Coral cover surveys corroborate predictions on reef adaptive potential to thermal stress

Abstract

As anomalous heat waves are causing the widespread decline of coral reefs worldwide, there is an urgent need to identify coral populations tolerant to thermal stress. Heat stress adaptive potential is the degree of tolerance expected from evolutionary processes and, for a given reef, depends on the arrival of propagules from reefs exposed to recurrent thermal stress. For this reason, assessing spatial patterns of thermal adaptation and reef connectivity is of paramount importance to inform conservation strategies. In this work, we applied a seascape genomics framework to characterize the spatial patterns of thermal adaptation and connectivity for coral reefs of New Caledonia (Southern Pacific). In this approach, remote sensing of seascape conditions was combined with genomic data from three coral species. For every reef of the region, we computed a probability of heat stress adaptation, and two indices forecasting inbound and outbound connectivity. We then compared our indicators to field survey data, and observed that decrease of coral cover after heat stress was lower at reefs predicted with high probability of adaptation and inbound connectivity. Last, we discussed how these indicators can be used to inform local conservation strategies and preserve the adaptive potential of New Caledonian reefs.

Worldwide analysis of reef surveys sorts coral taxa by associations with recent and past heat stress

“…Over the last decade, the combination of field survey records with remote sensed data for sea surface temperature has become one of the major tools used to measure coral decline associated with heat stress. Multiple studies have shown associations between heat stress events and coral cover decline at both local (Head et al, 2019;Babcock et al, 2020;Selmoni et al, 2020a) and global scales (Selig et al, 2012). In other studies, the bleaching intensity metric was found to be positively associated with heat stress on the Australian Great Barrier Reef (Hughes et al, 2018;Hughes et al, 2019), as well as across larger spatial scales (for instance, the Indo-Pacific region; Sully et al, 2019;McClanahan et al, 2020a).…”

Worldwide analysis of reef surveys sorts coral taxa by associations with recent and past heat stress

“…Recent studies on coral evolutionary adaptive potential suggest that reef conservation efforts should be oriented toward reefs exposed to recurrent stress, as these might be the sources for adapted corals in the years to come (Matz et al, 2020; Selmoni et al, 2020a). As coral taxa are likely to have different potentials for adaptation (Darling et al, 2012; Guest et al, 2012; McClanahan et al, 2020), the effectiveness of such conservation strategies will also depend on the community structure of the reefs.…”

“…Over the last decade, the combination of field survey records with remote sensed data for sea surface temperature has become one of the main tools used to measure coral decline driven by heat stress. Multiple studies have shown associations between heat stress events and coral cover decline both at local (Head et al, 2019; Babcock et al, 2020; Selmoni et al, 2020a) and global scales (Selig et al, 2012). In other studies, the metric of bleaching intensity was found to be positively associated with heat stress on the Australian Great Barrier Reef (Hughes et al, 2018, 2019), as well as across larger spatial scales (for instance, the Indo-Pacific region; (Sully et al, 2019; McClanahan et al, 2020).…”

“…In other studies, the metric of bleaching intensity was found to be positively associated with heat stress on the Australian Great Barrier Reef (Hughes et al, 2018(Hughes et al, , 2019, as well as across larger spatial scales (for instance, the Indo-Pacific region; (Sully et al, 2019;McClanahan et al, 2020). Notably, some of these studies investigated how past and recent thermal stress interact to drive coral cover decline/bleaching intensity, suggesting the existence of coral adaptation but without being able to distinguish acclimatization from evolutionary adaptation (Head et al, 2019;Hughes et al, 2019;Sully et al, 2019;Selmoni et al, 2020a). Few of these works focus on the differences in heat stress responses between coral species (Guest et al, 2012;Hughes et al, 2018;McClanahan et al, 2020), and thus very little information was collected to assess differences in heat stress adaptive potential between coral taxa.…”

“…In other studies, the bleaching intensity metric was found to be positively associated with heat stress on the Australian Great Barrier Reef (Hughes et al, 2018, 2019), as well as across larger spatial scales (for instance, the Indo-Pacific region; Sully et al, 2019; McClanahan et al, 2020a). Notably, some of these studies investigated how past and recent thermal stress interact to drive coral cover decline/bleaching intensity, suggesting the existence of changes in thermal tolerance driven by past heat exposure (Thompson and van Woesik, 2009; Guest et al, 2012; Hughes et al, 2018, 2019; Head et al, 2019; Sully et al, 2019; McClanahan et al, 2020a; Selmoni et al, 2020a). Yet, few of these works focused on the differences in heat stress responses between coral taxa (Guest et al, 2012; Hughes et al, 2018; Head et al, 2019), and even fewer investigated these responses across wide spatial scales (e.g.…”