Fungal succession and carbon quality as drivers of nitrogen removal capacity in a constructed salt marsh

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dc.contributor Cherry, Julia
dc.contributor Kuehn, Kevin
dc.contributor.advisor Mortazavi, Behzad Starr, Sommer Faith 2021-05-12T16:28:09Z 2021-05-12T16:28:09Z 2020
dc.identifier.other u0015_0000001_0003686
dc.identifier.other Starr_alatus_0004M_14346
dc.description Electronic Thesis or Dissertation
dc.description.abstract Coastal wetlands mitigate excess nutrient inputs by acting as important sites of denitrification. Despite their role in removing excess nitrogen, coastal wetland area has declined by more than 50% in the 20th century, representing a potential loss of ecosystem service. To restore lost function, managers have devoted much effort to salt marsh restoration and construction. However, constructed marshes have lower function than natural marshes even with similar plant biomass. I conducted two experimental studies to 1) compare nitrogen (N) cycling rates between constructed and natural marshes, and 2) to assess microbial biomass/activity and carbon (C) quality differences as potential factors influencing the return of N cycling in constructed Gulf of Mexico salt marshes. In the first experiment, sediment was collected from a constructed and natural marsh and treated with inhibitors to isolate bacterial and fungal contributions to total denitrification. The constructed marsh had 3x lower total denitrification, 4x lower sediment fungal biomass and lower fungal denitrification than the natural marsh. Increased process rates following microbial inhibition in the natural marsh indicate the occurrence of microbial competition for nitrate. These results suggest that fungi and bacteria contribute differently to rates of incomplete denitrification between natural and constructed marshes and that constructed marshes have lower fungal biomass than natural marshes. In the second experiment, sediment was incubated for 19 days in ~149L aquaria and treated with labile or recalcitrant C under ambient or high nitrate conditions. Denitrification and dissimilatory nitrate reduction to ammonium (DNRA) rates and microbial biomass were measured at three points during the incubation, and overlying water was sampled every two days for nutrient concentrations. Both denitrification and DNRA rates were similar between marshes, and labile C additions increased DNRA by more than 12x and reduced the ratio of denitrification to DNRA by as much as 22x. Nutrient concentrations were similar between marshes. Both fungal and bacterial biomass were lower in the constructed marsh. Collectively, the results of these experiments highlight that constructed marshes can reach functional recovery after 30 years and remove N as effectively as reference marshes, despite differences in microbial biomass and starting C and N stocks.
dc.format.extent 76 p.
dc.format.medium electronic
dc.format.mimetype application/pdf
dc.language English
dc.language.iso en_US
dc.publisher University of Alabama Libraries
dc.relation.ispartof The University of Alabama Electronic Theses and Dissertations
dc.relation.ispartof The University of Alabama Libraries Digital Collections
dc.relation.hasversion born digital
dc.rights All rights reserved by the author unless otherwise indicated.
dc.subject.other Biogeochemistry
dc.subject.other Environmental science
dc.subject.other Ecology
dc.title Fungal succession and carbon quality as drivers of nitrogen removal capacity in a constructed salt marsh
dc.type thesis
dc.type text University of Alabama. Department of Biological Sciences Biological Sciences The University of Alabama master's M.S.

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