Fungi populate deep-sea coral gardens as well as marine sediments in the Irish Atlantic Ocean

Fungi populate deep Oceans in extreme habitats characterized by high hydrostatic pressure, low temperature and absence of sunlight. Marine fungi are potential major contributors to biogeochemical events, critical for marine communities and food web equilibrium under climate change conditions and a valuable source of novel extremozymes and small molecules. Despite their ecophysiological and biotechnological relevance, fungal deep-sea biodiversity has not yet been thoroughly characterized. In this study, we describe the culturable mycobiota associated with the deepest margin of the European Western Continental Shelf: sediments sampled at the Porcupine Bank and deep-water corals and sponges sampled in the Whittard Canyon. Eighty-seven strains were isolated, belonging to 43 taxa and mainly Ascomycota. Ten species and four genera were detected for the first time in the marine environment and a possible new species of Arachnomyces was isolated from sediments. The genera Cladosporium and Penicillium were the most frequent and detected on both substrates, followed by Candida and Emericellopsis. Our results showed two different fungal communities: sediment-associated taxa which were predominantly saprotrophic and animal-associated taxa which were predominantly symbiotic. This survey supports selective fungal biodiversity in the deep North Atlantic, encouraging further mycological studies on cold water coral gardens, often overexploited marine habitats.