[Coral-List] Coral range expansion with global warming

Thomas Goreau goreau at bestweb.net
Tue Jan 15 10:24:23 EST 2008

Dear Jim,

Thanks, interesting points.

If you look at satellite maps of chlorophyll you can see that Broward  
County has the cleanest coastal waters in  Peninsular Florida because  
it is where the Gulf Stream sweeps closest to shore and pushes all  
that nasty terrestrial effluvia aside. At least sometimes......

But I think the northern limit of the corals in the Sea of Cortez was  
probably a winter cold temperature limit, as it was well south of the  
Colorado River surface plume, and the northern movement of the corals  
is taking place now, many decades after the freshwater was sucked  
away by the dams, the cities of the US southwest, and irrigating the  
California desert.

Best wishes,

On Jan 15, 2008, at 10:01 AM, James W.Porter wrote:

> Hi Tommy,
>         Northern expansion of corals in the Sea of Cortez may also  
> relate to the fact that the Colorado River no longer freshens the  
> upper reaches of this former estuary, not just to warming  
> temperatures in the region.
>         Also, on a related subject, as Caribbean coral larvae drift  
> northward, they encounter coastal salt-marsh sediments in near  
> shore environments (Gene Odum's "out welling" -- as opposed to up  
> welling hypothesis) that make all but deep-water outcrops, like the  
> Gray's Reef National Marine Sanctuary, all but uninhabitable for  
> most hard-bottom tropical organisms, even if the temperature is right.
> Jim Porter / University of Georgia
> At 08:45 PM 1/13/2008, Thomas Goreau wrote:
>> Dear Allen,
>> I don't have references handy, but here are some leads.
>> With regard to range expansion:
>> Mexican researchers have been following northward expansion of corals
>> in the Sea of Cortez for some years, and I hope they can point to
>> papers on this. Surveys at Sodwana reef in South Africa show that
>> live coral cover and diversity have been steadily increasing. It
>> would be most interesting to see if the corals are expanding
>> northward on Honshu, Japan, and there may be studies on this by
>> Japanese researchers. Australia should be seeing the same.
>> In SE Florida the local dive groups I work with there, Cry of the
>> Water in Broward County, and Reef Rescue in Palm Beach County, are
>> seeing expansion of the now rare Acropora cervicornis and Acropora
>> palmata northwards. But they are severely threatened by dredging
>> projects and algal blooms around the offshore sewage outfalls, which
>> we have now finally convinced the Governor, after years of appeals,
>> to shut down.  If we can get these reefs protected (which they are
>> not now),  clean up the water, and stop the new dredging projects,
>> which killed almost all the live reefs of the area in the 1960s and
>> 1970s, we should see significant northward coral expansion since
>> there is a good supply of coral and fish larvae swept out of the
>> Caribbean by the Gulf Stream.
>> Thanks to above average sea surface temperature rise, the
>> Mediterranean is now warm enough for reef building corals, but the
>> two local species with zooxanthellae don't build up large
>> aggregations, and there would be reluctance to introducing non-native
>> species. However, a few million years ago the Mediterranean area was
>> the global center of coral diversity.
>> But dreams of coral reef marching poleward, which have been proposed
>> by some in the past as a benefit of global warming, are probably
>> fiction. The reason is that the coastal areas of North America, Asia,
>> and Australia that they could expand to are densely populated and the
>> sewage and agricultural nutrients are way too high for coral reefs
>> even if the temperatures were acceptable.
>> With regard to the time it takes to form framework coral reef
>> structures that creates sheltered habitats, as opposed to coral reef
>> communities that are sparse veneers on non growing coral substrate,
>> that can take a long time since reefs (as opposed to corals)
>> typically grow millimeters a year.
>> Best wishes,
>> Tom
>> On Jan 13, 2008, at 7:15 PM, Allen Chen wrote:
>> > Hi, Thomas
>> >
>> > In your e-mail you have stated " There is clear evidence of
>> >> corals expanding into warmer water at the limits of their  
>> ranges, but
>> >> this results in coral communities, not coral reefs, which take
>> >> centuries to thousands of years to develop. Even if the corals  
>> could
>> >> adapt to warmer temperatures, and there seems to be no really good
>> >> evidence that they can on the time scale that would be needed, the
>> >> existing reefs would die quickly, and it could take thousands of
>> >> years for new reefs to be established."
>> >
>> > This is an interesting observation. I am wondering you can provide
>> > the list of references that we can read?
>> >
>> > thank you in advance.
>> >
>> > Cheers, Allen
>> >
>> >>
>> >
>> Thomas J. Goreau, PhD
>> President
>> Global Coral Reef Alliance
>> 37 Pleasant Street, Cambridge MA 02139
>> 617-864-4226
>> goreau at bestweb.net
>> http://www.globalcoral.org
>> _______________________________________________
>> Coral-List mailing list
>> Coral-List at coral.aoml.noaa.gov
>> http://coral.aoml.noaa.gov/mailman/listinfo/coral-list
> James W. Porter, Ph.D.
>      Meigs Professor of Ecology
> Odum School of Ecology
> University of Georgia
> 1033 Green St.
> Athens, GA 30602
> (706) 542-3410 Vox
> (706) 542-4819 Fax
> jporter at uga.edu

Thomas J. Goreau, PhD
Global Coral Reef Alliance
37 Pleasant Street, Cambridge MA 02139
goreau at bestweb.net

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