Volz, Jessica B.
[Author];
Mogollón, José M.
[Author];
Geibert, Walter
[Author];
Arbizu, Pedro Martínez
[Author];
Koschinsky, Andrea
[Author];
Kasten, Sabine
[Author]
Natural spatial variability of depositional conditions, biogeochemical processes and element fluxes in sediments of the eastern Clarion-Clipperton Zone, Pacific Ocean
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Media type:
E-Article
Title:
Natural spatial variability of depositional conditions, biogeochemical processes and element fluxes in sediments of the eastern Clarion-Clipperton Zone, Pacific Ocean
Contributor:
Volz, Jessica B.
[Author];
Mogollón, José M.
[Author];
Geibert, Walter
[Author];
Arbizu, Pedro Martínez
[Author];
Koschinsky, Andrea
[Author];
Kasten, Sabine
[Author]
imprint:
Elsevier, 2018-10
Language:
English
DOI:
https://doi.org/10.1016/j.dsr.2018.08.006
Origination:
Footnote:
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Description:
The manganese nodule belt within the Clarion and Clipperton Fracture Zones (CCZ) in the abyssal NE Pacific Ocean is characterized by numerous seamounts, low organic matter (OM) depositional fluxes and meter-scale oxygen penetration depths (OPD) into the sediment. The region hosts contract areas for the exploration of polymetallic nodules and Areas of Particular Environmental Interest (APEI) as protected areas. In order to assess the impact of potential mining on these deep-sea sediments and ecosystems, a thorough determination of the natural spatial variability of depositional and geochemical conditions as well as biogeochemical processes and element fluxes in the different exploration areas is required. Here, we present a comparative study on (1) sedimentation rates and bioturbation depths, (2) redox zonation of the sediments and element fluxes as well as (3) rates and pathways of biogeochemical reactions at six sites in the eastern CCZ. The sites are located in four European contract areas and in the APEI3. Our results demonstrate that the natural spatial variability of depositional and (bio)geochemical conditions in this deep-sea sedimentary environment is much larger than previously thought. We found that the OPD varies between 1 and 4.5 m, while the sediments at two sites are oxic throughout the sampled interval (7.5 m depth). Below the OPD, manganese and nitrate reduction occur concurrently in the suboxic zone with pore-water Mn2+ concentrations of up to 25 µM. The thickness of the suboxic zone extends over depth intervals of less than 3 m to more than 8 m. Our data and the applied transport-reaction model suggest that the extension of the oxic and suboxic zones is ultimately determined by the (1) low flux of particulate organic carbon (POC) of 1–2 mg Corg m−2 d−1 to the seafloor, (2) low sedimentation rates between 0.2 and 1.15 cm kyr−1 and (3) oxidation of pore-water Mn2+ at depth. The diagenetic model reveals that aerobic respiration is the main biogeochemical process driving OM degradation. Due to very ...