[B-BG01] Earth and Planetary Science Frontiers for Life and Global Environment

[BBG01-04] Toward decoding photoautotroph assemblage in the pelagic super ocean anoxia.

★Invited Papers

*Satoshi Takahashi¹, Kenta Asahina², Yui Kouketsu¹ (1.Department of Earth and Environmental Sciences Graduate School of Environmental Studies Nagoya University, 2.Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology)

Keywords:mass extinction, ocean anoxia, photoautotroph, chlorophyll, Permian-Triassic

We will introduce our study progress on the photoautotroph changes in the anoxic ocean which occurred in the geologic past. The Permian-Triassic mass extinction event (ca. 252 Ma) is associated with a widespread severe oxygen-depleted oceanic environment and the collapse of marine biota. It is worth revealing the nature of primary producers at that time for detecting photic zone anoxia records from sediments and adopted ecosystems after the environmental changes. However, organic compounds in sedimentary rocks such as Paleozoic-Mesozoic, which are preserved in the accretionary complex, are highly matured and not adequate for conventional bitumen analysis. Because of these situations, it has been hard to detect organic molecules such as from green-sulfur bacteria and cyanobacteria. The newly proposed Maleimid Index (Asahina et al., 2022) is a method which detects fossilised chlorophyll from matured kerogen organic matter through a chromium acid oxidation procedure. The application of this method based on the black shale materials from the mass extinction boundary will provide us with photoautotroph information across the severe oceanic environmental changes in the order of chlolophill a and bacteriochlolophills c and d.