BIOENERGETICS OF EARLY TRIASSIC PELAGIC ECOSYSTEMS: FAST METABOLISMS, FAST CARBON CYCLING (Invited Presentation)

The Early Triassic was a dramatic time for ammonoids: their collective diversity, morphology, abundance, and biogeography changed rapidly in concert with global and regional environmental shifts. Based on currently available data, a range of trophic structures and metabolic rates could be asserted to fit each species assemblage. These scales of paleobiologic change and uncertainty make it difficult to characterize how ammonoids contributed to overall marine ecological functioning after the mass extinction. I approach the problem by building and comparing simplified population-scale bioenergetics models of Early Triassic ammonoid trophic structure and metabolic demand. I simulate population dynamics in R, and add increasingly levels of complexity from a base-model of modern-day market squid. I highlight a few different models, and explain how they are shaped by outstanding questions regarding ammonoid biomechanics and paleophysiology. Cannibalism and shell growth are critical factors. Overall, I interpret that Early Triassic ammonoid species had high metabolic rates, that their communities had top-heavy trophic structures, and that these features drove rapid carbon cycling in the global oceans. This may have influenced a feedback loop that exacerbated taxonomic and ecological change-over throughout the Early Triassic. These interpretations can be refined with emerging biomechanics data, and can be further tested against geochemical proxies and abundance-specific collections in the future.