by Sheril Kirshenbaum, in a Science Progress cross-post
Marine chemist Richard Feely, a senior scientist with the National Oceanic and Atmosphere Administration, has been collecting water samples in the North Pacific for over 30 years. He’s observed a decrease in pH at the upper part of the water column, notably the region where carbon dioxide from automobile exhaust, coal-fired power plants, and other human activities has collected. This surface water is now acidic enough to dissolve the shells of some marine animals such as corals, plankton, and mollusks in laboratory experiments. Feely’s findings are just one sign of a troubling global phenomenon called ocean acidification.
We spend a lot of time worrying about carbon dioxide in the atmosphere, as a form of pollution and also as a key greenhouse gas that traps solar heat. But we pay less attention to the effects emissions have in the ocean. There is no debate that rapidly increasing seawater acidity is the result of man-made carbon emissions.
“The chemistry of the uptake of carbon dioxide and its changing pH of seawater is very, very clear,” explains Feely.
The oceans absorb an estimated 22 million tons of CO2 from the atmosphere every day. This buffers the greenhouse effect by drawing the planet-warming gas out of the atmosphere and storing it in water, but at a great cost to ocean life. This carbon mixes with the salt water to create carbonic acid, which immediately breaks down, forming bicarbonate and hydrogen. And this excess hydrogen increases the water’s acidity.
Higher acidity, in turn, makes life difficult for marine animals by hampering their ability to form shells and skeletons. For microscopic plankton and many other species at the base of marine food chains, this means slower growth and potential population decline. These problems trickle up to affect the large fish that depend on smaller organisms for food.
Acidification also causes some coral species to grow more slowly or disappear. Since coral reefs support 25 percent of the ocean’s species of fish, this spells widespread trouble. Marine ecosystems are so interconnected, in fact, that scientists cannot predict the full effects of acidification. They only know that changes in the availability of food and in community structure can scale up quickly.
Carbon emissions released since the start of the industrial revolution have sped the process of ocean acidification, leaving little time for plants and animals to adapt to altered conditions. Scientists now anticipate an average pH decline from 8.1 units to 7.8 in oceans by the end of this century. According to John Guinotte, a marine biogeographer at the Marine Biology Conservation Institute, in Washington, D.C., human activity is now increasing the amount of CO2 in the ocean at an accelerating rate. “Unless we alter human behavior,” he warns, “we may experience irreversible shifts in the marine environment that can have dire consequences for life on Earth.”
An international team of marine biologists recently traveled to Papua New Guinea where excess CO2 released from volcanic activity has already decreased local ocean pH to the levels that are expected globally by 2100. In this area, they found that more than 90 percent of the region’s coral reef species were lost. The study provided a glimpse of how oceans might one day change around the world and serves as a warning that we must curb carbon emissions as quickly as possible.
For us on land, ocean acidification will do more than raise the cost of seafood. A decline in reefs worldwide, for example, would make coastal communities more vulnerable to storm surges and hurricanes. Meanwhile, the fishing and shellfish industries stand to lose hundreds of millions of dollars, and countless jobs, because of acidification’s effects on shellfish, as well as associated changes in the populations of larger species. In the United States, oyster hatcheries in the Pacific Northwest have already experienced reduced shell growth due to higher acidity levels. No one can predict the full consequences of ocean acidification, but it’s clear our own species will experience them in many ways.
“About one billion people throughout the world depend on protein from fish for survival, so we have to think about what this means for international food security,” explains Feely.
Carbon emissions clearly cause problems beyond climate change. And because sea waters mix slowly, whether or not we reduce emissions now, acidification will continue for centuries. If Congress cannot act to restrict emissions, it must as least ensure that marine scientists have the funding needed to study the effects of changing pH on different marine species and, in the decades ahead, to search for ways to mitigate the effects of ocean acidification.
Sheril Kirshenbaum is an author and research associate at the Center for International Energy and Environmental Policy. You can find this post and many other good scientific pieces at Science Progress.
- Nature Geoscience study: Oceans are acidifying 10 times faster today than 55 million years ago when a mass extinction of marine species occurred
- Nature Geoscience study concludes ocean dead zones “devoid of fish and seafood” are poised to expand and “remain for thousands of years.”
- Geological Society: Acidifying oceans spell marine biological meltdown “by end of century” — Co-author: “Unless we curb carbon emissions we risk mass extinctions, degrading coastal waters and encouraging outbreaks of toxic jellyfish and algae.”