Abstract
Freshwater fungi are a poorly studied ecological group that includes a high taxonomic diversity. Most studies on aquatic fungal diversity have focused on single habitats, thus the linkage between habitat heterogeneity and fungal diversity remains largely unexplored. We took 216 samples from 54 locations representing eight different habitats in the meso-oligotrophic, temperate Lake Stechlin in North-East Germany. These included the pelagic and littoral water column, sediments, and biotic substrates. We performed high throughput sequencing using the Roche 454 platform, employing a universal eukaryotic marker region within the large ribosomal subunit (LSU) to compare fungal diversity, community structure, and species turnover among habitats. Our analysis recovered 1027 fungal OTUs (97% sequence similarity). Richness estimates were highest in the sediment, biofilms, and benthic samples (189–231 OTUs), intermediate in water samples (42–85 OTUs), and lowest in plankton samples (8 OTUs). NMDS grouped the eight studied habitats into six clusters, indicating that community composition was strongly influenced by turnover among habitats. Fungal communities exhibited changes at the phylum and order levels along three different substrate categories from littoral to pelagic habitats. The large majority of OTUs (> 75%) could not be classified below the order level due to the lack of aquatic fungal entries in public sequence databases. Our study provides a first estimate of lake-wide fungal diversity and highlights the important contribution of habitat heterogeneity to overall diversity and community composition. Habitat diversity should be considered in any sampling strategy aiming to assess the fungal diversity of a water body.
Highlights
Aquatic fungi play an important role in the cycling of carbon and nutrients in ecosystems (Gleason et al 2008; Wurzbacher et al 2010; Jobard et al 2010; Grossart and Rojas-Jimenez 2016)
The lower limit of shared estimated OTUs varied considerably among habitats, with the highest values found in Sediment, Benthos and Biofilm habitats, and the lowest in Plankton and water samples (Table 1)
The results extend previous research of fungal diversity and distribution in freshwaters and clearly indicate that lake biofilms can be hotspots for aquatic fungi
Summary
Aquatic fungi play an important role in the cycling of carbon and nutrients in ecosystems (Gleason et al 2008; Wurzbacher et al 2010; Jobard et al 2010; Grossart and Rojas-Jimenez 2016). Aquatic fungi form symbiotic relationships, such as endophytic or mycorrhiza-forming fungi (Kohout et al 2012) or Chytridiomycota symbioses with algae (Picard et al 2013). Despite their important functional role in lakes, the biodiversity of freshwater fungi remains poorly known
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