Exploring biogeochemical cycling in the abyssal Clarion-Clipperton Zone, Pacific Ocean

Continued and increasing demand for rare earth minerals is driving extensive curiosity in exploitation of mining deep-sea mineral-rich deposits. One area being investigated for deep-sea mining activities is polymetallic nodule fields at abyssal depths. Polymetallic nodules are mineral deposits that have precipitated around a nucleus (e.g., shark teeth) over millions of years, and are rich in metals such as copper, nickel , lithium, and cobalt as well as rare earth minerals. It is currently thought that these manganese oxide deposits may be involved in dark oxygen production in addition to other deep-sea biogeochemical processes that are not yet fully understood. Presently, a major concern is that the organisms and ecosystems around these mineral deposits may be especially vulnerable to deep-sea mining because of their long generation times and sensitivity to disturbance, and the fact that manganese oxide deposits that are home to a rich diversity of fauna are very slow growing. 

This PhD project investigates benthic biogeochemical cycling (e.g. oxygen and carbon dioxide fluxes) in areas being targeted for deep-sea mining, and assess specific ecosystem functions such as seafloor chemoautotrophy, and oxygen consumption and production. Abyssal samples will be collected using deep-sea landers at field sites in the Clarion-Clipperton Zone in the Pacific Ocean. Isotope labelling studies will be used to parameterise deep-sea biogeochemical cycling in addition to electrochemical studies on polymetallic nodules to better understand the role of electrochemistry and microbiology in deep-sea biogeochemical cycling. 

This project is part of the Dark Oxygen Research Initiative (DORI), funding by the Nippon Foundation.

Supervisors

Andrew Sweetman, SAMS

Bhavani Narayanaswamy, SAMS

Franz Geiger, Northwestern University

Jeffrey Marlow, Boston University

Start date: 02 Feb 2026

Funder: Nippon Foundation