Tuesday, January 31, 2006

Hot polyps

"The traces suggest we are tracking the temperature profile of 2001-2002, which led to the worst incidence of coral bleaching in the recorded measurements for the Great Barrier Reef" - Ove Hoegh-Guldberg.


Blogger Tom Goreau said...

Thank you for sending this to me. The concern is very real but still a bit premature.

The predictions made in this article are based on our HotSpot method of predicting bleaching from satellite data (Goreau & Hayes, 1994a,b, 2005a,b,c), which we have used successfully for 16 years. We map areas of reef that get 1 degree C above the normal maximum for one month.

At present (latest data, January 27), the entire Southern Barrier Reef is above the 1 degree excess temperature limit, but has only been above it for a few weeks, and the northern part is warming and just starting to reach the edge of this limit. So while some bleaching is starting in the south, it has not yet been hot enough for long enough for really serious bleaching. If these conditions remain, or intensify as they normally would at this time of the year, a serious bleaching event will take place within weeks in the south and a month in the north.

There was massive coral mortality all across the South Pacific in 2002, and across most of the Caribbean in 2005, but little quantitative data is yet available. The average live coral cover of the Great Barrier Reef, according to the long term monitoring program there, was down to about 20% in 2003. It could be a lot lower in a month from now.

Normally I do not forecast bleaching until conditions have already been hot long enough, as lucky weather fluctuations, heavy rains, shifts in ocean currents, or large typhoons could still cool the water and prevent serious bleaching. So it is just a little too soon to predict how bad it will be.

Best wishes,
Thomas J. Goreau, PhD
Global Coral Reef Alliance
37 Pleasant Street, Cambridge MA 02139

3:41 pm  

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