[Coral-List] Darwin was WRONG about reef formation
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.
“*...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!
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