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Vertical walls of submarine canyons represent features of high conservation value that can provide natural areas of protection for vulnerable marine ecosystems under increasing anthropogenic pressure from deep-sea trawling. Wall assemblages are spatially heterogeneous, attributed to the high environmental heterogeneity over short spatial scales that is a typical feature of canyons. Effective management and conservation of these assemblages requires a deeper understanding of the processes that affect faunal distribution patterns. Canyons are recognised as sites of intensified hydrodynamic regimes, with focused internal tides enhancing near-bed currents, turbulent mixing and nepheloid layer production, which influence faunal distribution patterns. Faunal patterns also respond to broad-scale hydrodynamics and gradients in water mass properties (e.g. temperature, salinity, dissolved oxygen concentration). Oscillating internal tidal currents can advect such gradients, both vertically and horizontally along a canyon's walls. Here we take an interdisciplinary approach using biological, hydrodynamic and bathymetry-derived datasets to undertake a high-resolution analysis of a subset of wall assemblages within Whittard Canyon, North-East Atlantic. We investigate if, and to what extent, patterns in diversity and epibenthic assemblages on deep-sea canyon walls can be explained by spatial and temporal variability induced by internal tides. Vertical displacement of water mass properties by the internal tide was calculated from autonomous ocean glider and shipboard CTD observations. Spatial patterns in faunal assemblage structure were determined by cluster analysis and non-metric Multi-Dimensional Scaling plots. Canonical Redundancy Analysis and Generalised Linear Models were then used to explore relationships between faunal diversity and assemblage structure and a variety of environmental variables. Our results support the hypothesis that internal tides influence spatial heteroge

Ocean ecosystems are at the forefront of the climate and biodiversity crises, yet we lack a unified approach to assess their state and inform sustainable policies. This blueprint is designed around research capabilities and cross-sectoral partnerships. We highlight priorities including integrating basin-scale observation, modelling and genomic approaches to understand Atlantic oceanography and ecosystem connectivity; improving ecosystem mapping; identifying potential tipping points in deep and open ocean ecosystems; understanding compound impacts of multiple stressors including warming, acidification and deoxygenation; enhancing spatial and temporal management and protection. We argue that these goals are best achieved through partnerships with policy-makers and community stakeholders, and promoting research groups from the South Atlantic through investment and engagement. Given the high costs of such research (€800k to €1.7M per expedition and €30–40M for a basin-scale programme), international cooperation and funding are integral to supporting science-led policies to conserve ocean ecosystems that transcend jurisdictional borders.

Marine litter is one of the most pervasive and fast-growing aspects of contamination in the global ocean, and has been observed in every environmental setting, including the deep seafloor where little is known about the magnitude and consequences of the problem. Submarine canyons, the main conduits for the transport of sediment, organic matter and water masses from shallow to abyssal depths, have been claimed to be preferential pathways for litter transport and accumulation in the deep sea. This is supported by ongoing evidence of large litter piles at great water depths, highlighting efficient transfer via canyons. The aim of this article is to present an overview of the current knowledge about marine litter in submarine canyons, taking a geological, process-based point of view. We evaluate sources, transport mechanisms and deposition of litter within canyons to assess the main factors responsible for its transport and accumulation in the deep sea. Few studies relate litter distribution to transport and depositional processes; nevertheless, results from available literature show that canyons represent accumulation areas for both land-based and maritime-based litter. Particularly, accumulation of fishing-related debris is mainly observed at the canyon heads and walls and is related to fishing activities carried out in and adjacent to canyons, while transport and accumulation of general waste and plastic along canyon axes can be related to different mechanisms, encompassing enhanced bottom currents, dense water cascading and turbidity currents, and is related to the proximity of canyons to shore. Global assessment of canyons exposure to riverine plastic inputs and fishing-related debris indicates varying susceptibility of canyons to litter, also highlighting that most of the canyons prone to receive large amounts of anthropogenic debris have not yet been surveyed. Considering that litter research in canyons is still in its infancy, several knowledge gaps need to be f

Sailing on scientific expeditions as an early career researcher (ECR) offers the beneficial opportunity to gain field experience and training. However, the number of available berths to achieve the scientific goals of an expedition limits the number of onboard participants. Telepresence and remote learning can be utilized to increase the number of active participants, broadening the reach of capacity development. The 2021 iMirabilis2 expedition on board the Spanish Research Vessel Sarmiento de Gamboa used telepresence to virtually involve ECRs from several countries in deep-sea science. One year post-expedition, a survey of onshore participants was conducted to assess and quantify the effectiveness of the peer-to-peer ECR ship-to-shore scheme. During the expedition, live, interactive training via WhatsApp and Zoom was utilized by onshore ECRs more than traditional static, unidirectional methods of blog posts and pre-recorded videos. All respondents either agreed or strongly agreed that the scheme provided an inclusive and accessible platform to share deep-sea science. These results suggest similar schemes could be used to supplement shorter-duration at-sea-training, used prior to a seagoing experience to better prepare ECRs, or to allow members of the science community unable to join an expedition in person to actively participate remotely, increasing inclusivity.

Cold-water corals (CWCs) are important species that provide habitat for other taxa but are sensitive to mechanical damage from bottom trawling. CWC conservation has been implemented in the form of marine protected areas (MPAs), but recovery from impact may be particularly slow in the deep-sea environment; consequently, the use of restoration techniques has been considered. To gain some insight into CWC recruitment and growth, in 2011 we deployed small seabed moorings in the Darwin Mounds MPA (~1,000 m water depth). This site hosts hundreds of CWC mounds, that had previously (until 2003) been impacted by deep-water trawling. In 2019, we carried out in situ visual surveys of these moorings and the surrounding seabed environment, then recovered two of the moorings. The mooring buoys, glass floats with plastic covers, were extensively colonized by a diverse epifauna that included the CWCs Desmophyllum pertusum and D. dianthus. The presence of coral recruits indicated that environmental conditions, and larval supply, remained favorable for the settlement and growth of CWCs within the MPA. Based on our observations, we consider four possible restoration methods, together with a “do-nothing” option, for the Darwin Mounds CWCs that have shown little, if any, natural recovery despite 16 years of protection. We conclude that seabed emplacement of high-relief artificial substrata is likely to be the most efficient and cost-efficient means of promoting enhanced recovery of the CWC

Accurate knowledge of the spatial extent of seagrass habitats is essential for monitoring and management purposes given their ecological and economic significance. Extent data are typically presented in binary (presence/absence) or arbitrary, semi-quantitative density bands derived from low-resolution satellite imagery, which cannot resolve fine-scale features and intra-habitat variability. Recent advances in consumer-grade unoccupied aerial vehicles (UAVs) have advanced our ability to survey large areas at higher resolution and at lower cost. This has improved the accessibility of mapping technologies to developing coastal nations, where a large proportion of the world’s seagrass habitats are found. Here, we present the application of UAV-gathered imagery to determine seagrass habitat extent and percent of canopy cover. Four contrasting sites were surveyed in the Turneffe Atoll Marine Reserve, Belize, and seagrass canopy cover was ground truthed from in situ quadrats. Orthomosaic images were created for each site from the UAV-gathered imagery. Three modelling techniques were tested to extrapolate the findings from quadrats to spatial information, producing binary (random forest) and canopy cover (random forest regression and beta regression) habitat maps. The most robust model (random forest regression) had an average absolute error of 6.8–11.9% (SE of 8.2–14), building upon previous attempts at mapping seagrass density from satellite imagery, which achieved errors between 15–20% approximately. The resulting maps exhibited great intra-habitat heterogeneity and different levels of patchiness, which were attributed to site energetics and, possibly, species composition. The extra information in the canopy cover maps provides greater detail and information for key management decisions and provides the basis for future spatial studies and monitoring programmes.

This work presents the geomorphologic characterization of the Blanes Canyon (northwestern Mediterranean), based on high- and very-high resolution multibeam bathymetry acquired in the framework of the ABRIC project. High-resolution hullmounted multibeam data (up to 5 m grid size) were collected along the entire submarine canyon head using a Kongsberg EM710 multibeam echo sounder (MBES). Additionally, the Hybrid Remotely Operated Vehicle (H-ROV) “Ariane” was used to acquire finescale morphology of vertical rocky walls within the canyon with unprecedented detail (80 cm grid size). The vertical mapping was performed using an EM2040 MBES mounted on the front of the H-ROV with a 45° orientation. High-resolution video footage was acquired on the same canyon walls with the ROV “Liropus”. Blanes Canyon has a marked structural character, deeply incising the margin and exposing Miocene to Pliocene successions. The tectonic control is evidenced by the rectilinear trajectories and sharp bends of the canyon axis, and by the presence of vertical rocky walls that can reach up 300 m in height. The canyon is asymmetric and has a smoothed eastern flank and a western flank dominated by a dendritic lattice of gullies. H-ROV bathymetric data on vertical cliffs allowed to trace the horizontal strata of Miocene ages, which offer the substrate for the development of benthic communities. Other identified fine-scale morphological elements include terraces, thalweg incision, under-cutting, scarps and rock avalanches. The study of the different-scale morphologies found in the canyon will allow a better understanding of its evolution trough time and the erosive processes involved

To investigate the topographic constraints caused by submarine canyon walls on near-bottom currents, four moorings arrays were deployed in the Blanes Canyon (NW Mediterranean) at ~600 m water depth during winter and spring 2020. Two moorings were placed at a main canyon head and two at the head of a canyon tributary, in regions characterized by narrow gorges and the presence of vertical canyon walls. This study was carried out during the Spanish ABRIC Project aimed to investigate sediment transport mechanisms and their influence on suspension feeder benthic communities. Preliminary results reveal that near-bottom currents were aligned with the canyon wall orientations and oscillated up- and down-canyon mainly at inertial frequencies. The highest current velocities measured at both study sites were ~35 cm/s and directed up-canyon, although the residual flows in both monitored sites were predominantly downcanyon. Suspended sediment concentrations did not exceed 4 mg/L and they mainly increased during down-canyon flows, which contributed to a continuous and persistent transfer of suspended particles towards deeper parts of the canyon. These new findings reveal a complex interaction between local hydrodynamics and steep canyon morphologies, which ultimately affect the ambient suspended sediment transport throughout the canyon, potentially driving the settlement and development of benthic communities inhabiting submarine canyon walls

Despite cold-water coral (CWC) reefs being considered biodiversity hotspots, very little is known about the main processes driving their morphological development. Indeed, there is a considerable knowledge gap in quantitative experimental studies that help understand the interaction between reef morphology, near-bed hydrodynamics, coral growth, and (food) particle transport processes. In the present study, we performed a 2-month long flume experiment in which living coral nubbins were placed on a reef patch to determine the effect of a unidirectional flow on the growth and physiological condition of Lophelia pertusa. Measurements revealed how the presence of coral framework increased current speed and turbulence above the frontal part of the reef patch, while conditions immediately behind it were characterised by an almost stagnant flow and reduced turbulence. Owing to the higher current speeds that likely promoted a higher food encounter rate and intake of ions involved in the calcification process, the coral nubbins located on the upstream part of the reef presented a significantly enhanced average growth and a lower expression of stress-related enzymes than the downstream ones. Yet, further experiments would be needed to fully quantify how the variations in water hydrodynamics modify particle encounter and ion intake rates by coral nubbins located in different parts of a reef, and how such discrepancies may ultimately affect coral growth. Nonetheless, the results acquired here denote that a reef influenced by a unidirectional water flow would grow into the current: a pattern of reef development that coincides with that of actual coral reefs located in similar water flow settings. Ultimately, the results of this study suggest that at the local scale coral reef morphology has a direct effect on coral growth thus, indicating that the spatial patterns of living CWC colonies in reef patches are the result of spatial self-organisation