Environmentally-Driven Variation in the Physiology of a New Caledonian Reef Coral

Anderson B Mayfield,Alexandra C Dempsey

doi:10.3390/oceans3010002

Abstract

Given the widespread threats to coral reefs, scientists have lost the opportunity to understand the basic biology of “pristine” corals whose physiologies have not been markedly perturbed by human activity. For instance, high temperature-induced bleaching has been occurring annually since 2014 in New Caledonia. Because most corals cannot withstand repeated years when bleaching occurs, an analysis was undertaken to showcase coral behavior in a period just before the onset of “annual severe bleaching” (ASB; November 2013) such that future generations might know how these corals functioned in their last bleaching-free year. Pocillopora damicornis colonies were sampled across a variety of environmental gradients, and a subset was sampled during both day and night to understand how their molecular biology changes upon cessation of dinoflagellate photosynthesis. Of the 13 environmental parameters tested, sampling time (i.e., light) most significantly affected coral molecular physiology, and expression levels of a number of both host and Symbiodiniaceae genes demonstrated significant diel variation; endosymbiont mRNA expression was more temporally variable than that of their anthozoan hosts. Furthermore, expression of all stress-targeted genes in both eukaryotic compartments of the holobiont was high, even in isolated, uninhabited, federally protected atolls of the country’s far northwest. Whether this degree of sub-cellular stress reflects cumulative climate change impacts or, instead, a stress-hardened phenotype, will be unveiled through assessing the fates of these corals in the wake of increasingly frequent marine heatwaves.

Highlights

Climate change threatens reefs across the globe [1,2], from locales once thought to be “pristine” (e.g., Chagos [3]) to those abutting high human population density areas such as Taiwan [4], Mexico’s Pacific Coast [5], and South Florida (USA) [6]
Reefs around New Caledonia’s main island, Grand Terre, have featured in prior works [10], the northern reefs and atolls (NRE) have not, and, given their remote and governmentally protected nature, we found that the physiology of the model scleractinian coral Pocillopora damicornis [11] was distinct from conspecifics of relatively more impacted reefs of the south [12]
Despite highly significant PERMANOVA p-values, the PLS models were not characterized by high predictive power, and misclassification rates ranged from ~25 to ~50% (Table 2); this is partially a testament to the high inter-colony variation associated with the dataset

Summary

Introduction

Climate change threatens reefs across the globe [1,2], from locales once thought to be “pristine” (e.g., Chagos [3]) to those abutting high human population density areas such as Taiwan [4], Mexico’s Pacific Coast [5], and South Florida (USA) [6]. This lack of data means that we may not even know or understand what will be lost in the coming decades as ocean temperatures continue to rise [8]. To this end, the Khaled bin Sultan Living Oceans Foundation (LOF) began its “Global Reef. Oceans 2022, 3 research missions (typically divided by country) can be found on the LOF website as field reports (https://www.livingoceansfoundation.org/publications/field-reports/, accessed on 1 December 2021), as well as in the peer-reviewed literature (e.g., [9]). For general information on the cruise (e.g., goals, itinerary, personnel, site meta-data, and maps), readers are referred to the field report: https://www.livingoceansfoundation.org/publication/newcaledonia-field-report/, accessed on 1 December 2021. In an attempt to develop a more rigorous understanding of the environmental drivers of variability [13,14,15] in the molecular physiology of this model coral species [16], we performed an additional analysis on previously published data [12]

Methods

Results

Discussion

Conclusion