Coral diseases occur in response to biotic and abiotic stresses. Biotic stresses are instigated by microorganisms including bacteria, fungi, viruses, and protozoans. Abiotic stresses occur in response to physical or chemical stresses, such as increased sea surface temperatures and UV radiation, anthropogenic input of nutrients, sediment, and other pollutants. Abiotic stresses may exacerbate the role of microorganisms in disease processes. Thus, the recent emergence of disease in corals is believed to be a consequence of deteriorating water quality that favors the proliferation of microorganisms, or of a reduced ability of a coral to defend itself against biotic and abiotic stresses.
Most diseases appear to be a response to multiple factors.
Although coral diseases are damaging reefs around the world, they have been documented most frequently in the western Atlantic. Coral diseases are also having an impact on other important reef-building corals worldwide, but assessments in regions other than the western Atlantic are limited to a few reefs. EPA scientists and other collaborators are currently making a preliminary assessment of the frequency and distribution of coral diseases within the Florida Keys National Marine Sanctuary and Dry Tortugas National Park and their relationship to water quality parameters. This year EPA is also hosting a workshop for coral disease specialists to develop terminology to describe different coral diseases. There is a need for ICRI's Global Coral Reef Monitoring Network to begin to incorporate coral disease observations into its monitoring efforts.