Hydrothermal vent ecosystems

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Lead: Cindy Lee Van Dover, Duke University

Background

At the boundary between Earth’s divergent tectonic plates deep on the ocean floor forms a collection of volcanic ridges, rifts, fault zones and other geologic features known as the mid-ocean ridge.  Along the ridge, seawater percolates into the crust through cracks and pores, it is heated by underlying magma and forced back to the surface through fissures in the rock as superheated jets laden with dissolved minerals.  Fuelled by this cocktail of chemicals and extreme high pressure, dense mats of chemosynthetic bacteria and archaea thrive around the jets – commonly referred to as hydrothermal vents – forming the base of a lightless food chain that supports a diverse community of giant tube worms, clams, snails and shrimp.  Relative to the majority of the deep sea, the areas around submarine hydrothermal vents are biologically more diverse and productive, with a high degree of specialisation and species endemism.  Almost nothing is known about how these vent assemblages form, recruit, spread or maintain themselves.

Northern Mid-Atlantic Ridge and location of mining exploration contracts

The unique physical and chemical conditions found at deep-sea hydrothermal vents have led to the formation of mineral deposits that are becoming increasingly valuable and commercially exploitable.  Mineral exploration companies have recently turned their attention to extraction of minerals from hydrothermal vent fields on the seafloor.  The deep-sea mining industry, though still in its infancy, has the potential to inflict environmental impacts including sediment and chemical plumes from mining machinery affecting filter-feeding organisms, collapsing or reopening vents, gas hydrate release, or even underwater landslides.  All of these impacts on such a fragile habitat and their broader ramifications into the deep-sea ecosystem are poorly understood, and are the subject of intense research so that control measures are implemented before exploitation commences.

This work is aimed at gaining a greater understanding of the physical and biological factors that shape hydrothermal vent communities on the northern Mid-Atlantic Ridge, and to identify and quantify the risks at which these communities will be put by the practice of deep-sea mining.  Identifying the risks and evaluating the effects of predicted impacts in the broader context of deep-sea ecosystem structure and function will entail the assessment of deep-sea connectivity pathways and dispersal capabilities of the organisms that depend upon them.  Outputs of these activities will contribute to the development and assessment of spatial management options to safeguard such unique features, and include recommendations to stakeholders in industry, coastal nations and the International Seabed Authority (ISA) so that deep-sea mining can be regulated to achieve minimal environmental impact.

Objectives

  • To design spatial strategies to protect ecosystem structure, function and diversity at deep-sea hydrothermal vents.
  • To increase the capacity of coastal states and the ISA to sustainably manage the seabed environment, with a particular view to conserving biological diversity at deep-sea hydrothermal vents.

Approach

This work will involve the following steps:

  • Assessment of risks to biodiversity on the northern Mid-Atlantic Ridge through desk study and expert interviews.  A review of risk assessment approaches before selection of the most appropriate approach is to be performed in consultation with an advisory group of experts.
  • Development of a genetic connectivity model for hydrothermal vent invertebrates of the northern Mid-Atlantic Ridge using both genetic and hydrographic data.
  • Development followed by revision of multiple scientifically justified spatial management design options, including network design options spanning active and inactive vents, for the preservation of hydrothermal vent biodiversity in the light of potential deep-sea mining operations along the northern Mid-Atlantic Ridge.
  • Development and provision of a multi-authored Technical Report with final recommendations on the management of deep-sea mining activities targeted at the International Seabed Authority.
  • Publication and dissemination of scientific results in the peer-reviewed literature.

Results to date

A review of all protected hydrothermal vents, including their management schemes, has been performed, together with a detailed exposition of the scientific rationale and the international obligations for their protection.

An evaluation of potential risks to the marine environment from deep-sea mining activities has been completed, as well as a risk register which includes associated survey data and assessment outcomes to evaluate each risk.

The scarce existing data on inactive hydrothermal vents – ones that no longer discharge super-heated fluids but retain mineral-rich deposits – have been reviewed to ascertain the biological and ecological status of such features. A key result is that animal communities of inactive vents vary from one locality to another, adding to the challenge of understanding their ecology and of assessing their vulnerability to risk from mining activities.

Based on existing knowledge and the precautionary principle, a regional environmental management plan for the North Atlantic Ocean has been devised, whilst constantly addressing challenges that arise with evolving processes and technologies.

Publications that have emerged from this work include:

  • A Strategy for the Conservation of Biodiversity on Mid-ocean Ridges from Deep-sea Mining, by D Dunn and colleagues, in Science Advances 2018, Vol. 4 Issue 7 (download).
  • Scientific Rationale and International Obligations for Protection of Active Hydrothermal Vent Ecosystems from Deep-sea Mining, by C Van Dover and colleagues, in Marine Policy 2018, Vol. 90 (download).
  • An Atlas of Protected Hydrothermal Vents, by E Menini and C Van Dover, in Marine Policy 2019, Vol. 108 (download).
  • Inactive Sulfide Ecosystems in the Deep Sea: A Review, by C Van Dover, in Frontiers in Marine Science 2019, Vol. 6 (download).
  • Ecological Risk Assessment for Deep-sea Mining, by T Washburn and colleagues, in Ocean and Coastal Management 2019, Vol. 176 (download).
  • Research is Needed to Inform Environmental Management of Hydrothermally Inactive and Extinct Polymetallic Sulfide (PMS) Deposits, by C Van Dover and colleagues, in Marine Policy 2020, in press (download).
  • Biophysical Models of Persistent Connectivity and Barriers on the Northern Mid-Atlantic Ridge, by JM Yearsley and colleagues, in Deep-Sea Research Part II 2020, in press (download).

Application

Deep-sea mining, although still not commercially operational, is a fast-evolving field driven not only by technological advances in the industry’s race to readiness, but also by the shifting political climate and a growing environmentally concerned society.  As such, progress can be hard to gauge.  Proposals for the designation of Areas of Particular Environmental Interest (APEI) around hydrothermal vent fields will be informed by the most appropriate risk assessment process and justified based on the most up-to-date scientific knowledge.  The criteria for identifying and designating APEIs – the ISA’s own tool for excluding mining activities from areas of ecological significance – are compatible with criteria for identifying EBSAs.  By driving the process of knowledge acquisition and contributing to the formulation of best mining practices around deep-sea hydrothermal vents, this work is at the centre of efforts to protect and preserve the unique biodiversity of deep-sea hydrothermal vents and in areas beyond national jurisdiction.  Such outcomes represent the overall goal of both GOBI and the EBSA process.

Hydrothermal vent fauna – NOAA Okeanos Explorer Programme.