RRS James Cook Cruise 35, 7-19 Jun 2009. Sidescan sonar mapping of the Whittard Canyon, Celtic Margin

James Cook cruise 035 was aimed at the detailed mapping of the Whittard Canyon system along the Celtic Margin (NE Atlantic). In 12 days, &gt;700 km of track-lines were surveyed with the Towed Ocean Bottom Instrument (TOBI, carrying a 30 kHz sidescan sonar system with phase bathymetry capability, an 8 kHz chirp profiler and a magnetometer) and 6130 km2 of shipborne multibeam data was acquired over the 4 main branches of the canyon. This comprehensive and highly detailed dataset will provide new insights in canyon morphology, formation, sediment transport processes and into the resulting spatial distribution of benthic habitats. In addition, the data formed an indispensable base map for the planning of ROV dives during the follow-on cruise JC036.<br/

RRS James Cook Cruise 60, 09 May-12 Jun 2011. Benthic habitats and the impact of human activities in Rockall Trough, on Rockall Bank and in Hatton Basin.

The main aim of cruise JC060 was to carry out habitat mapping work in selected areas of the Rockall Trough, Rockall Bank and Hatton Basin in order to assess the status of different benthic habitats in relation to human activities, especially deep-sea bottom trawling. The cruise included a revisit of the Darwin Mound cold-water coral reefs, discovered in 1998 and protected in 2003, and an assessment of the status of two fisheries closure areas on Rockall Bank. In addition, two pilot studies of a more geological nature were carried out as well: one was targeting a Polygonal Fault System in the Hatton Basin, potentially linked to fluid flow, while the other focused on the history of the Rockall Bank Mass Flow.The tools used to achieve these objectives included the Autosub6000 Autonomous Underwater Vehicle (AUV), newly equipped with an EdgeTech dual frequency high-resolution sidescan sonar plus chirp profiler and a monochrome stills camera, a commercial inspection class ROV, and more traditional equipment including piston-, mega- and boxcore, CTD and shipborne multibeam (EM120 and EM710).Although the unsettled weather hampered the operations to a certain extent (including a forced return to the shelter of the Minches, resulting in an ad hoc survey of the E Shiant Bank), the cruise was a success, with 88h of ROV footage &amp; photography collected, 125km2 of seabed mapped at high resolution (metre to centimetre-scale) by the Autosub6000, 400km2 mapped with the EM710 on Rockall Bank, and 52 coring operations for geological and biological studies.The first results of the cruise stress again the importance of a sound management of the marine realm, including the deep ocean, and underline the continuous need for detailed information and high-resolution data to underpin such management

Of sands and corals : the sedimentary environment of the Darwin Mounds, N. Rockall Trough

The Darwin Mounds, small mounded features colonised by deep-water coral species such as Lophelia pertusa and Madrepora oculata, are found in the Northern Rockall Trough, at water depths between 900 and 1100 m. They were discovered in 1998 during a TOBI (Towed Ocean Bottom Instrument) 30 kHz sidescan sonar survey, where they appeared as circular to oval high-backscatter features on a generally lowbackscatter background. A typical mound can be up to 75 m across and 5 m high, and may have a scoured ‘tail’ feature of moderate backscatter in the down-current direction. High-resolution sidescan sonar and video imagery confirmed the presence of deep-water corals, and their confinement to the mounds. However, it also illustrated damage caused by deep-water trawling activities. As a result of these findings, the European Commission adopted a regulation in March 2004 to permanently ban bottom trawling from the area, while the UK government has the intention to designate the province as Special Area of Conservation under the Habitats Directive.The specific setting in which the Darwin Mounds occur, just south of the Wyville Thomson Ridge (WTR), creates a particular oceanographic regime : while most of the Continental Slope Current of the eastern Rockall margin continues its northward course across the WTR, the lower parts (<500 m) of the current are deflected to the south-west. This resulted in the formation of a sediment drift complex in the area, including a broad sheeted drift upon which upstream flank the Darwin Mounds are located. Further to the southwest, on the down-stream flank, a large field of pockmarks has also been discovered. Piston and box cores indicate that the general sedimentary sequence in the area consists of a thin upper layer of Holocene contourite sands overlying glacigenic muds. Cores in the mounds however show several meters of homogeneous sands. Masson et al. (2003) therefore proposed that the mounds might have a genetic relationship to the pockmarks, suggesting that the mounds formed as a result of fluid escape and the eruption of sand on the seafloor. Their higher elevation above the seafloor would subsequently have attracted coral colonisation. Alternatively, it is often suggested that small coral mounds can be formed through the baffling of sand by the coral framework.Detailed grainsize and mineralogical analyses of the piston and box cores reveal the nature of the sands in the area, and show a sorting effect in the down-current (SW-ly) direction throughout the Darwin Mound Province. However, they are less effective in discriminating clearly between the on-mound and off-mound sands, or between the sands of different depths within the mounds themselves. New information from highresolution TOPAS profiles and from foraminifera studies gives more insight in the mound origin and in the position of the mounds/corals within the contourite system, including the change of current regime related to the last deglaciation

RRS Discovery Cruise DY108‐109, 6 Sept - 2 Oct 2019. CLASS – Climate‐linked Atlantic System Science Darwin Mounds Marine Protected Area habitat monitoring, BioCAM ‐ first equipment trials. BLT‐ Recipes: pilot study

DY108/109 was a combined expedition, integrating a series of scientific and technological objectives related to three different projects. The main study area was the Darwin Mounds Marine Protected Area, an area of small cold‐water coral mounds in the Northern Rockall Trough, discovered by NOC scientists in 1998 and protected from bottom contact fisheries (mainly bottom trawling) since 2003. As part of the NERC CLASS programme (Climate‐Linked Atlantic Sector Science), the aim was to assess the status of the coral mounds, in order to identify and quantify any long‐term changes to this deep‐sea habitat. The mounds were surveyed with the Autosub6000 AUV (sidescan sonar), the HyBIS video platform and a series of targeted boxcores, repeating a first round of monitoring efforts undertaken in 2011 (expedition JC060). In addition, two settlement experiments deployed in 2011 were recovered on board. The second aim of the cruise was to demonstrate and test the latest innovation in survey technology as a potential new method for monitoring this type of seafloor habitat. The new BioCam system, a combined stereo camera and double laser line scanner integrated in the Autosub6000, was developed under the NERC Oceanids Marine Sensor Capital programme. BioCam enabled millimetre‐resolution 3D colour reconstructions of the seabed over areas that are an order of magnitude larger than typically covered with conventional visual methods (~30ha/day). This type of technology will revolutionise marine habitat monitoring in the future, both in terms of area covered and level of information obtained. In addition to these habitat mapping and monitoring activities in the Darwin Mound area, DY108/109 also supported two oceanographic studies of the Rockall Trough. For the NERC‐funded project BLT‐Recipes, two 24h CTD stations were occupied on the Irish margin, as pilot study to support further work in 2020 and 2021. For the oceanographic part of the CLASS programme, a number of single CTD casts were taken along the “Ellett Line”, while the turn‐around of a lander with upward‐looking ADCP was attempted. Unfortunately, investigation with the HyBIS platform confirmed that the lander was severely damaged and could not be recovered. Despite some time lost to weather and unfortunate equipment malfunctioning, the expedition was a success, with 10 HyBIS dives completed (76h seabed video), two sidescan sonar surveys repeated, 20 successful boxcores taken, sieved an analysed on board, one mooring deployed and 48 CTD casts completed. Most of all, the BioCam system performed excellently, staightaway from its first deployment, and acquired two dense grid survey datasets covering ~60ha in total. KEYWORDS Cold‐water coral, BioCam, CLASS, Marine Protected Area, Darwin Mounds, monitoring, habitat mapping, Autosub6000, AUV, Rockall Trough, Ellett Line, OSNAP, turbulent mixin

RRS James Cook Cruise 124-125-126 09 Aug-12 Sep 2016. CODEMAP2015: Habitat mapping and ROV vibrocorer trials around Whittard Canyon and Haig Fras

The main aim of JC125 was to carry out habitat mapping work in the Whittard Canyon, NE Atlantic, in order to obtain a better insight in the biodiversity patterns, benthic habitat distributions and sediment transport processes of submarine canyons. At the same time, the objective was also to test a number of novel habitat mapping techniques, including sideways multibeam mapping of steep and overhanging cliffs using the Autosub6000 AUV (Autonomous Underwater Vehicle), which was specifically adapted for this task. The four-week expedition was the second cruise of the CODEMAP project (COmplex Deep-sea Ecosystems: Mapping habitat heterogeneity As Proxy for biodiversity), funded by the European Research Council (Grant No 258482). Two short ‘tag-on’ cruises were added to this main expedition: JC124 covered four days of seabed monitoring in the Haig Fras and Canyons Marine Conservation Zones as part of the DEFRA-funded project “Novel AUV and Glider deployments to inform future MPA and MSFD monitoring strategy in UK shelf waters?”. JC126 consisted of three days of ROV vibrocorer trials for the NERC-funded technology grant NERC Grant NE/0176581. Together, the five-week voyage was nick-named ‘CODEMAP2015’. To achieve its goals, CODEMAP2015 made extensive use of deep-water marine robotics: in a first for UK science, the Autosub6000 AUV, the Isis ROV (Remotely Operated Vehicle) and a Seaglider provided by the University of East Anglia were operating in the canyon, simultaneously, deployed from the RRS James Cook. They provided an unprecedented insight in the structure and processes of the submarine canyon. The nested survey design that was adopted throughout the cruise combined canyon-wide shipboard and glider surveys with AUV-based acoustics and ROV-based multibeam and HD video recordings. This enabled the integrated observation of different canyon processes at the scale they occur, ranging from 10s of km to a few mm

Effectiveness of a deep-sea cold-water coral Marine Protected Area, following eight years of fisheries closure

Pressure on deep-sea ecosystems continues to increase as anthropogenic activities move into ever deeper waters. To mitigate impacts on vulnerable habitats, various conservation measures exist, such as the designation of Marine Protected Areas (MPAs). So far, however, little evidence is available about their effectiveness. This paper presents a unique follow-up study assessing the status and recovery of a deep-sea fisheries closure and MPA at ~1000 m water depth in the NE Atlantic, eight years after designation. The Darwin Mounds cold-water coral ecosystem was discovered in 1998, and closed to all bottom contact fisheries, especially trawling, in 2003. Our repeat survey in 2011 used both high-resolution sidescan sonar data collected by Autonomous Underwater Vehicle (AUV) and video footage from a Remotely Operated Vehicle (ROV) to evaluate recovery. The results demonstrate that (1) protection was successful and fishing impact was largely avoided in the Western Darwin Mounds, which contained similar proportions of live cold-water coral occurrence in 2011 as observed in 1998-2000; however (2) the Eastern Darwin Mounds suffered severe damage pre-closure, and by 2011 showed no coral recolonisation and very little regrowth. These results are further evidence for the low resilience and slow recovery potential of deep-sea ecosystems, and underline once again the importance of the precautionary principle in deep-sea conservation

Current induced seabed features along the eastern Rockall Trough, NE Atlantic – an interpretation of TOBI side-scan sonar imagery

The Rockall Trough, located west of Ireland, bordered by the Rockall Bank in the west and the Porcupine Bank in the east, has been intensively studied during the last decade. Numerous seabed structures were discovered along its eastern and western margin including cold-water coral covered carbonate mounds. The investigations in the Rockall Trough also included TOBI 30 kHz sidescan sonar surveys along its eastern margin.The TOBI data (TOBI stands for ‘Towed Ocean Bottom Instrument’) revealed that this margin is characterised by an inhomogeneous and complex topography. Mound, scarp and hedge structures can be found, often associated with cold-water corals. Furthermore, hardgrounds, outcrops of banked carbonates observed with ROVs and sediment waves occur, indicating erosion and sediment movement. All of the previously mentioned features are the result of, or affected by, strong bottom currents. Maps based on TOBI data display that most of the pronounced features (e.g. scarps and mound chains) strike parallel to the contours thus parallel to the northward oriented shelf edge current.Sediment waves manly strike slope-parallel indicating across-slope currents. In addition, oblique structures can be found which are neither parallel nor perpendicular to the slope. These complex patterns are probably the expression of the interplay of different bottom currents (main flow, tidal currents). As the spatial effects of these currents remain largely unknown, this study interprets the observed seabed features to reconstruct the prevailing relative bottom current velocities (direction and intensity) along the eastern Rockall Trough margin.This publication uses data and survey results acquired during a project undertaken with support of the European Union (EASSS III programme, ‘Improving Human Potential’, contract HPRI-CT-1999-00047) and on behalf of the Porcupine Studies Group (PSG) of the Irish Petroleum Infrastructure Programme Group 3. The PSG comprises: Agip Ireland BV, Chevron UK Ltd, Elf Petroleum Ireland BV, Enterprise Energy Ireland Ltd, Marathon International Hibernia Ltd, Phillips Petroleum Company United Kingdom Ltd, Statoil Exploration (Ireland) Ltd and the Petroleum Affairs Division of the Department of Communication, Marine and Natural Resource

Seamount seascape composition and configuration shape Southwest Indian Ridge fish assemblages

Seamounts are commercially important fishing grounds. Yet, little is known about their physical characteristics as fish habitat, important for informing conservation and ecosystem-based management. This study examines how multiscale seabed spatial heterogeneity influences commercially important fish families at three Southwest Indian Ridge seamounts (Coral Seamount, Melville Bank and Atlantis Bank). We quantified seascape heterogeneity from bathymetry and geomorphological habitat maps and identified 15 focal fish families from video data. Fish-habitat associations were examined using spatial pattern metrics that measured terrain morphology, seascape composition (variety and relative abundance of patch types) and seascape configuration (spatial arrangement of patches). Broader seascape context was characterised by geographic location and water depth. Multivariate regression trees and random forests modelled fish-habitat associations and identified the most influential explanatory variables. Assemblage characteristics and individual families were strongly influenced by geographic location and depth, and at finer scales (500 m buffers) seascape composition and configuration helped explain fish-habitat associations. Spatially continuous summit habitat and complex shaped ridge features supported high abundance and diversity of commercial fish families. Metrics of seascape composition and configuration (i.e., habitat size, shape and structural connectivity) had higher predictive power than the terrain metrics commonly used in developing proxies for deep-water fish species and biodiversity. These outcomes indicate that seascape metrics, commonly applied on land and in shallow marine environments, are also relevant environmental predictors of fish distributions in deep-sea environments. We highlight strong context dependency and depth-specific associations that hinder attempts to draw wider generalisations on fish-seascape linkages for seamounts

Perspectives in visual imaging for marine biology and ecology: from acquisition to understanding

Durden J, Schoening T, Althaus F, et al. Perspectives in Visual Imaging for Marine Biology and Ecology: From Acquisition to Understanding. In: Hughes RN, Hughes DJ, Smith IP, Dale AC, eds. Oceanography and Marine Biology: An Annual Review. 54. Boca Raton: CRC Press; 2016: 1-72