Journal article Open Access
Combes, M; Vaz, S; Morato, T; Fauconnet, L; Arnaud-Haond, S; Dominguez-Carrió, C; Fox, A; González-Irusta, J-M; Carreiro-Silva, M; Davies, A; Durán Muñoz, P; Egilsdóttir, H; Henry, L-A; Kenchington, E; Lirette, C; Murillo-Perez, FJ; Orejas, C; Ramiro-Sánchez, B; Rodrigues, L; Ross, SW; van Oevelen, D; Pham, CK; Pinto, C; Golding, N; Ardron, JA; Neat, F; Bui, X; Callery, O; Grehan, A; Laffargue, P; Roberts, JM; Stirling, D; Taranto, G; Woillez, M; Menot, L
The last two decades have witnessed a complete shift in our perception of the deep sea, from a homogeneous, mostly muddy and unspoiled seafloor to a vast patchwork of diverse and fragile habitats as well as a reservoir of living resources, both energy and mineral. Growing and concomitant awareness of the potential for blue growth and vulnerability of deep-sea ecosystems triggered the implementation of management measures and Marine Spatial Planning (MSP) at national, regional and international levels, which are now cumulating in the UN Decade of Ocean Science for Sustainable Development and the International Conference on Marine Biodiversity of Areas Beyond National Jurisdiction (ABNJ). Based on the best available knowledge collated and produced in the framework of ATLAS, the objective of the present deliverable was to integrate all available data into a common analytical framework for systematic conservation planning at the scale of the North Atlantic.
Regional-scale MSP in the deep sea unfortunately suffers from a lack of knowledge on the distribution of species and habitats. Such large-scale endeavours to date have thus been mainly relying on biogeochemical and physiographic proxies to design networks of marine protected areas. In just three years, ATLAS has taken an unprecedented step forward in synthesising the data available for the North Atlantic on the distribution of the most vulnerable deep-sea habitats where fragile and long-lived engineering species, such as corals and sponges, are aggregating. Such a synthesis has been enabled through trans-Atlantic collaboration. The 13 case studies (CS), evenly distributed from north to south and east to west of the northern Atlantic, provided new discoveries of deep-sea vulnerable habitats off Greenland, in the Alboran Sea and the Gulf of Cádiz, as well as on Formigas and Tropic seamounts. Beyond new discoveries, ATLAS CS confirmed and improved knowledge on the distribution, ecology and functionality of those vulnerable habitats in the North Atlantic. For Case Study 1 – LoVe Observatory, 1417 records of Lophelia pertusa coral reefs along the Norwegian coast are included. For Case Study 6 - Bay of Biscay, a total of 450 records of 12 different VME types, including coral reefs, coral rubbles, scleractinians, Antipatharians, gorgonians, seapens or pennatulids, mixed corals, aggregation of actiniarians, sponge community and Xenophyophores, are reported. For Case Study 7, VMEs are reported for two areas: 1) for Seco de los Olivos, in the Alboran Sea, 17 VMEs that include sea pen fields, deep-sea sponge aggregations and diverse coral gardens are reported, and 2) for the Volcano of Gazul, in the Gulf of Cádiz, 16 VMEs are reported, that include diverse coral gardens, mud and sand emergent fauna, cold-water coral reef of Lophelia pertusa / Madrepora oculata and deep-sea sponge aggregations. For Case Study 8, VMEs from different areas of the Azores are included: in the Formigas Seamount, 18 VMEs including diverse coral gardens and deep-sea sponge aggregations are reported. Cavalo Seamount, a ridge on the Mid-Atlantic Ridge, Gigante Seamount, Condor Seamount, Dom João de Castro Seamount, and Mar de Prata Seamount also host various coral gardens; the South of Pico Island hosts a deep-sea sponge aggregation of Pheronema carpenteri. The newly discovered Hydrothermal Vent Luso is also reported as a VME for the Azores. For Case Study 10 – Davis Strait, Eastern Arctic, 8 VME areas of deep-sea sponges, 5 VME areas of large gorgonian corals, 4 of small gorgonian corals and 13 of sea pens are reported. Under Case Study 10, the only known Lophelia pertusa reef in Greenland waters is also reported. For Case Study 11 – Flemish Cap, three VME types were identified by the Northwest Atlantic Fisheries Organization (NAFO) and for each, several VME areas are reported: 13 VME areas for sponges, 6 for sea pens and 7 for large gorgonians. For Case Study 12 - Mid-Atlantic Canyons and SE USA, four VMEs are included: 1) Cape Lookout Coral Banks, dominated by large bioherms built by Lophelia pertusa, 2) Hatteras Middle Slope, a physically and biologically unique area of rugged mini-canyons (composed of consolidated muds), 3) Norfolk Canyon, and 4) Baltimore Canyon and vicinities, two rugged submarine canyons that contain extensive cold-water corals. For Case Study 13 - Tropic Seamount is host to multiple VMEs, including dense patches of reef framework-forming scleractinian, dense aggregations of coral gardens, dense monospecific sponge ground of Poliopogon amadou, mixed deep-sea sponge aggregations, Xenophyophore field, and dense crinoid fields. Knowledge gained from ATLAS CS significantly increases the database of vulnerable marine ecosystem (VME) occurrences in the northern Atlantic but the species that define VMEs have been known about for over a century. In order to get an overview of the distribution of VMEs, data coming from sources as various as historical cruises, by-catch of fisheries surveys and Remotely Operated Vehicle (ROV) surveys must be compiled. The reliability of these data however varies and a confidence index has thus been developed in order to objectively and quantitatively rank the reliability of VME records according to the source of records. The ranking ranges from low, for inferred records, to high, for visually assessed records. In addition, not all VMEs equally meet the criteria of rarity, functional significance, fragility and recovery, which vary according to taxa and the abundance of indicator taxa. A VME index has thus been developed to quantitatively and objectively score the vulnerability of VME records. The VME index and the confidence index have been applied to the records of the VME database created and curated by the joint ICES/NAFO Working Group on Deep-water Ecology (WGDEC). This spatial grid of VME likelihood was completed with the unequivocal VMEs mapped in the ATLAS CS.
In general, the VME index provides a simplified, spatially aggregated and weighted estimate of the degree to which an area could be considered to contain VMEs under the Food and Agriculture Organisation of the UN (FAO) definition. The VME index clearly highlights areas where a VME is more likely to occur while the associated estimate of confidence gives an indication of how (un)certain that assessment is. The methodology is transparent, science based and data driven, and the aggregate cells can be explored in greater detail to reveal the individual data points that have contributed to the assessment. It integrates far more information than previous methods and as such, better captures the underlying reasoning for identifying VME areas or benthic deep-sea Ecologically or Biologically Significant Marine Areas (EBSAs). The VME index is expected to be updated each year as new data are submitted and will therefore provide an up to date, repeatable and defensible source upon which to base advice as new information is received. The VME index appears to capture most of the important elements of the VME database. This methodology may be considered as a first step towards a systematic approach for the identification and protection of VMEs and EBSAs in the North Atlantic. Our methodology clearly considered several of the steps proposed by Ardron et al. (2014), namely step 1 on assessing potential VME indicator taxa and habitats in a region, step 3 on considering areas already known for their ecological importance, step 4 on compiling information on the distributions of likely VME indicator species and habitats, step 6 on considering fishing impacts, and step 8 on identify ecologically important areas. However, at least one important aspect of the Ardron et al. (2014) framework is missing in the current VME index which refers to understanding the natural distribution of VMEs before significant impacts occurred. This aspect could be considered in future improvements of the VME index to encompass predicted distribution of VME as discussed in Vierod et al. (2014) and Anderson et al. (2016b).
Systematic conservation planning is an explicit, objective-based and quantitative approach for allocating areas for biodiversity conservation, for instance used in Marine Protected Area (MPA) networks design process. It aims to identify priority areas answering specific conservation objectives for each considered species or habitat, whilst minimising the socioeconomic costs of conservation over the study area. For the purpose of systematic conservation planning, data on known or inferred VMEs are still too sparse at the scale of the northern Atlantic. The spatial prioritisation developed here aimed to identify zones of conservation importance for seabed species and habitats associated with VMEs in a comprehensive approach, by complementing the records of unequivocal VMEs and the VME likelihood over the basin resulting from the VME index with supplementary information targeting deep-sea species and habitats. ATLAS modelled the present and future distributions of six coral species indicators of VMEs as well as six exploited fish species (D3.3). Through a collaboration with the H2020 Blue Growth SponGES project, the present and future distribution of one sponge species have also been modelled to provide maps of the distribution of key VME indicator taxa with different environmental requirements, life-history strategies and functional significance. The overlap between the present and future distribution of these species under climate change scenarios further allowed the mapping of their future climate refugia, constituting resilient areas that were given a high conservation target in simulations. Although the primary focus of ATLAS is on cold-water corals, there is more at stake in terms of conversation in the northern Atlantic. In order to increase the scope of this systematic conservation planning exercise, chemosynthetic ecosystems that qualify as VMEs as well as large physiographic features known to be functional hotspots such as canyons, seamounts and fracture zones have also been considered. Conservation scenarios integrated current management and human activities aspects over the basin, to combine the conservation and socioeconomic stakes during the prioritisation process. While areas already profiting from conservation designations such as fishing closures, MPAs and EBSAs were favoured, areas situated in major bottom-fishing grounds or within deep-sea mining contracts were penalised. In order to suggest a geographically balanced protection network, conservation objectives were replicated within 13 provinces, which considered the main biogeographic and geographical boundaries over the basin as well as a dissociation between broad shallow (<800m) and deep (>800m) habitats. This regionalisation approach ensured a regional replication and representativity of each conservation feature within the main deep-sea biotopes. Finally, this work addressed benthic connectivity aspects, by using the results of larvae drift models to favour connected networks of conservation as best as possible.
Emerging from an incremental scenario complexification process, the final simulation (“all management”, Figure 1) resulted in an ecologically coherent conservation network that gave insight into spatial planning possibilities to better protect seabed vulnerable habitats and species. In particular, continental margin slopes, the Mid-Atlantic Ridge, and shelf areas comporting fishing grounds appeared as crucial zones for preserving deep-sea biodiversity (Figure 1). These identified areas comprised of specific habitats (e.g. canyons, ridges, seamounts), concentrating diverse substrates and representing key areas for nutrient circulation, that sustain VMEs and deep-water fish. Even if their depth range is larger, most of the VME indicator taxa used in this study largely occur between 500 and 2500m depths, which were prioritised here. For some species, including gorgonians (Acanella arbuscula, Acanthogorgia armata), scleratinian coral (Lophelia pertusa) and the sponge species (Geodia barretti), future climate refugia are almost exclusively predicted along margin slopes (ATLAS D3.3), that appeared as the most prioritised areas in conservation scenarios. In addition, the Mid-Atlantic Ridge concentrates sites of hydrothermal activity, giving rise to unique chemosynthetic ecosystems. As all known hydrothermal vents south of the Azores Exclusive Economic Zone (EEZ), but also several other VMEs, are located in areas already pre-empted for massive sulphide exploration, these latter contained substantial conservation potential. Identified conservation areas situated within the International Seabed Authority (ISA) contracts could inform the regional management plan to be implemented for preserving the Mid-Atlantic Ridge biodiversity from adverse mining impacts. Finally, the prioritisation results suggest that conservation objectives, especially for demersal fish species, could not be achieved without including large fished areas situated on shelves. This result may promote the development of conservation measures on fishing grounds, from full closures for the most efficient, to species-based catch limitation or minimum fish size. The implementation of such restrictions in EEZs or Regional Fisheries Management Organisations (RFMOs) regulatory areas in Areas Beyond National Jurisdictions (ABNJs) would also contribute to fisheries’ sustainability objectives. Selecting the most prioritised planning units allowed delineation of the main priority areas for deep-sea conservation (Figure 2). Covering approximatively 17% of the study area, these priority areas would answer a relatively high conservation goal for the deep sea, nonetheless they suffer from poor conservation at the moment (Figure 2). Less than 1% of the study area falls into fishing closures and marine reserves that already protect the priority areas for benthic deep-sea ecosystems. For instance, only a few unequivocal VMEs, species climate refugia or canyons currently benefit from some form of protection. In that respect, our systematic planning exercise has shown that, as important as they are, the sum of all Area-Based Management Tools (ABMTs) of the northern Atlantic still suffer from a lack of conservation efficiency, representativity and viability. Moreover, our results highlighted that a more continuous conservation network, displaying corridors or shorter distances between conservation areas, would lead to a more connected and thus more resilient benthic conservation framework. Ultimately, climate change pressures are likely to largely affect deep-sea oceanography and biodiversity, and the ability of current ABMTs to preserve them. Protecting the priority areas herein identified, which hold substantial resilience potential to future environmental changes through the central place of climate refugia in scenarios, could promote the long-term viability of the deep-sea conservation for the North Atlantic. To our knowledge, this study is the first in systematic conservation planning to address the conservation of deep-sea benthic and demersal biodiversity across a whole oceanic basin. These results contribute to the development of systematic approaches for large scale MSP, such as the conservation management of ABNJs currently the object of ongoing international discussions. Lacking of a coordinated framework as well as efficient, permanent and recognised protection measures, the North-Atlantic high seas conservation network could benefit from the suggestions provided by our scientific evaluation. Finally, this basin scale prioritisation will provide general material for local conservation, through a transfer to the MSP work implemented for ATLAS case studies in ATLAS Work Package 6.