Scars  in  the  Abyss: Reconstructing  sequence,  location  and temporal change of the 78 plough tracks of the 1989 DISCOL deep sea disturbance experiment in the Peru Basin

The release of potentially toxic metals, such as copper (Cu), into the water column is of concern during polymetallic nodule mining. The bioavailability and thus toxicity of Cu is strongly influenced by its speciation which is dominated by organic ligand (L) complexation in seawater, with L-complexes being considered less bioavailable than free Cu2+. The presence of CuL-complexes in deep-sea sediments has, however, not been systematically studied in the context of deep-sea mining. We thus analyzed the Cu-binding L concentration ([L]) in deep-sea pore waters of two polymetallic nodule provinces in the Pacific Ocean, the Peru Basin and the Clarion-Clipperton-Zone, using competitive ligand equilibration–adsorptive stripping voltammetry. The pore-water dissolved Cu concentration ([dCu]) ranged from 3 to 96 nM, generally exceeding bottom water concentrations (4–44 nM). Based on fitting results from ProMCC and Excel, Cu was predominantly complexed by L (3–313 nM) in bottom waters and undisturbed pore waters. We conclude that processes like deep-sea mining are unlikely to cause a release of toxic Cu2+ concentrations ([Cu2+]) to the seawater as > 99% Cu was organically complexed in pore waters and the [Cu2+] was < 6 pM for 8 of 9 samples. Moreover, the excess of L found especially in shallow pore waters implied that even with a Cu release through mining activities, Cu2+ likely remains beneath toxic thresholds.

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“…For details see Table 1 . Close-up maps: data from EM 122 multibeam echosounder during SO242 45 and SO268 46 , 47 . …”

Section: Study Sitesmentioning

confidence: 99%

Copper-binding ligands in deep-sea pore waters of the Pacific Ocean and potential impacts of polymetallic nodule mining on the copper cycle

Paul

Zitoun

Noowong

et al. 2021

Sci Rep

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“…Authors Response: The abbreviation explanation has been added. Authors Response: 1989 -SO061 (Thiel and Schriever, 1989): USBL (RS904) in conjunction with GPS. The GPS position varied considerably with navigation errors >55m.…”

Section: Technical Correctionsmentioning

confidence: 99%

Author’s Responses to the comments of Anonymous Referee #1

Hennke¹

2020

Preprint

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This manuscript provides legacy data from previous cruises and new data from a recent research cruise from the Disturbance and Recolonization Experiment area (DISCOL) in the Peru Basin, SE Pacific. In 1989 an area of about 11 km 2 was ploughed using a plough harrow to simulate Mn nodule mining in this area. The data used in the provided study include ship-based multibeam bathymetric data (MBES), video data C1

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Scars in the Abyss: Reconstructing sequence, location and temporal change of the 78 plough tracks of the 1989 DISCOL deep sea disturbance experiment in the Peru Basin

Cited by 2 publications

References 16 publications

Copper-binding ligands in deep-sea pore waters of the Pacific Ocean and potential impacts of polymetallic nodule mining on the copper cycle

Copper-binding ligands in deep-sea pore waters of the Pacific Ocean and potential impacts of polymetallic nodule mining on the copper cycle

Author’s Responses to the comments of Anonymous Referee #1

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