ORCID Profile
0000-0002-3723-6098
Current Organisation
University of Colorado at Boulder
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Publisher: Springer Science and Business Media LLC
Date: 29-01-2019
DOI: 10.1038/S41467-019-08306-X
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.
Publisher: Springer Science and Business Media LLC
Date: 23-11-2021
DOI: 10.1038/S41559-020-01336-5
Abstract: The absence of unambiguous animal body fossils in rocks older than the late Ediacaran has rendered fossil lipids the most promising tracers of early organismic complexity. Yet much debate surrounds the various potential biological sources of putative metazoan steroids found in Precambrian rocks. Here we show that 26-methylated steranes-hydrocarbon structures currently attributed to the earliest animals-can form via geological alteration of common algal sterols, which carries important implications for palaeo-ecological interpretations and inhibits the use of such unconventional 'sponge' steranes for reconstructing early animal evolution.
Publisher: Springer Science and Business Media LLC
Date: 07-06-2023
Publisher: Elsevier BV
Date: 02-2021
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 11-2018
Publisher: American Association for the Advancement of Science (AAAS)
Date: 09-2017
Abstract: Biosynthesis of C 29 sterols, enhancing eukaryotic temperature resistance, evolved during the global Neoproterozoic glaciations.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 25-08-2023
Abstract: The body fossil and biomarker records hint at an increase in biotic complexity between the two Cryogenian Snowball Earth episodes (ca. 661 million to ≤650 million years ago). Oxygen and nutrient availability can promote biotic complexity, but nutrient (particularly phosphorus) and redox dynamics across this interval remain poorly understood. Here, we present high-resolution paleoredox and phosphorus phase association data from multiple globally distributed drill core records through the non-glacial interval. These data are first correlated regionally by litho- and chemostratigraphy, and then calibrated within a series of global chronostratigraphic frameworks. The combined data show that regional differences in postglacial redox stabilization were partly controlled by the intensity of phosphorus recycling from marine sediments. The apparent increase in biotic complexity followed a global transition to more stable and less reducing conditions in shallow to mid-depth marine environments and occurred within a tolerable climatic window during progressive cooling after post-Snowball super-greenhouse conditions.
Publisher: Research Square Platform LLC
Date: 07-11-2022
DOI: 10.21203/RS.3.RS-2202848/V1
Abstract: Fossilized lipids offer one of only few windows into ancient ecosystems. The utility of such biomarkers is determined by the phylogenetic distribution of lipid biosynthetic capabilities in extant organisms and extrapolation of this information into the past. 2-Methylhopanes in sedimentary rocks were once used to infer the importance of Cyanobacteria as primary producers in the geological past. However, the discovery of the hopanoid C-2 methyltransferase (HpnP) in Alphaproteobacteria led to the downfall of this molecular proxy. In the present study, we re-examined the distribution of HpnP in a new phylogenetic framework including novel candidate phyla, and re-interpreted a revised geological record of 2-methylhopanes based on contamination-free s les. We show that HpnP was likely present in the last common ancestor of Cyanobacteria, while the gene appeared in Alphaproteobacteria only around 750 million years ago. A subsequent rise of sedimentary 2-methylhopanes around 600 Ma likely reflects the expansion of Alphaproteobacteria that coincided with the rise of eukaryotic algae — possibly connected by algal dependency on microbially-produced vitamin B12. Our findings re-establish 2-methylhopanes as cyanobacterial biomarkers prior to 750 Ma and thus as a potential tool to measure the importance of oxygenic Cyanobacteria as primary producers on the early Earth. Our study illustrates how genetics can improve the diagnostic value of biomarkers and refine the reconstruction of early ecosystems.
No related grants have been discovered for Lennart M. van Maldegem.