Environmental controls on Jurassic marine ecosystems during global warming

The fossil record has the potential to provide valuable insights into species response to past climate change if paleontological data are combined with appropriate proxies of environmental change. Here we use a novel, multivariate approach that combines a suite of geochemical proxies with high-resolution quantitative macroinvertebrate fossil data to study responses to early Toarcian warming (ca. 183 Ma). We show that benthic and nektonic ecosystems became decoupled during warming and were driven by different environmental variables. Benthic turnover was mostly driven by variations in seawater dissolved oxygen concentration, whereas turnover among the nektonic cephalopods was primarily controlled by variations in weathering, nutrient runoff, and primary productivity. Although rapid warming has been invoked as the main trigger of this event, the paleotemperature proxy was a poor predictor of marine community dynamics, and abiotic factors indirectly linked to temperature were more important. Given that similar environmental changes characterize other episodes of global warming and are impacting present-day marine communities, we predict that similar ecological responses occurred during other past events and are a probable outcome of current changes.