Date of Award

12-10-2022

Document Type

Thesis

Degree Name

Master of Science in Coastal Marine and Wetland Studies

Department

Coastal and Marine Systems Science

College

College of Science

First Advisor

Vladislav Gulis

Second Advisor

Megan Cevasco

Third Advisor

John J. Hutchens, Jr.

Abstract

Under climate change predictions, surface air temperature is expected to continue to rise and will likely affect functioning of stream ecosystems and microbial communities. Aquatic hyphomycetes are key fungal decomposers of plant litter in headwater streams controlling carbon, energy, and nutrient flows to higher trophic levels. This project addressed the effects of temperature on stream fungal communities in two recently conducted experiments (microcosm and streamside channel studies) using Illumina sequencing. The objectives were to determine (1) if temperature affects community structure of stream fungi based on relative abundances of ITS2 rDNA sequences, (2) if the effects of temperature on aquatic fungal communities vary for substrates of different carbon quality, and (3) if next-generation sequencing provides similar insights to those obtained earlier based on microscopic approach (spore counts). The microcosm experiment with natural stream microbial assemblages, five temperature treatments (4, 8, 12, 16, 20 ̊C) and four sampling dates showed that temperature had a significant effect on fungal community structure as some species increased or decreased their relative abundances. The streamside channel experiment (ambient, +2 ̊C and +4 ̊C treatments) with wood and two types of leaf litter and two sampling dates showed no significant effect of temperature on fungal community structure regardless of substrate type, however, litter type did control community structure. Thus, larger shifts in temperature (microcosms) did affect fungal communities while smaller increases (streamside channels) did not. Illumina sequencing showed much higher fungal diversity (e.g., 330 species in channels) than previously recorded by spore counts, however, aquatic hyphomycetes dominated fungal communities regardless of the approach. Temperature effects may have important implications for stream fungal communities and ecosystem functioning under climate change scenarios.

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