A novel paleo-bleaching proxy using boron isotopes and high-resolution laser ablation to reconstruct coral bleaching events

摘要

Coral reefs occupy only ~ 0.1 percent of the ocean's habitat, but arethe most biologically diverse marine ecosystem. In recent decades, coralreefs have experienced a significant global decline due to a variety ofcauses, one of the major causes being widespread coral bleaching events. Duringbleaching, the coral expels its symbiotic algae, thereby losing its main source ofnutrition generally obtained through photosynthesis. While recent coralbleaching events have been extensively investigated, there is no scientificdata on historical coral bleaching prior to 1979. In this study, we employhigh-resolution femtosecond Laser Ablation Multiple Collector InductivelyCoupled Plasma Mass Spectrometry (LA-MC-ICP-MS) to demonstrate a distinctbiologically induced decline of boron (B) isotopic composition (δ11B) as a result of coral bleaching. These findings and methodology offera new use for a previously developed isotopic proxy to reconstructpaleo-coral bleaching events. Based on a literature review of publishedδ11B data and our recorded vital effect of coral bleaching onthe δ11B signal, we also describe at least two possible coralbleaching events since the Last Glacial Maximum. The implementation of thisbleaching proxy holds the potential of identifying occurrences of coralbleaching throughout the geological record. A deeper temporal view of coralbleaching will enable scientists to determine if it occurred in the pastduring times of environmental change and what outcome it may have had oncoral population structure. Understanding the frequency of bleaching eventsis also critical for determining the relationship between natural andanthropogenic causes of these events.