Biomass recycling and Earth's early phosphorus cycle

Area of Science:

• Geochemistry
• Marine Biology
• Paleoclimatology

Background:

• Marine biological productivity is largely controlled by phosphorus availability.
• Precambrian phosphorus levels are estimated to be low, with iron scavenging previously suggested as the cause.
• Understanding early ocean nutrient cycling is crucial for interpreting Earth's history.

Purpose of the Study:

• To propose an alternative hypothesis for low Precambrian phosphorus levels.
• To investigate the role of biomass remineralization in regulating marine phosphorus.
• To explain the impact of limited phosphorus on early marine productivity and atmospheric oxygen.

Main Methods:

• Investigated phosphorus cycling through biomass remineralization.
• Analyzed the stoichiometric constraints on nutrient liberation in early oceans.
• Contrasted aerobic recycling in modern oceans with limited oxidation in the Archean.

Main Results:

• Muted liberation of phosphorus during biomass remineralization, not iron scavenging, likely constrained early marine phosphorus reservoirs.
• Limited oxidizing power in early oceans restricted the capacity for aerobic remineralization of biomass-bound phosphorus.
• Low phosphorus concentrations significantly hampered marine primary productivity.

Conclusions:

• The inefficiency of phosphorus recycling via remineralization was a key factor limiting marine productivity in the Precambrian.
• This phosphorus limitation likely contributed to the delayed rise of atmospheric oxygen.
• Revises our understanding of nutrient controls on early Earth's biogeochemical cycles.