Fungi in the floodplain wetlands of lowland rivers

Kerr, Janice (2010). Fungi in the floodplain wetlands of lowland rivers PhD Thesis, Department of Environmental Science and Technology, La Trobe University, La Trobe University.

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Author Kerr, Janice
Thesis Title Fungi in the floodplain wetlands of lowland rivers
School, Centre or Institute Department of Environmental Science and Technology, La Trobe University
Institution La Trobe University
Publication date 2010-11
Thesis type PhD Thesis
Supervisor Suter, Philip J.
Baldwin, Darren S.
Rees, Gavin N.
Total pages 298
Language eng
Subjects 050102 Ecosystem Function
050104 Landscape Ecology
050205 Environmental Management
060204 Freshwater Ecology
060203 Ecological Physiology
Abstract/Summary Fungal decomposition processes are recognised for their importance in terrestrial ecosystems, but their role in aquatic ecosystems is not as well established. In particular, the function of fungi in wetland carbon cycles is poorly understood. Indeed, one of the few studies of fungi in Australian wetlands suggested that fungi played no role in carbon cycling, based on an absence of fungal phospholipid biomarkers in sediments. In this thesis I examine the community dynamics of aquatic fungi and their functional role in floodplain wetlands. An initial survey of fungal diversity in a floodplain wetland (Chapter 3) clearly showed that fungi were present on a range of submerged and exposed substrates. A mesocosm experiment then examined the influence of leaf age and moisture availability on fungal dynamics (chapter 4). A period of terrestrial aging was found to promote fungal colonisation of Eucalyptus camaldulensis leaves during aquatic decomposition, potentially impacting wetland food chains, water quality and carbon dynamics. DNA from a range of fungal species was extracted from the sediments of a floodplain wetland undergoing drawdown (Chapter 5), while fungal biomass was below detection limits. The results suggest that fungi do not grow in wetland sediments. Rather, the sediments act as “seed bank” that stores fungal propagules until the wetland refills. Aged E. camaldulensis leaves undergoing aquatic decomposition in river and wetland ecosystems were examined to compare fungal and Oomycete community dynamics (Chapter 6) and changes in leaf chemical composition (Chapter 7). Fungal biomass was consistently lower in wetlands, when compared to streams and Oomycete biomass comprised a substantial proportion of total fungal biomass at various times in both ecosystems. Initial increases in fungal and Oomycete biomass were correlated with temporary improvement in leaf food value. Infra-red mapping of these partially decomposed E. camaldulensis leaves (Chapter 7) showed changes in the distribution of polysaccharides, protein and lignin over time, and changes in lignin distribution occurred earlier in the wetland than in the stream. The activity of oxidative fungal enzymes was indicated as an important mechanism in the transformation of refractory carbon compounds in aquatic ecosystems.
Keyword Aquatic Fungi
Ecosystem resilience
Carbon Cycle
Flood pulse concept

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Created: Tue, 09 Apr 2013, 11:32:10 EST by Janice Kerr on behalf of Centre for Water in the Minerals Industry