More Bleaching Agents

McCarty and Peters McCarty_and_Peters at compuserve.com
Tue May 15 22:37:40 EDT 2001


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  [And continuing unpublished observations]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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