Background
Climate alarmists have long claimed that global-warming-induced bleaching of corals will lead to the worldwide destruction of coral reefs and the concomitant extinction of great numbers of coral species, simply because so many of them appear to be living uncomfortably close to the upper limit of their thermal tolerance. Nevertheless, as the saying goes, appearances can be deceiving; and scientists are beginning to realize that this contention is one of those deceptive cases.

What was done
Working with samples of the widely distributed massive corals Porites lobata and Porites lutea - which they collected from Kaneohe Bay, Hawaii - the authors compared the identity and diversity of Symbiodinium symbiont types obtained using cloning and sequencing of internal transcribed spacer region 2 (ITS2) with that obtained using the more commonly applied downstream analytical techniques of denaturing gradient gel electrophoresis (DGGE).

What was learned
Apprill and Gates report that "sequence analysis of PCR [polymerase chain reaction] -amplified ITS2 clone libraries identified a total of 11 ITS2 types in Porites lobata and 17 in Porites lutea with individual colonies hosting from one to six and three to eight ITS2 types for P. lobata and P. lutea, respectively." In addition, they report that "of the clones examined, 93% of the P. lobata and 83% of the P. lutea sequences are not listed in GenBank," noting that they resolved "sixfold to eightfold greater diversity per coral species than previously reported."

What it means
In a "perspective" that accompanies Apprill and Gates' important new paper, van Oppen (2007) writes that "the current perception of coral-inhabiting symbiont diversity at nuclear ribosomal DNA is shown [by Apprill and Gates] to be a significant underestimate of the wide diversity that in fact exists." These findings, in her words, "have potentially far-reaching consequences in terms of our understanding of Symbiodinium diversity, host-symbiont specificity and the potential of corals to acclimatize to environmental perturbations through changes in the composition of their algal endosymbiont community," which assessment, it is almost unnecessary to say, suggests a far greater-than-previously-believed ability to do just that in response to any further global warming that might occur.

Reference
Van Oppen, M.J.H. 2007. Perspective. Molecular Ecology 16: 1125-1126.