[Coral-List] Fast coral extension rates DO NOT equate with a healthy coral in a warming ocean
swooldri23 at gmail.com
Thu Aug 10 21:21:50 EDT 2017
Dear Fellow Coral Researchers, most particularly young scientists who are
keen to design experiments that will advance the science behind coral reef
I urge you to reconsider the outdated concept that fast skeletal extension
rates in symbiotic corals equates to a healthy and resilient coral. In
fact, in a warming (and high pco2) ocean, I contend that it is the complete
Here is a very simple experiment that can be done to test. Raise corals
under optimal 'spring' temperature and irradiance conditions. Add variable
concentrations of dissolved inorganic nutrients to different treatments
such as to alter symbiont densities. You will find that under these optimal
'spring-type' conditions, the corals with the largest symbiont densities
will have the fastest growth (extension) rates. Now apply these same corals
to a warming treatment to replicate anomalous summer heat/beaching event.
You will discover that the corals (with elevated symbiont densities) that
have the highest growth as 'optimal' conditions, will be the first to
bleach and die at the anomalous temperatures.
I have previously described this phenomenon in the following manuscript in
which builds on a new (improved) understanding of the coral
This new conceptualisation also explains that 'high' bleaching risk areas,
will also be the areas with the highest growth rates in non-bleaching
years. See for example, the Great Barrier reef Porites dataset (cf fig.8)
in paper 2.
Other researchers have also documented the fact that fast skeletal growth
is indicative of areas where the health/resilience of the coral host is
actually the most compromised. For example, Denis et al. 2013, conclude, “High
growth rates seem to impair regeneration capacity. We show that
environmental conditions conducive to high zooxanthellae densities in
corals are related to fast skeletal growth but also to reduced lesion
regeneration rates “
Denis V, Guillaume MMM, Goutx M, de Palmas S, Debreuil J, Baker AC, et al.
(2013) Fast Growth May Impair Regeneration Capacity in the Branching
muricata*. PLoS ONE 8(8): e72618.
In conclusion, I contend, perhaps more contentiously, that all of these
findings lead to the obvious conclusion that symbiotic corals are “the
living dead” in the modern “Anthropocene” ocean.
That is, unless they have plasticity for heterotrophic feeding during
periods of autotrophic stress.
My hope, is that these ideas will challenge us to move forward with some
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