The deep sea is immeasurable in not only its scale and beauty, but also for how vital it is for both the ocean and for life on earth. A planet without the deep sea would be inhospitable. Which is why it is shocking to hear of the plans and developments currently underway in order to harvest this environment for human profit. Let us explore deep-sea mining
Mining for what?
So, what on earth is down there? Well, Polymetallic Ferromanganese Nodules are. In other words, pebble shaped metallic rocks that lay scattered on the bottom of the seabed. On the surface of these nodules, the fixation of trace metals occurs (e.g. of manganese and iron hydroxides), resulting in a build-up of spherical layers of metals around the core [1]. It is this fixation that imperils the deep sea, by making these nodules an incredibly easy and attractive source of copper, nickel, zinc, lithium and aluminium.
On the surface of each noddle is a living community and ecosystem that thrives
Seeing as these metallic rocks can be reached so easily, through simply plucking them from the floor, you might start to question the impact of such activities. Unfortunately, what scientists are slowly starting to see, is the monumental environmental disaster that will occur should the harvesting of nodules take place [2].
What makes the deep-sea mining so bad?
These polymetallic nodules are key components to each of the critical deep-sea processes, such as that all important carbon cycling process or the dissolution of calcium carbonate. On the surface of each one is a living community and ecosystem that thrives. A polymetallic nodule could be compared to a small coral reef hosting unique microbial communities, distinct even to the nodule lying next to it. Therefore, the nodules become the basis of the primary production on the ocean’s plains and the bedrock of the food chain for an extensive network of organisms [3].
A track mark made by scientists 30 years ago still exists today in its same ‘pristine’ condition and not even microbes have returned to that point
When considering the deep sea and its processes, it is important to remember that nothing has significantly (or even just slightly) altered for an extremely long time. This means evolution happens incredibly slowly [4] and organisms are highly specialised to these specific conditions which haven’t been altered for millennia. So, when we disturb this environment, even ever so slightly, the habitat simply does not recover. For example, a track mark made by scientists 30 years ago still exists today in its same ‘pristine’ condition and not even microbes have returned to that point [5]. What’s more worrying is that processes such as carbon burial all but ceased here.
Destroying the deep-sea
The impacts of deep-sea mining start with habitat removal. Nodules take millions of years to regrow. Furthermore, 50% of deep-sea organisms live on these nodules while at the next ‘trophic level’ scavenger diversity is positively correlated with them, so there will be no avoiding a catastrophic reduction in biodiversity. Another negative impact of mining and biodiversity relates to rugosity (i.e. the texture of marine environments);’: the more textured a surface, the greater number of organisms exists there. Mining will therefore remove essential habitats that the remaining percentage of deep-sea organisms rely upon. These impacts begin to indicate to us the lifeless two-dimensional ocean we will create, should mining take place.
Sedimentation will starve the organisms below
Meanwhile, vast ‘plumes’ will be created by the vehicles used to carry out deep-sea mining. In a normal circumstances on the ocean floor, the process of sedimentation (the suspension and settling of particles) doesn’t really happen. An experiment looking at the impact of removing just one nodule demonstrated that a year after nodule removal, sedimentation rates had increased by 5,000 x in the surrounding zone and up to 50 x more up to hundreds of miles away [6]. Therefore, sediment plumes will smother the ocean for up to hundreds of miles. A multitude of impacts will be felt as a result: Sediments may bury the organisms living on the seabed, clog the respiratory surfaces of filter feeders, and cover and dilute the already limited food supply. Consequently, sedimentation will starve the organisms below. Lastly, some of these particles may remain suspended in the water column for decades, completely altering the basic oceanographic processes that have occurred down here for centuries. This is a major footprint being planted across the ocean floor, in the shape of catastrophic loss of life and diversity.
Is there more to it?
There is more though, such as the compaction of sediments, noise and light pollution, the mechanical and ecotoxicological effects of mining, and so on… meanwhile, these results have been found with limited scientific research and data. Therefore, what we know and understand now is simply the tip of the iceberg. However, the process of Deep-Sea Mining seems to be steam roll ahead with as much gumption as HS2. The following article will therefore bring these two tales of an explorer’s paradise turned two-dimensional wasteland and look into the factors making this transition an increasing likelihood.
References
- Dale & Inall, Unpublished
- Fauna and Flora International, 2020. The risks and impacts of deep-seabed mining to marine ecosystems
- Halbach, P., 1986. Processes controlling the heavy metal distribution in Pacific ferromanganese nodules and crusts. Geologische Rundschau, 75(1), pp.235-247.
- Halfar, J. and Fujita, R.M., 2007. Danger of deep-sea mining. SCIENCE-NEW YORK THEN WASHINGTON-, 316(5827), p.987.
- Roberts, C.M., 2002. Deep impact: the rising toll of fishing in the deep sea. Trends in ecology & evolution, 17(5), pp.242-245.
- Stratmann, T., Lins, L., Purser, A., Marcon, Y., Rodrigues, C.F., Ravara, A., Cunha, M.R., Simon-Lledó, E., Jones, D.O., Sweetman, A.K. and Köser, K., 2018. Abyssal plain faunal carbon flows remain depressed 26 years after a simulated deep-sea mining disturbance. Biogeosciences, 15(13), pp.4131-4145.