Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 117, Issue 22, Pages 11961-11967Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1916738117
Keywords
Ediacaran; biosphere; sulfate; phopshorus; phosphorite
Categories
Funding
- NASA Astrobiology Institute
- NSF Division of Environmental Biology [1747731]
- Division Of Environmental Biology
- Direct For Biological Sciences [1747731] Funding Source: National Science Foundation
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The Ediacaran Period (635 to 541 Ma) marks the global transition to a more productive biosphere, evidenced by increased availability of food and oxidants, the appearance of macroscopic animals, significant populations of eukaryotic phytoplankton, and the onset of massive phosphorite deposition. We propose this entire suite of changes results from an increase in the size of the deep-water marine phosphorus reservoir, associated with rising sulfate concentrations and increased remineralization of organic P by sulfate-reducing bacteria. Simple mass balance calculations, constrained by modern anoxic basins, suggest that deep-water phosphate concentrations may have increased by an order of magnitude without any increase in the rate of P input from the continents. Strikingly, despite a major shift in phosphorite deposition, a new compilation of the phosphorus content of Neoproterozoic and early Paleozoic shows little secular change in median values, supporting the view that changes in remineralization and not erosional P fluxes were the principal drivers of observed shifts in phosphorite accumulation. The trigger for these changes may have been transient Neoproterozoic weathering events whose biogeochemical consequences were sustained by a set of positive feedbacks, mediated by the oxygen and sulfur cycles, that led to permanent state change in biogeochemical cycling, primary production, and biological diversity by the end of the Ediacaran Period.
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