Fluorescence on coral reefs

Abstract

Coral reefs are highly biodiverse ecosystems and provide vital resources for the human population. Due to increasing pressure by climate change and local stressors, these ecosystems currently face a global crisis. The development of tools to monitor how coral reefs respond to environmental change is a key aspect of the conservation of their biodiversity and resources. A number of reef organisms produce fluorescent molecules, including photosynthetic pigments and green fluorescent protein (GFP)-like pigments found in Anthozoa. These pigments are responsive to environmental conditions and can be optically monitored in vivo, making them a promising tool to investigate organism- and community-level processes on coral reefs. In this thesis, the fundamental principles and technological developments necessary for the application of fluorescence as a biomarker are explored. First, the mechanisms regulating coral fluorescence are considered for two functionally and biochemically distinct groups of GFP-like proteins. In mesophotic and depth-generalist symbiotic corals, incomplete light-driven maturation of the red GFP-like protein pool is shown to determine the spectrum of fluorescence emission. A role of this mechanism in adaptation to the reduced mesophotic light spectrum is discussed. In corals from shallow water environments, enhancement of internal light fluxes due to reduced absorption by symbiont pigments during bleaching is shown to induce expression of GFPlike proteins. High-level expression of these pigments in bleached tissue is shown to promote recovery of the symbiotic algae complement after a stress event. Second, a novel approach to fluorescence imaging for coral reef surveys is presented. The method enables automatic classification of reef benthic organisms based on the intensity of fluorescent signal in different excitation and emission bands. These findings demonstrate the potential of fluorescence as an in vivo marker for physiological and ecological studies of coral reef organisms, contributing to ongoing efforts to monitor and preserve the health of these ecosystems.

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Identifiers

ORCID for Elena Bollati: orcid.org/0000-0003-3536-4587

ORCID for Joerg Wiedenmann: orcid.org/0000-0003-2128-2943

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