Figure by John Burns


The mortality rate of a disease is a useful measure for determining the threat it poses to coral survival.

This value can be calculated by dividing the number of colonies that die per unit time by the total number of colonies surveyed. In coral studies, sometimes the partial mortality rate is measured since portions of a colony can die while other portions survive.

The figure on the right shows a reef plot before (above) and after (below) several disturbances and a severe coral bleaching event. A large proportion of colonies died, as evidenced in the figure, which caused a loss of approximately 45% in overall coral cover.