Julian Sprung's email.

[Ove Hoegh-Guldberg]

Dear Bill,

Interesting comments.  My feeling is that oxygen is involved (either as an promoter of the
photoinhibitory production and build-up of active oxygen within the zooxanthellae - that is, as a
secondary variable).  We know that thermal stress collapses oxygen production and increases
respiration (see papers by Coles and Jokiel: Marine Biology. 1977; 43:209-216, Hoegh-Guldberg and
Smith - J. Exp. Mar. Biol. Ecol. 1989; 129:279-303 and others). If the photosynthetic production of
oxygen is down and respiration is up (and probably, bacterial consumption up due to decaying
tissue), then oxygen at night over reefs under low flow (especially on reefs where corals dominate)
would be expected to decrease, perhaps to critical levels.  While not a primary factor, I would see
this as an important follow on effect.  It may actually be an important determinant of mortality.

I am interested in following up the aggravating effect of oxygen - it would be useful if oxygen was
monitored during the next set of bleaching events.  Perhaps water motion (over small patches of
reef) might help ameliorate the ultimate impact of a thermal event.  Just a thought.  That and
shading a reef might be useful for managers of small show pieces of reefs.  But - just for those
journalists our there - this would not be useful for anything more than a few hundred square metres!

Cheers to all,

Ove

-----Original Message-----
From: owner-coral-list at coral.aoml.noaa.gov
[mailto:owner-coral-list at coral.aoml.noaa.gov]On Behalf Of Billy Causey
Sent: Monday, 28 August 2000 1:25 AM
To: oveh at uq.edu.au
Cc: Bruce Carlson; Bernard A. Thomassin; coral-list at coral.aoml.noaa.gov
Subject: Re: Julian Sprung's email.


Ove and others,

I am interested in your comments about the role of oxygen.  For years I have sounded like a broken
record, exclaiming that while hot water is one of the stressors leading to coral bleaching, that I
suspect the slick-calm, doldrum weather patterns lead to a drop in dissolved oxygen levels in the
coral
reef environment, especially at night.  I sometimes think we take the level of dissolved oxygen on
coral reefs for granted .... and tend to not believe there could be a significant enough change to
affect corals for example.

During years when we have had severe bleaching in the Florida Keys, I have observed reef fish
respiring
very heavily .... in the middle of the day.  So I have often suspected the oxygen levels as being
low
.... during "hot water" events ... even during daylight hours.

Is it possible that the zooxanethellae, existing inside the coral polyp tissue starts competing with
the coral polyp for oxygen at night ... when dissolved oxygen levels are low anyway .... and
something
has to give?  Imagine ... day after day and night after night, during periods of low mixing and
natural
aeration of surface waters, the oxygen level drops below a threshold and the coral polyp is in a
state
of competing for oxygen with the zooxanethellae.

Folks ... be kind to me!  I am not a coral physiologist, in fact I wasn't very good in biochemistry
.... just a coral reef manager with thousands of hours of observations that make me think the coral
bleaching trigger and mechanisms are simpler than we realize.  I am curious about opinions on this
idea.

Cheers, Billy Causey

Ove Hoegh-Guldberg wrote:

> Flow probably has some effect through the removal of some of the feedback effects of the high
oxygen
> tensions that occur during the daylight hours.  If the increased production of active oxygen after
> thermal stress (a'la Jones et al 1998, reviewed in Hoegh-Guldberg 1999), then flow might have an
> ameliorating effect through the decreased boundary layer thickness and hence oxygen tensions close
> to coral surfaces.
>
> Survival near rivers might be related to the decreased light stress due to the higher turbidity of
> rivers.
>
> Just some ideas ...
>
> Cheers,
>
> Ove
>
> Professor Ove Hoegh-Guldberg
> Director, Centre for Marine Studies
> University of Queensland
> St Lucia, 4072, QLD
>
> Director, Heron, Stradborke and Low Isles Research Stations
> President, Australian Coral Reef Society
>
> Phone:  +61 07 3365 4333
> Fax:       +61 07 3365 4755
> Email:    oveh at uq.edu.au
> http://www.marine.uq.edu.au/ohg/index.htm
>
> -----Original Message-----
> From: owner-coral-list at coral.aoml.noaa.gov
> [mailto:owner-coral-list at coral.aoml.noaa.gov]On Behalf Of Bruce Carlson
> Sent: Saturday, 26 August 2000 4:15 AM
> To: Bernard A. Thomassin; coral-list at coral.aoml.noaa.gov
> Subject: Re: Julian Sprung's email.
>
> Bernard,
>
> Did you also notice that corals in areas with swift flowing water (usually
> from tides) also survived better than nearby reefs with low flows?  I
> noticed this in Fiji on the shallow barrier reef of the University of the
> South Pacific, and in Palau near the lighthouse reef -- both are similar
> reef environments with strong laminar water flow (the water is shallow
> enough to stand up at mid-tide, but the current knocks you over -- I don't
> have a more precise current measurement).  Why would flow rate matter?
> Perhaps there is something related to diffusion rates (which would increase
> in strong water flow) which offers some protection during bleaching????  If
> Ove is right about superoxides forming during warm water events, maybe this
> observation is relevant.
>
> Also, in Fiji, we noticed that reefs near river mouths also showed good
> survival rates.  The outer barrier reefs in Palau and Fiji seemed to be hit
> the hardest.
>
> Bruce
>
> ----- Original Message -----
> From: Bernard A. Thomassin <thomassi at com.univ-mrs.fr>
> To: <coral-list at coral.aoml.noaa.gov>
> Sent: Friday, August 25, 2000 6:30 AM
> Subject: Re: Julian Sprung's email.
>
> >
> > Jonathan.Kelsey at noaa.gov wrote :
> >
> > >-Are these generally accepted concepts?
> > >-Can one accurately assess coral mortality rates associated with a
> bleachin
> > >event after "a matter of just a few days"?
> > >-Are there quantitative studies showing that there is a greater bleaching
> > >survival rate among corals in polluted waters versus those in
> non-polluted
> > >water? -Any comments and/or further discussion would be greatly
> appreciated.
> >
> > We will presented a poste about the subject at bali meeting. In Mayotte
> > Is., North Mozambique Channel, a huge bleaching occurred in 1998 spring
> > (end of summer season there) and most of 90 percent of the shallow coral
> of
> > the barrier reefs died.
> > Those corals that surveyed the best are from the muddy environnements in
> > bays, on fringing reef fronts and patches, even the harbour !why ? Because
> > the corals living in oceanic cooler waters of the barrier reef belt (170
> km
> > long) are less adapted to tolerate hot waters and high level of light
> (some
> > got "sun burns" as table acroporas). In opposite population of corals
> (same
> > species) living in neritic coastal waters, in inner areas of the lagoon,
> > are genetically more adapted to tolerate : high temperature, turbid waters
> > after rainfalls, even falls of salinity. Today in Mayotte, probably the
> > recovering ibn coral of the mid-lagoon patch reefs (recruitement) is due
> to
> > larvae coming from these coastal coral populations. These is one of the
> > main reasons to protect these "special" reefs in muddy environments from
> > all the effects of coastal works (marinas, dredgings, infilling of
> littoral
> > for roads, etc...).
> >
> > This is a good way for researches.. and from where larvae that recruit are
> > coming.
> >
> > Bernard A. Thomassin
> > Directeur de recherches au C.N.R.S.
> >
> > G.I.S. "Lag-May"
> > (Groupement d'Int=E9r=EAt Scientifique Environnement marin et littoral de
> > Mayotte")
> > & Centre d'Oceanologie de Marseille,
> > Station Marine d'Endoume,
> > rue de la Batterie des Lions,
> > 13007 Marseille
> > 9l. (33) 04 91 0416 17
> > 9l. GSM 06 63 14 91 78
> > fax. (33) 04 91 04 16 35 (0 l'attention de...)
> > e-mail : thomassi at sme.com.univ-mrs.fr
> >
> >
> >

--
Billy D. Causey, Superintendent
Florida Keys National Marine Sanctuary
PO Box 500368
Marathon, FL 33050
Phone (305) 743.2437, Fax (305) 743.2357
http://www.fknms.nos.noaa.gov/