What was done
The authors review the subject of emerging diseases in tropical coral reef ecosystems within the context of "the possibility that the changing profile of these diseases is being promoted by climate changes."

What was found
Hayes and Goreau conclude that "the recent emergence of diseases in corals may be interpreted as the consequence of (1) changing coastal ocean water quality favoring the proliferation, attachment and colonization of microbes, and (2) reduced efficiency of the coral's normal defenses."

What it means
In the words of the authors, their analysis suggests "that at least some of the emerging coral diseases may be explained by a decline in the capacity of coral colonies to mount effective protection against the increasing prevalence and varied invasive strategies of marine pathogens."  It therefore seems likely that at least some of the coral bleaching events of the past decade or so may similarly be explained by a decline in the capacity of coral colonies to mount effective protection against the increasing water temperatures of that period.  Furthermore, the decline in thermal protective ability may well be due to the same changing coastal ocean water quality that Hayes and Goreau associate with reduced coral ability to withstand microbial assaults.  In fact, the increasing stress of fighting emerging diseases may itself render corals more susceptible to thermal-induced bleaching.