Assessing increased temperature and light effects on black band coral disease

Background/Question/Methods   Coral disease is a significant contributor to declining coral health observed worldwide. Numerous monitoring efforts and reports have demonstrated that during summer months with increased seawater temperature and light irradiance, both black band disease (BBD) incidence and prevalence increase. However, the mechanisms that underlie this pattern are still unknown. An ex situ controlled experiment was conducted to investigate the relative effects of temperature and light on BBD. The reef building coral Montastraea faveolata was artificially infected with BBD and exposed to ecologically relevant temperature (~ 28oC, 31oC) and light (35% ambient, 12.5% ambient) regimes.

Results/Conclusions   There were no significant differences in BBD progression rates amongst the temperature and light treatments, suggesting an upper threshold for the enhancement of BBD progression by temperature or light. However, differences were observed among fragments from different host coral colonies. Length heterogeneity PCR was used to characterize the bacterial assemblages of both coral mucus and BBD in the various light and temperature treatments and among the different coral colonies. Clarifying the relationships between temperature, light, and BBD by looking for functional changes that contribute to increased coral susceptibility may provide critical information to improve management techniques in declining coral ecosystems. Ongoing efforts in our research group will identify changes in coral gene expression and coral immune response that result from BBD infection as well as experimental changes in temperature and light.