Biosorbents derived from the biomass of marine algae have shown to have high uptake capacities for heavy metals and the internal structure has been generally assumed to be pseudo-homogenous. In this paper, the microstructures of biosorbents derived from Australian marine alga Durvillaea potatorum were analysed using scanning electron microscopy. The structural components of the biosorbent resembled fiber-like cylinders. The internal structure was a highly connected network of cylinders with varying sizes. Methods of drying and pre-treatment of the biomass also affected the details of the internal structure. Calcium chloride followed by thermal treatment provided the most uniform cylinder networks for the biosorbents. Heavy metal Cu2+ and Cd2+ binding in the biomass was confirmed by using an electron probe microanalyser.