[Coral-List] Coral bleaching and light levels

Thomas Goreau goreau at bestweb.net
Fri Feb 13 10:14:53 EST 2009

> From: Thomas Goreau <goreau at bestweb.net>
> Date: February 13, 2009 10:11:18 AM EST
> To: billraymond10 at yahoo.com
> Subject: Re: [Coral-List] Coral bleaching and ocean acidification
> Dear Bill,
> Absolutely! But it is a secondary factor.
> 20 years ago I did a bunch of experiments in Jamaica with corals in  
> tanks at different temperatures and light level combinations.  
> Bleaching took place only above a certain temperature, but the more  
> light the faster it happened. Peter Glynn did similar experiments in  
> Okinawa and reached the same conclusions. The reason I did this was  
> our field observations in the first Caribbean bleaching event in  
> 1987, where shaded corals were much less bleached, in fact where  
> they were shaded by overhangs you could see the shadow, and we've  
> seen that everywhere in the Indian Ocean and Pacific since too.
> But the discussion was about bleaching versus acidification, so I  
> did not get into secondary factors affecting bleaching. And  
> temperature has been rising worldwide whereas light levels are  
> basically unchanged because solar radiation variations are so small.  
> In fact surface light has been going down for decades because of  
> atmospheric pollution, but now starting to rise slowly as  
> atmospheric sulfur and nitrogen pollution are controlled.
> Hans Creek is an interesting area, and you may know that I proposed  
> it as a coral reef restoration site. I still hope this is possible,  
> but it really depends on blocking the marina and golf course. Which  
> I guess is still a pending issue. There is a small chance that I may  
> get back to BVI later this year.
> Best wishes,
> Tom

> Thomas J. Goreau, PhD
> President, Global Coral Reef Alliance
> Coordinator, United Nations Commission on Sustainable Development  
> Partnership in New Technologies for Small Island Developing States
> 37 Pleasant Street, Cambridge MA 02139
> 617-864-4226
> goreau at bestweb.net
> http://www.globalcoral.org

> On Feb 13, 2009, at 9:57 AM, Bill Raymond wrote:
>> Tom Goreau:
>> Don't you consider solar intensity a factor in coral bleaching? In  
>> Tortola I found bleached corals in late October, offshore, but  
>> mangrove-shaded Siderastreas in warm Hans Creek
>> were not bleached.

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