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1.1-billion-year-old Porphyrins Establish A Marine Ecosystem Dominated By Bacterial Primary Producers

Title: 1.1-billion-year-old Porphyrins Establish A Marine Ecosystem Dominated By Bacterial Primary Producers.
Name(s): Gueneli, N., author
McKenna, A. M., author
Ohkouchi, N., author
Boreham, C. J., author
Beghin, J., author
Javaux, E. J., author
Brocks, J. J., author
Type of Resource: text
Genre: Journal Article
Journal Article
Date Issued: 2018-07-24
Physical Form: computer
online resource
Extent: 1 online resource
Language(s): English
Abstract/Description: The average cell size of marine phytoplankton is critical for the flow of energy and nutrients from the base of the food web to higher trophic levels. Thus, the evolutionary succession of primary producers through Earth's history is important for our understanding of the radiation of modern protists similar to 800 million years ago and the emergence of eumetazoan animals similar to 200 million years later. Currently, it is difficult to establish connections between primary production and the proliferation of large and complex organisms because the mid-Proterozoic (similar to 1,800-800 million years ago) rock record is nearly devoid of recognizable phytoplankton fossils. We report the discovery of intact porphyrins, the molecular fossils of chlorophylls, from 1,100-million-year-old marine black shales of the Taoudeni Basin (Mauritania), 600 million years older than previous findings. The porphyrin nitrogen isotopes (delta N-15(por) = 5.6-10.2 parts per thousand) are heavier than in younger sedimentary sequences, and the isotopic offset between sedimentary bulk nitrogen and porphyrins (epsilon(por) = -5.1 to -0.5 parts per thousand) points to cyanobacteria as dominant primary producers. Based on fossil carotenoids, anoxygenic green (Chlorobiacea) and purple sulfur bacteria (Chromatiaceae) also contributed to photosynthate. The low epsilon(por) values, in combination with a lack of diagnostic eukaryotic steranes in the time interval of 1,600-1,000 million years ago, demonstrate that algae played an insignificant role in mid-Proterozoic oceans. The paucity of algae and the small cell size of bacterial phytoplankton may have curtailed the flow of energy to higher trophic levels, potentially contributing to a diminished evolutionary pace toward complex eukaryotic ecosystems and large and active organisms.
Identifier: FSU_libsubv1_wos_000439574700004 (IID), 10.1073/pnas.1803866115 (DOI)
Keywords: organic-matter, black-sea, anoxic events, chlorophyll, compound-specific nitrogen isotopes, diazotrophic cyanobacteria, Mesoproterozoic, microbial mats, nitrogen isotopes, oil-shale, primary producers, purple sulfur bacteria, sedimentary-rocks, taoudeni basin, Taoudeni Basin
Publication Note: The publisher’s version of record is available at
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Host Institution: FSU
Is Part Of: Proceedings of the National Academy of Sciences of the United States of America.
Issue: iss. 30, vol. 115

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Gueneli, N., McKenna, A. M., Ohkouchi, N., Boreham, C. J., Beghin, J., Javaux, E. J., & Brocks, J. J. (2018). 1.1-billion-year-old Porphyrins Establish A Marine Ecosystem Dominated By Bacterial Primary Producers. Proceedings Of The National Academy Of Sciences Of The United States Of America. Retrieved from