Seamounts are proposed to be hotspots of deep-sea biodiversity, a pattern potentially arising from increased productivity in a heterogeneous landscape leading to either high species co-existence or species turnover (beta diversity). However, studies on individual seamounts remain rare, hindering our understanding of the underlying causes of local changes in beta diversity. Here, we investigated processes behind beta diversity using ROV video, coupled with oceanographic and quantitative terrain parameters, over a depth gradient in Annan Seamount, Equatorial Atlantic. By applying recently developed beta diversity analyses, we identified ecologically unique sites and distinguished between two beta diversity processes: species replacement and changes in species richness. The total beta diversity was high with an index of 0.92 out of 1 and was dominated by species replacement (68%). Species replacement was affected by depth-related variables, including temperature and water mass in addition to the aspect and local elevation of the seabed. In contrast, changes in species richness component were affected only by the water mass. Water mass, along with substrate also affected differences in species abundance. This study identified, for the first time on seamount megabenthos, the different beta diversity components and drivers, which can contribute towards understanding and protecting regional deep-sea biodiversity.

Video and image data are regularly used in the field of benthic ecology to document biodiversity. However, their use is subject to a number of challenges, principally the identification of taxa within the images without associated physical specimens. The challenge of applying traditional taxonomic keys to the identification of fauna from images has led to the development of personal, group, or institution level reference image catalogues of operational taxonomic units (OTUs) or morphospecies. Lack of standardisation among these reference catalogues has led to problems with observer bias and the inability to combine datasets across studies. In addition, lack of a common reference standard is stifling efforts in the application of artificial intelligence to taxon identification. Using the North Atlantic deep sea as a case study, we propose a database structure to facilitate standardisation of morphospecies image catalogues between research groups and support future use in multiple front-end applications. We also propose a framework for coordination of international efforts to develop reference guides for the identification of marine species from images. The proposed structure maps to the Darwin Core standard to allow integration with existing databases. We suggest a management framework where high-level taxonomic groups are curated by a regional team, consisting of both end users and taxonomic experts. We identify a mechanism by which overall quality of data within a common reference guide could be raised over the next decade. Finally, we discuss the role of a common reference standard in advancing marine ecology and supporting sustainable use of this ecosystem.

Deep-sea fish species are targeted globally by bottom trawling. The species captured are often characterized by longevity, low fecundity and slow growth making them vulnerable to overfishing. In addition, bottom trawling is known to remove vast amounts of non-target species, including habitat forming deep-sea corals and sponges. Therefore, bottom trawling poses a serious risk to deep-sea ecosystems, but the true extent of deep-sea fishery catches through history remains unknown. Here, we present catches for global bottom trawling fisheries between years 1950-2015. This study gives new insight into the history of bottom trawled deep-sea fisheries through its use of FAO capture data combined with reconstructed catch data provided by the Sea Around Us -project, which are the only records containing bycatches, discards and unreported landings for deep-sea species. We illustrate the trends and shifts of the fishing nations and discuss the life-history and catch patterns of the most prominent target species over this time period. Our results show that the landings from deep-sea fisheries are miniscule, contributing less than 0.5% to global fisheries landings. The fisheries were found to be overall under-reported by as much as 42%, leading to the removal of an estimated 25 million tons of deep-sea fish. The highest catches were of Greenland halibut in the NE Atlantic, Longfin codling from the NW Pacific and Grenadiers and Orange roughy from the SW Pacific. The results also show a diversification through the years in the species caught and reported. This historical perspective reveals that the extent and amount of deep-sea fish removed from the deep ocean exceeds previous estimates. This has significant implications for management, conservation and policy, as the economic importance of global bottom trawling is trivial, but the environmental damage imposed by this practice, is not.

Modeling of Deep-Sea Sponge Grounds GAMs, Maxent and RF showed similar performance in terms of evaluation statistics but a different prediction, with RF showing the highest differences. This algorithm only retained depth and maximum currents whereas GAM and Maxent included bathymetric position index, slope, aspect and backscatter. In these latter two models, P. amadou showed a preference for high backscatter values and areas slightly elevated, flat or with gentle slopes and with a NE orientation. The lack of significant differences in model performance permitted to merge all predictions using an ensemble model approach. Our results contribute toward understanding the environmental drivers and biogeography of the species in the Atlantic. Furthermore, we present a case toward designating the Tropic Seamount as an Ecologically or Biologically Significant marine Area (EBSA) as a contribution to address biodiversity conservation in ABNJs.

International audienc

75Video and image data are regularly used in the field of benthic ecology to document 76 biodiversity. However, their use is subject to a number of challenges, principally the 77 identification of taxa within the images without associated physical specimens. The 78 challenge of applying traditional taxonomic keys to the identification of fauna from 79 images has led to the development of personal, group, or institution level reference 80 image catalogues of operational taxonomic units (OTUs) or morphospecies. Lack of 81 standardisation among these reference catalogues has led to problems with 82 observer bias and the inability to combine datasets across studies. In addition, lack 83 of a common reference standard is stifling efforts in the application of artificial 84 intelligence to taxon identification. Using the North Atlantic deep sea as a case 85 study, we propose a database structure to facilitate standardisation of 86 morphospecies image catalogues between research groups and support future use 87 in multiple front-end applications. We also propose a framework for coordination of 88 international efforts to develop reference guides for the identification of marine 89 species from images. The proposed structure follows the Darwin Core standard to 90 allow integration with existing databases. We suggest a management framework 91 where high-level taxonomic groups are curated by a regional team, consisting of 92 both end users and taxonomic experts. We identify a mechanism by which overall 93 quality of data within a common reference guide could be raised over the next 94 decade. Finally, we discuss the role of a common reference standard in advancing 95 marine ecology and supporting sustainable use of this ecosystem. 96 6 97 100 the sunlit Mediterranean seabed, for the first clear images to be produced [2]. 101 Following this, the use of underwater photography became widespread in shallow 102 seas, opening up this environment to a wider public (e.g. [3]). The first deep-sea 103 photograph was taken from the porthole of a bathysphere in the early 1930s [4] and 104 shortly after, the first self-contained deep-sea photographic systems were developed 105in the 1940s at the Woods Hole Oceanographic Institution [5,6]. Whilst there were 106 many good deep-sea photographs available between this time and the early 1970s 107 [7,8], few biologists studied them, as often no corresponding samples of animals 108 were taken, making identification difficult [9]. The notable exceptions to this [9,10, 11, 109 12, 13, 14] paved the way for photography to become established as an important 110 tool for the study of deep-water environments [15, 16, 17, 18, 19]. Today, with the 111 routine use of seafloor cameras, towed camera platforms, remotely operated and 112 autonomous underwater vehicles (ROVs and AUVs), photographic assessment of 113 marine fauna and faunal assemblages is a vital tool for research used by both 114 scientists and industry [20, 21, 22]. 115 Imaging is an important non-destructive tool for studying ...

Evidence of hydrothermal venting on the ultra-slow spreading Gakkel Ridge in the Central Arctic Ocean has been available since 2001, with first visual evidence of black smokers on the Aurora Vent Field obtained in 2014. But it was not until 2021 that the first ever remotely operated vehicle (ROV) dives to hydrothermal vents under permanent ice cover in the Arctic were conducted, enabling the collection of vent fluids, rocks, microbes, and fauna. In this paper, we present the methods employed for deep-sea ROV operations under drifting ice. We also provide the first description of the Aurora Vent Field, which includes three actively venting black smokers and diffuse flow on the Aurora mound at ~3,888 m depth on the southern part of the Gakkel Ridge (82.5°N). The biological communities are dominated by a new species of cocculinid limpet, two small gastropods, and a melitid amphipod. The ongoing analyses of Aurora Vent Field samples will contribute to positioning the Gakkel Ridge hydrothermal vents in the global biogeographic puzzle of hydrothermal vents.

Deep-sea fisheries occur at depths between 200 and 1800 m, using bottom trawls, long lines, and occasionally pots and gillnets. These fisheries were of minor interest and value until the mid-1980s when large stocks of fish were discovered, mostly on high-seas seamounts. However, because of the life-history characteristics of deep-dwelling fish, most seamount fish stocks were soon overfished, and few have recovered. Total deep-sea fish catch since 1950 represents about 3 per cent of the global catch, yet the environmental harm caused to deep-sea bottom communities by bottom trawling is extensive and long lasting, far exceeding the value of the fishery. In response, the United Nations has passed several resolutions since 2004 requiring the establishment of regional fisheries management organisations (RFMOs) who would be responsible for setting catch limits for the target species and requiring actions that would limit the damage to the habitat by fishing gear. To date, the latter of these two requirements, at least, has not been successfully met.