Matthew Spann



Degree Name

Bachelor of Environmental Science (Honours)


School of Earth, Atmospheric and Life Sciences


Jeffrey Kelleway


Coastal vegetated ecosystems, including wetlands and saltmarsh, have been widely recognised as providing a range of environmental, social, and cultural benefits. They have the ability to store more carbon than nearly any other vegetated system, making them the target of increasing study due to the potential play a role in the mitigation of some effects of climate change. Wetland vegetation have been recognised for having a high carbon sequestration rate. But the carbon cycling dynamics between vegetation types in Australian saltmarshes is lesser known. Framed within a small wetland on the New South Wales South Coast, this research project aimed to monitor greenhouse gas fluxes and how environmental variables influence these fluxes. Monitoring was carried out through the erection of two eddy covariance flux towers which measure fluxes of CO2 from the wetland surface. Soil and water sampling was conducted to analyse salinity, bulk density, carbon content and pH, while measuring biomass across vegetation communities. Using these measurements, expected differences in fluxes between two vegetation communities with differing vegetation structures and compositions were identified. These two communities were differentiated by their dominant species, one by Sarcocornia quinqueflora, and the other by Juncus kraussii. The comparison of the two communities allowed for potential drivers of CO2 fluxes to be identified, based on the sampled environmental variables, and their location within the wider wetland itself. Fluxes of CO2 differed between the two monitored vegetation communities. This difference occurred when comparing both the 24-hour average of half-hourly flux data and the daytime-only half-hourly average flux data. The Juncus-dominated community had a stronger negative CO2 flux than the Sarcocornia-dominated community, indicating a stronger ability to drawn down more carbon out of the atmosphere (-0.078 ± 0.013 and -0.029 ± 0.0063 mg CO2 m-2 s-1 respectively). The possibility of a freshwater lens occurring beneath the Juncus community was identified as being a potential driver between the differing CO2 fluxes, as this would subsequently control the salinity and productivity of the community. Biomass was higher in the Juncus community, with an average biomass of 1.40 kg m2, and soil salinity in this community was lower than the Sarcocornia community on both sampling occasions. iii It was also found that the monitored wetland was acting as a net sink for CO2 using the two measured vegetation communities. However, it is important to consider that this project only measured atmospheric fluxes and is missing information on lateral exchanges of carbon within the groundwater. Further sampling and monitoring of fluxes and environmental variables are recommended to form a more complete picture of the driving forces of CO2 fluxes in this wetland. It is also recommended to monitor methane fluxes from the wetland, as this would allow for a more holistic few of the carbon exchanges within the wetland. So, while the Lake Tilba salt marsh site is relatively small, monitoring here could provide a starting point for predicting how fluxes of CO2 are influenced within wetlands along the NSW South Coast.

FoR codes (2008)

960503 Ecosystem Assessment and Management of Coastal and Estuarine Environments



Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.