[Coral-List] Darwin was WRONG about reef formation

tomascik at novuscom.net tomascik at novuscom.net
Tue Oct 27 21:46:50 UTC 2020

Hi everyone,
Great comments by Walter and David regarding the recent atoll review. 
Some of my most enjoyable times that I spent learning about coral reefs 
was the times when I was reading the early works by some of the great 
minds that came before us. Sadly we don’t see many references to these 
great works in recent literature especially in reviews. You would be 
surprised what you can learn from the past, and indeed some “new 
discoveries” in coral reef science were actually discovered in not too 
distant past buried in literature few had access to. My favourite 
example is the early work by Sluiter (1890) who sunk 15 bore-holes sunk 
into a fringing reef in Sumatra and found that the growth of this 
fringing reef was initiated on soft substrate which was contrary to the 
general assertion that coral reef initiation required a hard rocky or 
volcanic basement. In 1931 a paper by Umbgrove (1931) actually mentioned 
Sluiter’s 1890 study and commented that:

“The reef has not grown on a rocky volcanic substratum or against the 
andesitic coastal lava, but rests entirely on the muddy bottom of the 
bay, as is also the case with the reefs in the Bay of Batavia, The 
Thousand-Islands, and the Spermonde Archipelago.”

However, the general assertion that hard substrate was required for reef 
initiation lasted for decades till Hopley and Partain (1987) who wrote:

  “Reefs have long been regarded as requiring hard substrate for 
initiation. However, there is increasing evidence that from North 
Queensland reefs that the presence of even a muddy sedimentary structure 
with positive relief may greatly enhance or speed up reef flat 

Access to the early works has been made much easier so I would urge all 
those that are starting their exciting careers in coral reef science to 
reach back in time and read some of the great early works. Anyone 
interested to get references for some of this early coral reef science 
materiel can visit the following links:




  David Blakeway via Coral-List wrote:
> Doug - Their interpretation for the Maldives is that the carbonate 
> sequence
> was all produced in shallow water, over the subsiding volcanic plateau.
> Deposition rates varied across the plateau, some areas remaining 
> shallow
> and other areas drowning. The areas that remained shallow developed 
> into
> flat-topped sea-level banks during a long period of relatively stable 
> sea
> level just over 3 million years ago. Atoll morphology subsequently
> developed over the flat-topped banks, and is therefore independent of 
> the
> deeply buried volcanic substrate. I think it is a good model, with some
> solid supporting evidence from the Maldives. But the article would be 
> so
> much better if it exercised more restraint and balance; e.g. by 
> conceding
> that there may be multiple paths to atoll morphology, by acknowledging 
> that
> Darwin had already suggested some atolls develop from submerged banks, 
> and
> by citing previous work apparently contradictory to their conclusions.
> By the way, Darwin's tentative explanation of the Maldives was to 
> slowly
> submerge a large elongate island surrounded by a barrier reef, like New
> Caledonia. The reef "*...after repeated subsidences, would become 
> during
> its upward growth separated into distinct portions; and these portions
> would tend to assume an atoll-like structure, from the coral growing 
> with
> vigour round their entire circumferences, when freely exposed to an 
> open
> sea." *Referring to these sub-atolls, he later says* "...these again,
> during long periods of subsidence, would sometimes become dissevered 
> into
> smaller atolls.*" I know it is just logic, but sure seems like magic!
> On Tue, Oct 27, 2020 at 3:22 AM Dennis Hubbard 
> <dennis.hubbard at oberlin.edu>
> wrote:
>> Thanks David:
>> Going back to a thread from a couple years back, this is the reason 
>> that
>> extensive citing of the literature (and not just the most recent and 
>> "hot"
>> articles) is so important.
>> Dennis
>> On Mon, Oct 26, 2020 at 10:57 AM David Blakeway <
>> fathom5marineresearch at gmail.com> wrote:
>>> 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
>> --
>> Dennis Hubbard - Emeritus Professor: Dept of Geology-Oberlin College
>> Oberlin OH 44074
>> (440) 935-4014
>> * "When you get on the wrong train.... every stop is the wrong stop"*
>>  Benjamin Stein: "*Ludes, A Ballad of the Drug and the Dream*"
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