PT  - JOURNAL ARTICLE
AU  - Netanel Kramer
AU  - Raz Tamir
AU  - Or Ben-Zvi
AU  - Steven L. Jacques
AU  - Yossi Loya
AU  - Daniel Wangpraseurt
TI  - Light-harvesting in mesophotic corals is powered by a spatially efficient photosymbiotic system between coral host and microalgae
AID  - 10.1101/2020.12.04.411496
DP  - 2020 Jan 01
TA  - bioRxiv
PG  - 2020.12.04.411496
4099  - http://biorxiv.org/content/early/2020/12/06/2020.12.04.411496.short
4100  - http://biorxiv.org/content/early/2020/12/06/2020.12.04.411496.full
AB  - The coral-algal photosymbiosis fuels global coral-reef primary productivity, extending from sea level to as deep as 150 m (i.e., mesophotic). Currently, it is largely unknown how such mesophotic reefs thrive despite extremely limited light conditions. Here, we show that corals exhibit a plastic response to mesophotic conditions that involves a spatially optimized regulation of the bio-optical properties by coral host and symbiont. In contrast to shallow corals, mesophotic corals absorbed up to three-fold more light, resulting in excellent photosynthetic response under light conditions of only ~3% of the incident surface irradiance. The enhanced light harvesting capacity of mesophotic corals is regulated by average refractive index fluctuations in the coral skeleton that give rise to optical scattering and facilitate light transport and absorption by densely pigmented host tissue. The results of this study provide fundamental insight into the energy efficiency and light-harvesting mechanisms underlying the productivity of mesophotic coral reef ecosystems, yet also raise concerns regarding their ability to withstand prolonged environmental disturbances.Competing Interest StatementThe authors have declared no competing interest.