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A physiological crisis drives the coral recruitment bottleneck

Edmunds, Peter1; Cheh, Adrian1; Burgess, Scott2

Research facility: Gump South Pacific Research Station
Published Jun 16, 2025 on Dryad. https://doi.org/10.5061/dryad.4tmpg4fnx

Data files

Jun 16, 2025 version files 41.68 KB

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Abstract

Recruitment failure is a leading cause of population decline for tropical corals. Because the causes of death for small corals are unclear, it is challenging to predict how recruitment bottlenecks will change in the future. We tested the hypothesis that depletion of biomass causes high mortality of small corals under thermal stress. The biomass of small colonies (< 30 mm diameter) of genetically identified broadcast spawning Pocillopora from Moorea, French Polynesia, was manipulated using elevated temperature to increase respiration, and reduced day length to decrease photosynthesis. Corals with high or low biomass were incubated at ambient summer (28°C) and elevated (31°C) temperatures. Small P. meandrina with high biomass were six times more likely to die at 31°C versus 28°C, but corals with low biomass were 48 times more likely to die at 31°C versus 28°C. When small Pocillopora were grown in seawater augmented with bicarbonate to reduce the energetic expenditure on skeletogenesis, growth rates were not affected but energy expenditure was reduced by 20%. Resource-limitation of small corals therefore can affect their response to elevated temperatures, supporting the hypothesis that a physiological crisis initiated by resource limitation mediates the stringency of recruitment bottlenecks and the rate of coral community recovery. Data in support of this publication are supplied in 11 files.