New Zealand Lake Snow: The Structural Characterisation of Extracellular Polysaccharides Associated with the Invasive Diatom Lindavia intermedia

The mucilaginous biomass ‘lake snow’ first appeared in the low nutrient Southern Great Lakes of New Zealand in 2004. Lake snow has been fouling the inlet filters of hydroelectric dams, boating and fishing equipment, and residential filters. New Zealand lake snow is caused by copious extracellular polymeric substances (EPS) produced by the centric diatom species Lindavia intermedia. Diatom EPS is comprised mostly of polysaccharides, including chitin and adhesive non-chitin polysaccharides. The aim of this project was to analyse the non-chitin EPS polysaccharides of lake snow. This thesis studied the extraction, isolation, and characterisation of these polysaccharides. Various synthetic modifications and chromatography techniques were employed for this work, including constituent sugar analysis by HPAEC-PAD and glycosyl linkage analysis by GC-MS. A structure is proposed for the main acidic polysaccharide produced by Lindavia intermedia. Consistent with the adhesive characteristics of lake snow, this previously unknown polysaccharide is rich in glucuronic acid and contains significant levels of neutral, endogenously O-methylated side chains.