A coral disease outbreak highlights vulnerability of remote high-latitude lagoons to global and local stressors.

Outbreaks of coral disease are often associated with global and local stressors like changes in temperature and poor water quality. A severe coral disease outbreak was recorded in the primary reef-building taxa spp. in a high-latitude lagoon at Norfolk Island following heat stress and pollution events in 2020. Disease signs suggest the occurrence of a Montiporid White Syndrome with four distinct phases and maximum measured tissue loss of 329 mm day. In December 2020 and April 2021, 60% of the community were impacted and disease severity increased by 54% over this period. Spatial patterns in prevalence indicate the disease is associated with exposure to poor water quality in addition to size class of coral colonies. High prevalence levels make this event comparable to some of the most severe coral disease outbreaks recorded to date demonstrating the vulnerability of this system to combined impacts of warming and pollution.