Abstract
Eukaryotic algae rose to ecological relevance after the Neoproterozoic Snowball Earth glaciations, but the causes for this consequential evolutionary transition remain enigmatic. Cap carbonates were globally deposited directly after these glaciations, but they are usually organic barren or thermally overprinted. Here we show that uniquely-preserved cap dolostones of the Araras Group contain exceptional abundances of a newly identified biomarker: 25,28-bisnorgammacerane. Its secular occurrence, carbon isotope systematics and co-occurrence with other demethylated terpenoids suggest a mechanistic connection to extensive microbial degradation of ciliate-derived biomass in bacterially dominated ecosystems. Declining 25,28-bisnorgammacerane concentrations, and a parallel rise of steranes over hopanes, indicate the transition from a bacterial to eukaryotic dominated ecosystem after the Marinoan deglaciation. Nutrient levels already increased during the Cryogenian and were a prerequisite, but not the ultimate driver for the algal rise. Intense predatory pressure by bacterivorous protists may have irrevocably cleared self-sustaining cyanobacterial ecosystems, thereby creating the ecological opportunity that allowed for the persistent rise of eukaryotic algae to global importance.
Original language | English |
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Article number | 476 |
Number of pages | 11 |
Journal | Nature Communications |
Volume | 10 |
Issue number | 1 |
DOIs | |
Publication status | Published - 29 Jan 2019 |
Funding
We thank Arne Leider and Franziska Guenther for discussions; Paul Pringle and Xavier Prieto Mollar for laboratory support; Heike Geilmann, Holm Frauendorf, Györgyi Sommer-Udvarnoki, Aleksandra Poshibaeva and Mareike Neumann for analyses and data; the National Park Service (GRCA-00645) and Scottish National Wildlife Trust for sampling permissions; and Royal Dutch Shell for permission to publish. This work was funded by the Max-Planck-Society and the Deutsche Forschungsgemeinschaft (Research Center/Cluster of Excellence 309 - MARUM - Center for Marine Environmental Sciences; WO 1491/4–2 grant to K.W.; FOR 934 grant to C.G.) and by the “Laboratoire d’Excellence” LabexMER (Grant ANR-10-LABX-19). Sampling in Brazil was supported by CAPEX-COFECUB (442/04/06), sampling in Siberia and the Urals was supported by the Russian Ministry of Education and Science (14.Z50.31.0017 and 2017-220-06-304).
Funders | Funder number |
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Administrative Headquarters of the Max Planck Society | |
Deutsche Forschungsgemeinschaft (Research Center/Cluster of Excellence 309 - MARUM -Center for Marine Environmental Sciences) | WO 1491/4-2, FOR 934 |
"Laboratoire d'Excellence" LabexMER | ANR-10-LABX-19 |
CAPEX-COFECUB | 442/04/06 |
Ministry for Education and Science of the Russian Federation | 14.Z50.31.0017, 2017-220-06-304 |
Keywords
- Methyl-group
- Crude oils
- Sediments
- Dolomite
- Evolution
- Precipitation
- Biodegradation
- 25-norhopanes
- Gammacerane
- Biomarkers