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Depth-dependent microskeletal features modify light harvesting in Turbinaria reniformis corals

Kramer, Netanel1

Published Jul 11, 2025 on Dryad. https://doi.org/10.5061/dryad.41ns1rnr9

Data files

Jul 11, 2025 version files 3.94 GB

Abstract

Coral skeletal morphology plays a crucial role in modulating light exposure in symbiotic algae, thereby influencing photosynthetic performance and overall energy acquisition. This function is particularly important in environments with limited light availability, such as in mesophotic and deep-water reefs. However, quantifying light capture and distribution within complex coral structures remains challenging. Using optical coherence tomography and high-resolution X-ray scanning, we explored the depth-dependent bio-optical properties of Turbinaria reniformis from shallow and mesophotic environments in the Gulf of Eilat/Aqaba, Red Sea. Our results reveal distinct skeletal layers: a highly scattering superficial layer (~100 μm thick) and a deeper, more light-penetrating layer. Mesophotic corals exhibited a higher scattering coefficient and lower anisotropy of scatter, yielding increased reflectivity, thereby optimizing light use under low-light conditions. Structural features played distinct optical roles: coenosteum grooves facilitated forward scattering and light trapping, while protruding features such as spines and septa increased surface reflectivity and distributed light more broadly. Light simulations further demonstrated an enhanced fluence rate at the skeleton-water interface, with mesophotic corals amplifying the available light up to 2.7-fold. These findings reveal previously unrecognized depth-dependent adaptations that enhance coral light-harvesting efficiency, providing insights into how skeletal morphology supports coral survival across varying light environments.