Human Activities in the Deep Sea

For thousands of years humans have been travelling the world’s oceans and using their resources. These days, activities in the deep sea include oil and gas extraction, shipping, fishing and exploratory work for seabed mining. The industries built around these activities provide not only important resources and services to support the growing demands of modern society, such as oil and gas for fuel and the transport of goods, but also provide millions of jobs as well as food security for many.

With advancements in technology and dwindling terrestrial resources, many human activities are moving into deeper and more remote parts of the ocean. Most of these leave an impact of some sort on the marine environment, whether this is negligible or significant. During just one ROV dive on this cruise we recorded more than 20 instances of human impacts on the seabed, including trawl marks, fishing line, trawl gear, tin cans and plastic cups. Many other cruises have observed traces of human activities in the deep sea and it appears we are leaving our mark on even these most remote of places on our planet.


Litter observed on ROV dives: a tin can; the head of a spade; tubing

Apart from depleting fish stocks, certain types of fishing can cause physical damage to the seafloor. These activities include dragging nets or dredges along the bottom of the sea, breaking corals and disturbing animals. Another potentially damaging practice, deep-sea mining, has not yet started on a commercial scale, but has also been shown to cause physical damage to the seafloor and associated animals. Clouds of disturbed sediment may also smother animals in surrounding areas. Waste materials disposed at sea by ships or through activities like oil and gas exploitation may be toxic to marine organisms or may result in the covering of animals living on the seafloor.


Ropes overgrown by corals, anemones, and other animals

Marine litter is also found in even the deepest parts of the oceans, and can cause death to marine organisms as a result of ingestion or entanglement. On a longer time scale, humans are indirectly impacting the deep sea through warming temperatures and ocean acidification associated with climate change.


A beer can recorded on a dive

Despite the fact that the deep sea covers over 60% of the earth’s surface and carries out vital functions, such as influencing our climate and weather patterns, it is still one of the most understudied environments on our planet. This is due to its remoteness, making it difficult and expensive to reach, and the sheer expanse of the area. What is more, most of the deep sea is found outside the territorial waters of countries, in what is called the high seas, or areas beyond national jurisdiction (ABNJ). This means that it belongs to no one country, but is free for all to use. Protecting the deep sea is therefore difficult, as we not only know very little about it, but also require collaboration on a global scale to develop legislation for its conservation.

So – what is being done to protect the deep sea from human activities, and where do our connectivity studies fit in to this? There are many different legal instruments at the global and regional level that are relevant to managing human impacts in the high seas. The United Nations Convention on the Law of the Sea (UNCLOS) establishes the rights and responsibilities of nations with regard to use of the world’s oceans, but includes only a short section on conservation and management of living resources in the high seas. Other important instruments include the Convention on Biological Diversity (CBD); the OSPAR Convention – international legislation for the protection of the marine environment in the North-East Atlantic; regional fisheries management organisation (RFMO) regulations; the International Convention for the Prevention of Pollution from Ships (also called MARPOL 73/78); the 1992 United Nations (UN) Framework Convention on Climate Change (UNFCCC); and the International Seabed Authority (ISA) regulations for deep-sea mining. What is currently lacking from the governance of activities in the deep sea is a comprehensive, over-arching instrument for the protection of marine biodiversity in those parts of the ocean beyond national jurisdiction. This means that a huge portion of our planet is being used without a comprehensive legal framework to provide for its protection!

In June 2015, a landmark resolution was adopted by UN member states to develop a new, international, legally binding treaty that will address the conservation and sustainable use of marine biodiversity in the high seas. This legislation will build and elaborate on UNCLOS and will include regulations on creating new Marine Protected Area (MPA) networks in the high seas, improving environmental assessments, addressing benefits sharing and improving transparency of activities on the high seas.

As far as connectivity studies are concerned, Deep Links’ participant JNCC explained in a previous blog the importance of understanding connectivity in designing efficient and effective MPA networks. MPAs are an important tool used to protect ecosystems from human impacts, and in recent years there has been an increased effort to establish MPAs in the high seas. These areas play a role in protecting the marine environment from activities like fishing, oil and gas exploitation and seabed mining. By understanding how marine communities are connected, we can make sure that the size, spacing and positioning of MPAs are such that connectivity among populations is maintained. In other words, we can ensure that animals are able to move between areas to breed. What is more, information on connectivity and larval dispersal is important for estimating rates of recovery from human impacts, such as deep-sea mining, particularly for the slow-growing organisms that can inhabit these areas. If we understand how far marine animals travel, we can estimate how well an area that has been mined will recover.

Although there are many different human activities in the deep sea, it is important to note that the size and remoteness of this area has played a key role in limiting human impacts, and the extent of damage and disruption is therefore relatively low compared to other environments.  An important step in managing impacts and protecting the deep sea is to continuously advance our understanding of this wondrous part of our world, and it is through research cruises, such as Deep Links, that this can be done!

Text by Kirsty McQuaid, PhD student, Plymouth University

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