Natural iron fertilization by shallow hydrothermal sources fuels diazotroph blooms in the ocean - Université de Bretagne Occidentale Access content directly
Journal Articles Science Year : 2023

Natural iron fertilization by shallow hydrothermal sources fuels diazotroph blooms in the ocean

Sophie Bonnet
Cécile Guieu
Cédric Boulart
Angela Knapp
Olivier Grosso
Nathalie Leblond
Caroline Lory

Abstract

Iron is an essential nutrient that regulates productivity in ~30% of the ocean. Compared with deep (>2000 meter) hydrothermal activity at mid-ocean ridges that provide iron to the ocean’s interior, shallow (<500 meter) hydrothermal fluids are likely to influence the surface’s ecosystem. However, their effect is unknown. In this work, we show that fluids emitted along the Tonga volcanic arc (South Pacific) have a substantial impact on iron concentrations in the photic layer through vertical diffusion. This enrichment stimulates biological activity, resulting in an extensive patch of chlorophyll (360,000 square kilometers). Diazotroph activity is two to eight times higher and carbon export fluxes are two to three times higher in iron-enriched waters than in adjacent unfertilized waters. Such findings reveal a previously undescribed mechanism of natural iron fertilization in the ocean that fuels regional hotspot sinks for atmospheric CO 2 .

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Geochemistry
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hal-04172298 , version 1 (13-10-2023)

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Sophie Bonnet, Cécile Guieu, Vincent Taillandier, Cédric Boulart, Pascale Bouruet-Aubertot, et al.. Natural iron fertilization by shallow hydrothermal sources fuels diazotroph blooms in the ocean. Science, 2023, 380 (6647), pp.812-817. ⟨10.1126/science.abq4654⟩. ⟨hal-04172298⟩
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