T324 The Co-Evolution of Life and Its Environment during the Precambrian: The “Boring Billion” and Mid-Proterozoic Emergence of Complex Life

Wednesday, 25 October 2017
8:00 AM - 12:00 PM
Skagit 5

LIMITATIONS ON LIMITATION

Paper number: T324-1
Program: Technical Sessions
Time: 8:00 AM – 8:15 AM

Authors

Abstract

In the low-oxygen, low-sulfate environments of the Proterozoic, efficient burial of organic carbon would have slowed the recycling of nutrients to the photic zone, limiting global rates of photosynthesis. A series of steady-state mass balance calculations suggests that the rate of primary production in the ocean was no more than 10% of its modern value during the Proterozoic eon, and possibly less than 1%. The supply of nutrients in such a world is dominated by river inputs, rather than upwelling, leading to a small marine biosphere focused in estuarine environments. The resulting demand for nutrients is so low that nitrogen could not have limited the rate of primary production following the evolution of extant nitrogenases. Molybdenum and iron supplies are more than large enough to support the required rate of biological nitrogen fixation, even if abiotic fixation was slow and denitrification was extremely rapid. Phosphorus demand was approximately equal to the modern riverine flux, making P the most likely candidate for the limiting nutrient during the Proterozoic, and possibly during the Archean.

Geological Society of America Abstracts with Programs. Vol. 49, No. 6

doi: 10.1130/abs/2017AM-306231

© Copyright 2017 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.