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The abyssal seafloor in the Clarion-Clipperton Zone (CCZ) in the NE Pacific hosts the largest abundance of polymetallic nodules in the deep sea and is being targeted as an area for potential deep-sea mining. During nodule mining, seafloor sediment will be brought into suspension by mining equipment, resulting in the formation of sediment plumes, which will affect benthic and pelagic life not naturally adapted to any major sediment transport and deposition events. To improve our understanding of sediment plume dispersion and to support the development of plume dispersion models in this specific deep-sea area, we conducted a small-scale, 12-hour disturbance experiment in the German exploration contract area in the CCZ using a chain dredge. Sediment plume dispersion and deposition was monitored using an array of optical and acoustic turbidity sensors and current meters placed on platforms on the seafloor, and by visual inspection of the seafloor before and after dredge deployment. We found that seafloor imagery could be used to qualitatively visualise the redeposited sediment up to a distance of 100 m from the source, and that sensors recording optical and acoustic backscatter are sensitive and adequate tools to monitor the horizontal and vertical dispersion of the generated sediment plume. Optical backscatter signals could be converted into absolute mass concentration of suspended sediment to provide quantitative data on sediment dispersion. Vertical profiles of acoustic backscatter recorded by current profilers provided qualitative insight into the vertical extent of the sediment plume. Our monitoring setup proved to be very useful for the monitoring of this small-scale experiment and can be seen as an exemplary strategy for monitoring studies of future, upscaled mining trials. We recommend that such larger trials include the use of AUVs for repeated seafloor imaging and water column plume mapping (optical and acoustical), as well as the use of in-situ particle size sensors and/or particle cameras to better constrain the effect of suspended particle aggregation on optical and acoustic backscatter signals.

Special issue 9th MARTECH: International Workshop on Marine Technology: 16-18 June 2021, Vigo, Spain.-- 1 page, 1 figure, The development of new cabled oceanographic observatories is becoming of extreme importance to monitor in real-time a continuously changing environment. In this context, a local coastal network of fxed and mobile videomonitoring platforms was created at the OBSEA (www.obsea.es; [1]) as European Multidisciplinary Seafoor and water column Observatory EMSO Testing-Site [2]. The cabled platform is located 4 km ofshore of Vilanova i la Geltrú coast (Barcelona, Spain), at a depth of 20 m. The observatory has been used to install a network of cameras including OBSEA fxed camera, plus a movable satellite tripod. Also, a mobile camera will be installed on an Internet Operated Vehicle (IOV), as a coastal crawler. These tele-operated vehicles are being used by marine scientists, to carry out multiparametric environmental studies (via the diversifed set of oceanographic and geochemical sensors) centered on faunal monitoring via imaging. As far as cabled seafoor observatories (and also OBSEA) are not able to move and their data collection capability is limited, it was decided to expand the monitoring capacity of the OBSEA, by connecting it to a new costal crawler. This crawler is a modifed prototype of the “Wally” platform series, which is operating at the Ocean Networks Canada (ONC; www.oceannetworks. ca) since 2010 [3]. This coastal crawler will be used to perform back and forth video transects between the fxed OBSEA camera and its satellite tripod camera (80 m away), to analyze the possible efect of environmental heterogeneity on the perceived fsh community abundance and composition. This will also allow scaling the biodiversity gathered data over a larger and more ecologicallyrepresentative area. In this scenario, we aim to present the technological design and specifcations of the modifed coastal crawler (Fig. 1). A mobile camera (1) in a glass sphere (rated for 3000 m depth) with 360° pan and 180° tilt operability has been installed, to allow the operator to perform SCUBA divers as visual census transects, by looking forward during transect progression, widening the visual feld with panoramic sweeps when needed. The tracks (2) are independent parts allowing to scale the inner part of the vehicle simply by mounting a broader main plait. The chains are made of rubber with embedded steel. Each track is driven by a powerful DC motor with a reduction gear of 989:1. The motor housings are pressure compensated by fuid flling. The junction cylinder (3) contents the driving electronics and an Ethernet switch to connect the camera and the control cylinder to the main communication cable. This housing can variate in material and dimensions to allow its use at diferent depths. The main cable (4) is a of special underwater Ethernet foating type to avoid problems like seabed abrasion and platform entanglement. A control cylinder (5) is used for controlling the crawler and the camera, providing power from the junction cylinder to supply motors. Finally, there are two 12V, 3W lights (6) that can turn on for flming at night, This work is partially funded by Generalitat de Catalunya “Sistemas de Adquisición Remota de datos y Tratamiento de la Información en el Medio Marino” (SARTI-MAR)” 2017 SGR 371 and by the Spanish Ministry of Education and Science (MEC) with the project “Redes de sensores submarinos autónomos y cableados aplicados a la monitorización remota de indicadores biológicos” TEC2017-87861-R. Researchers want to acknowledge the support of the Associated Unit Tecnoterra composed by members of Universidad Politécnica de Cataluña (UPC) and the Consejo Superior de Investigaciones Científicas (CSIC). This work used the EGI infrastructure with the dedicated support of INFN-CATANIA-STACK. The crawler was provided by OceanLab of Jacobs University Bremen (L. Thomsen)

Ocean Sciences Meeting (OSM), 16-21 February 2020, San Diego, CA, USA.- 1 page, 3 figures, The deep sea remains one of the less known environment on Earth and is characterized by high pressure, low availability of organic matter and absence of light. While there are still numerous discoveries concerning the diversity and adaptations of deep-sea organisms to their environement, this ecosystem is under an increasing anthropogenic pressure such as climate-related stressors (warming, acidification and deoxygenation), deep-sea fishing, human pollution (microplastics, POP), oil and gas extraction and could face new threats from emerging industries (e.g. mineral mining). How these changes will affect biodiversity and ecosystem functioning is one question of major importance for the future. In the darkness of the oceans, several organisms have the capability to emit light: called bioluminescence. Recent studies quantified that as much as 75% of pelagic and about 40% of benthic organisms are known to be bioluminescent. In this framework, we present a new deep-sea crawler, BathyBot, to be dedicated to the long-term exploration of deep-sea ecosystems allowing biological and-geochemical surveys. BathyBot will be deployed in 2020 in the Mediterranean Sea, at the MEUST-NUMerEnv/KM3NeT site, to strength the ecological-based monitoring capability of the European Multidisciplinary Seafloor and water column Observatory (EMSO ERIC) network. BathyBot will be able to explore an area of about 15 000 m2 at a depth of 2500m and will be devoted to 1) observe and monitor the dynamics of deep-sea pelagic and benthic organisms, 2) better define the occurrence and functions of bioluminescence in situ (increasing the dataset of bioluminescence records), 3) explore relationships between deep-sea organisms, biogeochemical (carbon content, oxygen concentrations) and environmental variables (temperature, salinity, current) in the context of global changes and their effects on the deep ocean, and 4) investigate benthic biogeochemical processes through the use of oxygen microprofiling in sediment porewaters, This work is funded by UE FEDER NUMerEnv project (number: 1166-39417, 2017), CNRS-INSU Moyens Mi-Lourd 2019 and VICAT-Tangram-MIO project

Knowledge on basic biological functions of organisms is essential to understand not only the role they play in the ecosystems but also to manage and protect their populations. The study of biological processes, such as growth, reproduction and physiology, which can be approachedin situor by collecting specimens and rearing them in aquaria, is particularly challenging for deep-sea organisms like cold-water corals. Field experimental work and monitoring of deep-sea populations is still a chimera. Only a handful of research institutes or companies has been able to installin situmarine observatories in the Mediterranean Sea or elsewhere, which facilitate a continuous monitoring of deep-sea ecosystems. Hence, today’s best way to obtain basic biological information on these organisms is (1) working with collected samples and analysing thempost-mortemand / or (2) cultivating corals in aquaria in order to monitor biological processes and investigate coral behaviour and physiological responses under different experimental treatments. The first challenging aspect is the collection process, which implies the use of oceanographic research vessels in most occasions since these organisms inhabit areas between ca. 150 m to more than 1000 m depth, and specific sampling gears. The next challenge is the maintenance of the animals on board (in situations where cruises may take weeks) and their transport to home laboratories. Maintenance in the home laboratories is also extremely challenging since special conditions and set-ups are needed to conduct experimental studies to obtain information on the biological processes of these animals. The complexity of the natural environment from which the corals were collected cannot be exactly replicated within the laboratory setting; a fact which has led some researchers to question the validity of work and conclusions drawn from such undertakings. It is evident that aquaria experiments cannot perfectly reflect the real environmental and trophic conditions where these organisms occur, but: (1)in most cases we do not have the possibility to obtain equivalentin situinformation and (2) even with limitations, they produce relevant information about the biological limits of the species, which is especially valuable when considering potential future climate change scenarios. This chapter includes many contributions from different authors and is envisioned as both to be a practical “handbook” for conducting cold-water coral aquaria work, whilst at the same time offering an overview on the cold-water coral research conducted in Mediterranean laboratories equipped with aquaria infrastructure. Experiences from Atlantic and Pacific laboratories with extensive experience with cold-water coral work have also contributed to this chapter, as their procedures are valuable to any researcher interested in conducting experimental work with cold-water corals in aquaria. It was impossible to include contributions from all laboratories in the world currently working experimentally with cold-water corals in the laboratory, but at the conclusion of the chapter we attempt, to our best of our knowledge, to supply a list of several laboratories with operational cold-water coral aquaria facilities.