JCU ePrints

Abstract

Ocean warming due to climate change could increase the frequency and severity of infectious coral disease outbreaks by increasing pathogen virulence or host susceptibility. However, little is known about how temperature anomalies may affect disease severity over broad spatial scales. We hypothesized that the frequency of warm temperature anomalies increased the frequency of white syndrome, a common scleractinian disease in the Indo-Pacific. We created a novel 4 km satellite temperature anomaly dataset using data from NOAA’s Pathfinder program and developed four different temperature anomaly metrics, which we correlated with white syndrome frequency at 47 reefs spread across 1500 km of the Great Barrier Reef. This cross-sectional epidemiological analysis used data from disease field surveys conducted by the Australian Institute of Marine Science six to twelve months after the summer of 2002, a year of extensive coral bleaching. We found a highly significant positive relationship between the frequency of warm temperature anomalies and the frequency of white syndrome. There was also a highly significant, nearly exponential relationship between total coral cover and the number of disease cases. Furthermore, coral cover modified the effect of temperature on disease frequency. Both high coral cover (>50%) and anomalously warm water appear to be necessary for white syndrome outbreaks to occur and these two risk factors explained nearly 75% of the variance in disease cases. These results suggest that rising ocean temperatures could exacerbate the effects of infectious diseases on coral reef ecosystems.