Fungi from the Depths: A Preliminary Survey Using Hybrid Underwater Robotics in the Bathypelagic Zone off the Coast of Toulon (SE France)

The deep sea is characterized by unique and extreme habitats. The absence of light, high salinity, hydrostatic pressure, low temperature, and high competition led to the evolution of physiological and biochemical adaptations necessary for survival. Marine fungi represent a significant part of deep-sea microbial communities. Studying bathypelagic sediment fungi helps us to understand their little-known communities and ecology, as well as their metabolic potential and ecophysiological properties, which have applications in pharmaceutical biotechnologies and bioremediation protocols. During an oceanographic campaign off the coast of Toulon (France, northwest Mediterranean Sea) in October 2021, as part of the KM3NeT Project, the Hybrid Remotely Operated Vehicle (HROV) Ariane collected a composite sediment sample at a depth of 2417 m. The sediment was physically, geochemically and mycologically characterized. Culturable fungi were isolated, and vital fungal strains were identified morphologically and molecularly. A total of 17 strains were isolated and identified in pure culture. The major taxa belonged to the Penicillium, Aspergillus, and Cladosporium genera, but widespread species such as Wallemia sebi were also found. This study also paves the way for further research into the advantages and disadvantages of using HROV technology for mycological cultural investigations at prohibitive depths.