biological feedbacks as cause and demise of neoproterozoic icehouse astrobiological prospects for faster evolution and importance of cold conditions生物反馈的原因和死亡新元古代制冰厂天体生物学的前景更快的进化和寒冷的条件的重要性.pdfVIP

Biological Feedbacks as Cause and Demise of Neoproterozoic Icehouse: Astrobiological Prospects for Faster Evolution and Importance of Cold Conditions 1,2 3 4,5 6,7 6,8 Pekka Janhunen *, Hermanni Kaartokallio , Ilona Oksanen , Kirsi Lehto , Harry Lehto 1 Department of Physical Sciences, University of Helsinki, Helsinki, Finland, 2 Finnish Meteorological Institute, Space Research, Helsinki, Finland, 3 Finnish Institute of Marine Research, Helsinki, Finland, 4 Department of Applied Chemistry and Microbiology, University of Helsinki, Helsinki, Finland, 5 Department of Botany, University of Stockholm, Stockholm, Sweden, 6 Nordic Institute for Theoretical Physics (NORDITA), Copenhagen, Denmark, 7 Department of Biology, University of Turku, Turku, Finland, 8 Tuorla Observatory, University of Turku, Turku, Finland Several severe glaciations occurred during the Neoproterozoic eon, and especially near its end in the Cryogenian period (630– 850 Ma). While the glacial periods themselves were probably related to the continental positions being appropriate for glaciation, the general coldness of the Neoproterozoic and Cryogenian as a whole lacks specific explanation. The Cryogenian was immediately followed by the Ediacaran biota and Cambrian Metazoan, thus understanding the climate-biosphere interactions around the Cryogenian period is central to understanding the development of complex multicellular life in general. Here we present a feedback mechanism between growth of eukaryotic algal phytoplankton and climate which explains how the Earth system gradually entered the Cryogenian icehouse from the warm Mesoproterozoic greenhouse. The more abrupt termination of the Cryogenian is explained by the increase in gaseous carbon release caused by