Foraminiferal Mn/Ca as Bottom‐Water Hypoxia Proxy: An Assessment of Nonionella stella in the Santa Barbara Basin, USA - Université d'Angers Accéder directement au contenu
Article Dans Une Revue Paleoceanography and Paleoclimatology Année : 2021

Foraminiferal Mn/Ca as Bottom‐Water Hypoxia Proxy: An Assessment of Nonionella stella in the Santa Barbara Basin, USA

I. Brinkmann
S. Ni
V E Oldham
N B Quintana Krupinski
K. Medjoubi
  • Fonction : Auteur
A. Somogyi
C M Hansel
J M Bernhard
H L Filipsson

Résumé

Hypoxia is of increasing concern in marine areas, calling for a better understanding of mechanisms leading to decreasing dissolved oxygen concentrations ([O2]). Much can be learned about the processes and implications of deoxygenation for marine ecosystems using proxy records from low-oxygen sites, provided proxies, such as the manganese (Mn) to calcium (Ca) ratio in benthic foraminiferal calcite, are available and well calibrated. Here we report a modern geochemical data set from three hypoxic sites within the Santa Barbara Basin (SBB), USA, where we study the response of Mn/Caforam in the benthic foraminifer Nonionella stella to variations in sedimentary redox conditions (Mn, Fe) and bottom-water dissolved [O2]. We combine molecular species identification by small subunit rDNA sequencing with morphological characterization and assign the SBB N. stella used here to a new phylotype (T6). Synchrotron-based scanning X-ray fluorescence (XRF) imaging and Secondary Ion Mass Spectrometry (SIMS) show low Mn incorporation (partition coefficient DMn < 0.05) and limited proxy sensitivity of N. stella, at least within the range of dissolved [O2] (2.7–9.6 μmol/l) and Mnpore-water gradients (2.12–21.59 μmol/l). Notably, even though intra- and interspecimen Mn/Ca variability (33% and 58%, respectively) was only partially controlled by the environment, Mn/Caforam significantly correlated with both pore-water Mn and bottom-water [O2]. However, the prevalent suboxic bottom-water conditions and limited dissolved [O2] range complicate the interpretation of trace-elemental trends. Additional work involving other oxygenation proxies and samples from a wider oxygen gradient should be pursued to further develop foraminiferal Mn/Ca as an indicator for hypoxic conditions.
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Dates et versions

hal-03927335 , version 1 (06-01-2023)

Identifiants

Citer

I. Brinkmann, S. Ni, Magali Schweizer, V E Oldham, N B Quintana Krupinski, et al.. Foraminiferal Mn/Ca as Bottom‐Water Hypoxia Proxy: An Assessment of Nonionella stella in the Santa Barbara Basin, USA. Paleoceanography and Paleoclimatology, 2021, 36 (11), pp.e2020PA004167. ⟨10.1029/2020PA004167⟩. ⟨hal-03927335⟩
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