By John Harley
The next time you shiver and shuffle into the ocean wishing it was a few degrees warmer, you might want to bite your chattering lip.
The latest threat to ocean ecosystems to join the usual suspects of pollution and overfishing is none other than global warming and the absorption of excess carbon dioxide into the water. The dissolving CO2 changes the pH level of the water, making it more acidic, and decreases the ability of many animals like coral to build their protective shells from calcium carbonate.
This is a huge concern for coral reefs, which depend on the extraction of calcium carbonate. Studies of the Great Barrier Reef in Australia have shown that the production of protective shells has dropped 21 percent in the past 16 years.
“As many as 50 percent of the world’s coral reefs could be destroyed by 2050,” said Duane Silverstein, executive director of Seacology, an organization that works to preserve island environments around the world. “It’s a staggering statistic.”
Of the 49 billion tons of carbon dioxide emitted into the atmosphere every year, anywhere from 40 to 50 percent is absorbed by the ocean. According to a Royal Society report, the amount of surface seawater hydrogen ions, responsible for acidity, has increased by 30 percent since 1800 and could triple by 2100.
“It’s only recently that the great majority of scientists have realized the scale of the problem has suddenly taken off,” said Peter Brewer, ocean chemist at Monterey Bay Aquarium Research Institute.
Humans rely on coral reefs in a variety of ways. Species of marine animals living in a coral habitat provide critical links in the food chain, as well as seafood for people. Reefs provide barriers to fast-moving ocean swells, protecting island communities from severe waves. Scientists are also concerned that if coral reefs decline in size and productivity, the amount of carbon dioxide able to be absorbed in the ocean will decline drastically.
Is there a viable solution for remedying the acidity of the ocean?
Brewer says no.
“Everyone wishes there is, but there is not,” Brewer said. “The very long run is that mother nature [reduces acidity] by chemical weathering of rocks, but that takes thousands of years.”
James Zachos, professor of earth and planetary science at UC Santa Cruz, has been studying ocean chemistry by analyzing sediment cores drilled from the ocean floor.
“The only way to fix the problem is to somehow reduce emissions,” says Zachos. “The main trick is to keep [carbon dioxide] from getting into the atmosphere.”