ATLAS advanced our understanding of deep Atlantic marine ecosystems and populations by collecting and integrating high-resolution measurements of ocean circulation with functioning, biological diversity, genetic connectivity, and socioeconomic values. In the Azores, new deep-sea species, new biotopes, new species associations, and even new hydrothermal vent systems have been discovered. We showed that cold-water corals are vulnerable to predicted ocean acidification. Experimental studies combined with meta-analysis on chemical dissolution and biological erosion of coral reefs worldwide showed that the increased dissolution of the coral framework under OA is a key factor determining the future survival of reef ecosystems. Statistical models showed that many VME indicator taxa and commercially important deep-sea fish species might be facing a reduction in the suitable habitat and a northward shift in distribution under future climate change scenarios. We assisted in developing innovative technological solutions for deep-sea research and informed marine policy at the regional, national, European, and international levels.

1. Deep-sea discoveries: The Azores region was found to harbour particularly diverse coral gardens, forming at least seven distinct coral garden communities dominated by different species of octocorals discovered during ATLAS cruises. Both historical and new knowledge generated during ATLAS have demonstrated the Azores as a hotspot of CWC diversity, representing the highest species richness known of Octocorallia in Europe and in any of the North Atlantic archipelagos. ATLAS also contributed to the identification of several new species to science.
2. New hydrothermal vent discovered: A new hydrothermal vent field was discovered on the slopes of Gigante, a seamount on the Mid-Atlantic Ridge in the seas of the Azores. This system differs considerably from other known hydrothermal fields along the MAR in terms of fluid chemistry with dominance of hydrogen and iron, and low temperature.
3. New areas that fit the Vulnerable Marine ecosystem criteria: Eight areas in the Azores were identified as VMEs composed of diverse coral gardens, deep-sea sponge aggregations and hydrothermal vent. These were Cavalo Seamount, a ridge on the Mid-Atlantic Ridge, Gigante Seamount, Condor Seamount, Dom João de Castro Seamount, and Mar de Prata Seamount because of various coral gardens; the South of Pico Island because of a deep-sea sponge aggregation of Pheronema carpenteri; and the newly discovered Hydrothermal Vent Luso.
4. Predicted distribution: Habitat suitability models developed for 13 vulnerable marine ecosystems indicator taxa in the Azores EEZ, showed a strong association of the predicted distribution of CWC taxa with areas of local relief, being them island shelves or slopes, ridges or seamounts. However, even among areas of similar depths, models discriminated between suitable and unsuitable zones showing that model outputs were not exclusively driven by depth correlated changes in environmental predictors.
5. Impact of climate change on food supply and survival of deep-sea ecosystems: Results from a series of ATLAS experiments on the physiology of cold-water corals and deep-water sponges revealed that cumulative effects of climate change on food supply and ocean acidification impact the distribution and function of corals. This work highlighted that, as a result of climate change, predicted decreases in food availability and responses to ocean acidification will likely impact long-term growth and life cycles of corals. A better understanding of the interactive effects of climate change on deep-sea ecosystems supports accurate monitoring, modelling and future predictions.
6. Predictive maps for future habitat suitability: ATLAS partners have modelled and developed predictive maps of habitat suitability for six cold-water coral and six deep-sea fish species under current conditions and forecast changes under future projected high-emission climate conditions for the whole North Atlantic Ocean. The results forecasted that over 50% of cold-water coral habitats could be at risk, and suitable habitats for commercially important deep-sea fish could shift by up to 100 km northwards. This work has important implications for the designation of effective area-based conservation measures and adaptive management strategies.
7. Good Environmental Status in the deep-sea: We participated in a preliminary assessment of the environmental status of selected North Atlantic deep-sea ecosystems. We suggested that the low availability of long-term data sets limits our knowledge about natural variability and human impacts in the deep sea, preventing a more systematic assessment of habitat and ecosystem components in the deep sea.
8. Low-cost imaging systems to observe the deep sea: Two custom-made underwater camera systems (live-view drift camera and a stereo-baited remote video) have been developed in collaboration with MapGES and iAtlantic projects, allowing greater data collection and spatial coverage at a reduced cost. The design and development of both systems will improve the capacity to monitor and explore the deep-sea bed and commercially important fish populations.
9. An index to identify biodiversity hotspots: ATLAS developed a novel multi-criteria assessment method to more objectively identify Vulnerable Marine Ecosystems (VMEs) in the North-East Atlantic Ocean, often biodiversity hotspots. The method evaluates how likely a given area of the seafloor is to represent a VME, providing a more systematic and standardised approach (robust and repeatable numeric method) for assessing and identifying VME regions in the North-East Atlantic Ocean.
10. Using eDNA and quantitative PCR to assess biodiversity in the open ocean: we contributed to the development and test of six species-specific environmental (e)DNA assays. This work demonstrates that eDNA methods can be developed for detecting the presence of target species in pelagic and deep-water environments, and can be used to assess species distributions over space and time.
11. ‘Luso’ hydrothermal vent field declared as Marine Protected Area: The Luso hydrothermal vent field was discovered during the Blue Azores Expedition in 2018, in which ATLAS led Remotely Operated Vehicle operations. In September 2019, the Regional Government of the Azores declared the Luso hydrothermal vent field a Marine Protected Area (Portaria no. 68/2019), based on the ATLAS findings. This transformation of ATLAS research into policy will ensure deep-sea ecosystems in the Azores are preserved and can be incorporated into plans for sustainable exploitation.
12. Input to the Convention on Biological Diversity (CBD) regional workshop on Ecologically or Biologically Significant marine Areas (EBSA) in the North-East Atlantic Ocean: The data provided by ATLAS contributed to the submission of several features that meet the EBSA criteria, including the Mid-Atlantic Ridge. This work supports the implementation of the EBSA process and informs future management measures in the deep sea.
13. Area-based resource management plans for ATLAS case studies: ATLAS has developed systematic conservation planning approaches to support area-based management plans in the Azores and the North Atlantic Ocean.