Elevated temperature decreases stony coral tissue loss disease transmission, with little effect of nutrients.

Stony coral tissue loss disease (SCTLD) is the deadliest scleractinian coral disease reported, causing significant coral loss in the Western Atlantic reefs. Environmental conditions are known to influence disease dynamics, but determining the specific conditions that exacerbate SCTLD remains challenging. We developed a robotic multi-stressor system to study the effects of temperature and ammonium on SCTLD transmission. For a month, coral fragments were preconditioned to two temperatures (28 °C and 31 °C) and nutrient treatments (with and without ammonium dosing), and subsequently exposed to SCTLD. Environmental treatments only caused modest effects in the corals (based on calcification, photochemical efficiency, and symbiotic algal communities). However, SCTLD incidence was strongly reduced at higher temperature (17% at 31 °C compared to 70% at 28 °C), contrasting with other coral diseases that typically worsen with increased heat. Disease management approaches may involve concentrating SCTLD treatment efforts during warmer periods when reduced incidence might enhance treatment efficacy.