Prior heat stress increases pathogen susceptibility in the model cnidarianExaptasia diaphana

Abstract

Anthropogenic climate change has significantly altered terrestrial and marine ecosystems globally, often in the form of climate-related events such as thermal anomalies and disease outbreaks. Although the isolated effects of these stressors have been well documented, a growing body of literature suggests that stressors often interact, resulting in complex effects on ecosystems. Recent declines in coral cover from a variety of climate-related stressors make reef ecosystems well-suited to investigate sequential associations between climate impacts, particularly heat stress and disease. Here we used the model cnidarian Exaiptasia diaphana to investigate mechanisms linking heat stress to increased disease susceptibility. We examined anemone pathogen susceptibility and physiology (symbiosis, immunity, and energetics) following recovery from heat stress. We observed significantly increased pathogen susceptibility in anemones exposed to heat stress, likely linked to observed suppression of multiple immunological parameters. Furthermore, our data suggest that changes in resource allocation might drive observed reductions in immunity following thermal stress. These findings are an important first step towards understanding temporal associations between two of the most significant climate-associated stressors, heat and disease.