The deep sea plays a critical role in global climate regulation through uptake and storage of heat and carbon dioxide. However, this regulating service causes warming, acidification and deoxygenation of deep waters, leading to decreased food availability at the seafloor. These changes and their projections are likely to affect productivity, biodiversity and distributions of deep‐sea fauna, thereby compromising key ecosystem services. Understanding how climate change can lead to shifts in deep‐sea species distributions is critically important in developing management measures. We used environmental niche modelling along with the best available species occurrence data and environmental parameters to model habitat suitability for key cold‐water coral and commercially important deep‐sea fish species under present‐day (1951–2000) environmental conditions and to project changes under severe, high emissions future (2081–2100) climate projections (RCP8.5 scenario) for the North Atlantic Ocean. Our models projected a decrease of 28%–100% in suitable habitat for cold‐water corals and a shift in suitable habitat for deep‐sea fishes of 2.0°–9.9° towards higher latitudes. The largest reductions in suitable habitat were projected for the scleractinian coral Lophelia pertusa and the octocoral Paragorgia arborea, with declines of at least 79% and 99% respectively. We projected the expansion of suitable habitat by 2100 only for the fishes Helicolenus dactylopterus and Sebastes mentella (20%–30%), mostly through northern latitudinal range expansion. Our results projected limited climate refugia locations in the North Atlantic by 2100 for scleractinian corals (30%–42% of present‐day suitable habitat), even smaller refugia locations for the octocorals Acanella arbuscula and Acanthogorgia armata (6%–14%), and almost no refugia for P. arborea. Our results emphasize the need to understand how anticipated climate change will affect the distribution of deep‐sea species including commercially important fishes and foundation species, and highlight the importance of identifying and preserving climate refugia for a range of area‐based planning and management tools.

summaRY: The fauna of molluscs associated with deep subtidal Zostera marina beds (12-16 m) in southern spain (alboran sea) has been characterised in terms of micro-habitat preference, feeding guilds and biogeographical affinity. The species list (162 taxa) is based on sampling completed before the strong eelgrass decline experienced in 2005-2006, using different methods (small agassiz trawl covering 222 m 2 and quadrates covering 0.06 m 2 ) and different temporal scales (months, day/night). dominant epifaunal species are Jujubinus striatus, Rissoa spp. and Smaragdia viridis in the leaf stratum and Nassarius pygmaeus, Bittium reticulatum and Calliostoma planatum on the sediment. nevertheless, the infauna dominated the epifauna in terms of number of individuals, including mainly bivalves (Tellina distorta, T. fabula, Dosinia lupinus). The epifauna of both the sediment and leaf strata included high numbers of species, probably due to the soft transition between vegetated and unvegetated areas. The dominant feeding guilds were deposit feeders, filter feeders and peryphiton grazers, but ectoparasites (eulimids), seagrass grazers (Smaragdia viridis) and an egg feeder (Mitrella minor) also occurred, unlike in other eelgrass beds of europe. The molluscan fauna of these Z. marina beds is essentially derived from the local fauna, which includes many widely distributed species along european coasts, with a low representation of strictly mediterranean or strictly atlantic species. This fauna is richer than that found in other eelgrass beds of europe, and deserves important attention for conservation.Keywords: bivalves, gastropods, seagrass, biodiversity, alboran sea, biogeographical distribution.Resumen: Una comunidad altamente diversa de moluscos asociados a praderas de Zostera marina del mar de Alborán: preferencias de micro-hábitat, grupos tróficos y distribución biogeográfica. -La fauna de moluscos asociada a praderas infralitorales profundas de Zostera marina (12-16 m) del sur de españa (mar de alborán) ha sido caracterizada en relación a su micro-hábitat preferente, grupo trófico y distribución biogeográfica. el listado faunístico (162 especies) se obtuvo antes de la fuerte regresión sufrida entre los años 2005 y 2006, usando diferentes métodos (pequeño patín de agassiz que muestreaba 222 m 2 y cuadrantes que muestreaban 0.06 m 2 ) y escalas temporales (meses, día/noche). Las especies dominantes asociadas al estrato foliar son Jujubinus striatus, Rissoa spp. y Smaragdia viridis y al sedimento son Nassarius pygmaeus, Calliostoma planatum y Bittium reticulatum, entre otras. no obstante, la endofauna domina a la epifauna, incluyendo principalmente bivalvos como Tellina distorta, T. fabula y Dosinia lupinus. La epifauna asociada al sedimento y al estrato foliar tiene una gran riqueza de especies, probablemente debido a la suave transición entre zonas cubiertas y no cubiertas. Los grupos tróficos dominantes fueron los depositívoros, filtradores o ramoneadores, pero ectoparásitos (eulímidos) y consumidores de fanerógamas ma...

Circulation patterns in the North Atlantic Ocean have changed and reorganized multiple times over millions of years, influencing the biodiversity, distribution, and connectivity patterns of deep-sea species and ecosystems. In this study, we review the effects of the water mass properties (temperature, salinity, food supply, carbonate chemistry, and oxygen) on deep-sea benthic megafauna (from species to community level) and discussed in future scenarios of climate change. We focus on the key oceanic controls on deep-sea megafauna biodiversity and biogeography patterns. We place particular attention on cold-water corals and sponges, as these are ecosystem-engineering organisms that constitute vulnerable marine ecosystems (VME) with high associated biodiversity. Besides documenting the current state of the knowledge on this topic, a future scenario for water mass properties in the deep North Atlantic basin was predicted. The pace and severity of climate change in the deep-sea will vary across regions. However, predicted water mass properties showed that all regions in the North Atlantic will be exposed to multiple stressors by 2100, experiencing at least one critical change in water temperature (+2 • C), organic carbon fluxes (reduced up to 50%), ocean acidification (pH reduced up to 0.3), aragonite saturation horizon (shoaling above 1000 m) and/or reduction in dissolved oxygen (>5%). The northernmost regions of the North Atlantic will suffer the greatest impacts. Warmer and more acidic oceans will drastically reduce the suitable habitat for ecosystem-engineers, with severe consequences such as declines in population densities, even compromising their long-term survival, loss of biodiversity and reduced biogeographic distribution that might compromise connectivity at large scales. These effects can be aggravated by reductions in carbon fluxes, particularly in areas where food availability is already limited. Declines in benthic biomass and biodiversity will diminish ecosystem services such as habitat provision, nutrient

Table S1. List of the mollusc species collected in the survey between Cabopino and Calaburras, Málaga province, Spain. T1: transect off Torre de Calahonda; T2: transect off Torre Pesetas, T3: transect west of the river "Cala del Moral"; T4: transect west of "Cabezo del Fraile". The numbers given for each sampling point are the total live collected specimens for all replicates and all seasonal sampling campaigns.

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