Nearshore vs. offshore bleaching

Sat May 19 15:51:47 EDT 2001

Bob,
I wish I had seen your excellent response before I sent mine yesterday.
Unfortunately I am making my way down a list of hundreds of back-logged messages and
just came to your comments.  Excellent!  Billy

Bob Buddemeier wrote:

> On the basis of evidence available at the time we (Buddemeier, R. W. and Fautin,
> D. G., 1993, Coral Bleaching as an Adaptive Mechanism, Bioscience 43:320-326)
> observed that:
> "There are consistent habitat differences in bleaching resistance at a given
> locale; corals in habitats that are more variable or more prone to stresses of
> various sorts, including thermal (such as shallow water or fringing reefs), tend
> to be less bleached than those in more normally equable environments."
>
> Apparently the field observational patterns are more consistent than attention to
> the literature.
>
> The reasons can be described as aclimatization, adaptation, or different
> 'ecospecies' occupying the different habitat niches, but they all boil down to the
> fact that both 'corals' and their microenvironments exhibit systematic differences
> over rather small scales.
>
> Bob Buddemeier
>
> John Naughton wrote:
>
> > To add to the mix, I concur with Bruce's statements below. During the recent
> > severe bleaching event in Palau, we noted that corals in the lagoon close to
> > the main island of Babeldaob were basically not impacted, while much of the
> > coral (particularly Acropora) on the barrier reef was hammered.  Could this be
> > attributed to the possible lowering of nearshore water temps from runoff?
> >
> > Mahalo,  John
> >
> > John Naughton
> > NMFS, Pacific Islands Area Office
> > Honolulu, HI
> >
> > Bruce Carlson wrote:
> >
> > > RE: Offshore vs nearshore bleaching
> > >
> > > Bernard Thomassin disagreed with the general statement that bleaching is
> > > usually more severe nearshore.   I concur.
> > >
> > > The other day, Gregor posted a message that "The pattern of bleaching
> > > follows a consistent trend globally that suggests that following bleaching
> > > events, reefs located in areas with less water column mixing are usually
> > > the worst affected. Typically these are inshore reefs where both nutrient
> > > flux and absolute levels of nutrients are likely higher than outer reefs."
> > >
> > > I wrote to Gregor saying that my data indicate that both nearshore and
> > > offshore reefs in Fiji (south of Viti Levu) suffered significant bleaching
> > > last year.  When I revisited my transects this year I found that both areas
> > > suffered high mortality (>95% Acropora dead), but I also found significant
> > > regrowth ("phoenix" corals) and significant recruitment in the lagoons
> > > (Acropora spp.), whereas the remote offshore barrier reef showed virturally
> > > no survival and no new recruitment (the "virtually" means that whereas last
> > > year I counted on average over 100 acroporid colonies per 30 x 1 meter belt
> > > transect, this year I found only one tiny survivor on one transect and one
> > > tiny recruit on the other transect).  The nearshore patchreefs and barrier
> > > reef where recovery is good, are located near the mouth of a large river
> > > and the water in this lagoon area is typically turbid most of the
> > > time.  The remote barrier reef is typically in a pristine ocean
> > > environment, often crystal clear, and subjected to large open ocean swells
> > > much of the year.
> > >
> > > Gregor wrote back to me and qualified his statement:
> > >
> > > "What I was referring to was that in "moderate" bleaching events, when
> > > there was less than say 50% mortality, the inner reefs typically showed
> > > higher mortality than the outer reefs due to mixing at the outer reefs.....
> > > When it is a" bad" event there is little difference as you have seen in
> > > mortality.  But your observations of faster recovery on the inner reefs are
> > > interesting and one wonders if this has more to do with a higher number of
> > > nearby parent colonies, water retention in those areas which facilitated
> > > recruitment, rather than with the nutrients being a beneficial stimulus.
> > > But all these are open questions deserving of more research."
> > >
> > > So what is the "global trend"?  Do nearshore reefs or remote barrier reefs
> > > suffer higher mortality and lower recovery rates?  Or should we even try to
> > > make such a generalization with so many unique factors at each locality?
> > >
> > > Aloha
> > > Bruce
> > >
> > > At 12:33 PM 5/16/2001 -0300, Bernard THOMASSIN wrote:
> > > >To: Debbie MacKenzie <<debimack at auracom.com>
> > > >From: Bernard THOMASSIN <<thomassi at com.univ-mrs.fr>
> > > >Subject: Re: nutrient deficiency and bleaching -and- Perhaps you need =20
> > > >to do a bit more reading ...
> > > >
> > > >Dear Debbie and all colleagues interested by coral bleaching,
> > > >
> > > >To the comment:
> > > >
> > > > > How come that bleaching is usually more severe nearshore, where
> > > > > nutrients are enhanced to levels, which in turn can become detrimental
> > > > > to many coral reef organisms, which are highly adapted to exist in
> > > > > oligotrophic conditions? Could that maybe relate to some patchiness,
> > > > > too: too much 'food' and maybe toxic substances?
> > > >
> > > >I don't agree with this opinion taking as example that occured around
> > > >Mayotte Island in the North of the Mozambique Channel, SW Indian Ocean,
> > > >where I studied since 1983 several bleachings of various intensity.
> > > >
> > > >Here the huge bleaching event of the April-June 1998 (when an warmer
> > > >mass of oceanic seawater coming from the North reached this SW Indian
> > > >Oc. area) -the bleaching was undubfully caused by the seawater
> > > >temperature increase : T=B0 C reached up to 32=B0 C in ocean open sea and
> > > >stayed as during near 3 months, it was the corals from the outer slopes
> > > >of the barrier reefs (187 km long) that bleached  and then died, mainly
> > > >in the shallow depths (3m down to 15-20m  - but encrusting corals at
> > > >down 30m also bleached -) : all the tabular and branched Acroporids,
> > > >all the Pocillopora, some Diploastrea, some massive Porites (but on
> > > >some of them parts were kept alive, if most of the colonies died). Even
> > > >Sarcophyton and Sinularia bleached, as well as the large sea-anemones
> > > >as Heterotactis magnifica, and some Tridacnids. So, consequently, the
> > > >barrier reef slope coral communities were destroyed at more than 85
> > > >percent.
> > > >
> > > >On the slopes of lagoonal reefs, as well as on the slope of the
> > > >fringing reefs, also the bleaching occured, but on the fringing reefs
> > > >in muddy environments of deep coastal bays, most of the corals
> > > >survived.
> > > >
> > > >My opinion (exposed in one of our Bali's Conf. posters) is that corals
> > > >living in clear oceanic waters on the barrier reef slopes or lagoonal
> > > >reef slopes near large passages, live in oceanic seawaters showing more
> > > >constant parameters (according to the seawater temperature they are
> > > >more "stenothermes"). In contrary, corals living in nearshore
> > > >environments where seawater parameters are more variable (increase of
> > > >temperature due to closed environments, or decrease of temperature due
> > > >to cool groundwater seepages ; salinity variations due to rainfalls and
> > > >river flows ; variation of the turbidity due to alluvial inputs
> > > >associated with rainfalls or to phytoplankton blooms ; bacterial
> > > >attacks from terrigeneous materials ; etc...).=20
> > > >
> > > >In fact coastal populations of corals (for the same species) are more
> > > >resistant to all the possible stresses that coral populations living in
> > > >more stable and constant seawater conditions.
> > > >
> > > >In this conditions I disagree with your opinion.
> > > >
> > > >But be very carefull with the biology/physiology of corals. I begin to
> > > >believe that the same species of corals have not the same biology (and
> > > >physiology) in region located fare away. So extrapolations of results
> > > >from one area to another one are not possible. This is true for the
> > > >biologists and ecologists, but also for our paleo-geologist
> > > >colleagues.
> > > >
> > > >This can explain the opposite views between different researchers!
> > > >
> > > >Have a good day.
> > > >
> > > >Sincerely yours.
> > > >
> > > >Bernard
> > > >
> > > >Bernard A. THOMASSIN
> > > >CNRS-UMR 6540 "Dimar",
> > > >Centre d'Oc=E9anologie de Marseille,
> > > >Station marine d'Endoume,
> > > >Chemin de la batterie des Lions,
> > > >13007 Marseille,
> > > >France
> > > >
> > > >(33) 04 91 04 16 17 (ligne directe)
> > > >(33) 04 91 04 16 00 (standart)
> > > >mobile (33) 06 63 14 91 78
> > > >fax  (33) 04 91 04 16 35 (=E0 l'attention de....)
> > > >
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> > >
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>
> --
> Dr. Robert W. Buddemeier
> Kansas Geological Survey
> University of Kansas
> 1930 Constant Avenue
> Lawrence, KS 66047 USA
> Ph (1) (785) 864-2112
> Fax (1) (785) 864-5317
> e-mail:  buddrw at kgs.ukans.edu
>
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--
Billy D. Causey, Superintendent
Florida Keys National Marine Sanctuary
PO Box 500368
Marathon, FL 33050
(305) 743-2437 phone
(305) 743-2357 Fax
billy.causey at noaa.gov
http://www.fknms.nos.noaa.gov/

~~~~~~~
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