Diversity and community composition of aquatic ascomycetes varies between freshwater, estuarine and marine habitats in western Scotland

Aquatic ascomycetes occur in freshwater and marine environments where they facilitate nutrient cycling and energy flow through the water column, and are the foundations of aquatic food webs. This study investigates the diversity and abundance of aquatic ascomycetes on submerged wood in freshwater, estuarine and marine habitats in north-west Scotland. The fresh water habitat exhibits lowest temperature and salinity with an increasing gradient through the estuarine and marine habitats. Morphological identification and molecular analysis were used to identify taxa. A detailed description is given for Sporoschisma juvenile and Chalara anamorph of Calycina parilis and their phylogenetic placement is discussed based on their morphological variability and both ITS and LSU rDNA. Diversity of aquatic ascomycete taxa decreased along temperature and salinity gradients, being lowest in the estuarine and marine habitats. The composition of fungal communities varied between the three sampled habitats with some taxa common to all three and others exclusive to one habitat. A wide range of biotic, abiotic and anthropogenic factors affect aquatic fungal diversity. It is therefore important to improve our understanding of these effects on aquatic fungal diversity to successfully conserve aquatic ecosystems in light of changing global environments.