Feb. 19, 2019
Research Highlight

Productivity of Earth's Biosphere before Oxygenic Photosynthesis

The SeaWiFS instrument looks at the world's oceans and land to observe the plant life and phytoplankton. By monitoring the color of reflected light via satellite, scientists can determine how successfully plant life is photosynthesizing.
The SeaWiFS instrument looks at the world's oceans and land to observe the plant life and phytoplankton. By monitoring the color of reflected light via satellite, scientists can determine how successfully plant life is photosynthesizing. A measurement of photosynthesis is essentially a measurement of successful growth. Photosynthesis on Earth today provides most of the energy at the base of food chains that ultimately supports the planet's biosphere.Image credit: NASA GSFC.

Researchers have integrated estimates of primary production by early anaerobic organisms into a model to provide a better understanding of the productivity of Earth’s biosphere prior to the advent of oxygenic photosynthesis. On Earth today, photosynthesis ultimately fuels most life, and the raw materials used by organisms that perform photosynthesis are readily available. Prior to photosynthesis, it is unclear how productive the biosphere could have been.

The team of researchers looked at compounds that would have been required for early metabolisms on the ancient Earth, including iron and hydrogen compounds. Such compounds could have acted as electron donors, and would have been limited on the Earth due to the fact that they would be supplied geologically over long periods of time. This means that before life evolved the ability to use water as an electron donor in photosynthesis, productivity of the biosphere would have been magnitudes of order lower than today. The study has implications for understanding ancient life on Earth, and could also be relevant in understanding potential biospheres on worlds with subsurface oceans, where photosynthesis would not be possible.

Artist's concept of Europa's ice shell.
A study on the productivity of Earth's biosphere before the advent of photosynthesis could have implications for understanding potential biospheres on worlds with subsurface oceans. Photosynthesis would not be a means of primary production for life on a world like Jupiter's moon Europa (pictured in this artist impression).Image credit: NASA/JPL-CalTech.

The study, “Primary Productivity Was Limited by Electron Donors Prior to the Advent of Oxygenic Photosynthesis,” was published in the journal JGR Biogeosciences. The work was supported by NASA Astrobiology through the Exobiology Program.