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PALEOBIOLOGY DATABASE

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Physiological Crises - Ancient Analogues for the 21st Century Marine ecosystems are increasingly stressed by rapid warming and ocean acidification caused by greenhouse gas emissions and by spreading hypoxic "dead zones" in coastal waters.  These stressors act synergistically to negatively impact the respiratory physiology and metabolism of marine invertebrates.  A number of major and minor biotic crises, such as the Guadalupian, Permian, Triassic, and Toarcian extinctions, were selective for respiratory physiology and resulted from stresses such as warming, ocean acidification, and/or hypoxia, providing ancient analogues for 21st century stresses.  Thus, understanding the nature of selectivity during ancient physiological extinctions, on traits such as shell mineralogy, life position, body size, or geographic range, will refine our knowledge of taxonomic susceptibility to ongoing anthropogenic stresses. I focus on late Paleozoic through mid-Mesozoic physiological crises to elucidate the role of various individual- and population-level traits in promoting survivorship during ocean acidification and hypoxic events.  This timespan includes events such as the late Paleozoic ice age, typical of background rates of environmental change and featuring minimal physiological stresses, minor extinctions with increased stress and more intense acidification or hypoxia, and catastrophic mass extinctions with extreme environmental stress.  I approach these questions using large databases like the Paleobiology Database, to document taxonomic and ecological correlates of extinction selectivity, and with field data, to understand the ecological consequences of physiological extinctions. Paleozoic-Modern Fauna Transition The shift from the brachiopod, bryozoan, and crinoid-dominated Paleozoic Fauna to the mollusc-dominated Modern Fauna was one of the fundamental biotic transitions of the Phanerozoic.  Although the end-Permian extinction was the primary driver of this taxonomic shift, the transition was more complex when assessed by ecological measures such as relative abundance.  My research has documented incremental ecological shifts towards greater Modern Fauna importance associated with the Guadalupian extinction, also a physiological crisis, and in the mid-Jurassic.  The coincidence of episodes of increased Modern Fauna dominance and physiological crises suggests that the composition of modern marine ecosystems has been shaped by repeated ocean acidification crises in the ancient past.  My ongoing research projects seek to link the broader context of the Paleozoic-Modern Fauna transition with ancient physiological crises, in order to understand how major secular changes in taxonomic composition have influenced susceptibility of marine ecosystems to the types of stresses faced in the 21st century.