Exploring productivity hotspots in the Precambrian biosphere

Earth’s earliest biosphere was likely limited by metabolic energy. Nutrient limitation, which imparts a strong control on productivity today, only began with the origin of oxygenic photosynthesis ca 3 billion years ago (Ga). This contribution builds upon these concepts to explore how the spatial distribution of primary producers evolved across this transition from energy- to nutrient-limited. While on the modern Earth hotspots of primary productivity are centred around deep-marine upwelling zones and estuaries, preliminary calculations suggest that the early chemotrophic biosphere may have been fuelled by hydrothermal injections of H₂ and Fe²⁺, making volcanically active basins at least 2–8 times more productive relative to background. The rise of oxygenic photosynthesis in the Neoarchean likely enabled the expansion of primary producers into freshwater habitats, which provided nutrients by weathering and perhaps boosted biological diversification. In the Proterozoic, when the deep ocean was nutrient-depleted, primary productivity was probably clustered around estuarine settings, where it may have been enhanced by a factor of 3–25. In conclusion, the spatial distribution of primary producers has likely evolved over the past 4 billion years. Accounting for this trend may help identify biogeochemical limits and opportunities in future studies of the early Earth and other habitable words.

This article is part of the discussion meeting issue ‘Chance and purpose in the evolution of biospheres’.