The water column of a freshwater stream or river represents an ecosystem where one might expect to find a relatively small amount of fungal genomic material. This is especially true in the fraction of detectable fungi smaller than 1µm in size. Using next generation sequencing, we were able to detect an abundance of unexpectedly diverse fungal sequences across 25 stream and river sites representing a strong phosphorous gradient in water samples containing only the 0.2µm-1µm size fraction.
Results/Conclusions
These sequences represent what is likely allochthonous, transient genomic material which can be weakly tied to stream environmental metrics but is likely more related to catchment factors rather than representing active stream ecosystem taxa. Lower taxonomic groupings are unique and specific to each site, however, seemingly random patterns of domination by Basidiomycota, Ascomycota, and Chytridiomycota can be found across stream sites. Guild assignment of functional information to OTUs via FUNGuild shows the majority of sequences to be representative of pathogens affecting both plants and animals as well as the expected saprotrophs. These findings have the potential to affect future approaches and methods for studying aquatic fungi as these abundant sequences could represent a significant amount of noise in aquatic ecosystem study.