Effects of a changing climate on the dynamics of coral infectious disease: a review of the evidence.

A close examination of the coral disease literature reveals many hypothesized mechanisms for how coral disease may be linked to climate change. However, evidence has been largely circumstantial, and much uncertainty remains. Here, I review the latest information on both the predicted effects of climate change in coastal marine ecosystems and current research on coral-pathogen dynamics in relation to climate variables. The published evidence supports the hypothesis that coral infectious diseases are emerging and demonstrates that coral disease research has been exponentially expanding over the last few decades. Current research suggests that environmental factors, such as ocean warming, altered rainfall, increased storm frequency, sea level rise, altered circulation, and ocean acidification may play a role in coral disease. These climate variables likely alter coral epidemiology through effects on pathogen growth rates, transmission, virulence, and susceptibility. Despite recent advances, discovering the causes of coral disease emergence at large spatial and temporal scales has been hindered by several factors including (1) the inability to rely on Koch's postulates for diseases with multifactorial etiologies, (2) the paucity of long-term, coordinated, coral disease data, and (3) the difficulty in detecting correlations in inherently non-linear, dynamic disease systems. In a rapidly changing global environment, the consequences of increasing coral disease may be severe, leading to elevated extinction risk and loss of critical reef habitat. Current evidence is still preliminary but is increasingly suggestive that mitigating the effects of climate change may help reduce the emergence of disease and improve the health of coral reef ecosystems.