PhD Confirmation of Candidature - Seasonal variations in sources and cycling of nitrogen and carbon in a tropical mangrove-lined creek impacted by treated sewage effluent

PhD Confirmation of Candidature - Seasonal variations in sources and cycling of nitrogen and carbon in a tropical mangrove-lined creek impacted by treated sewage effluent

Wed, 12/02/2014 - 14:00

About the Presenter

Kanchana  is a PhD student with the Research Institute for the Environment and Livelihoods, Charles Darwin University. She will use the latest stable isotope techniques to study sources and cycling of nitrogen and carbon in Buffalo Creek, NT impacted by treated sewage effluent. Kanchana’s PhD is part of an ARC-funded project titled Microbiology of a tropical creek impacted by sewage effluent: novel impact assessment methods using N-cycle functional markers and changes in community composition. Her project is supported by the Power and Water Corporation (PWC) and Charles Darwin University (CDU). She has also won the International Postgraduate Research Scholarship (IPRS) and Australian Postgraduate Award (APA).

Kanchana completed her Masters Degree in Environmental Science from the Graduate School of Environmental Science, Hokkaido University, Japan in 2012, where she was investigating the interaction between scallop culture and primary production in Mutsu bay, Japan by means of stable isotope determination of diet sources. She has a Bachelor of Science Special Degree (Hons) from University of Peradeniya, Sri Lanka and has worked as a junior lecturer at Open University of Sri Lanka for few years.


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Tropical estuaries are among the most biogeochemically active regions in the biosphere, but the processes are complex due to factors such as highly variable hydrodynamics, particularly in macrotidal systems. Anthropogenic nutrient loadings from diverse sources such as urban and rural run-off and sewage discharges are well known to make changes in the structure and function of estuaries. Tropical estuaries are under increasing pressure worldwide from human impacts, but are poorly studied compared with temperate systems. Developing an understanding of the changes occurring in tropical estuaries as a result of nutrient enrichment from point and non-point sources is vital in understanding the functioning of these ecosystems and to assess the health of the ecosystems.  

Buffalo Creek is a macrotidal creek flowing into Darwin Harbour, northern Australia, and has received treated sewage effluent for over 30 years from the Leanyer Sanderson Treatment Plant, which is the largest waste stabilization pond system in the Northern Territory. The impact of the effluent as a main point source for the nutrient load in Buffalo Creek is poorly understood and early detection of any effects of nutrient enrichment  is required in order to prevent degradation of the aquatic habitat. 

This PhD project seeks to address these knowledge gaps by identifying the major reservoirs, sources and pathways of carbon and nitrogen in Buffalo Creek and seeking to define the spatial and temporal variation in the dispersal of treated sewage effluent utilizing natural abundance of multiple stable isotopes (15N, 13C, 2H, 18O) in water, sediment and indicator organisms. 

The study’s outcomes will assist in the development of carbon and nitrogen stable isotope tools for long term monitoring and identification of suitable ecological indicators of sewage effluent. The identification of nutrient sources and the extent of nutrient dispersal will assist water resource managers and policy makers in selecting measures that can directly deal with specific sources or flow paths of nutrients. Possible options in those cases would include the management or planning of urban development and a more effective targeting of future investments to maintain or improve ecosystem quality.

The novelty of the proposed study is the integrated use of multiple stable isotope systems to track the pathways and dispersal of sewage derived nutrients in a tropical ecosystem. 

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