Meeting Abstract
Scleractinian reef corals exist in an obligate symbiosis with single-cell dinoflagellates (Symbiodinium spp.). Reef corals live 1 – 2°C from their upper thermal limit, and episodic or seasonal ocean warming facilitates the breakdown of the coral-Symbiodinium partnership (i.e., coral bleaching) that can cause coral mortality. The performance of reef corals during (and following) temperature stress depends on characteristics of the coral holobiont (host + symbiont + microbes). Symbiodinium assemblages and bacterial communities are integral to coral host nutrition, defense, and physiology, and have been shown to influence coral stress responses. Here, we examine how both Symbiodinium and bacterial communities contribute to the thermal tolerance of four coral species in Kāne‘ohe Bay, Hawai‘i (Montipora capitata, Porites compressa, Pocillopora acuta, and Pavona varians) that differ in key functional traits: skeletal morphology, tissue thickness, and Symbiodinium transmission mode and assemblages. Twelve genotypes per species (n=5 genotype-1) were placed into ambient (ca. 28°C) or high (ca. 31°C) temperature treatments for 2 weeks, and then held at 28°C for one month for a period of physiological recovery. DNA was assayed at three time points: prior to heat stress, after high temperature exposure, and after one month of recovery. Treatment effects on microbial community assemblages were identified through amplicon sequencing of 16S and ITS2. Together, our across species comparison of coral physiological performance with microbial communities offers clarity on their role in holobiont thermal tolerance. As global climate change and ocean warming continue to threaten coral reefs, this knowledge can be leveraged to improve conservation and management of coral reefs.
