coral reefs doomed?
riskmj at mcmail.cis.mcmaster.ca
Sat Sep 8 12:26:09 EDT 2001
Although I share your concerns in general, the bad news is: the conclusion
is probably correct. I don't read that as a funding ploy-Rupert clearly says
there's stuff-all we can do about it, leading funding agencies to say why
Notwithstanding the recent stimulating work by Jackson et al on overfishing,
the hard evidence from the 20th century (and this one, too) is that
land-based sources of pollution have ineradicably slain more coral reefs
than all other causes put together. The references on this are close to
countless. This trend continues unabated, and science seems slow to respond.
(I invite other readers, perhaps offended by this comment, to submit
examples of coral reef monitoring programs that are linked to legislation
and enforcement by a proper detection/identification/amelioration process.)
Will reefs colonise new shelf areas? Sure. In fact, the rate at which this
will occur may be estimated from the drilling work done long ago by Walter
Adey, in the Virgin Islands. It takes the ocean about 1,000 years to clean
up the shoreline and make it ready for new corals. Presumably, this same
process in the future will take even longer, given the necessity for
reworking condos and Hondas: plus, that ocean will not be nearly as clean as
the advancing Holocene seas were. So: but don't hold your breath. For sure,
it will happen after the next election.
Concern about ocean warming is well-placed. One of the best references to
this is by Francis Rougerie, in...1988?. This is in French, and hence not as
widely read and cited as it should be. Quelle honte.
Concern about oceanic pH is probably overblown:
1. we seem to have forgotten the seminal work of Sillen, in the 60's,
showing that silicates, not carbonates, are the long-term oceanic buffers.
Lord knows we have done lots to "protect" tropical coastlines from pH change
by loading them with chemically-reactive silicates (feldspars, illite,
montmorillonite, etc). Large quantities of these minerals are in fact bound
up in coral skeletons, hence corals carry with them their own personal
buffers (Cortes and Risk, 1985, BMS).
2. the pH of tropical coastlines will no doubt shift-after all the
high-mag calcite has dissolved. As HMC makes up a large proportion of reef
sediments, this may take some time.
3. as the climate changes and we shift to the other metastable condition
of global climate, this will be accompanied by a fundamental reorganisation
of the oceans. This will involve (far as we know) vertical mixing, which
will put low-pH surface waters into contact with bottom sediments and bottom
waters of higher pH. This process was outlined in Smith et al, 1997, April
Nature. This process can occur within five years. None of the present ocean
models allows for mixing on this vertical and temporal scale, hence all need
recalibration. (Some of this work is under way now, using data from
4. McConnaughey and colleagues, and Barnes and colleagues, in separate
publications within the last 12 months, have shown that corals calcify
faster at elevated temps, and in the presence of fleshy algae.
My prediction (Risk, 1999) was that coral reefs, as some of us knew them
(and you were one, Jim), will be eradicated by land-based sources from most
of the world's shelves long before pH shifts appreciably-in fact, my
prediction was even more dismal than Rupert's. I think I said 2020.
I am hesitant about statements, usually made (I'm afraid) by geologists,
along the lines of "Corals have been around for a long time, they will
survive." It's true, but misleading. Yes, coral relatives-burrowing sea
anemones-are the oldest metazoan fossils yet found: Proterozoic, McKenzie
Mountains, NWT. Such statements need to have appended to them the comment
that large proportions of the geologic record are virtually barren of reefs,
of any type. I consider these statements similar to: "The globe's been hot
before, we survived", which we have also heard lately. The globe has been
quite hot before, involving a fundamental rethinking of real estate values.
Every North American Grade Six kid should do the exercise of drawing the
+15-m sealevel contour onto the globe, and estimating the human population
involved. Or perhaps we should start with those politicians whose
development seems to have been arrested at Grade 6...
It may very well be that some of those we refer to as "deep-water" corals
may be a recolonisation/biodiversity resource-let us hope so. This has
recently become an extremely productive area of research, and interested
persons should log on to the coolcoral site, or contact me for preprints.
This email is devoid of specific page #'s, etc, for refs: my office is being
moved, I am fileless, and am celebrating by being a carpenter for a while.
Another guy who tried it came back, so what have I got to lose?
Yours in gloom: Mike
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