More Bleaching Agents

Ove Hoegh-Guldberg oveh at uq.edu.au
Wed May 16 00:35:34 EDT 2001


Good discussion so far.  Can I suggest we also keep distinct agents that cause
"bleaching" (many) and agents that cause "mass coral bleaching" (a subset of the
former)?  We should also keep in mind the distinction between primary agents
(directly causal) and those that are secondary (aggravating).  In this way,
thermal events (primary) that trigger mass coral bleaching events are often
aggravated by secondary factors like high PAR light, UVR, hypoxia due to reduced
water movement, perhaps starvation and other factors that might not have been
the primary trigger.

Congratulations Debbie - a useful thread has developed.

Cheers,

Ove

Professor Ove Hoegh-Guldberg
Director, Centre for Marine Studies
University of Queensland
St Lucia, 4072, QLD

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 McCarty and
Peters
Sent: Wednesday, 16 May 2001 12:38 PM
To: Coral Reef List Server
Subject: More Bleaching Agents


Dear All,

In addition to increases in temperature, UV, and vibrios (bacteria, see
also K.B. Ritchie and G.W. Smith, 1998, Type II white band disease, Rev.
Trop. Biol. 46 Suppl. 5:199-203), bleaching of reef corals has also been
associated with (citing only a few studies):

Cold water

Steen, R.G., and L. Muscatine.  1987.  Low temperature evokes rapid
exocytosis of symbiotic algae by a sea anemone.  Biol. Bull. 172:246-263.

Turbidity and sedimentation

Rogers, C.S.  1979.  The effect of shading on coral reef structure and
function.  J. Exp. Mar. Biol. Ecol.  41:269-288.

Rogers, C.S.  1983.  Sublethal and lethal effects of sediments applied to
common Caribbean reef corals in the field.  Mar. Pollut. Bull. 14:378-382.

Reduced salinity

Goreau, T.F.  1964.  Mass expulsion of zooxanthellae from Jamaican reef
communities after Hurricane Flora.  Science  145:383-386.

and

Protozoan infections

Upton, S.J. and E.C. Peters.  1986.  A new and unusual species of coccidium
(Apicomplexa: Agammococcidorida) from Caribbean scleractinian corals.  J.
Invertebr. Pathol. 47:184-193.  [And continuing unpublished observations]

Bleaching might be the result of exposure to extreme physical conditions,
pollutants, parasites, or pathogens, in which the symbiotic relationship is
disturbed and the algae are released from the gastrodermal cells by
exocytosis or the algal pigments are damaged in situ.  Bleaching might also
occur by sloughing of the gastrodermal epithelium, as observed in:

Gates, R.D., G. Baghdasarian, and L. Muscatine.  1992.  Temperature stress
causes host cell detachment in symbiotic cnidarians: implications for coral
bleaching.  Biol. Bull. 182:324-332.

Each case of bleaching should be evaluated to determine which causal agent
and mechanism is affecting the condition of the host.

Esther Peters
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