Netanel Kramer (1), Raz Tamir (1) (2), Or Ben-Zvi (1) (2), Steven L. Jaques (3), Yossi Loya (4), Daniel Wangpraseurt (4) (5)
Functional Ecology. Volume 36, Issue 9, Pages 406-418 (February 2022). DOI: https://doi.org/10.1111/1365-2435.13948

Keywords

Bio-optics, ecophysiology, light-harvesting, mesophotic coral ecosystems (MCEs), photobiology, red sea

Abstract

Sustained light-dependent coral reef communities can be found at a wide range of light environments, extending from the sea level to as deep as 150 m (i.e. esophotic). How mesophotic corals thrive despite extremely limited light conditions still requires further investigation. Here, we undertook a comprehensive ecophysiological and bio-optical study on four depth-generalist coral species aiming to delineate the functional role that optical trait properties have in light-harvesting, at contrasting light regimes. We show that the optical traits of coral skeletons are adjusted to their ambient light conditions and complement the microalgal demands for sufficient light, thus exhibiting a spatially efficient photosymbiotic system. 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 was achieved by redistributing light in the coral skeleton through optical scattering, thereby facilitating light transport and absorption by densely pigmented host tissue. Our findings provide fundamental insight into the light-harvesting mechanisms underlying the productivity of mesophotic coral reef ecosystems, yet also raise concerns regarding their ability to withstand prolonged environmental disturbances.

How Our Software Was Used

Quantitative analysis was performed using Dragonfly.

Author Affiliation

(1) School of Zoology, Tel-Aviv University, Tel Aviv, Israel
(2) The Interuniversity Institute for Marine Sciences of Eilat, Eilat, Israel
(3) Department of Bioengineering, University of Washington, Seattle, WA, USA
(4) Department of Nanoengineering, University of California San Diego, San Diego, CA, USA
(5) Department of Chemistry, University of Cambridge, Cambridge, UK