[Coral-List] starvation?

jmcmanus jmcmanus at rsmas.miami.edu
Wed May 31 13:06:49 EDT 2006 

Most likely we are dealing with two phenomena in severe bleaching events:

1. Stresses related to the loss of Symbiodinium
2. Thermal stress per se. 

All organisms have upper thermal tolerance limits, set by various
physiological mechanisms (oxygen uptake, other aspects of metabolism,
protein and enzyme production, etc.). Many organisms live nearer the upper
than the lower tolerance limits, which is why it is usually safer to
transport marine organisms in colder water than they are used to than in
warmer water. During periods of very warm water, other species on a reef may
die suddenly, such as mollusks and fish. It may be that coral death that is
too quick to be explained in terms of starvation may not necessarily be
related to the loss of the Symbiodinium. 

Cheers! 

John
 
John W. McManus, PhD
Professor, Marine Biology and Fisheries
Coral Reef Ecology and Management Laboratory (CREM Lab)
Director, National Center for Coral Reef Research (NCORE)
Rosenstiel School of Marine and Atmospheric Science
University of Miami, 33149
Office: 305-421-4814/4820, Fax: 305-421-4910, Website: www.ncoremiami.org
 
If I cannot build it, I do not understand it. -- Richard Feynman, Nobel
Laureate
 

-----Original Message-----
From: coral-list-bounces at coral.aoml.noaa.gov
[mailto:coral-list-bounces at coral.aoml.noaa.gov] On Behalf Of Julian Sprung
Sent: Wednesday, May 31, 2006 10:15 AM
To: coral-list at coral.aoml.noaa.gov
Subject: [Coral-List] starvation?

As a follow up to the post I just sent, I have not yet seen this recent
paper in Nature and look forward to reading it- My comments about starvation
are not in any way intended to dismiss the conclusions of the paper.

I am only commenting on what I believe to be true with regard to temperature
induced bleaching and mass die off of corals-- that the majority of the die
off usually occurs in a matter of days, far too quickly to be caused by
starvation.

It is an interesting point to compare what can be achieved in an aquarium
with respect to food inputs as opposed to food supply on reefs. In general
the live and particulate food supply on reefs is greater than what is the
norm for most aquariums, but I agree aquariums could achieve higher inputs
to meet the demands of a particular coral, given the effort of an aquarist
to make it happen. The idea that some corals might not be able to get enough
food in the wild if they lack zooxanthellae is new to me- if true, it would
mean I have to revise my opinion about starvation as being too broad!

Julian



> ----------
> From: 	coral-list-bounces at coral.aoml.noaa.gov on behalf of Andréa
Grottoli
> Sent: 	Tuesday, May 30, 2006 3:37 PM
> To: 	coral-list at coral.aoml.noaa.gov; goreau at bestweb.net
> Subject: 	[Coral-List] coral bleaching: response to Goreau
> 
> Dear Tom,
> 
> I read your contribution on the coral list about 
> coral bleaching with interest.  As the lead 
> author of the recent Nature paper on 
> heterotrophic plasticity in bleached corals, I 
> would like to comment.  You stated:
> 
> "The recent paper that claims to have discovered "for the first time"
> that corals eat zooplankton and can survive bleaching better if fed is
> not new either. The fact that corals don't get their carbon from
> zooxanthellae is also very old knowledge, but for decades people have
> ignored the old literature and have mistaken the net oxygen balance to
> assume that corals are also autotrophic in carbon. This recent error has
> become dogma, despite being wrong, because nowadays people don't read
> the literature or ask those who know it. The first radiocarbon tracer
> experiments, done by Thomas F. Goreau and Nora I. Goreau more than 50
> years ago showed that very little zooxanthella carbon translocation
> contributed to coral carbon, and that corals relied on zooplankton for
> the vast bulk of their carbon needs. They kept corals completely
> bleached in the dark for years, feeding them on zooplankton. So survival
> of bleached fed corals has been known for over half a century and is not
> a "new discovery" at all. Like so much else in the current literature."
> 
> I would like to point out that our paper showed 
> that only one species, Montipora capitata, 
> consumed enough zooplankton to meet all of its 
> metabolic demand heterotrophically when 
> bleached.   When healthy, M. capitata met less 
> than 15% of its metabolic demand 
> heterotrophically.  The other two species we 
> studied, Porites compressa and Porites lobata, 
> only met 21-35% of their daily metabolic demand 
> heterotrophically when they were either healthy 
> or bleached.   In all cases, our corals were 
> exposed to naturally occurring zooplankton on the 
> reef.  Thus under natural reef conditions, not 
> all bleached corals can meet all of their 
> metabolic needs heterotrophically.  Under 
> artificially fed conditions (i.e., coral exposed 
> to higher than ambient concentrations of 
> zooplankton or brine shrimp in tanks), things can 
> be quite different.   As you pointed out, the 
> fact that corals do get some fixed carbon from 
> zooplankton has been know for a very long 
> time.  However, the fact that when bleached at 
> least one species can  increase heterotrophic 
> feeding to meet all of its metabolic needs while 
> two others could not, is novel.  Our results 
> suggest that not all species of corals would be > 
> able to meet their metabolic demand when 
> maintained in the dark under natural 
> concentrations and abundance of zooplankton (i.e, 
> P compress and P lobata probably could not get 
> all of their energy needs met heterotrophically 
> when bleached under darkness... but this would 
> need to be specifically tested).   In addition, 
> bleaching induced by keeping corals in the dark 
> is not necessarily the same as 
> temperature-induced bleaching.  The chain of 
> physiological stress responses that occur under 
> high temperature include free radical and stress 
> protein production, making any heterotrophic 
> responses under tempreature-induced bleaching 
> possibly quite different than hetertrophic 
> responses under sustained darkness.
> 
> Sincerely,
> 
> Andrea Grottoli
> 
> *******************************************************
> Andréa G. Grottoli, Assistant Professor
> Ohio State University
> Department of Geological Sciences
> 125 South Oval Mall
> Columbus, OH 43210-1398
> office:  614-292-5782
> lab: 614-292-7415
> fax: 614-292-7688
> email: grottoli.1 at osu.edu
> web: www.geology.ohio-state.edu/~grottoli
> Office location: 329 Mendenhall Labs
> 
> ******************************************************* 
> 
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