Mass coral bleaching and mortality events jeopardize the persistence of coral reefs worldwide. Galápagos corals experience a wide range of temperatures and inhabit marginal conditions compared to other tropical reefs. The stress tolerance of corals remaining after recent warm- and cold-water bleaching events in the archipelago may be the product of adaptation and acclimatization. In the spring of 2019, we investigated thermal tolerance differences in Pocillopora sp., a widespread reef-building coral in the Indo-Pacific found throughout the Galápagos. We unexpectedly found that corals from northern sites–which experience warmer and less variable annual average temperatures–were more resilient than those from central and southern sites, having both greater heat and cold tolerances. In this study, we sequenced the mitochondrial open reading frame (ORF) to determine Pocillopora haplotype, amplified actin using quantitative PCR to determine symbiont type, and used RNAseq to explore gene expression patterns in our samples. We aim to understand how these variables correlate with heat and cold tolerance. Preliminary results suggest that the thermally-tolerant symbiont Durisdinium is absent from most central and southern sites and a thermally tolerant Pocillopora ORF haplotype (type 1) exists in far northern and most central southeastern communities, possibly explaining differences in thermal tolerance across regions. Our results can provide insight into the adaptive potential of reefs worldwide as they endure warm and cold stress events.

Primary Presenter: Katrina Giambertone, CSU Monterey Bay and Moss Landing Marine Laboratories (kgiambertone@csumb.edu)

Authors:

Katrina Giambertone, California State University, Monterey Bay  (kgiambertone@csumb.edu)

Margarita Brandt, Universidad San Francisco de Quito  (mbrandt@usfq.edu.ec)

Cheryl Logan, California State University, Monterey Bay  (clogan@csumb.edu)