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The physical structure and chemical properties of detrital floc and their role in wetland nutrient dynamics

Detrital flocculent material (floc) is a form of suspended sediment found in a range of permanent and seasonal wetlands. It is a complex matrix of micro-organisms (generally bacteria and protozoa), organic particles (cellular debris, detritus, and extracellular proteins, fibrils), inorganic particles (clay, silts), and interfloc spaces called pores. Detrital floc may control a variety of biogeochemical processes such the fate of particle associated contaminates by altering the hydrodynamic properties of particles in transport. Detrital floc may respond to, or be a direct consequence of, sustained nutrient enrichment events and regulate the overall water quality through physical and biological processes. It is also likely to constitute an important part of the food chain in wetlands and may play crucial biogeochemical and ecological roles in these ecosystems.

While new developments in sampling, microscopy, molecular science, and modelling permit increasingly revealing investigations into flocculation processes, there is still a fundamental lack of knowledge related to many aspects of detrital floc in wetlands. These include physical structure and chemical properties of the floc, the variability of the floc between wetlands and the links between detrital floc structures and nutrient dynamics of wetlands.

Detrital floc samples from five wetlands known to contain detrital floc will investigated for each site by means of correlative microscopy using confocal microscopy, scanning electron microscopy and electron probe micro-analyzer techniques. Correlative microscopy will provide information on the number of fibrils, number and species of bacteria, microbes and other constituents of detrital floc from each site. A focus will be quantification of the components, microscopy work, method development and analysis will be performed at The University of Western Australia. Detrital floc chemical composition will be investigated for each site using atomic emission spectrometry and x-ray fluorescence spectrometry (total elements/nutrients) at the Perth Assay Laboratory.

This project will provide conceptual models of floc types in wetlands of the Swan Coastal Plain and will improve our knowledge of these wetlands for their management. The project will shed light on currently underexplained occurrences in these wetlands including eutrophication, midge plague patterns and nutrient retention. This is work which has not been achieved before on the Swan Coastal Plain and will provide a reference point to any future research on wetland management in the future locally, nationally and internationally.


Mr William Phelps
Dr Bea Sommer
Associate Professor Mark Lund

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