Managing deep-sea ecosystems

Our latest expert feature dives into the area of deep-sea ecosystems and considers challenges and opportunities in research and management at the scale of ocean basins.
Published: 9 May 2018

​​​​​​​​​​​​​​​Murray Roberts University of Edinburgh, UK

My first postdoc project set out to look at the biology and ecology of cold-water corals, particularly the hard coral Lophelia pertusa. According to the Web of Science in the years up to 2000 there were fewer than ten papers published a year that mention 'deep-sea' or 'cold-water' corals, but in the years since then the number has grown exponentially, averaging around 60 a year for the last decade.

Twenty years ago, this resurgence of interest in cold-water corals was prompted both by academic curiosity and a growing concern that coral habitats were being damaged by bottom trawling and could be threatened as oil and gas exploration moved to deeper waters. Curiosity was super-charged by the intriguing hypothesis that cold-water corals like Lophelia, were fuelled by chemosynthesis related to methane seepage from subsurface hydrocarbon reservoirs. This motivated the scientists to get out to sea and understand what allowed such flourishing habitats to grow in deep, dark, and apparently food-poor environments.

A shift in perspective

Throughout the 2000s studies examining the isotopic composition of cold-water corals and following food input in the field showed that, rather than being linked directly to the geosphere, these habitats were instead fed from surface productivity that was rapidly transported by local hydrodynamic conditions to the suspension-feeding corals on the seabed, sometimes at hundreds of metres depth. Many of these studies were supported through international research projects funded by the European Union. During these projects, and others around the world, it became increasingly clear that deep-seabed ecosystems, including corals and sponge grounds, had been substantially damaged by bottom trawling, leading to intense efforts to develop strategies to prevent this damage.

In 2002 it was recommended that the UN General Assembly improve management of vulnerable deep-sea ecosystems, many of which are outside any nation's jurisdiction. In 2003 and 2004 petitions were gathered and the 'Deep-sea Conservation Coalition' was formed, all steps towards the first UN General Assembly resolution in 2006 calling upon states '…to protect vulnerable marine ecosystems, including seamounts, hydrothermal vents and cold water corals, from destructive fishing practices…'.

Building momemtum

But how can you possibly manage deep-sea ecosystems without good information on their biodiversity, biogeography, longevity, and connectivity? How can you create long-term management measures without understanding how climate change, ocean acidification, and other stressors will alter the ecosystems? It was now extremely clear that international ocean-basin scale projects would be essential for providing the evidence base for such ambitious conservation and management measures.

Fast-forward another ten years and we have entered an unprecedented period of opportunity at the intersection of deep-sea science and offshore conservation. In 2016 the UN embarked upon discussions to develop an international legally binding instrument under the UN Convention on the Law of the Sea on the conservation and sustainable use of biodiversity in areas beyond national jurisdiction. This Biodiversity Beyond National Jurisdiction process has produced recommendations to the UN General Assembly on what might constitute new international legislation to manage biodiversity beyond national jurisdiction.

There is now real political momentum behind efforts to create the international partnerships needed to study marine ecosystems at ocean basin scale. In the Atlantic the Galway Declaration on Atlantic Cooperation was signed in 2013 between Europe, Canada, and the USA, followed shortly by the start of projects like ATLAS  and SponGES designed to better understand deep Atlantic ecosystems and develop plans for their management.

Gathering knowledge

At the ICES Annual Science Conference (ASC) in 2018 the session “Ocean basin-scale research and management: challenges and opportunities" will explore themes emerging as assessments of marine ecosystem connectivity, biogeography, and function are being embraced at broader geographical scales. Research and policy development at ocean basin has been driven by the realization that climatic change and human impacts are rapidly altering ecosystems at the same time as governments seek to promote increased economic output from the marine environment.

The session will bring together key advances and approaches relevant to ocean basin-scale research and management. Studies on discoveries from poorly-understood deep ocean ecosystems are highlighting the opportunities to create a new evidence base for long-term management. For example, advances in oceanographic data availability, modelling resolution, and understanding of larval biology and dispersal are fostering more partnerships between physicists and biologists to model ecosystem connectivity. Analyses can now be ground-truthed by population genetic approaches built on datasets developed from next generation sequencing technologies, opening the window to a new understanding of connectivity.

Alongside community ecology and taxonomic assessments, the improved understanding of connectivity sets the stage for an enhancement in our ability to define biogeographic patterns at regional and full basin scales. In turn, a more robust understanding of connectivity and biogeography provides the foundation for a new generation of predictive models better tuned to reflect the occurrence of key species and make inferences about their future distributions. Such understanding is now making it possible for socio-economic assessments of ecosystem value to be conducted at larger and larger scales.

Changing landscape

Finally, the ocean policy and management landscape is currently evolving rapidly at all scales. Robust and adaptable policies are needed in response to climate change and human use of the open ocean and deep seabed from established sectors including fisheries and hydrocarbons to emerging sectors including blue biotechnology and deep-sea mining. This session will also explore the industry and policy landscape. For example, how may frameworks of offshore marine protected areas interact with assessments made through the United Nations Food & Agriculture Organization (i.e vulnerable marine ecosystems) and Convention on Biological Diversity (ecologically or biologically significant areas)? How might the present United Nations deliberations on a new legally-binding instrument to manage biodiversity in areas beyond national jurisdiction evolve and shape offshore management in the future?

Murray Roberts is one of the conveners of Theme Session G at the ICES ASC 2018 in September, and an invited speaker at Session 6: "The deep ocean under climate change" at the 4th i​​​​​nternational symposium on the effects of climate change on the world's oceans in June.  

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​Logachev cold-water coral carbonate mounds (from the Changing Oceans Expedition, 2012)

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Managing deep-sea ecosystems

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