Ocean Acidification Worst in 300 Million Years, Study Warns

[Carolyn Bailey]

Oceans may be acidifying at an accelerated rate due to emissions, according to a study recently published in the journal Science. The Earth Institute at Columbia University revealed Thursday in a blog post that humans have increased carbon emission levels by 30 percent and decreased the pH of the oceans by 30 percent over the last hundred years.

According to a press release from the Lamont-Doherty Earth Observatory, the study represents the first effort of its kind to examine the geologic record for signs of ocean acidification over a time period of 300 million years. Researchers from the Lamont-Doherty Earth Observatory warn that the oceans may be acidifying more quickly today due to carbon emissions than they did when “natural pulses of carbon sent global temperatures soaring.”

“What we’re doing today really stands out,” said the study’s lead author Bärbel Hönisch, a paleoceanographer at Columbia University’s Lamont-Doherty Earth Observatory, according to the Earth Institute. “We know that life during past ocean acidification events was not wiped out—new species evolved to replace those that died off. But if industrial carbon emissions continue at the current pace, we may lose organisms we care about—coral reefs, oysters, salmon,” Ms. Hönisch added.

A research team, which included scientists from five countries, discovered that only one period in the last 300 million years saw acidification in the world’s oceans at a rate as fast as today: The Paleocene-Eocene Thermal Maximum (PETM), which occured 56 million years ago. During this period, a strange increase in carbon emissions doubled atmospheric concentrations, which forced average global temperatures up by about 6 degrees Celsius.

The Impact of Acidification on the World’s Oceans

The impact of the speedy acidification of the world’s oceans during the PETM gives scientists clues as to what could happen in today’s oceans. After global temperature rose by 6 degrees Celsius, nearly 50 percent of a species of benthic foraminifers went extinct. This suggests that organisms higher in the food chain may have also suffered as the oceans acidified, suggests study co-author Ellen Thomas, a paleoceanographer at Yale University. “It’s really unusual that you lose more than 5 to 10 percent of species over less than 20,000 years,” she said. “It’s usually on the order of a few percent over a million years,” Ms. Thomas added.

The Earth Institute’s Kim Martineau cited a 2011 study of coral reefs off Papua New Guinea in which researchers discovered that when pH decreased to 7.8, reef variance dropped by up to 40 percent. According to scientists, acidification of the world’s oceans is a difficult problem to combat.

“It’s not a problem that can be quickly reversed,” said the co-author of the 2011 study on Papua New Guinea reefs Christopher Langdon, a biological oceanographer at the University of Miami, according to the Earth Institute. “Once a species goes extinct it’s gone forever. We’re playing a very dangerous game,” Mr. Langdon added.

The study warns that scientists may not know the full impact of a higher rate of acidification in the oceans for many years. “These studies give you a sense of the timing involved in past ocean acidification events—they did not happen quickly,” said Richard Feely, an oceanographer at the National Oceanic and Atmospheric Administration who was not involved in the study, according to the Lamont-Doherty Earth Observatory. “The decisions we make over the next few decades could have significant implications on a geologic timescale,” Mr. Feely added.

Futures Consequences

The authors of study left readers with a disturbing vision of the future of the world’s oceans: “The current rate of CO₂ release stands out as capable of driving a combination and magnitude of ocean geochemical changes potentially unparalleled in at least the last ~300 of Earth history, raising the possibility that we are entering an unknown territory of marine ecosystem change.”

“The geological record suggests that the current acidification is potentially unparalleled in at least the last 300 million years of Earth history, and raises the possibility that we are entering an unknown territory of marine ecosystem change,” said co-author Andy Ridgwell of Bristol University, according to the AFP.

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