How does rising atmospheric CO2 affect marine organisms?

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The Hybridization of Reef Corals
Volume 10, Number 28: 11 July 2007

In an important paper published a few months back in the Annual Review of Ecology, Evolution, and Systematics, Willis et al. (2006) report that "on tropical coral reefs, the simultaneous mass spawning of many species of stony corals represents a unique breeding strategy among animals and suggests that hybridization might have played a role in the evolution of this functionally important group," which they describe as "the cornerstone of the coral reef ecosystem," which they say is "increasingly threatened by human and climate-related impacts." They also note that "an upsurge of studies on the reproduction of scleractinian corals has shown that synchronized spawning among more than two species occurs in the majority of reef regions," and that "in highly synchronized events, up to 35 species in sympatry may spawn within two hours of each other."

Considering these several observations from the world of nature, is it possible that the hybridization of reef corals may be a viable strategy for their successfully adapting to continued global warming? After analyzing reams of materials found in a host of peer-reviewed scientific papers reporting information pertinent to this vital question, the five biologists who reviewed the subject arrived at the following conclusions.

(1) "Hybridization has contributed to the evolution of many ecologically dominant and structurally important corals in diverse and significant ways." (2) "Greater growth and survival of juvenile hybrids in environmentally variable and extreme habitats suggest a role for hybrids in adaptation to new environments." (3) "The capacity of the hybrid Acropora prolifera to colonize marginal habitats distinct from its parent species and evidence of hybridization at geographical boundaries of the Caribbean Montastraea support an evolutionary role for hybridization in range expansion and adaptation to changing environments." (4) "Outcomes of hybridization are likely to be significant for the future resilience of reef corals ... by providing options for rapid response to changing environments and climatologies as well as increasing resilience to novel disease challenges."

Last of all, Willis et al. conclude that (5) "given the implications of ocean warming for increasing frequency and severity of mass bleaching events and emerging coral diseases, it is important to realize that hybridization has contributed to the evolutionary diversification of corals and that it has the potential to contribute significantly to the resilience of coral species and the coral reef ecosystem into the future [our italics]."

In light of these several real-world and data-driven conclusions, it would appear that global warming - even "unprecedented" global warming, as climate alarmists are fond of predicting - need not spell the demise of earth's coral reef ecosystems. The tenacious scleractinian corals have been around since the Triassic (Veron, 1995), or some 200 to 250 million years ago; and considering the findings of Willis et al., they will probably be around for a good long time to come.

Sherwood, Keith and Craig Idso

Veron, J.E.N. 1995. Corals in Space and Time. Cornell University Press, Ithaca, New York, USA.

Willis, B.L., van Oppen, M.J.H., Miller, D.J., Vollmer, S.V. and Ayre, D.J. 2006. The role of hybridization in the evolution of reef corals. Annual Review of Ecology, Evolution, and Systematics 37: 489-517.