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Disease, aided by global warming, threatens coral reefs

Implications of 'yellow band disease' could be dire

Source:  Copyright 2009, Cape Cod Today
Date:  January 30, 2009
Byline:  James Kinsella
Original URL: Status DEAD


The coral reefs of the Caribbean, an underwater paradise of life and color, are legendary for their beauty around the world.

Scientist James Cervino, who does research at the Woods Hole Oceanographic Institution, sees global warming as a key culprit in an environmental crime that's turning the paradise of coral reefs into a dead zone.

But there's trouble in paradise. And a scientist who does research at the Woods Hole Oceanographic Institution sees global warming as a key culprit in an environmental crime that's turning that paradise into a dead zone.

Dr. James Cervino, a professor at Pace University in New York who is a guest scientist at WHOI, has been investigating yellow band disease, a bacterial infection that affects coral colonies.

Cervino said yellow band disease, also known as YBD, is relatively new. The infection first started receiving notice from researchers in the mid-1990s, when Cervino was finishing up his dissertation as a participant in the Boston University Marine Program at WHOI. That's when he started working on YBD.

According to WHOI, the affliction etches a swath of pale-yellow or white lesions (the so-called "yellow band") along the surface of an infected coral colony.

The discolored band is a mark of death, indicating where the bacterial infection has killed the coral's photosynthetic symbionts, called zooxanthellae.

When they lose those symbionts, Cervino said, the corals "starve to death."

The initial thinking on YBD was that the disease was spurred by thermal stress to the corals, stemming from the rise in seawater temperature around them.

But Cervino said he's found the root cause to be a pathogen, an organism similar to pathogens that afflict a number of other marine organisms, such as shellfish and crabs. He said the coral pathogen probably is a mutation of one of those pathogens.

Cervino, a guest investigator in WHOI's Marine Chemistry and Geochemistry Department, was the lead author in a paper published in the November 2008 issue of the Journal of Applied Microbiology.

In the article, Cervino and his colleagues report isolating the bacteria that cause YBD: a group of four new Vibrio species, which combine with existing Vibrio on the coral to attack the zooxanthellae.

Pathogen, higher temperatures pose 'double-whammy'

Cervino found the disease exists in seawater at normal temperatures. But when the seawater temperature rises, placing the corals under thermal stress, the bacteria pose an even greater danger to the corals.

"Thermal stress and pathogenic stress are a double-whammy for the organism," Cervino stated.

With the Vibrio core group occurring in tropical oceans all over the world and water temperatures on the rise, the scientist has said, the prognosis for corals and the spread of YBD is rather grim.

YBD, Cervino said, has reached epidemic levels. The disease now has spread to coral reefs off every island in the Caribbean, he said, and also can be found in reefs in tropical areas of the Pacific Ocean, such as around Indonesia.

YBD, he said, has reached epidemic levels. The disease now has spread to coral reefs off every island in the Caribbean, he said, and also can be found in reefs in tropical areas of the Pacific Ocean, such as around Indonesia.

What to do about YBD?

The world, Cervino said, needs to address climate change caused by the emissions that result in global warming.

Further, he said people along coastlines in affected areas need to stop cutting down mangrove swamps, placing fish farms along the coasts, and allowing sewage to flow into the ocean. Any aquatic farms, he said, need to be kept in enclosed systems away from the ocean.

At stake, he said, are the fisheries that rely on the coral reefs as a cornerstone of thriving marine life, as well as the integrity of entire coastal zones.

The effects of yellow band disease (YBD) can be seen on the coral Montastraea (A and C) and Diploastraea (B and D), which are found in the Caribbean and the Florida Keys, and the Indo-Pacific, respectively.

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