In 2019 I was given the incredible opportunity to spend 12 weeks working 1,700 km offshore the coast of Mexico in the international waters of the Clarion-Clipperton Zone (CCZ), located in the Central Pacific Ocean. Water depth at the project site ranged between 3,000 and 4,600 m below sea level. The work was supporting Deep Green (now the Metals Company) to characterise the biological and chemical environments on the seafloor to determine the potential impacts associated with future deep sea mining of polymetallic nodules.
Polymetallic (or manganese) nodules form on or just below the seafloor of the abyssal plains. The nodules comprise dissolved metals, which form around a nucleus, usually a tooth or bone fragment. The formation of nodules is one of the slowest geological processes on the planet, with nodules forming at a rate of a centimeter every several million years. Nodules can contain an abundance of rare metals at much higher quality than ores from terrestrial mining.
The nodules support a variety of organisms, which live both on the nodules themselves and in the surrounding seafloor sediments. Photographs of large fauna were taken, as well as preservation of samples for taxonomic identification in the laboratory. Environmental DNA (eDNA) samples were also taken to look for species which may be less easy to detect than using traditional taxonomic sampling methodology. The sheer volume of samples and time spent offshore lends itself to some pretty fascinating observations. For example, we found multiple teeth belonging to the megalodon shark (Otodus megalodon), which went extinct over 3.6 million years ago.
The data we collected has helped the client to understand existing environment around their operation and what the potential impacts may be. This information will be used to help plan for future activities and help guide the development of management and mitigation measures.