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CEE 269C EnvEng Seminar: Nathan Mollica "Using proxies to assess anthropogenic effects on under-monitored equatorial Pacific reefs"

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Abstract: Coral reefs are struggling as anthropogenic warming fuels an increase in the frequency and intensity of Marine Heat Waves, causing widespread bleaching and coral death. Yet some reefs, including those in the bullseye of El Niño’s impact, endure. Uncovering their secret could shed critical new light on the mechanisms by which coral reefs could withstand 21st century climate change. However, a paucity of ocean temperature and coral bleaching observations in the remote equatorial Pacific renders conclusions elusive. Massive, centenarian corals have lived through the effects of anthropogenic warming, archiving ocean conditions in their skeletons as they grow. In this seminar I will use novel geochemical and structural proxy techniques to access past ocean conditions, and the reef response. I will showcase a new thermometer sampled with laser ablation ICPMS to extract monthly resolved ocean temperatures from coral skeleton. I will then use reconstructed bleaching histories of the reefs based on CT images revealing skeletal stress bands formed during bleaching. Using these tools, I uncover a long history of bleaching in the CEP, and reef-specific differences in thermal tolerance linked to past heatwave exposure. Over time, reef communities have adapted to tolerate their unique thermal regimes – but are they prepared for the future?

Bio: Nathan Mollica is a researcher on Woods Hole Oceanographic Institution’s Digital Reefs initiative. His research interests include coral geochemistry and calcification, anthropogenic impacts on corals, and the development of tools and techniques to assist conservation and restoration of coral reef ecosystems. He completed his PhD in Oceanography from the MIT WHOI joint program in 2020.