[Coral-List] Cold-water stresses on the Florida reef

Tianran Chen chentianran2008 at gmail.com
Fri Jan 15 23:19:38 EST 2010


Dear Mr. Gramer
        Extreme low SST has been regarded as the main limit to relatively
high-latitude coral reefs (or no-reefal coral communities). Southern China
experienced an extreme cold event during early 2008 (13 January―13
February), the result of which was likely driven by a combination of both La
Niña climatic shifts, and anomalous atmospheric circulation.
        The Daya Bay (114º29′42″―49′42″E, 22º31′12″―50′00″N), northern South
China Sea, has also been subjected to occasional extreme cold events during
the past 50 years, with the most recent occurring in early 2008 . During the
2008 cold event, the lowest air temperature reaches only 6.6℃, and the mean
sea surface temperature for February fall to < 14℃, including six continuous
days at 12.3℃. Significantly, the sea surface temperatures fall below the
hypothesized critical lower temperature threshold (~13℃) that commonly leads
to mass mortality in scleractinian coral communities. Surprisingly, our
coral community surveys, conducted both before (August 2007) and after (late
February 2008) the extreme 2008 cold event, demonstrated that the Daya Bay
coral ecosystems are barely impacted upon during the cold period (Chen,
2009). However, we observed many coral taxa such as Turbinaria peltata,
Plesiastrea versipora and Acropora pruinosa, that commonly spread their
tentacles during the daytime, spread their tentacles only partially, or did
not spread their tentacles at all, suggesting they suffered a cold-water
stress.
       Besides the coral death reported from Florida (Porter,1982; Roberts,
1982), the coral mortality events caused by low SST stress were also found
in other areas. For example, at Manifa coral reefs (27°40′N), Western
Arabian Gulf, mass mortalities of Acropora pharaonis and Platygyra daedalea
occurred during a cold phase when mean daily temperature was <13℃ for 30
days between December 1988 to March 1989, including four consecutive days
where SST fell below 11.5℃(Coles, 1991).

Reference
Porter J W, Battey J F, Smith G J. Perturbation and change in coral reef
communities. Proc Natl Acad Sci USA, 1982, 79: 1678―1681.
Roberts H H, Rouse L J. Cold-water stress in Florida Bay and northern
Bahamas: a product of winter cold-air outbreaks. J Sediment Petrol, 1982,
52: 145―155.
Coles S L, Fadlallah Y H. Reef coral survival and mortality at low
temperatures in the Arabian Gulf: new species-specific lower tem-perature
limits. Coral Reefs, 1991, 9: 231―237.
Chen T R, Yu K F, Shi Q, et al. Twenty-five years of change in scleractinian
coral communities of Daya Bay (northern South China Sea) and its response to
the 2008 AD extreme cold climate event. Chinese Sci Bull, 2009, 54:
2107-2117.

Cheers,
Dr. Tianran Chen
South China Sea Institute of Oceanology, Guangzhou, China
email: chentianran2008 at gmail.com



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