Past excess CO2 worlds: biota responses to extreme warmth and ocean acidification

Anthropogenic burning of fossil fuels have introduced environmental stress that biota are forced to survive. The influence of CO2 concentration on global warming and seawater chemistry is thus subject of much scientific debate. The complex interplay between pCO2, climate change and instability, oceanic acidification and CaCO3 saturation still has to be fully understood, preventing reliable predictions of ecosystem responses. Understanding of the Earth system at time scales longer than human observations has become imperative, because anthropogenic activities are likely to telescope by order of magnitude the rates of climatic change that usually result from geologic processes. The ocean is the oldest and largest ecosystem on Earth; global warming and ocean acidification are major threatens to biologic diversity and functioning of pelagic and neritic habitats. The Phanerozoic record clearly indicates that our planet has experienced similar conditions many times over geological times and sedimentary successions offer the possibility of analyzing episodes when the atmosphere and the ocean experienced CO2 levels comparable or even higher than those projected by CO2 emission scenarios. The general aim of our effort is to investigate the response of pelagic and carbonate platform ecosystems to paleoenvironmental perturbations associated with rapid CO2 addition to the atmosphere-ocean, and in particular to past episodes of global warming and ocean acidification: the Paleozoic-Mesozoic history of planktonic and shallow-water calcifiers indicates that their biodiversity and evolution is intimately linked to the environment. We selected case-histories of past high- CO2 scenarios with geological evidence of climate change, environmental stress, biota adaptation and accelerated evolutionary rates. Specifically, we are investigating: (1) END PERMIAN- EARLY TRIASSIC (253-251 Ma); (2) TOARCIAN OAE (183-182 Ma); (3) EARLY APTIAN OAE1a (120-119 Ma); (4) LATEST CENOMANIAN OAE 2 (94-93 Ma). For all these intervals there is evidence that extreme environmental changes impacted the oceanic biota but consequences on calcifying organisms to be fully understood. Our familiarity with the stratigraphic (pelagic and neritic) records of OAEs provides the background for undertaking a high-resolution analysis of tempo and mode of the oceanic ecosystem response and dynamics under excess CO2- induced ocean acidification, warming and anoxia. OAEs are analyzed in pelagic and neritic ecosystems, while the P/T is studied in shallow-water environments. We aim at contributing to the major issues of recent global changes, by investigating geological examples of extreme warmth and ocean acidification to provide guidance as to the response of biota to an abrupt massive CO2 release.