Collaborative Research: NSF-BSF: Photophysiology and bio-optics of Red Sea mesophotic corals

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Tropical coral reefs are hotspots of biodiversity and provide critical services to numerous coastal communities worldwide. A combination of global and local stressors have led to the unprecedented degradation of shallow water coral reef communities. Most importantly, elevated water temperatures combined with excess solar radiation can cause coral bleaching, which describes the loss of the coral’s symbiotic algae and is regarded as the major threat to the future existence of shallow-water reefs. Thus, corals from deep waters are gaining interest as they are expected to be buffered from extreme environmental impacts more commonly experienced in shallow waters. Surprisingly, corals are flourishing in habitats where sunlight barely reaches, and 30-150 m depth mesophotic coral reef ecosystems (MCEs) are characterized by unique coral communities that could serve as a refuge for shallow water corals. In this project, we aim to study the light-harvesting mechanisms that allow corals to thrive under such light-limited conditions using a multidisciplinary approach that combines state-of-the-art bioengineering, bio-optics, and coral physiology tools. Since corals are among the most efficient aquatic photosynthetic systems, studying coral bio-optics can also lead to the discovery of novel light-harvesting mechanisms and the development of novel coral-inspired photonic materials to build more efficient and sustainable photobioreactors. This is a US-Israel binational project that aims to promote international collaboration and diversity through a range of public outreach activities, including museum exhibitions and the design of creative experiences to support the participation of under-represented groups in STEM.Light is a key driver of coral community change along the coral reef depth gradient. However, the importance of irradiance for the existence and growth of corals has been predominantly studied in shallow species, and knowledge of how mesophotic corals thrive despite extremely limited light conditions is largely lacking. This study will provide a quantitative assessment of light-harvesting at mesophotic depths and offer novel insights into the role of bio-optics and irradiance in structuring coral communities. To achieve our goal, we will employ an interdisciplinary approach to establish the bio-optical properties of mesophotic corals. Our workflow combines (1) in-situ coral reef fieldwork in Eilat (Red Sea, Israel) to collect and analyze corals along a depth-irradiance gradient, (2) lab-based light microsensor measurements combined with analyses of endogenous green fluorescent protein and photosynthetic assays; (3) optical coherence tomography and microcomputed tomography to characterize tissue and skeletal morphology for the development of 3D light-capture models using Monte Carlo simulations; and (3) a novel 3D bioprinting approach to experimentally determine the roles of coral skeleton morphology on photosynthesis. Altogether, this research will provide the essential basis for theoretical models that seek to understand the spatial distribution of mesophotic coral reef ecosystems and predict their responses to environmental change, therefore offering a practical tool for reef management and conservation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.