End of summer coral bleaching.

Yusef H. Fadlalla yfadlal at kfupm.edu.sa
Sat Sep 23 10:09:54 EDT 2000


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 °C 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 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°C (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 symptoms of
> > bleaching) following stress. Observations of bleaching and 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 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 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°C 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°C.  But this visit last weekend
> > the coral was bleached about 80% and water temperature around 32°C 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



More information about the Coral-list-old mailing list