End of summer coral bleaching.

[Steve Coles]

I agree with Yusef.  Surprisingly, rapid temperature fluctuations don't=20
seem to impart much stress. For a description of summer temperatures
off=20 Oman that fluctuated daily up to 8 deg. C with maxima up to 33 deg.
C and=20 had no apparent effect on an abundant coverage of 26 species of
corals,=20 please see Coles, S. L. (1997) Coral Reefs 16:269-272, and
Quinn and=20 Johnson (1997) Coral Reefs 15:214.  I also observed high
temperature=20 fluctuations near upper thermal limits with no negative
effects on corals=20 near the Kahe Point thermal outfall in Hawaii (Coles
[1975] Pacific Science= =20 29:15-18).

Steve Coles

At 05:09 PM 9/23/2000 +0300, you wrote:
>Bleaching threshold(s) in the Gulf apparently are a function of
>dose-duration.  It was extremely hot this past summer, and
>for a long time.  Extreme temperatures are experienced by
>the Gulf's "tough" corals almost every year, yet bleaching
>occurs only when exposure duration lasts beyond a certain
>threshold.  The 1996 and 1998 episodes suggest such a
>mechanism, with a delayed response.  Therefore, I am not
>convinced that we can attribute bleaching to rapid temperature
>fluxes, because here indeed is where Gulf corals are exceptionally
>tough. Almost every year, between November and December,
>seawater temperature drops 10-12 =B0C in less than two weeks,
>with corals showing no ill effects.
>
>Yusef Fadlalla
>Dhahran, Saudi Arabia
>
>Bob Buddemeier wrote:
>
> > What were sea state (wind) and light conditions?  Since the "high
> > temperature" bleaching certainly involves light and probably reduced
> > water motion as synergistic stressors, it's not surprising that there
> > isn't a monotonic response to any single variable viewed in isolation.
> >
> > Bob Buddemeier
> >
> > Ray Berkelmans wrote:
> > >
> > > Hello Shaker! (and C-listers)
> > >
> > > They breed corals tough where you come from! But obviously still not=
=20
> tough
> > > enough...
> > > Your observations about increasing bleaching while temperatures cool=
 are
> > > very interesting. These sound remarkably like the observations we made=
 at
> > > Hardy Reef on the GBR (offshore) in early 1998. Temperatures peaked at
> > > 29.9=B0C (av. daily) on 23-24 Feb, but bleaching was not observed=
 until 13
> > > March (18 days later), well after temperatures had cooled. Bleaching=
 was
> > > only mild, suggesting that the bleaching threshold was only exceeded=
 by a
> > > relatively small amount (& probably for a short duration).=
 Observations
> > > about the state of the corals were made every day by a biologist=
 (Jackie
> > > Shields) aboard a tourist vessel. To me these observations suggest=
 that
> > > there may be a delay in the onset of bleaching (at least visible=20
> symptoms of
> > > bleaching) following stress. Observations of bleaching and=20
> temperatures at
> > > other sites indicate that this delay is considerably reduced (or=
 absent)
> > > when stress temperatures are exceeded by a large amount. These field
> > > observations are consistent with the delayed bleaching response I=20
> reported
> > > in Coral Reefs (18:219-228) following experimentally induced=
 temperature
> > > stress. Does any one else have similar observations?
> > >
> > > Ray Berkelmans
> > > AIMS
> > > PMB 3
> > > Townsville Q4810
> > > Ph 47534268
> > >
> > >  -----Original Message-----
> > > From:   owner-coral-list at coral.aoml.noaa.gov
> > > [mailto:owner-coral-list at coral.aoml.noaa.gov] On Behalf Of Shaker=20
> Alhazeem
> > > Sent:   Wednesday, 20 September 2000 9:18 PM
> > > To:     Coral List
> > > Subject:        End of summer coral bleaching.
> > >
> > > Dear Coral-Listers,
> > >
> > > Kuwait is experiencing a major coral bleaching event now. Bleaching is
> > > occurring in excess of about 80% in some areas.  The phenomenon is
> > > recent having started within the last week. This is the end of the hot
> > > season so temperature had fluctuated last week, so temperature shock
> > > most likely was the effect on corals. The water temperature was around
> > > 32=B0C on the time of observing coral bleaching.
> > > About three weeks ago I have visited Kubbar island coral reef in=
 Kuwait
> > > in August 12th 2000. I have found there was about 10% bleached coral
> > > colonies and water temperature was 35=B0C.  But this visit last=
 weekend
> > > the coral was bleached about 80% and water temperature around 32=B0C=
 in
> > > September 14th 2000. But Quro coral reef had showed about 40% coral
> > > bleaching only, that could be for the reason it is less stressed coral
> > > around in Quro, as it is farther away from the coast so less human
> > > impact. Last week we had sudden drop in the temperature and it came=
 back
> > > up after that week, which could be the real cause of the coral=
 bleaching
> > > is temperature shock.
> > >
> > > With Best Wishes,
> > >
> > > Shaker Alhazeem
> > >
> > > Research Associate
> > > Mariculture and Fisheries Dept.
> > > Kuwait Institute for Scientific Research
> > > P.O. Box : 1638
> > > 22017 Salmiya - Kuwait
> > > Fax : (965) 5711293
> > > Email: shazeem at safat.kisr.edu.kw
> >
> > --
> >
> > Dr. Robert W. Buddemeier
> > Senior Scientist, Geohydrology
> > Kansas Geological Survey
> > University of Kansas
> > 1930 Constant Ave.
> > Lawrence, KS 66047
> >
> > ph (785) 864-2112
> > fax (785) 864-5317
> > buddrw at kgs.ukans.edu
> > http://water.kgs.ukans.edu

S. L. Coles, Ph. D.
Research Zoologist
Bishop Museum
1525 Bernice St.
Honolulu, HI 96817, USA
Ph. (808) 847-8256
Fax (808) 847-8252