Increasing comparability among coral bleaching experiments

Abstract

Coral bleaching is the single largest global threat to coral reefs worldwide. Integrating the diverse body of work on coral bleaching is critical to understanding and combating this global problem. Yet investigating the drivers, patterns, and processes of coral bleaching poses a major challenge. A recent review of published experiments revealed a wide range of experimental variables used across studies. Such a wide range of approaches enhances discovery, but without full transparency in the experimental and analytical methods used, can also make comparisons among studies challenging. To increase comparability but not stifle innovation, we propose a common framework for coral bleaching experiments that includes consideration of coral provenance, experimental conditions, and husbandry. For example, reporting the number of genets used, collection site conditions, the experimental temperature offset(s) from the maximum monthly mean (MMM) of the collection site, experimental light conditions, flow, and the feeding regime will greatly facilitate comparability across studies. Similarly, quantifying common response variables of endosymbiont (Symbiodiniaceae) and holobiont phenotypes (i.e., color, chlorophyll, endosymbiont cell density, mortality, and skeletal growth) could further facilitate cross-study comparisons. While no single bleaching experiment can provide the data necessary to determine global coral responses of all corals to current and future ocean warming, linking studies through a common framework as outlined here, would help increase comparability among experiments, facilitate synthetic insights into the causes and underlying mechanisms of coral bleaching, and reveal unique bleaching responses among genets, species, and regions. Such a collaborative framework that fosters transparency in methods used would strengthen comparisons among studies that can help inform coral reef management and facilitate conservation strategies to mitigate coral bleaching worldwide.

Remarkably high and consistent tolerance of a Red Sea coral to acute and chronic thermal stress exposures

“…An important consideration of the present study, and how it might relate to previous thermal stress studies on this species, is the heating rate and duration of the experiments (Grottoli et al 2020). There is evidence that short, yet sudden and severe, marine heatwaves can yield distinct physiological responses compared to longer and more progressive bleaching events (Fordyce et al 2019; Leggat et al 2019).…”

Contrasting heat stress response patterns of coral holobionts across the Red Sea suggest distinct mechanisms of thermal tolerance

“…All corals were kept at 30°C overnight until sampling the following morning, completing the 18-hour short-term thermal stress assay . All tanks were continuously supplied with Red Sea seawater and light intensity was set to photosynthetic active radiation of 600 µmol photons m −2 s −1 to match in situ light elds (Grottoli et al 2020).…”

Consensus Guidelines for Advancing Coral Holobiont Genome and Specimen Voucher Deposition

“…The power of a consensus framework was recently outlined for coral bleaching experimentation, which detailed response variables to increase comparability and hasten scientific insight (Grottoli et al, 2021). Given the pervasive lack of long-term funding for data centralization (including logistics, sorting, and collection), the alternative bottom-up, community-driven model is a more realistic goal to attain, and will be particularly valuable if it manages to incentivize data and meta-data deposition.…”

“…The majority of sequenced genomes are currently available from the genus Symbiodinium, with many genera not yet having genome assemblies available (Supplementary Table 4). Rather, Symbiodiniaceae associations are commonly described through means of marker gene elucidation using a range of different methodologies (Sampayo et al, 2009;LaJeunesse et al, 2018;Hume et al, 2019;Grottoli et al, 2021). Common markers that are sometimes used in conjunction include ITS, ITS2, psbA ncr , SSU, LSU, and cp23S, which are utilized along with morphological data and host associations (Sampayo et al, 2009;LaJeunesse et al, 2018;Hume et al, 2019).…”

“…Underlying this problem is that most molecular databases focus largely on sequencing data deposition and do not provide a comprehensive framework for the deposition of associated metadata (Riginos et al, 2020). The association between sequencing data and contextual, environmental (meta)data makes interpretation of these data more meaningful and allows the alignment of molecular patterns with phenotypes (Hume et al, 2020;Grottoli et al, 2021). The recently established Genomic Observatories Metadatabase (GEOME) aims to expedite and improve deposition and retrieval of molecular data and metadata for biodiversity research (Deck et al, 2017;Riginos et al, 2020).…”