A simple but pertinent example of one form of thermal adaptation is described by Fang et al. (1997), who experimented with samples of the coral Acropora grandis taken from the hot water outlet of a nuclear power plant near Nanwan Bay, Taiwan.  In 1988, the year the power plant began full operation, corals there were completely bleached within two days of exposure to a temperature of 33°C.  Two years later, however, Fang et al. report that "samples taken from the same area did not even start bleaching until six days after exposure to 33°C temperatures."

So how is it done?  How do corals adjust to rising temperatures?  One adaptive mechanism that corals have developed to survive the thermal stress of high water temperature is to produce heat shock proteins that help repair other heat-damaged constituents of their bodies (Black et al., 1995; Hayes and King, 1995; Fang et al., 1997). Sharp et al. (1997), for example, have demonstrated that sub-tidal specimens of Goniopora djiboutiensis typically have much lower constitutive levels of a 70-kD heat shock protein than do their intertidal con-specifics; and they have shown that corals transplanted from sub-tidal to intertidal locations (where temperature extremes are greater and more common) typically increase their expression of this heat shock protein.

Similar results have been reported by Roberts et al. (1997) in field work with Mytilus californianus.  In addition, Gates and Edmunds (1999) have observed an increase in the 70-kD heat shock protein after six hours of exposure of Montastraea franksi to a 2-3°C increase in temperature, which is followed by another heat shock protein increase at the 48-hour point of exposure to elevated water temperature.  They state that the first heat shock protein increase "provides strong evidence that changes in protein turnover during the initial exposure to elevated temperature provides this coral with the biological flexibility to acclimatize to the elevation in sea water temperature," and that the second increase "indicates another shift in protein turnover perhaps associated with an attempt to acclimatize to the more chronic level of temperature stress."

So how resilient are corals in this regard?  No one knows for sure; but they've been around a very long time, during which climatic conditions have changed dramatically, from cold to warm and back again, over multiple glacial and interglacial cycles.  And in this regard, we see no reason why history can not be expected to successfully repeat itself, even as the current interglacial experiences its "last hurrah."

References
Black, N.A., Voellmy, R. and Szmant, A.M.  1995.  Heat shock protein induction in Montastrea faveoluta and Aiptasia pallida exposed to elevated temperature.  Biological Bulletin 188: 234-240.

Fang, L.-S., Huang, S.-P. and Lin, K.-L.  1997.  High temperature induces the synthesis of heat-shock proteins and the elevation of intracellular calcium in the coral Acropora grandis.  Coral Reefs 16: 127-131.

Gates, R.D. and Edmunds, P.J.  1999.  The physiological mechanisms of acclimatization in tropical reef corals.  American Zoologist 39: 30-43.

Hayes, R.L. and King, C.M.  1995.  Induction of 70-kD heat shock protein in scleractinian corals by elevated temperature: Significance for coral bleaching.  Molecular Marine Biology and Biotechnology 4: 36-42.

Roberts, D.A., Hofman, G.E. and Somero, G.N.  1997.  Heat-shock protein expression in Mytilus californianus: Acclimatization (seasonal and tidal height comparisons) and acclimation effects.  Biological Bulletin 192: 309-320.

Sharp, V.A., Brown, B.E. and Miller, D.  1997.  Heat shock protein (hsp 70) expression in the tropical reef coral Goniopora djiboutiensis.  Journal of Thermal Biology 22: 11-19.