Geological Society of America

T110 Evolving Perspectives on the Tonian Biosphere and Environmental Change

Wednesday, 28 October 2020
10:00 AM - 12:00 PM
Meeting Rooms

EVIDENCE OF PHOTOSYNTHESIS SHOWED BY NI-PORPHYRIN PRESERVATION IN ~1 GYR-OLD EUKARYOTES

Paper number: T110-4
Program: Technical Sessions
Time: 10:45 AM – 11:00 AM

Authors

Marie Catherine Sforna Presenting Author
University of Liege, Liège
Corentin Loron
University of Liege, Liège
Catherine F. Demoulin
University of Liege, Liège
Camille François
Commission for the Geological Map of the World, Paris
Yohan Cornet
University of Liege, Liège
Yannick J. Lara
University of Liege, Liège
Daniel Baudet
Royal Museum for Central Africa, Tervuren
Emmanuelle J. Javaux
University of Liège, Liège, N/A

Abstract

Photosynthetic eukaryotes are key constituents of modern ecosystems. Their appearance is an important step in the evolution of Life, leading to the complexification of trophic networks and making possible the later colonization of land. The early fossil record of eukaryotic algae is not well constrained as their identification is mostly based on their morphological comparison to modern algae, despite possible convergence between clades. Important work has been done to decipher the Precambrian fossil rock record and to characterize new taxonomic tracers within the eukaryotic domain. However, none of these approaches permit to detect the presence of chlorophyll, an essential criteria for evidencing phototrophy.

Here we show, by combining synchrotron-based X-ray fluorescence and X-ray absorption techniques, the earliest in-situ evidence of preserved Ni-porphyrins (degraded chlorophyll) within an organic-walled microfossil, Arctacellularia tetragonala, from the ca. 1 Ga Mbuji-Mayi Supergroup (Congo Basin, Democratic Republic of Congo). This geochemical approach combined to morphological, ultrastructural and spectroscopic analyses support the interpretation of this multicellular branching microfossil as a eukaryotic photosynthetic algae, part of the Archaeaplastidae supergroup.

This discovery, supports the evolution of eukaryotic photosynthesis and the supergoup Archaeaplastidae by at least 1 Ga, consistent with the red algae fossil record. For the first time we were able to identify Proterozoic eukaryotes not only in terms of morphology, but based on their metabolic machinery.

Geological Society of America Abstracts with Programs. Vol. 52, No. 6

doi: 10.1130/abs/2020AM-357052

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