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Information on the spatial distribution of habitats and vulnerable species is important for conservation planning. In particular, detailed knowledge on connectivity of marine ecosystems in relation to depth and seafloor characteristics is crucial for any proposed conservation and management actions. Yet, the bulk of the seafloor remains under-sampled, unstudied and unmapped, thereby limiting our understanding of connections between shallow and deep-water communities. Recent studies on mesophotic coral ecosystems (MCEs) have highlighted the Western Indian Ocean as a particularly understudied marine region. Here we utilise an autonomous underwater vehicle (AUV) to collect in-situ temperature, oxygen concentration, bathymetry, acoustic backscatter and photographic data on benthic communities from shallow (

The ocean floor, its species and habitats are under pressure from various human activities. Marine spatial planning and nature conservation aim to address these threats but require sufficiently detailed and accurate maps of the distribution of seabed substrates and habitats. Benthic habitat mapping has markedly evolved as a discipline over the last decade, but important challenges remain. To test the adequacy of current data products and classification approaches, we carried out a comparative study based on a common dataset of multibeam echosounder bathymetry and backscatter data, supplemented with groundtruth observations. The task was to predict the spatial distribution of five substrate classes (coarse sediments, mixed sediments, mud, sand, and rock) in a highly heterogeneous area of the south-western continental shelf of the United Kingdom. Five different supervised classification methods were employed, and their accuracy estimated with a set of samples that were withheld. We found that all methods achieved overall accuracies of around 50%. Errors of commission and omission were acceptable for rocky substrates, but high for all sediment types. We predominantly attribute the low map accuracy regardless of mapping approach to inadequacies of the selected classification system, which is required to fit gradually changing substrate types into a rigid scheme, low discriminatory power of the available predictors, and high spatial complexity of the site relative to the positioning accuracy of the groundtruth equipment. Some of these issues might be alleviated by creating an ensemble map that aggregates the individual outputs into one map showing the modal substrate class and its associated confidence or by adopting a quantitative approach that models the spatial distribution of sediment fractions. We conclude that further incremental improvements to the collection, processing and analysis of remote sensing and sample data are required to improve map accuracy. To assess the progress in benthic habitat mapping we propose the creation of benchmark datasets.

The number of marine protected areas (MPAs) has increased dramatically in the last decade and poses a major logistic challenge for conservation practitioners in terms of spatial extent and the multiplicity of habitats and biotopes that now require assessment. Photographic assessment by autonomous underwater vehicle (AUV) enables the consistent description of multiple habitats, in our case including mosaics of rock and sediment. As a case study, we used this method to survey the Greater Haig Fras marine conservation zone (Celtic Sea, northeast Atlantic). We distinguished 7 biotopes, detected statistically significant variations in standing stocks, species density, species diversity, and faunal composition, and identified significant indicator species for each habitat. Our results demonstrate that AUV‐based photography can produce robust data for ecological research and practical marine conservation. Standardizing to a minimum number of individuals per sampling unit, rather than to a fixed seafloor area, may be a valuable means of defining an ecologically appropriate sampling unit. Although composite sampling represents a change in standard practice, other users should consider the potential benefits of this approach in conservation studies. It is broadly applicable in the marine environment and has been successfully implemented in deep‐sea conservation and environmental impact studies. Without a cost‐effective method, applicable across habitats, it will be difficult to further a coherent classification of biotopes or to routinely assess their conservation status in the rapidly expanding global extent of MPAs., Article impact statement: AUVs offer a solution to monitoring challenges posed by the mixed habitats and growing spatial extent of marine protected areas globally.

The decarbonisation of our energy supply is reliant on new technologies that are raw material intensive and will require a significant increase in the production of metals to sustain them. Ferromanganese (FeMn) crusts are seafloor precipitates, enriched in metals such as cobalt and tellurium, both of which have a predicted future demand above current production rates. In this study, we investigate the texture and composition of FeMn crusts on Tropic Seamount, a typical Atlantic guyot off the coast of western Africa, as a basis for assessing the future mineral resource potential of Atlantic Seamounts. The majority of the summit is flat and covered by FeMn crusts with average thicknesses of 3&ndash, 4 cm. The crusts are characterized by two dominant textures consisting of either massive pillared growth or more chaotic, cuspate sections of FeMn oxides, with an increased proportion of detrital and organic material. The Fe, Mn, and Co contents in the FeMn oxide layers are not affected by texture. However, detrital material and bioclasts can form about 50% of cuspate areas, and the dilution effect of this entrained material considerably reduces the Fe, Mn, and Co concentrations if the bulk samples are analyzed. Whilst Tropic Seamount meets many of the prerequisites for a crust mining area, the thickness of the crusts and their average metal composition means extraction is unlikely to be viable in the near future. The ability to exploit more difficult terrains or multiple, closely spaced edifices would make economic feasibility more likely.

The demand for marine-related spatial information has become increasingly apparent in recent years at a European and national scale, due to the increased pressures on the sea-floor environments and marine resources of UK territorial waters. The advent of economically viable swath bathymetry data acquisition in the coastal zone and effective collaborative partnerships between the Channel Coastal Observatory, Maritime and Coastguard Agency, UK Hydrographic Office, British Geological Survey and academic institutions, have opened up new opportunities to produce a robust scientific evidence base to inform integrated coastal zone management objectives and contribute to wider scientific initiatives. Interpretation of high-quality bathymetric data, acoustic backscatter and ground-truthing data allows zones of exposed bedrock, rock outcrops and pinnacles to be identified, along with areas of mobility or stability of surficial sediments. Temporal and spatial analyses of coastal and marine monitoring datasets also contribute to improved understanding of interactions between natural coastal process and coastal-defence and beach-management operations. Furthermore, developments in three-dimensional mapping techniques and visualisation technologies have enabled seamless high-resolution coastal geology maps to be re-interpreted and extended offshore, providing a more complete picture of the baseline geology, physical properties, structure and geohazards in the coastal and nearshore zone. The full paper details the methodology developed to produce a range of indicative marine mapping layers, and presents examples from eastern and southern England where marine-related spatial data has contributed to the multi-disciplinary scientific evidence base to inform development of UK marine policy and planning, coastal management and coastal zone geological mapping.

The increased use of backscatter measurements in time series for environmental monitoring necessitates the comparability of individual results. With the current lack of pre-calibrated multibeam echosounder systems for absolute backscatter measurement, a pragmatic solution is the use of natural reference areas for ensuring regular assessment of the backscatter measurement repeatability. This method mainly relies on the assumption of a sufficiently stable reference area regarding its backscatter signature. The aptitude of a natural area to provide a stable and uniform backscatter response must be carefully considered and demonstrated by a sufficiently long time-series of measurements. Furthermore, this approach requires a strict control of the acquisition and processing parameters. If all these conditions are met, stability check and relative calibration of a system are possible by comparison with the averaged backscatter values for the area. Based on a common multibeam echosounder and sampling campaign completed by available bathymetric and backscatter time series, the suitability as a backscatter reference area of three different candidates was evaluated. Two among them, Carré Renard and Kwinte, prove to be excellent choices, while the third one, Western Solent, lacks sufficient data over time, but remains a valuable candidate. The case studies and the available backscatter data on these areas prove the applicability of this method. The expansion of the number of commonly used reference areas and the growth of the number of multibeam echosounder controlled thereon could greatly contribute to the further development of quantitative applications based on multibeam echosounder backscatter measurements.

Carbonate escarpments are submarine limestone and dolomite cliffs that have been documented in numerous sites around the world. Their geomorphic evolution is poorly understood due to difficulties in assessing escarpment outcrops and the limited resolution achieved by geophysical techniques across their steep topographies. The geomorphic evolution of carbonate escarpments in the Mediterranean Sea has been influenced by the Messinian salinity crisis (MSC). During the MSC (5.97–5.33 Ma), the Mediterranean Sea became a saline basin due to a temporary restriction of the Atlantic-Mediterranean seaway, resulting in the deposition of more than one million cubic kilometres of salt. The extent and relative chronology of the evaporative drawdown phases associated to the MSC remain poorly constrained. In this paper we combine geophysical and sedimentological data from the central Mediterranean Sea to reconstruct the geomorphic evolution of the Malta Escarpment and infer the extent and timing of evaporative drawdown in the eastern Mediterranean Sea during the MSC. We propose that, during a MSC base-level fall, fluvial erosion formed a dense network of canyons across the Malta Escarpment whilst coastal erosion developed extensive palaeoshorelines and shore platforms. The drivers of geomorphic evolution of the Malta Escarpment after the MSC include: (i) canyon erosion by submarine gravity flows, with the most recent activity taking place, This research was undertaken with funding from Marie Curie Career Integration Grant PCIG13-GA-2013-618149 (SCARP), ERC Starting Grants n°258482 (CODEMAP) and n°677898 (MARCAN), and collaborative project n°228344 (EUROFLEETS), all within the 7th European Community Framework Programme and the Horizon 2020 Programme. Financial support was also provided by the Fulbright Visiting Scholar Program, Royal Society of New Zealand (through the International Mobility Fund), New Zealand Crown Research Institute SSIF funding to NIWA, the Griffith Geoscience Awards (Department of Communications, Energy and Natural Resources under the National Geoscience Programme 2007–2013 of Ireland), and the David and Lucile Packard Foundation. MAG acknowledges INSU for cruise-related funding and the European Union FP7 project ASTARTE for post-cruise financial support. The article is based upon work from COST Action CA15103 “Uncovering the Mediterranean salt giant” (MEDSALT) supported by COST (European Cooperation in Science and Technology).

In this paper we present the seabed maps of the shallow-water areas of Lampedusa and Linosa, belonging to the Pelagie Islands Marine Protected Area. Two surveys were carried out (“Lampedusa 2015” and “Linosa 2016”) to collect bathymetric and acoustic backscatter data through the use of a Reson SeaBat 7125 high-resolution multibeam system. Ground-truth data, in the form of grab samples and diver video-observations, were also collected during both surveys. Sediment samples were analyzed for grain size, while video images were analyzed and described revealing the acoustic seabed and other bio-physical characteristics. A map of seabed classification, including sediment types and seagrass distribution, was produced using the tool Remote Sensing Object Based Image Analysis (RSOBIA) by integrating information derived from backscatter data and bathy-morphological features, validated by ground-truth data. This allows to create a first seabed maps (i.e. benthoscape classification), of Lampedusa and Linosa, at scale 1:20 000 and 1:32 000, respectively, that will be checked and implemented through further surveys. The results point out a very rich and largely variable marine ecosystem on the seabed surrounding the two islands, with the occurrence of priority habitats, and will be of support for a more comprehensive maritime spatial planning of the Marine Protected Area.

The most significant breakthroughs in science are often made as a result of technological developments and innovation. A new capacity to gather more data, measure more precisely or make entirely new observations generally leads to new insights and fundamental understanding. The future of ocean research and exploration therefore lies in robotics: marine robotic systems can be deployed at depths and in environments that are out of direct reach for humans, they can work around the clock, and they can be autonomous, freeing up time and money for other activities. To advance the field of submarine geomorphology, the two types of robots that currently make the biggest difference are Remotely Operated Vehicles (ROVs) and Autonomous Underwater Vehicles (AUVs). Other autonomous or robotic systems are available for marine research (e.g. gliders, autonomous surface vehicles, benthic crawlers etc.), but their application for geomorphological studies is less extensive. This chapter gives an overview of the main characteristics of ROVs and AUVs, their advantages and disadvantages, and their main applications for geomorphological research. In comparison to the other geomorphological methods discussed in this book, however, it has to be made clear that ROVs and AUVs are not so much methods per se, instead they are platforms from which existing and new approaches can be applied.

Submarine carbonate escarpments, documented in numerous sites around the world, consist of thick exposures of Mesozoic shallow water carbonate sequences – primarily limestones and dolomites – with reliefs of >1 km and slope gradients of >70°. Whilst most research efforts have focused on the processes that shaped carbonate escarpments into complex and extreme terrains, little attention has been paid to the geomorphology of shelves upslope of carbonate escarpments. In this study we investigate high resolution geophysical, sedimentological and visual data acquired from the eastern Malta Plateau, central Mediterranean Sea, to demonstrate that the outer shelf of a carbonate escarpment is directly influenced by escarpment-forming processes. We document forty eight erosional scars, six long channels and numerous smaller-scale channels, three elongate mounds, and an elongate ridge across the eastern Malta Plateau. By analysing their morphology, seismic character, and sedimentological properties, we infer that the seafloor of the eastern Malta Plateau has been modified by three key processes: (i) Mass movements – in the form of translational slides, spreading and debris flows – that mobilised stratified Plio-Pleistocene hemipelagic mud along the shelf break and that were likely triggered by seismicity and loss of support due to canyon erosion across the upper Malta Escarpment; (ii) NNW-SSE trending sinistral strike-slip deformation in Cenozoic carbonates – resulting from the development of a mega-hinge fault system along the Malta Escarpment since the Late Mesozoic, and SE-NW directed horizontal shortening since the Late Miocene – which gave rise to NW-SE oriented extensional grabens and a NNW-SSE horst; (iii) Flow of bottom currents perpendicular and parallel to the Malta Escarpment, associated with either Modified Atlantic Water flows during sea level lowstands and/or Levantine Intermediate Water flows at present, which was responsible for sediment erosion and deposition in the form of channels and contouritic drifts.