[Coral-List] Darwin was WRONG about reef formation

David Blakeway fathom5marineresearch at gmail.com
Mon Oct 26 14:55:47 UTC 2020

The Droxler & Jorry article provides a valuable perspective but, as has
been pointed out by others, it sells Darwin short. The article claims that
most modern atolls have developed over flat-topped Pliocene banks, and
therefore that Darwin’s fringing reef to barrier reef to atoll model is
wrong. However, Darwin already knew his model did not apply to all atolls.
For example:

“*...if, therefore, corals were to grow up from a bank, with a level
surface some fathoms submerged, having steep sides and being situated in a
deep sea, a reef not to be distinguished from an atoll, might be formed..*.”
(Darwin 1842, chapter 5)

Furthermore, the article fails to cite a recent paper that describes a
fringing reef to barrier reef transition at Tahiti, reconstructed from 35
logged and dated cores (Blanchon et al. 2014; open access at
https://www.nature.com/articles/srep04997).  Such selective citation is
especially disappointing in a review article.

An additional problem with the article, from my perspective, is that it
invokes the antecedent karst hypothesis to explain the atoll rims. A more
parsimonious explanation, developed by the first scientists to survey
atolls in the early 17th century, is simply that corals and coralline algae
grow better in the turbulent and well-oxygenated water on the outer edges
of submerged structures.

The karst hypothesis, in my opinion, is impeding coral reef science because
it views reefs as passive structures – it denies the reef-building
organisms any agency in creating reef form. We really need some young
ecologists to take reef geomorphology forward!

David Blakeway

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