TY - JOUR
T1 - Transition metals in alkaline Lost City vent fluids are sufficient for early-life metabolisms
AU - Evans, Guy N.
AU - Ji, Shichao
AU - Kaçar, Betül
AU - Anbar, Ariel D.
AU - Seyfried, William E.
N1 - Publisher Copyright:
© 2024 Elsevier Ltd
PY - 2024/11/15
Y1 - 2024/11/15
N2 - Despite the importance of alkaline seafloor hydrothermal vents in broadening our understanding of deep-sea hydrothermal ecosystems, little is known about the mobility and concentrations of micronutrient transition metals in these environments. Here, we present new analyses of micronutrient transition metal concentrations in vent fluids from the iconic Lost City Hydrothermal Field (LCHF) and report concentrations of Fe = 2.9–18.3 µmol/kg, Zn = 1.30–5.86 µmol/kg, Cu = 0.43–5.06 µmol/kg, Ni = 86.4–556 nmol/kg, Mn = 8.3–274 nmol/kg, V = 25.9–127 nmol/kg, Mo = 24–94 nmol/kg, Co = 8.0–135 nmol/kg, W = 4.8–16 nmol/kg, and Cd = 1.7–4.5 nmol/kg. We additionally present results of a hydrothermal lherzolite alteration experiment conducted at 300 °C, 500 bar. Transition metal concentrations and major chemical parameters of experimental reaction fluids are broadly similar to LCHF vent fluids, indicating that transition metal concentrations in LCHF vent fluids, and alkaline hydrothermal fluids more generally, reflect metal solubility controlled by underlying rock-buffered hydrothermal reactions. Concentrations of Ni and Mo are especially noteworthy because of their recognized importance for biological methanogenesis (Ni) and nitrogen fixation (Mo). When compared with known biological thresholds, our findings indicate that Ni concentrations in LCHF vent fluids are sufficient to support the robust methane-metabolizing microbial communities observed in the immediate vicinity of LCHF vents and suggest that Ni availability influences the spatial distribution of LCHF methanogens. Furthermore, our laboratory hydrothermal experiments demonstrate that Mo concentrations of similar magnitude to those observed in LCHF vent fluids (and also modern seawater) can be obtained by hydrothermal alteration of ultramafic rocks with Mo-free (Na, Ca) Cl aqueous solution. Thus, we conclude that alkaline hydrothermal fluids were likely similarly enriched in Mo prior to oxidation of the Earth's atmosphere and ocean, providing localized Mo-rich geochemical environments capable of supporting Mo-dependent nitrogen fixation at currently recognized threshold concentrations.
AB - Despite the importance of alkaline seafloor hydrothermal vents in broadening our understanding of deep-sea hydrothermal ecosystems, little is known about the mobility and concentrations of micronutrient transition metals in these environments. Here, we present new analyses of micronutrient transition metal concentrations in vent fluids from the iconic Lost City Hydrothermal Field (LCHF) and report concentrations of Fe = 2.9–18.3 µmol/kg, Zn = 1.30–5.86 µmol/kg, Cu = 0.43–5.06 µmol/kg, Ni = 86.4–556 nmol/kg, Mn = 8.3–274 nmol/kg, V = 25.9–127 nmol/kg, Mo = 24–94 nmol/kg, Co = 8.0–135 nmol/kg, W = 4.8–16 nmol/kg, and Cd = 1.7–4.5 nmol/kg. We additionally present results of a hydrothermal lherzolite alteration experiment conducted at 300 °C, 500 bar. Transition metal concentrations and major chemical parameters of experimental reaction fluids are broadly similar to LCHF vent fluids, indicating that transition metal concentrations in LCHF vent fluids, and alkaline hydrothermal fluids more generally, reflect metal solubility controlled by underlying rock-buffered hydrothermal reactions. Concentrations of Ni and Mo are especially noteworthy because of their recognized importance for biological methanogenesis (Ni) and nitrogen fixation (Mo). When compared with known biological thresholds, our findings indicate that Ni concentrations in LCHF vent fluids are sufficient to support the robust methane-metabolizing microbial communities observed in the immediate vicinity of LCHF vents and suggest that Ni availability influences the spatial distribution of LCHF methanogens. Furthermore, our laboratory hydrothermal experiments demonstrate that Mo concentrations of similar magnitude to those observed in LCHF vent fluids (and also modern seawater) can be obtained by hydrothermal alteration of ultramafic rocks with Mo-free (Na, Ca) Cl aqueous solution. Thus, we conclude that alkaline hydrothermal fluids were likely similarly enriched in Mo prior to oxidation of the Earth's atmosphere and ocean, providing localized Mo-rich geochemical environments capable of supporting Mo-dependent nitrogen fixation at currently recognized threshold concentrations.
KW - Alkaline hydrothermal vents
KW - Methanogenesis
KW - Molybdenum
KW - Nickel
KW - Nitrogen fixation
KW - Serpentine
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U2 - 10.1016/j.gca.2024.08.020
DO - 10.1016/j.gca.2024.08.020
M3 - Article
AN - SCOPUS:85204457164
SN - 0016-7037
VL - 385
SP - 61
EP - 73
JO - Geochimica et Cosmochimica Acta
JF - Geochimica et Cosmochimica Acta
ER -