Shallow corals acclimate to mesophotic depths while maintaining their heat tolerance against ongoing climate change

Mar Pollut Bull. 2024 Dec;209(Pt B):117277. doi: 10.1016/j.marpolbul.2024.117277. Epub 2024 Nov 18.

Abstract

Global warming poses a significant threat to coral reefs. It has been assumed that mesophotic coral ecosystems (MCEs, 30 to 150 m depths) may serve as refugia from ocean warming. This study examined the acclimation capacity and thermal tolerance of two shallow coral species, Porites cylindrica and Turbinaria reniformis, transplanted to mesophotic depths (40 m) for 12 months. Fragments from 5 and 40 m were exposed to control (28 °C), moderate (30 °C), and high (32 °C) temperatures over 14 days. MCE-acclimated fragments showed higher thermal thresholds and survival rates, delayed onset of bleaching, and less decline in photosynthesis efficiency (Fv/Fm) compared to shallow fragments. Both species maintained high thermal tolerance despite prolonged exposure to cooler temperatures of mesophotic depth. These findings suggest that low light intensity in MCEs can act as a modulator of bleaching, supporting the potential of these ecosystems as refugia for shallow corals in a rapidly changing world.

Keywords: Acclimation; Coral; Global warming; Mesophotic coral ecosystem (MCE); Refugia; Thermal threshold.

MeSH terms

  • Acclimatization*
  • Animals
  • Anthozoa* / physiology
  • Climate Change*
  • Coral Reefs
  • Ecosystem
  • Global Warming
  • Hot Temperature
  • Photosynthesis
  • Thermotolerance*