Article (Scientific journals)
1.1 billion years old porphyrins and their isotopic composition establish a marine ecosystem dominated by bacterial primary producers
Gueneli, Nur; McKenna, AC; Ohkouchi et al.
2018In Proceedings of the National Academy of Sciences of the United States of America, p. 1-9
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Abstract :
[en] 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 ∼800 million years ago and the emergence of eumetazoan animals ∼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 (∼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 (δ15Npor = 5.6–10.2‰) are heavier than in younger sedimentary sequences, and the isotopic offset between sedimentary bulk nitrogen and porphyrins (εpor = −5.1 to −0.5‰) 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 εpor 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.
Disciplines :
Physical, chemical, mathematical & earth Sciences: Multidisciplinary, general & others
Author, co-author :
Gueneli, Nur;  Australian national University Canberra
McKenna, AC;  Florida state university
Ohkouchi;  Japan Agency for Marine-earth Science and Technology
Boreham;  Geoscience Australia
Beghin, Jérémie ;  Université de Liège - ULiège > Doct. sc. (géologie - Bologne)
Javaux, Emmanuelle  ;  Université de Liège - ULiège > Département de géologie > Paléobiogéologie - Paléobotanique - Paléopalynologie (PPP)
Brocks, Jochen;  Australian National University Canberra
Language :
English
Title :
1.1 billion years old porphyrins and their isotopic composition establish a marine ecosystem dominated by bacterial primary producers
Publication date :
July 2018
Journal title :
Proceedings of the National Academy of Sciences of the United States of America
ISSN :
0027-8424
eISSN :
1091-6490
Publisher :
National Academy of Sciences, United States - District of Columbia
Pages :
1-9
Peer reviewed :
Peer Reviewed verified by ORBi
European Projects :
FP7 - 308074 - ELITE - Early Life Traces, Evolution, and Implications for Astrobiology
Funders :
Belspo PAI Planet Topers
EU FP7 ERC Stg ELite 308074
ARC - Australian Research Council [AU]
NSF - National Science Foundation [US-VA]
JAMSTEC
CE - Commission Européenne [BE]
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since 24 July 2018

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