BathyBot – a Deep-sea Crawler to See the Unseen in the NW Mediterranean Sea

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.