Meeting Abstract
Rising sea surface temperatures pose the greatest threat to corals and lead to coral bleaching. Predictions about the likelihood of coral bleaching typically consider the duration and magnitude of elevated temperatures relative to a locally defined threshold. However, recent work suggests that heterogeneity in observed bleaching patterns may be better explained by the degree of diel thermal variation (DTV) experienced on a reef. Here, we sourced colonies of the reef-building coral Siderastrea siderea from six sites across the Bocas del Toro archipelago, which ranged in mean DTV (~2-4 °C). We conducted a 50-day common garden experiment to assess the influence of low, moderate, and high DTV (2, 3, and 4 °C, respectively) on growth and performance of S. siderea and then performed a two-week thermal challenge followed by a two-week recovery. Results suggest that corals sourced from higher DTV sites outperformed corals from less variable sites, regardless of treatment. In addition, experimental DTV had a positive influence on corals, with high DTV leading to increased growth and corals experiencing moderate DTV maintained higher symbiont densities after recovery. Analyses of baseline and post-recovery physiological traits as well as baseline algal and microbiome community compositions are ongoing. These analyses will shed light on how corals from higher DTV environments are able to maintain higher growth rates and how DTV modulates coral stress and ultimate recovery. Overall, our data support the hypothesis that DTV on the coral’s native reef and in husbandry conditions plays a central role in growth and symbiosis of reef-building corals, highlighting the need to consider DTV when evaluating the resilience of corals to global change.
