wild places | wild happenings | wild news
make a difference for our wild places

home | links | search the site
  all articles latest | past | articles by topics | search wildnews
wild news on wildsingapore
  National Geographic 2 Jul 07
Hurricanes Heal Reefs in Surprising Cases
Helen Scales

Yahoo News 2 Jul 07
Study: Hurricanes may aid stressed coral

Corals stressed by warming conditions may benefit from the passage of a hurricane — as long as it doesn't slam right into them.

Bleaching of corals has been a growing problem in recent years with the loss of algae or reduction of pigment in the living corals that occurs when they are stressed by warming water.

Now, a team of researchers led by Derek P. Manzello of the National Oceanic and Atmospheric Administration reports that hurricanes mix the warm surface water and colder deep water enough to lower the temperature as much as 9 degrees Fahrenheit.

The researchers studied damaged reefs in Florida and the Virgin Islands that suffered in a 2005 bleaching event.

They report their findings in Tuesday's issue of Proceedings of the National Academy of Sciences. In September, bleaching was similar in both regions, but following the passage of Hurricane Rita in September the Florida corals began to recover, and recovery accelerated after Hurricane Wilma passed by in October.

Bleaching continued in the Virgin Island corals, which had not been approached by the storms.

The researchers concluded that while a direct hit by a hurricane can damage corals, passage of a storm within 250 miles or so can mix and cool the water enough to benefit corals.

The research was funded by NOAA's Coral Reef Conservation Program, the National Center for Coral Reef Research, the Project Aware Foundation, the U.S. Virgin Islands department of natural resources and NOAA's National Center for Coastal Ocean Science.

National Geographic 2 Jul 07
Hurricanes Heal Reefs in Surprising Cases
Helen Scales for National Geographic News

Hurricanes may actually provide a healing balm of sorts for dying coral reefs, a new study shows.

By mixing up cool deep layers of the ocean, a distant hurricane reduces sea-surface temperatures by several degrees—enough to help heat-stressed corals survive bleaching.

Bleaching occurs when sea temperatures warm, even slightly. This causes corals to eject their symbiotic, food-producing algae known as zooxanthellae (zoo-zan-thell-ay), leaving behind only the transparent coral tissue and bone white skeletons.

"It is well known that hurricanes can be catastrophic for reefs," said study co-author Derek Manzello, a marine biologist from the Cooperative Institute of Marine and Atmospheric Studies in Miami, Florida. "[But] our results show that in [the study's Florida test area] hurricanes may actually have been beneficial," he said.

Critical Changes

The hurricanes also promote bleaching recovery on corals across a wide area. The research team used temperature data from across Florida's reef tract, which arcs from just south of Miami to beyond Key West to show that winds whipped up by a hurricane can cool an 800 kilometer-wide (497 mile-wide) swath of water by an average of 1.5 degrees Celsius (2.7 degrees Fahrenheit) for ten days.

"Even such small temperature changes can be critical for the survival and recovery of bleached corals," Manzello said. "Every extra day a coral is bleached increases the chances it might die."

Hurricane-induced cooling appears to have been important in aiding reef recovery in Florida during a mass Caribbean bleaching event in 2005. Florida waters were cooled by Hurricane Rita in September 2005 and then again in October 2005 by Hurricane Wilma.

"Our underwater surveys showed that bleached corals in Florida immediately responded to the cooler water," Manzello said. By November the reefs had almost completely recovered.

At the same time, elsewhere in the Caribbean, the U.S. Virgin Islands remained hurricane free, and the reefs underwent far more intense and persistent coral bleaching than their Florida counterparts.

U.S. Virgin Islands reefs only began to recover in January 2006, when sea temperatures finally dropped, Manzello said.

A Silver Lining?

"There is rigorous scientific debate on whether warmer oceans will result in increased storm frequency," Manzello noted. In one sense, more storms would mean more direct damage to reefs.

But "they could result in increased cooling pulses to temperature-stressed reefs," he said. Nancy Knowlton, a marine biology professor at the Scripps Institution of Oceanography in La Jolla, California, said the study offers a different perspective on what is normally considered a disaster for reefs.

"This is a classic example of every cloud having a silver lining," Knowlton said. "I'll take any good news for coral reefs."

Study co-author Manzello said that the study, which will appear in an upcoming issue of the journal Proceedings of the National Academy of Sciences, suggests hurricane cooling won't completely nullify the dire prognosis for coral reefs under climate change.

"Nonetheless, a well-timed hurricane has the potential to [lessen] the negative effects of increased temperatures."
links
Related articles on Global: marine issues
about the site | email ria
  News articles are reproduced for non-profit educational purposes.
 

website©ria tan 2003 www.wildsingapore.com