Coral starving and survival

Mike Risk riskmj at
Sat Mar 23 18:00:34 EST 2002

Hello, and thanks for some interesting postings.

Without getting into the validity, or lack thereof, of the starvation
hypothesis: I think you have touched on a key point in mentioning the
Medieval Warm. The problem is, the data do not exist. They should be sought,
as indeed should those from the Little ice Age.

Acropora arose in the Miocene, and quickly spread to become the predominant
"weed" coral of Late Cenozoic and Modern reefs. It is abundant in fossil
deposits, virtually always as storm-derived rubble: storm berms, beach
windrows and the like. These storm deposits can range in elevation from
metres below where the coral grew to, in the case of the Hurricane Alan
berms on Jamaica, several metres above present sea level. (This should
give pause to some who base sea-level estimates on dated Acropora, but it
doesn't seem to have. I once saw a TV interview with a group who were
suggesting catastrophically rapid sea level rises at the beginning of the
Holocene-when they held up the key Acropora sample, and the camera zoomed
in, one could plainly see it was Cliona-bored on all surfaces, whereas the
theory was based on it having been found in life position. Yes, a colossal
scientific blunder-but it got them a paper in Science.)

If the coral deaths we see now are due to elevated sea surface temperatures,
then Yes, you are correct, corals would have died like flies. This event
would be recorded in storm berms of Acropora rubble, all over (say) the
Caribbean, at approx. 1000 YBP. These deposits will have been overprinted by
subsequent storms, overgrown by vegetation, and removed by 5-star hotels,
but enough should remain for dating purposes. Finding berms on one island
would not be sufficient-one would have to prove the coexistence of
contemporaneous deposits, basin-wide. Paleotemperatures from these corals
would nail down SST values. The deposits may very well be there, it's just
that no one's ever looked systematically.

A study of this nature would seem to be a natural, given the present slant
 reefy thinking, but here's why no one's going to do it: Funding agencies
these days do not fund hypothesis-testing, they fund more-of-the-same. To
test this hypothesis, one would have to visit (say) a half-dozen different
locations. At each location, extensive shoreline mapping would have to be
done to describe the location and extent of storm deposits. From each of
these, maybe a half-dozen samples would have to be dated. Hundreds of dates,
months of field work. Maybe a half-million $ for
testing an hypothesis, with no guaranteed result. Never happen-but it

BTW: I do not discount sea-level curves based on Acropora, but I take them
with a grain of salt. I trust curves based on mangrove peats, Tridacna,

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