Date Thesis Awarded

4-2022

Access Type

Honors Thesis -- Open Access

Degree Name

Bachelors of Science (BS)

Department

Environmental Science and Policy

Advisor

James Skelton

Committee Members

Randolph Chambers

Matthias Leu

Rowan Lockwood

Abstract

Freshwater fungi comprise a phylogenetically and functionally diverse group which contributes to wide-ranging ecosystem processes in aquatic systems. Saprotrophic fungi convert detritus into nutrient-rich food sources for fish and invertebrates, whereas pathogenic and parasitic fungi can cause disease and population declines of other aquatic organisms. With their diverse and important roles, changes in freshwater fungal community structure may have far-reaching impacts on ecosystems. To understand how natural and anthropogenic stressors to freshwater systems impact fungal-mediated ecosystem processes, a greater understanding of the taxonomic and functional composition of freshwater fungal communities is needed. We assessed relationships among freshwater habitat types, water quality variables, and fungal community composition using multi-marker DNA metabarcoding and water quality monitoring data from a Chesapeake Bay watershed in Virginia, USA. Standardized water samples were collected using eDNA backpack samplers at 17 stream, pond, and tidal creek sites exhibiting a range of pH, dissolved oxygen, salinity, temperature, and organic and inorganic nitrogen and phosphorus profiles. We targeted two regions of the ribosomal RNA gene, ITS2 and LSU, and sequence data were processed using the AMPtk pipeline. The resulting fungal community data from each site were correlated with habitat type and water quality data using distance-based redundancy analysis and generalized linear models. Habitat type and water quality factors were found to be significant drivers of freshwater fungal community composition. Fungal community composition differed significantly among streams, ponds, and tidal creeks, with stream and pond communities being more similar to one another than to tidal creek communities. Average fungal richness measured in number of Operational Taxonomic Units (OTUs) per site was highest in ponds and lowest in tidal creeks. Effects of habitat type and water quality varied between fungal phyla, with habitat type and water quality explaining a significant proportion of variation in Chytridiomycota and Ascomycota community composition, but not variability in Basidiomycota community composition. Water quality factors also had significant power in explaining community composition of aquatic hyphomycetes, a functional group that contributes largely to leaf litter decomposition in streams. The responsiveness of freshwater fungal communities to their environment can help us predict how important fungal communities may be altered as freshwater ecosystems face natural and anthropogenically-driven changes to water quality.

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