Affiliation:
1. Laboratoire d’Océanographie de Villefranche Sorbonne Université CNRS Villefranche‐sur‐Mer France
2. Géosciences Environnement Toulouse CNRS Université de Toulouse IRD Toulouse France
3. Aix Marseille University Université de Toulon CNRS IRD Marseille France
4. University Bordeaux CNRS Bordeaux INP EPOC Pessac France
5. Centre de Formation et de Recherche sur l'Environnement Méditerranéen (CEFREM, UMR CNRS 5110) Bât. U, Université de Perpignan Via Domitia (UPVD) Perpignan France
Abstract
AbstractIron (Fe) is an essential micronutrient for diazotrophs, which are abundant in the Western Tropical South Pacific Ocean (WTSP). Their success depends on the numerous trace metals, particularly Fe, released from shallow hydrothermal vents along the Tonga Arc. This study aimed to explore the spatio‐temporal impact of hydrothermal fluids on particulate trace metal concentrations and biological activity. To identify the composition of sinking particles across a wide area of the WTSP, we deployed sediment traps at various depths, both close and further west of the Tonga Arc. Seafloor sediments were cored at these deployment sites, including at a remote location in the South Pacific Gyre. The sinking particles were composed of a large amount of biological material (up to 88 mg d−1), indicative of the high productivity of the region. A significant portion of this material (∼21 ± 12 wt.%) was lithogenic of hydrothermal origin, as revealed through Al‐Fe‐Mn tracing. The sinking material showed similar patterns between lithogenic and biogenic fractions, indicating that hydrothermal input within the photic layer triggered surface production. A hydrothermal fingerprint was suggested in the sediments due to the high sedimentation rates (>47 cm kyr−1) and the presence of large, heterogeneous, metal‐rich particles. The presence of nearby active deep hydrothermal sources was suspected near the Lau Ridge due to the large particle size (1–976 μm) and the significant excess of Fe and Mn (2–20 wt.%). Overall, this study revealed that hydrothermal sources have a significant influence on the biogeochemical signature of particles in the region.
Funder
Agence Nationale de la Recherche
Publisher
American Geophysical Union (AGU)
Subject
Earth and Planetary Sciences (miscellaneous),Space and Planetary Science,Geochemistry and Petrology,Geophysics,Oceanography