Abstract: Corals engineer reef ecosystems by building massive calcium carbonate skeletons that provide habitat to 25% of marine biodiversity and buffer coastlines against waves. Calcification is an energetically demanding process that requires precise pH regulation in different tissue layers, and many cnidarians rely on photosynthetically fixed sugar from their endocellular dinoflagellate algae to grow. However, ocean warming disrupts the coral-dinoflagellate symbiosis in a process known as coral bleaching, which can kill corals and ultimately jeopardize coastal integrity. As our oceans get hotter, it is urgent to identify how corals and other symbiotic cnidarians can persist through heat stress. My research goal is to identify traits of cnidarian-dinoflagellate mutualisms that can stabilize the symbiosis in the face of climate change. I will share results from my PhD demonstrating that heat impairs host acid-base homeostasis in tropical cnidarians while independently disrupting symbiotic sugar exchange. In contrast, I found that pH-dependent processes in a Northern Atlantic coral are more heat-resilient, suggesting that thermal variability in temperate environments primes this species to keep pH stable across temperatures. I will also share future research directions to uncover coral thermotolerance mechanisms in hopes of extending a lifeline to reefs in the Anthropocene.

Bio: Luella Allen-Waller is currently a PhD candidate in Dr. Katie Barott's coral ecophysiology lab at the University of Pennsylvania. Her research combines cellular and organismal approaches to understand how climate change will impact symbiotic relationships and the ecosystems they shape. Previously, she received a bachelor's degree from Swarthmore College, studied virulence modulation in nematode-bacterial mutualism at the University of Tennessee Department of Microbiology, and researched coral diseases at the Madagascar National Center for Oceanographic Research (CNRO) and Mote Marine Lab in Florida. Outside of the lab, she enjoys running, cooking for friends, and poetry.