Description: Landscape maps based on multivariate cluster analyses provide an objective and comprehensive view on the (marine) environment. They can hence support decision making regarding sustainable ocean resource handling and protection schemes. Across a large number of scales, input parameters and classification methods, numerous studies categorize the ocean into seascapes, hydro-morphological provinces or clusters. Many of them are regional, however, while only a few are on a basin scale. This study presents an automated cluster analysis of the entire Atlantic seafloor environment, based on eight global datasets and their derivatives: Bathymetry, slope, terrain ruggedness index, topographic position index, sediment thickness, POC flux, salinity, dissolved oxygen, temperature, current velocity, and phytoplankton abundance in surface waters along with seasonal variabilities. As a result, we obtained nine seabed areas (SBAs) that portray the Atlantic seafloor. Some SBAs have a clear geological and geomorphological nature, while others are defined by a mixture of terrain and water body characteristics. The majority of the SBAs, especially those covering the deep ocean areas, are coherent and show little seasonal and hydrographic variation, whereas other, nearshore SBAs, are smaller sized and dominated by high seasonal changes. To demonstrate the potential use of the marine landscape map for marine spatial planning purposes, we mapped out local SBA diversity using the patch richness index developed in landscape ecology. It identifies areas of high landscape diversity, and is a practical way of defining potential areas of interest, e.g. for designation as protected areas, or for further research. Clustering probabilities are highest (100%) in the center of SBA patches and decrease towards the edges (〈 98%). On the SBA point cloud which was reduced for probabilities 〈98%, we ran a diversity analysis to identify and highlight regions that have a high number of different SBAs per area, indicating the use of such analyses to automatically find potentially delicate areas. We found that some of the highlights are already within existing EBSAs, but the majority is yet unexplored.

Description: Understanding the dynamics and fate of methane (CH 4 ) release from oceanic seepages on margins and shelves into the water column, and quantifying the budget of its total discharge at different spatial and temporal scales, currently represents a major scientific undertaking. Previous works on the fate of methane escaping from the seafloor underlined the challenge in both, estimating its concentration distribution and identifying gradients. In April 2019, the Envri Methane Cruise has been conducted onboard the R/V Mare Nigrum in the Western Black Sea to investigate two shallow methane seep sites at ∼120 m and ∼55 m water depth. Dissolved CH 4 measurements were conducted with two continuous in-situ sensors: a membrane inlet laser spectrometer (MILS) and a commercial methane sensor (METS) from Franatech GmbH. Additionally, discrete water samples were collected from CTD-Rosette deployment and standard laboratory methane analysis was performed by gas chromatography coupled with either purge-and-trap or headspace techniques. The resulting vertical profiles (from both in situ and discrete water sample measurements) of dissolved methane concentration follow an expected exponential dissolution function at both sites. At the deeper site, high dissolved methane concentrations are detected up to ∼45 m from the seabed, while at the sea surface dissolved methane was in equilibrium with the atmospheric concentration. At the shallower site, sea surface CH 4 concentrations were four times higher than the expected equilibrium value. Our results seem to support that methane may be transferred from the sea to the atmosphere, depending on local water depths. In accordance with previous studies, the shallower the water, the more likely is a sea-to-atmosphere transport of methane. High spatial resolution surface data also support this hypothesis. Well localized methane enriched waters were found near the surface at both sites, but their locations appear to be decoupled with the ones of the seafloor seepages. This highlights the need of better understanding the processes responsible for the transport and transformation of the dissolved methane in the water column, especially in stratified water masses like in the Black Sea.

Description: The Ægir Ridge System (ARS) is an ancient extinct spreading axis in the Nordic seas extending from the upper slope east of Iceland (∼550 m depth), as part of its Exclusive Economic Zone (EEZ), to a depth of ∼3,800 m in the Norwegian basin. Geomorphologically a rift valley, the ARS has a canyon-like structure that may promote increased diversity and faunal density. The main objective of this study was to characterize benthic habitats and related macro- and megabenthic communities along the ARS, and the influence of water mass variables and depth on them. During the IceAGE3 expedition (Icelandic marine Animals: Genetics and Ecology) on RV Sonne in June 2020, benthic communities of the ARS were surveyed by means of a remotely-operated vehicle (ROV) and epibenthic sledge (EBS). For this purpose, two working areas were selected, including abyssal stations in the northeast and bathyal stations in the southwest of the ARS. Video and still images of the seabed were usedtoqualitatively describebenthic habitats based on the presence of habitat-forming taxa and the physical environment. Patterns of diversity and community composition of the soft-sediment macrofauna, retrieved from the EBS, were analyzed in a semiquantitative manner. These biological data were complemented by producing high-resolution bathymetric maps using the vessel’s multi-beam echosounder system. As suspected, we were able to identify differences in species composition and number of macro- and megafaunal communities associated with a depth gradient. A biological canyon effect became evident in dense aggregates of megafaunal filter feeders and elevated macrofaunal densities. Analysis of videos and still images from the ROV transects also led to the discovery of a number ofVulnerable Marine Ecosystems (VMEs) dominated by sponges and soft corals characteristic of the Arctic region. Directions for future research encompass a more detailed, quantitative study of the megafauna and more coherent sampling over the entire depth range in order to fully capture the diversity of the habitats and biota of the region. The presence of sensitive biogenic habitats, alongside seemingly high biodiversity and naturalness are supportive of ongoing considerations of designating part of the ARS as an “Ecologically and Biologically Significant Area” (EBSA).

Description: Aim Seamounts are conspicuous geological features with an important ecological role and can be considered vulnerable marine ecosystems (VMEs). Since many deep‐sea regions remain largely unexplored, investigating the occurrence of VME taxa on seamounts is challenging. Our study aimed to predict the distribution of four cold‐water coral (CWC) taxa, indicators for VMEs, in a region where occurrence data are scarce. Location Seamounts around the Cabo Verde archipelago (NW Africa). Methods We used species presence–absence data obtained from remotely operated vehicle (ROV) footage collected during two research expeditions. Terrain variables calculated using a multiscale approach from a 100‐m‐resolution bathymetry grid, as well as physical oceanographical data from the VIKING20X model, at a native resolution of 1/20°, were used as environmental predictors. Two modelling techniques (generalized additive model and random forest) were employed and single‐model predictions were combined into a final weighted‐average ensemble model. Model performance was validated using different metrics through cross‐validation. Results Terrain orientation, at broad scale, presented one of the highest relative variable contributions to the distribution models of all CWC taxa, suggesting that hydrodynamic–topographic interactions on the seamounts could benefit CWCs by maximizing food supply. However, changes at finer scales in terrain morphology and bottom salinity were important for driving differences in the distribution of specific CWCs. The ensemble model predicted the presence of VME taxa on all seamounts and consistently achieved the highest performance metrics, outperforming individual models. Nonetheless, model extrapolation and uncertainty, measured as the coefficient of variation, were high, particularly, in least surveyed areas across seamounts, highlighting the need to collect more data in future surveys. Main Conclusions Our study shows how data‐poor areas may be assessed for the likelihood of VMEs and provides important information to guide future research in Cabo Verde, which is fundamental to advise ongoing conservation planning.

Description: Multibeam bathymetry raw data was recorded in the North Atlantic during cruise SO276 MerMet 17-6 that took place between 2020-06-22 and 2020-07-26. The data was collected using the ship's own Kongsberg EM 122. Sound velocity profiles (SVP) were applied on the data for calibration. Please see environmental data (zip file) and the cruise report for details.

Description: Multibeam bathymetry raw data was recorded in the North Atlantic during cruise MSM103 that took place between and 2021-09-12 and 2021-11-15. The data was collected using the ship's own Kongsberg EM 122. Sound velocity profiles (SVP) were applied on the data for calibration. Please see environmental data (zip file) and the cruise report for details.

Description: Raw multibeam bathymetry data were collected aboard RV Meteor during cruise M180 using a Kongsberg EM122 multibeam echosounder. The expedition took place during 23.02.2022 - 14.04.2022 from Montevideo (Uruguay) - Cape Town (South Africa) in the Central and Southern Atlantic Ocean. The main aim of M180 is to better understand the fluxes and dissipation of oceanic and atmospheric energy cycles in the surface layer and the ocean interior to improve the parameterisation of these processes in climate models. Data were recorded outside EEZs. Sound velocity profiles (SVP) were applied on the data for calibration. Please see environmental data and the cruise report for details. The data are unprocessed and can therefore contain incorrect depth measurements (artifacts) if not further processed. Note that refraction errors may occur when no proper SVP is applied. Acquisition and provision of the data are part of the DAM Underway Project and published according to the FAIR principles.

Description: Raw multibeam water column data were collected aboard RV MARIA S. MERIAN during cruise MSM107 using a Kongsberg EM 712 multibeam echosounder. The expedition took place during 18.05.2022 and 03.06.2022 from Bremerhaven (Germany) - Tromsø (Norway) in the Northern Atlantic Ocean. Data were recorded outside EEZs. Sound velocity profiles (SVP) were applied on the data for calibration. Please see environmental data and the cruise report for details. The data are unprocessed and can therefore contain incorrect depth measurements (artifacts) if not further processed. Note that refraction errors may occur when no proper SVP is applied. The main aim of MSM107 was to study organic matter formation, transport and transformation on and off the western Irish shelf. The research is part of a larger research project to quantify the contribution from shelf production to deep ocean carbon storage. Acquisition and provision of the data are part of the DAM Underway Project.

Description: Multibeam bathymetry raw data was recorded in the North Atlantic during cruise SO276 MerMet 17-6 that took place between 2020-06-22 and 2020-07-26. The data was collected using the ship's own Kongsberg EM 122. Sound velocity profiles (SVP) were applied on the data for calibration. Please see environmental data (zip file) and the cruise report for details. The bathymetric data acquisition was carried out within the IceAge project which aims to investigate the North Atlantic ecosystem. Working areas have been selected to offer a variability of environments (e.g., variability of water depth, and geological setting (shelf, mid-ocean ridge, deep basin)). The bathymetric data were used to plan ROV dives and sampling stations as well as background for habitat mapping studies.