack Mountains and the Catskills in New York. Many forests in Europe, including Germany's famous Black Forest and the high-altitude forests throughout Scandinavia, are also in peril due to acid rain and snow.

The Effects of Acid Rain on Human Health

The amount of acid in rain is too small to have a serious impact on human health, and agricultural land is now amended with lime and other fertilizers to buffer the effect of acid rain.

However, the acid in rain and snow is strong enough to erode rock -- centuries-old buildings, monuments, and statues made of marble, limestone or other rock are slowly eroding away due to the effects of acid rain.

What Can Be Done About Acid Rain?

Though much has been done to reduce the impact of acid rain, much more needs to be accomplished. Smokestack scrubbers that reduce emissions from coal-generated power plants have helped, but with millions of sources like auto tailpipe emissions, sources of acid rain are difficult to manage.

And though international treaties have been signed and implemented throughout Europe and North America, their benefits have been limited, especially as rapidly developing countries in Asia and South America rely heavily on coal and oil for energy. Since the single largest source of acid rain and snow is coal-powered electrical plants, developing alternative sources of energy becomes more important than ever.

Until that time, however, acid rain will continue to destroy trees, forests, wildlife and historical buildings and monuments.

People who are concerned about acid rain can start by saving electricity in their homes, improving their gas mileage and taking other steps to save energy and reduce our dependence on the fossil fuels that cause acid rain.

Acid Rain Intensifies Threat To Marine Life

Human-generated carbon dioxide in the atmosphere is slowly acidifying the ocean, threatening a catastrophic impact on marine life. And just as scientists are starting to grasp the magnitude of the problem, researchers have delivered more bad news: Acid rain is making things worse.

Scientists estimate that one-third of the world’s acid rain falls near the coasts, carrying some 100 million tons of nitrogen oxide, ammonia, and sulfur dioxide into the ocean each year. Using direct measurements and computer models, oceanographer Scott Doney of Woods Hole Oceanographic Institution and his colleagues calculated that acid rain causes as much as 50 percent of the acidification of coastal waters, where the pH can be as low as 7.6. (The open ocean’s pH is 8.1.)

The findings increase the urgency of confronting the crisis of ocean acidity, says Richard Feely, a collaborator at the National Oceanic and Atmospheric Administration. In the laboratory, researchers have seen some effect on just about every ocean creature that forms a calcium carbonate shell, says Feely, including algae—the tiny creatures at the crucial bottom of the deepwater food chain—and coral, whose skeletons grow more slowly in water with a pH even slightly lower than normal. Soon-to-be-released field experiment findings “seem to be showing the same kind of thing,” Feely says. That’s bad news, he adds, since a third of the world’s fish species depend in part on coral reefs for their ecosystems.