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

2023

Article référencé dans le Web of Science WOS:001001476900002

Bonnet Sophie, Guieu C., Taillandier V., Boulart C., Bouruet-Aubertot P., Gazeau F., Scalabrin C., Bressac M., Knapp A. N., Cuypers Y., Gonzalez-Santana D., Forrer H. J., Grisoni J. M., Grosso O., Habasque Jérémie, Jardin-Camps M., Leblond N., Le Moigne F. A. C., Lebourges Dhaussy Anne, Lory Caroline, Nunige S., Pulido-Villena E., Rizzo A. L., Sarthou G., Tilliette C.

Science, 2023, 380 (6647), 812-817 ISSN 0036-8075

Iron is an essential nutrient that regulates productivity in similar to 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 CO2.

Limnologie physique / Océanographie physique [032] ; Ecologie, systèmes aquatiques [036]

TONGA

Fonds IRD [F B010088256]

fdi:010088256