Montgomery, R.S. and A.E. Strong, 1994: Coral Bleaching Threatens Ocean, 
Life. EOS 75[13]: 145-147.
 
ABSTRACT [Intro]
 
     People around the world depend on the resources provided by the ocean
to support life. But global-scale damage to the coral reefs, a large and
integral part of the ocean environment that supports a variety of sea
life, is a frightening scenario that may unfold in the coming years. 

     Recently, a phenomenon called coral bleaching has raised concerns 
about the deteriorating conditions in the world's oceans and the 
implications for life on our planet. Coral bleaching occurs as coral 
tissue expels zooxanthellae, a symbiotic algae that resides in the 
structure of the coral and is essential to its survival. The widespread 
nature of the bleaching threatens the state of the environment.

     The zooxanthellae, besides giving color to the otherwise white coral
skeleton, produce carbon compounds that nourish the coral. In return, the
coral provides the algae with a home inside its skeletal structure and
nitrogen and phosphorous, which are essential for its survival [Brown and
Ogden, 1993.]. 

     This delicate symbiosis can be disrupted by several factors, and this
causes the coral to expel the algae.  Disturbances such as extremes of
temperature, hypersalinity, pollutants in the water, or changes in
radiation flux cause coral bleaching. The correlation between high water
temperatures and coral bleaching is of acute concern. 

     In the 1980s, many reefs including those near Easter Island, the
Great Barrier Reef, and the coasts of Central America showed signs of
bleaching. 

     More nottceable events occurred in 1983 near Panama and in 1987-1988
in the Caribbean [Ghiild, 1990]. The Panama event is connected with the
1982-1983 El Nino, which raised water temperatures in the area to above
29C. 

     The Caribbean event, which lasted for 9 months, was associated with
widespread bleaching in the reefs off Jamaica.  Water temperatures in the
area were above 30C at the peak of the bleaching. This event in particular
raised concerns about a possible link between coral bleaching, rising
water temperatures, and global warming [Goreau et al., 1993]. 

     The possibility that a recent warming trend in the world's oceans is
responsible for the recent bleaching events merits further inquiry. 
Evidence favoring this hypothesis exists in oceanic and atmospheric
physical data, but until such evidence is examined with known bleaching
events, conclusions cannot be made.