Experimental Techniques to Assess Coral Physiology in situ Under Global and Local Stressors: Current Approaches and Novel Insights

Walter Dellisanti,Jeffery T. H. Chung,Mark L. Wells,Cher F. Y. Chow,Leo L. Chan,Jiajun Wu

doi:10.3389/fphys.2021.656562

Abstract

Coral reefs are declining worldwide due to global changes in the marine environment. The increasing frequency of massive bleaching events in the tropics is highlighting the need to better understand the stages of coral physiological responses to extreme conditions. Moreover, like many other coastal regions, coral reef ecosystems are facing additional localized anthropogenic stressors such as nutrient loading, increased turbidity, and coastal development. Different strategies have been developed to measure the health status of a damaged reef, ranging from the resolution of individual polyps to the entire coral community, but techniques for measuring coral physiology in situ are not yet widely implemented. For instance, while there are many studies of the coral holobiont response in single or limited-number multiple stressor experiments, they provide only partial insights into metabolic performance under more complex and temporally and spatially variable natural conditions. Here, we discuss the current status of coral reefs and their global and local stressors in the context of experimental techniques that measure core processes in coral metabolism (respiration, photosynthesis, and biocalcification) in situ, and their role in indicating the health status of colonies and communities. We highlight the need to improve the capability of in situ studies in order to better understand the resilience and stress response of corals under multiple global and local scale stressors.

Highlights

Coral reef ecosystems are hotspots of biodiversity and productivity in the ocean (Roberts et al, 2002) that exceed that of tropical rainforests (Ray, 1988)
The primary objective of this review is to summarize the current strategies for quantifying aspects of coral metabolism to highlight the benefits of non-destructive methodologies
The current knowledge of combined effects of local and global stressors comes from a wide breadth of manipulation studies on coral responses under predicted future scenarios but limited in representing complex abiotic factors in ecosystems

Summary

Introduction

Coral reef ecosystems are hotspots of biodiversity and productivity in the ocean (Roberts et al, 2002) that exceed that of tropical rainforests (Ray, 1988). They provide crucial ecosystem functions and services such as providing goods for subsistence and economic fisheries, coastline protection from storms, and centers of the growing field of ecotourism (Cesar et al, 2003; Knowlton et al, 2010; Van Zanten et al, 2014). Local stressors go hand in hand with global stressors, such as coastline erosion or development, which threaten the resilience of corals through pollution and sedimentation (D’Angelo and Wiedenmann, 2014; Silbiger et al, 2018; Loiola et al, 2019; Jones et al, 2020)

Objectives

Methods

Results

Conclusion