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 ...

The Madeira archipelago has a unique underwater landscape that is characterised by narrow shelves, steep slopes and a large submarine tributary system that boosts primary productivity in oligotrophic waters and thus offers a potential for hotspots of biodiversity. Despite this, there have been limited deep-water exploration activities with less than five expeditions since the 1960s. Here, we investigated the seabed on the southern side of the Madeira-Desertas Ridge using a manned submersible along a 3.8 km long transect starting at 366 m depth up the ridge shelf until its top at 73 m. Benthic habitats and community composition were documented with video along a depth gradient from mesophotic to deep sea. Six distinct biotopes were recognised (three deeper, and three shallower than 115 m depth). Our results showed a rich biodiversity with deep biotopes characterised by sponges and non-reef-building corals (e.g., Pachastrella monilifera, Viminella flagellum, Eunicella verrucosa) and shallow biotopes comprising macroalgae and the gorgonian Paramuricea cf. grayi. The pronounced benthic zonation reflects the steep environmental gradient that includes high topographic variation, heterogeneous substrates, and bidirectional regular wave-motion at the shallow mesophotic part. Together with biotic factors, such as low density of sea urchins and presence of predatory fish, this environment with unusual deep light penetration, a mesoscale cyclonic eddy, and deep wave-motion, has allowed the establishment of a mature deep-water kelp population of Laminaria ochroleuca in the plateau (max. >100 individuals p/100 m2). At the same time, a conspicuous coral fauna was observed on a wide range of soft to hard bottoms with several species taking advantage of the favourable hydrodynamic regime and seawater properties together with substratum availability to create coral gardens. These habitats were previously not known from Madeira, and their newfound discovery in the archipelago merit further investigation and protection.