Cold Kills Coral

Study shows record-breaking cold snap had devastating effect on Florida’s coral reefs.

RSMAS (August 29, 2011) — Florida’s record-breaking cold snap of early January 2010 had a devastating impact on the state’s coral reefs, destroying colonies of the diverse ecosystems in just a few days, a new study by scientists at the University of Miami has revealed.

“It was a major setback,” said Diego Lirman, associate professor of marine biology and fisheries at UM’s Rosenstiel School of Marine and Atmospheric Science and lead author of the study. “Centuries-old coral colonies were lost in a matter of days.”

The chilly January temperatures caused the most catastrophic loss of corals within the Florida Reef Tract, which spans 160 miles from Miami to the Dry Tortugas and is the only living barrier reef in the continental United States.

Members of the Florida Reef Resilience Program, a group made up of Florida scientists and resource managers, conducted a month-long survey of 76 reefs from Martin County to Key West, both during and shortly after the unusually cold weather.

The research team compared the mortality rates of corals from the cold event to warm-water events, such as the highly publicized bleaching event in 2005, and concluded that the cold-water event caused even more widespread morality than previous warm-water events. The results were published in the August 2011 issue of the journal PLoS One.

The study found coral tissue mortality exceeded 40 percent for several important reef-building species and that large colonies in shallow and near-shore reefs were hardest hit. This is in contrast to a less than 1 percent mortality rate caused by warm-water events since 2005. Coral species that had previously proven tolerant to higher-than-normal ocean temperatures were most affected by the cold-water event.
“This was undoubtedly the single worst event on record for Florida corals,” said Lirman.

Ice-cold Arctic air swept into Florida in early January 2010, plummeting air temperatures to an all-time low of 30 degrees and dropping ocean temperatures to a chilly 51 degrees.

“The 2010 cold-water anomaly not only caused widespread coral mortality but also reversed prior resistance and resilience patterns that will take decades to recover,” the study’s authors conclude.

Florida’s reefs are located in a marginal environment at the northernmost limit for coral development. Corals have adapted to a specific temperature range and are typically not found in areas where water temperatures drop below 60 degrees.

Changes in climate patterns as well as others impacts, such as coastal development, pollution, overfishing and disease, have put added stress on coral reefs worldwide. The authors cite the need to improve ecosystem resilience through reef restoration, pollution reduction efforts, and the use of management tools, such as marine protected areas, in order for coral reefs to survive future large-scale disturbances.

“We can’t protect corals from such an extreme event but we can mitigate other stresses to help them recover,” said Lirman.


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