Patterns in Marine Fungal Diversity and Community Structure on Native versus Invasive Macroalgae at a Local Geographic Scale

Nonindigenous marine species are a growing threat to coastal ecosystems, but invasive dynamics are understudied in marine environments. The microbiome of invasive macroalgal species has been recognised as contributing to their invasive success, but research to date has largely focussed on the prokaryotic fraction. This research compared the epiphytic fungal communities between a native (Fucus serratus) and an invasive (Sargassum muticum) macroalga, across a relatively small spatial scale (<800 m), in North Wales. DNA extracts from surfaces of macroalga were PCR-amplified with primers ITS1F and ITS2 and sequenced using Illumina MiSeq. Difference in fungal community composition was observed between all sample groups with the exception of S. muticum and F. serratus samples taken from within a few meters of each other, suggesting environmental drivers of the macroalgal fungal community are more important than host specificity. It also raises the question of whether S. muticum exerts a direct influence on the microbiome of neighbouring algal species, although further research is required to explore this potential interaction. No differences were detected in fungal biodiversity across any of the samples, supporting prior findings of a natural peak in fungal diversity at local scales.