Study: Acidic oceans pose threat to young coral

 Enlarge By Evan D'Alessandro, University of Miami Elkhorm coral provides daytime shelter for tropical fish near Key Largo, Fla. Ocean acidification due to global warming is happening at a rate that hasn't been known to occur naturally for the last 60 million years. 

By Doyle Rice, USA TODAY

Global warming that deposits carbon in the oceans and turns them more acidic is threatening the early life cycle of coral reefs near Florida and throughout the Caribbean Sea, a study published Monday says.

Although other research has looked at how the world's increasingly acidic oceans affect adult coral, this is the first one to document its impact on coral's early life stages.

Coral reefs don't just make pretty screen savers: They add $30 billion to the U.S. economy each year through tourism, diving, coastal protection and fishing, says study lead author Rebecca Albright of the University of Miami's Rosenstiel School of Marine and Atmospheric Science

"There have been very few, if any studies that had looked at the effects on early life-history stages, such as fertilization, larval settlement and recruitment," Albright says. "Recruitment" refers to the process of replacing dead coral with new coral.

Over the next century, the study found, recruitment of new corals could drop by as much as 73%.

The study appears in this week's issue of the journal Proceedings of the National Academy of Sciences.

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"Reproductive failure of young coral species is an increasing concern since reefs are already highly stressed from bleaching (because of unusually warm seawater), hurricanes, disease and poor water quality," says study co-author Chris Langdon, an associate professor at the Rosenstiel School.

Scientists in this study looked at one species of coral — Elkhorn coral, known as acropora palmata— a prime reef-building species that once dominated tropical coral reef ecosystems.

Elkhorn was placed on the U.S. Endangered Species List in 2006 because of severe population declines.

"In order for that species to not go extinct, we have to be replacing them as we're losing them," Albright says. "The implications of this work show that ocean acidification ... is interfering with that ability. "

Ocean acidification refers to the increased amounts of atmospheric carbon dioxide (caused by the burning of fossil fuels) absorbed into the world's oceans. This additional carbon not only warms the oceans, but also radically transforms their chemistry, according to a National Research Council report published this year.

Is the fear of ocean acidification overblown? Perhaps, say the authors of a study published in May 2009, also in Proceedings of the National Academy of Sciences.

The authors of that study, led by Rebecca Gooding of the University of British Columbia in Vancouver, dispute the belief that ocean acidification harms all marine life-forms and urged that caution should be taken when examining "overgeneralized predictions."

Albright says the field of ocean acidification research has only blossomed in the past 10 years, and it's only in the past couple of years that scientists have shifted their focus to look at the early life cycle in addition to the adults of various species, such as coral and shellfish.