Changes in feeding behavior of Pacific crown-of-thorns starfish (Acanthaster cf. solaris) following mass coral bleaching in the northern Great Barrier Reef, Australia

Abstract The Great Barrier Reef, like most reef ecosystems, is increasingly subject to major acute disturbances, including population irruptions of crown-of-thorns starfish (CoTS) and climate-induced coral bleaching. Given their increasing incidence, acute disturbances are likely to occur simultaneously or successively, though interactive effects of major disturbances are generally unknown. This study explores changes in the feeding behavior of CoTS during an emerging population irruption at Lizard Island that coincided with the 2024 mass bleaching, using in situ survey data. We conducted Scooter-Assisted Large Area Diver-Based surveys to investigate changes in CoTS demography and feeding, and point-intercept transects to examine changes in coral cover. From 2023 to 2025, there was a 49% decline in coral cover at Lizard Island, which was largely attributable to mass bleaching. Daily feeding rates of CoTS significantly declined over the same period, both in terms of the number of coral colonies (42.8% decline) and the combined tissue surface area of all corals consumed for each starfish (46.3% decline). CoTS density increased by 96.1% from 2023 to 2025 despite decreased feeding rates. Additionally, the relative consumption of different coral genera was consistent throughout the study period, with Acropora spp. contributing to > 80% of CoTS diet throughout the study. Though the 2024 bleaching event may have suppressed feeding rates and ecological impact of individual CoTS, the longer-term effects of CoTS are likely to conflate with coral loss due to mass bleaching, especially given sustained increases in CoTS densities.