Triple oxygen isotope evidence for limited mid-Proterozoic primary productivity

Abstract

The global biosphere is commonly assumed to have been less productive before the rise of complex eukaryotic ecosystems than it is today. However, direct evidence for this assertion is lacking. Here we present triple oxygen isotope measurements (∆O) from sedimentary sulfates from the Sibley basin (Ontario, Canada) dated to about 1.4 billion years ago, which provide evidence for a less productive biosphere in the middle of the Proterozoic eon. We report what are, to our knowledge, the most-negative ∆O values (down to -0.88‰) observed in sulfates, except for those from the terminal Cryogenian period. This observation demonstrates that the mid-Proterozoic atmosphere was distinct from what persisted over approximately the past 0.5 billion years, directly reflecting a unique interplay among the atmospheric partial pressures of CO and O and the photosynthetic O flux at this time. Oxygenic gross primary productivity is stoichiometrically related to the photosynthetic O flux to the atmosphere. Under current estimates of mid-Proterozoic atmospheric partial pressure of CO (2-30 times that of pre-anthropogenic levels), our modelling indicates that gross primary productivity was between about 6% and 41% of pre-anthropogenic levels if atmospheric O was between 0.1-1% or 1-10% of pre-anthropogenic levels, respectively. When compared to estimates of Archaean and Phanerozoic primary production, these model solutions show that an increasingly more productive biosphere accompanied the broad secular pattern of increasing atmospheric O over geologic time.

Geochemical and metagenomic characterization of Jinata Onsen, a Proterozoic-analog hot spring, reveals novel microbial diversity including iron-tolerant phototrophs and thermophilic lithotrophs

“…In particular, the concomitant increase in visible biomass at Jinata as the community shifts from lithotrophy toward water-oxidizing phototrophy (i.e. oxygenic photosynthesis) is consistent with estimates for greatly increased primary production following the evolution and expansion of Cyanobacteria around the GOE (20, 101, 106, 128, 135, 137).…”

“…At this time, productivity was low and fueled by metabolisms such as methanogenesis and anoxygenic photosynthesis (14, 66, 135). Following the expansion of oxygenic photosynthesis by Cyanobacteria and higher primary productivity around the Great Oxygenation Event ∼2.3 Ga (20, 31, 128, 137), the atmosphere and surface ocean accumulated some oxygen, and the ocean transitioned into a state with oxygenated surface waters but often anoxic deeper waters, rich in either dissolved iron or sulfide (13, 55, 56, 92). At Jinata Onsen, this range of geochemical conditions is recapitulated over just a few meters, providing a useful test case for probing the shifts of microbial productivity over the course of Earth history.…”

Free and kerogen‐bound biomarkers from late Tonian sedimentary rocks record abundant eukaryotes in mid‐Neoproterozoic marine communities

“…Lipid biomarker assemblages recovered from thermally well‐preserved sedimentary rocks can help unravel the temporal dynamics associated with the protracted emergence, diversification, and ecological expansion of Eukarya across the Proterozoic Eon (2,500–541 Ma) and may be used to assess the quantitative impact of early eukaryotes within ancient marine communities (Brocks et al, , , ; Dutkiewicz, Volk, Ridley, & George, ; Gallagher et al, ; Isson et al, ; Love et al, ; Luo, George, Xu, & Zhong, ; Nguyen et al, ). The mid‐Proterozoic (1,800–1,000 Ma) was characterized by a remarkably long period of biogeochemical, tectonic, and climatic stability, with marine community structures buffered by feedback operating within coupled nutrient–carbon cycles imposed on primary production in the surface ocean (Cole et al, ; Crockford et al, ; Hardisty et al, ; Holland, ; Lyons, Reinhard, & Planavsky, ; Ozaki, Reinhard, & Tajika, ; Planavsky et al, , ; Poulton & Canfield, ). A transition to a world with elevated surface oxygenation and nutrients, capable of supporting a more complex and productive marine biosphere, likely occurred during the Neoproterozoic Era (1,000–541 Ma).…”

The impact of marine nutrient abundance on early eukaryotic ecosystems

“…In addition, there is complementary evidence from the rock record and biogeochemical models that the inventory of dissolved phosphorus (P) in Earth's oceans has increased throughout Earth's history (Figure 1), broadly in step with the protracted oxygenation of the ocean-atmosphere system (Laakso & Schrag, 2014Lenton & Watson, 2004;Ozaki, Reinhard, & Tajika, 2019;Papineau, 2010;Planavsky et al, 2010;Reinhard et al, 2017). Existing empirical records suggest that global rates of primary productivity (and by inference marine nutrient levels) during some periods of the mid-Proterozoic (~1.8-0.8 billion years ago, Ga) were likely less than ~ 10% of the modern Earth (Crockford et al, 2018), which is also consistent with global biogeochemical models of the coupled carbon and oxygen cycles for this time interval (Derry, 2015;Laakso & Schrag, 2018;Ozaki et al, 2019).…”