A paper published recently in Nature Climate Change might be of interest to
list subscribers. It shows that corals with too many algal symbionts are
more susceptible to bleaching, contrary to conventional wisdom that corals
with more symbionts are protected from bleaching because they have “more
symbionts to lose”. It suggests that corals have to balance maximizing the
photosynthetic benefits provided by their algal symbionts against the risk
of having too many symbionts if exposed to high temperatures.
This has some real world implications, providing a mechanistic explanation
for why corals exposed to nutrient pollution are more sensitive to bleaching
(see also Wiedenmann et al. 2012 for another, not necessarily mutually
exclusive, mechanism). It may also influence the bleaching susceptibility of
corals exposed to increasing pCO2.
Reference: Cunning R, Baker AC (2012) Excess symbionts increase the
susceptibility of reef corals to bleaching. Nature Climate Change.
Pdf available on request from lead author Ross Cunning