[Coral-List] Excess algal symbionts increase coral susceptibility to bleaching

Andrew Baker abaker at rsmas.miami.edu
Wed Nov 28 15:17:35 EST 2012


My point in picking up on Gene's email about African dust and iron was that
iron is one of several parameters which seems to influence symbiont
densities in corals (including light, temperature, nutrients and possibly
pCO2). In that context, it's interesting to look at whether the increase in
algal densities influences bleaching susceptibility by exacerbating a
symbiont density-dependent bleaching cascade. 

There are probably many benefits to having more symbionts, as well as
tradeoffs against having them. Similarly there are probably many impacts of
iron on corals outside of its (potential) effects on symbiont density. As
mentioned in previous emails, the bioavailability of iron is also critical
and also difficult to measure properly. The "black reefs" reported in Kelly
et al. (2011), and discussed on this list over a year ago, are really
interesting and unusual places. But equally there are pilings, volcanic
substrates, and other places where corals appear, at least anecdotally, to
be doing well. I don’t think these observations invalidate each other; they
are different corals growing in different situations.  

The situation with nutrients is also likely to be complex in a similar kind
of way, but I think these are all interesting areas of research and we now
have new molecular assays that make answering these questions much easier
(In this context I should point out that the metric of symbiont density we
used in the Nature Climate Change paper, an actin-based symbiont:host cell
ratio based on Mieog et al. 2009, is different from standard areal metrics
of symbiont density. Ross and I discussed the differences, and their
implications, in the paper. It's possible one could get different results
using different metrics of symbiont density (something we are
investigating), but you could learn different things from each metric - it's
not that one method is "right" or "wrong".

Best

Andrew

Kelly LW, Barott KL, Dinsdale E, Friedlander AM, Nosrat B, Obura D, Sala E,
Sandin SA, Smith JE, Vermeij MJA, Williams GJ, Willner D, Rohwer F (2011)
Black reefs: iron-induced phase shifts on coral reefs. The ISME Journal
(2012) 6, 638–649; doi:10.1038/ismej.2011.114
Mieog JC, van Oppen MJH, Berkelmans R, Stam WT, Olsen JL (2009)
Quantification of algal endosymbionts (Symbiodinium) in coral tissue using
real-time PCR. Mol Ecol Res 9: 74–82.

___________________
Andrew C. Baker, Ph.D.
Associate Professor, University of Miami 
Pew Fellow in Marine Conservation

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-----Original Message-----
From: coral-list-bounces at coral.aoml.noaa.gov
[mailto:coral-list-bounces at coral.aoml.noaa.gov] On Behalf Of Szmant, Alina
Sent: Monday, November 26, 2012 6:44 PM
To: Delbeek, Charles; coral-list at coral.aoml.noaa.gov
Subject: Re: [Coral-List] Alga densities and bleaching

FYI, every place I dive where there is metal structure (old ship hulls,
navigation pilings etc) they are covered with nice looking corals of all
species.  There is a great example in the Dry Tortugas where there is an
shallow water old wreck (I can't remember the name now) near the old
Carnegie Station, that has huge corals growing on it!  These metal
substrates would make great coral habitat except for the fact that they
eventually rust, and the corals slough off.  I think the coral larvae like
the iron-rich substrates..  Iron-rich volcanic rocks seem to have the same
attraction to coral larvae.

*************************************************************************
Dr. Alina M. Szmant
Professor of Marine Biology
Center for Marine Science and Dept of Biology and Marine Biology University
of North Carolina Wilmington
5600 Marvin Moss Ln
Wilmington NC 28409 USA
tel:  910-962-2362  fax: 910-962-2410  cell: 910-200-3913
http://people.uncw.edu/szmanta
*******************************************************


-----Original Message-----
From: coral-list-bounces at coral.aoml.noaa.gov
[mailto:coral-list-bounces at coral.aoml.noaa.gov] On Behalf Of Delbeek,
Charles
Sent: Sunday, November 25, 2012 4:04 PM
To: coral-list at coral.aoml.noaa.gov
Subject: Re: [Coral-List] Alga densities and bleaching

What are the currents like?

J. Charles Delbeek, M.Sc.
Assistant Curator, Steinhart Aquarium
California Academy of Sciences

p 415.379.5303
f. 415.379.5304
cdelbeek at calacademy.org
www.calacademy.org

55 Music Concourse Drive
Golden Gate Park
San Francisco, CA 94118

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-----Original Message-----
From: coral-list-bounces at coral.aoml.noaa.gov
[mailto:coral-list-bounces at coral.aoml.noaa.gov] On Behalf Of Rudy Bonn
Sent: Wednesday, November 21, 2012 9:08 AM
To: coral-list at coral.aoml.noaa.gov
Subject: [Coral-List] Alga densities and bleaching

Interesting?  The Key West Marine Park is managed by Reef Relief here in Key
West.  It is a ~48 acre site on the south side of the island and fronts
Higgs beach, Dog beach, and extends from the duval street pier east to the
white street pier, (Gene is probably familiar with the area) anyway, years
ago the county/city put in a new pier at Higgs Beach and left portions of
the old one behind.  These submerged portions of the old pier are made of
iron, and there are corals attached to this iron substrate in amazing
numbers and diversity, and they are all in very good health, I can send
pictures if you contact me by my email, the water depth is 12 foot max on a
spring tide, so we know that during the summer months the temp probably
reaches the upper 80's  these corals show no signs of disease, alga
overgrowth, bleaching,  like I said in really good health.  Any ideas?  the
genera we have found include:  montastrea, siderastrea, porites, diploria
(several sp) meandrina, oculina, among others, all in good health all
attached to iron,    ideas?

Rudy S Bonn
Director of Marine Projects
Reef Relief
631 Greene Street
Key West, FL 33040
305-294-3100
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