What was done
The authors present information about a bleaching event that occurred in a southern Caribbean coral reef near the island of Bonaire, 85 km north of the Venezuelan coast.

What was learned
The significance of this coral bleaching event was its correlation with a large and rapid decrease in water temperature.  Within a period of 18 hours, the water temperature at the reef site fell from its normal value of 28°C to 25°C.  Coincident with the temperature decline was a dramatic increase in the amount of bleaching in several coral species, some of which experienced bleaching totals as high as 80%.

What it means
As the authors indicate, most of the coral bleaching events that are associated with temperature have occurred when water temperatures have risen, leading many persons to "favor a link between warming and bleaching."  However, the bleaching event examined by the authors "point[s] to cooling as a cause."  Yet, these same corals had experienced "massive bleaching ... as a result of a 4°C increase in water temperature" two years earlier.  Consequently, the authors hypothesize that "in many cases it may not be the absolute water temperature (whether warm or cool) in itself that precipitates a bleaching reaction, but rather the rapidity of temperature change in combination with the deviation from the normal temperatures to which corals in a region are adapted."