Ocean acidification is sometimes called “climate change’s equally evil twin,” and for good reason: it's a significant and harmful consequence of excess carbon dioxide in the atmosphere that we don't see or feel because its effects are happening underwater. At least one-quarter of the carbon dioxide (CO2) released by burning coal, oil and gas doesn't stay in the air, but instead dissolves into the ocean. Since the beginning of the industrial era, the ocean has absorbed some 525 billion tons of CO2 from the atmosphere, presently around 22 million tons per day.
At first, scientists thought that this might be a good thing because it leaves less carbon dioxide in the air to warm the planet. But in the past decade, they’ve realized that this slowed warming has come at the cost of changing the ocean’s chemistry. When carbon dioxide dissolves in seawater, the water becomes more acidic and the ocean’s pH (a measure of how acidic or basic the ocean is) drops. Even though the ocean is immense, enough carbon dioxide can have a major impact. In the past 200 years alone, ocean water has become 30 percent more acidic—faster than any known change in ocean chemistry in the last 50 million years.
Scientists formerly didn’t worry about this process because they always assumed that rivers carried enough dissolved chemicals from rocks to the ocean to keep the ocean’s pH stable. (Scientists call this stabilizing effect “buffering.”) But so much carbon dioxide is dissolving into the ocean so quickly that this natural buffering hasn’t been able to keep up, resulting in relatively rapidly dropping pH in surface waters. As those surface layers gradually mix into deep water, the entire ocean is affected. Such a relatively quick change in ocean chemistry doesn’t give marine life, which evolved over millions of years in an ocean with a generally stable pH, much time to adapt. Continue reading from Smithsonian Museum of Natural History
Take a moment to consider the variety of life in the sea. Ocean life is very diverse, and increased acidity can harm or help individual plant and animal species in different ways. It may not be obvious to us at first, but some organisms are likely to become more abundant, and others less so. For example, seagrasses may grow faster if more dissolved carbon dioxide is available, while the number of oysters may decrease as fewer larvae complete their life cycle due to increased acidity. In this way, scientists expect ocean and coastal acidification to affect entire ecosystems, including one animal at the top of the food chain— humans. Humans rely on the ocean for food and other economic resources. Ocean and coastal acidification may not just affect life underwater, but ultimately all of us. Continue reading from EPA