The impact of deep-sea mining is unpredictable

In which way could deep see mining and the removal from manganese nodules effect the ecosystem?

There is so little knowledge on this ecosystem that we really can’t do any prediction on what will happen if commercial mining of manganese nodules in the deep sea is allowed. We don’t know what will be impacts of the manganese nodules removal but we know that many species depend in such structures because they use them as a habitat. The mining equipment can be more or less compared to a vacuum cleaner, they are designed to collect the nodules from the seafloor but together with the nodules, they will collect sediments associated to the nodules. A very special habitat where thousands of animals live is precisely the upper layer of the sediment of the seafloor, that particular layer might be removed together with the nodules. Moreover, the machines are heavy, the bottom of the sea is very fluffy, so the sediment will be compacted, and several animals living there could be crashed and destroyed. These are some of the predictions about the impacts of the mining on the deep-sea benthic diversity, however to is hard to make precise predictions of what will exactly occur. Currently, scientist from all over the world are working in getting to know the communities of this particular habitat in order to make better estimations about the biodiversity and the environmental cost that deep-sea mining will generate.

Could the impact be confined on a local level?

Some models predict that the mining will have a local effect. However, many aspects must be considered. For instance, there are quite direct impacts such as the removal of nodules and sediments but there are also other indirect effects. For examples, by removing the nodules a sediment cloud will be produce and you have water currents that draft the sediments to other areas, where other animals will be affected, for example the filter feeders. Moreover, the ships and pipelines which will retrieve the nodules and sediments will cause noise and an increment in the water temperature that might affect plankton communities and fish, among many others.

What is happening currently?

It is a more complex than we can imagine. For example, coastal areas are very good legislated because they belong to a determined country. However, the areas beyond economic exclusive zones – such as the deep-sea – are considered a resource that belongs to all humans and it is hard to raise agreements about how these resources should be used. Until now the legislations only allows the exploration of such areas; this is made through license areas. This means that countries can apply to get a license area and when they are granted with such areas, they can explore the resources (for example: minerals, biodiversity) without economic benefit. What is happening now is that several research teams are working together in order to do a biodiversity assessment to have a better picture of how many species inhabit and depend on this particular ecosystem. Regarding the mining we need to do predictions how many species would be lost; another important aspect that has been discussed is the possibility to create marine protected areas that will help to preserve the diversity in the case that deep-sea is inevitable.

What do we even know about the deep sea?

We know very little about the deep sea, some people say we know more about the moon. About 95 percent that you bring out of deep see are new to science. So we know nothing. You have lots of species to describe, a different diversity in many aspects, morphological features that you’ve never seen before, different functions of the animals, and different habitats to explore too. In 2018 we did an expedition for a biodiversity assessment – in a small area that is about 300 square meter and only there, we found more than 400 species of copepods living there. We were able to study all these species by genetic methods (barcoding) but also we look on the morphology of the different animals. In fact, from all the animals we study, we could only assign one species to a previous describe species; probably the rest are new species to science. In this case, we were only studying the copepods, but for many groups it is the same. There are areas which never were explored, thus there is still a lot of work to do in this regard.

How come the deep sea is explored so little?

One reason is, that it takes a lot of effort to explore the deep sea, it’s a very complex research and economically intense. This place is difficult to access: You need very different expertise with the people leading the expeditions and the scientist that take part of them. Even reaching some areas can take several days, one also need a very particular set of gears to be able to sample and an experience crew that helps to make the best of each expedition.

How is the ecosystem like down there?

In the case of animals living within the sediments, the first five centimeters have a huge diversity of species. We are trying to understand their role in the ecosystem. Nematodes and copepods are the two groups which represent 95 Percent of the meiobenthic communities in the deep sea. They live in the sediment or swim close to it. Another interesting characteristic is that for many invertebrate groups, the species living in the deep-sea sediments are also considered the oldest or more ancestral of their groups. Thus, if you want to understand the evolution of a certain group – such as the copepods – you want to have these species in your analysis. Having these species, allows you to better understand how all the changes have been done through the evolutionary history of a group.

How can you as a scientist of the LIB support to protect the ecosystem?

We in the LIB in general and in the scientific community try to understand and to describe the diversity and function of the ecosystems and the different groups of animals. We want to provide more data so that the decision makers will be better informed and hopefully they will take the correct decisions that will ensure the preservation of the diversity and all the services that diversity provides.

Dr Nancy Mercado Salas has been employed as curator of the crustacean collection at LIB since August 1, 2021. Before, at Senckenberg am Meer (DZMB), she worked for six years on projects describing crustacean diversity and their colonization processes in the meiobenthos. Later, she worked on analyzing the diversity of deep-sea crustaceans living in areas threatened by deep-sea mining, such as the Clarion-Clipperton Fracture Zone.