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The Ability of Coral Reefs to Regenerate after Catastrophic Events
Anlauf, H., D'Croz, L. and O'Dea, A. 2011. A corrosive concoction: The combined effects of ocean warming and acidification on the early growth of a stony coral are multiplicative. Journal of Experimental Marine Biology and Ecology 397: 13-20.

The authors write that "under contemporary conditions, the unsuccessful recovery of degraded reefs is principally attributable to failed recruitment (Hughes and Tanner, 2000), yet little is known about how recruitment in stony corals will be affected by the combination of increased temperatures and oceanic acidity that are predicted for the future."

What was done
In exploring this latter challenge -- be it real or imaginary -- Anlauf et al., as they describe it, "used controlled culture to investigate the effects of a 1°C increase in temperature and a 0.2-0.25 unit decrease in pH on the settlement and survival of planulae [the free-swimming, flattened, ciliated, bilaterally symmetric larval form of various cnidarian species] and the growth of primary polyps in the Tropical Eastern Pacific coral Porites panamensis."

What was learned
In conducting their experiments, the three researchers determined that "primary polyp growth was reduced only marginally by more acidic seawater," but they state that "the combined effect of high temperature and lowered pH caused a significant reduction in growth of primary polyps by almost a third." Nevertheless, they report that "survival and settlement of planula larvae were unaffected by increased temperature, lowered acidity or the combination of both."

What it means
In summarizing the implications of their results, Anlauf et al. write that "the resilience of planulae to predicted climatic conditions suggests that healthy coral reefs should be able to regenerate naturally after catastrophic events (such as ENSO-induced coral bleaching), if source populations can provide planulae in sufficient quantity and local stressors such as over-fishing, pollution and habitat destruction are controlled." And they add that "this should be the case even in reefs that are exceptionally discontinuous, such as those across the Tropical Eastern Pacific."

Hughes, T.P. and Tanner, J.E. 2000. Recruitment failure, life histories, and long-term decline of Caribbean corals. Ecology 81: 2250-2263.

Reviewed 4 May 2011