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2024-07-23 01:00
A discovery in the dark depths of the Pacific Ocean is challenging the scientific consensus on how oxygen is produced, and could also introduce new questions into how life on Earth began. While conducting experiments on the seafloor to measure oxygen concentrations in preparation for deep sea mining, the international team found oxygen was actually being produced in darkness at 4,000m below the ocean surface, where no light can penetrate. Traditionally, oxygen in the sea is thought to come from photosynthetic organisms like plants and algae, which use sunlight to produce oxygen. But this team found nodules on the sea floor which effectively acted as small batteries, using electricity to split seawater into hydrogen and oxygen. These ‘dark oxygen’ findings call into question what we know about oxygen production, and have lead the team to question how mining could impact the deep sea ecosystems if these nodules were to be mined.
Journal/conference: Nature Geoscience
Link to research (DOI): 10.1038/s41561-024-01480-8
Organisation/s: The Scottish Association for Marine Science (SAMS), UK
Funder: The work was funded by The
Metals Company Inc. through its subsidiary Nauru Ocean Resources
Inc. (NORI). NORI holds exploration rights to the NORI-D contract
area in the CCZ and is regulated by the International Seabed Authority
and sponsored by the government of Nauru (A.K.S., C.W., W.B.H.).
UK Seabed Resources funded the research expedition to the UK1 and
OMS license areas in 2015 (A.K.S.), and the Gordon and Betty Moore
Foundation provided funding for the research cruise to APEIs 1, 4 and
7 in 2018 (A.K.S.). Research support from the Natural Environment
Research Council SMARTEX (Seabed Mining And Resilience To
Experimental impact) project (grant number NE/T003537/1) and the
European Commission project iAtlantic (grant number 818123) to
A.K.S. is also acknowledged. We thank K. Mizell at the US Geological
Survey for comments on our manuscript. Competing interests: A.K.S., C.W. and W.B.H. received research support (funding) from The
Metals Company, and A.K.S. also received research support from UK
Seabed Resources to carry out part of the work. The Metals Company
and UK Seabed Resources aided in the experimental design. S.F. and
T.K. also work for the Federal Institute for Geoscience and Natural
Resources, which holds exploration rights in the CCZ.
Media release
From: Springer Nature
1. Geoscience: Deep-sea mining target produces ‘dark oxygen’
Rare-earth metal-bearing nodules on the dark, deep seafloor can create oxygen—called ‘dark oxygen’—according to a paper published in Nature Geoscience. This finding suggests these nodules could influence deep-seafloor ecology.
Polymetallic nodules are common on the sediment-covered abyssal plains of oceans worldwide. They are primarily composed of oxides of iron and manganese, but also contain metals such as cobalt and rare-earth elements that are essential components of many advanced and low-carbon energy technologies. They are therefore a target for deep-sea mining; however, the potential environmental effects of doing so are not well understood.
Andrew Sweetman and colleagues conducted experiments using chambers placed on the seafloor at depths of about 4,200 metres to measure the oxygen concentration at multiple locations over 4,000 kilometres apart across the Clarion–Clipperton Zone in the central Pacific Ocean, where polymetallic nodules are found. Almost all these experiments showed the oxygen concentration steadily increasing over two days. The authors conducted follow-up laboratory analysis and propose that the polymetallic nodules are the source of the detected oxygen emissions. Based upon numerical simulations, Sweetman and colleagues hypothesise that the cause of oxygen generation is the electrical properties of the nodules.
While the authors note that it is difficult to estimate how much oxygen polymetallic nodules produce on a broader scale, they suggest that this oxygen source could support deep-seafloor ecosystems, which could be impacted if these nodules were to be mined.
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