The Byron Bay Sewage Treatment work consists of a conventional treatment system discharging into an 8 ha wetland. The wetland was constructed around the dune and swale remnants of a coastal beach ridge formation. The wetland design incorporated stands of broad leaf paperback, Melaleuca quinquenervia , in two distinct Sections, separated by, and each preceded by, open water Sections fringed by predominantly emergent macrophytes. Spatial and temporal patterns in sediment phosphorus concentrations were examined using sediment cores. Core consisted of three main sediment types - surface organic accumulation, pre-existing organic layers and sand. Results suggest that the design and management of wetland systems should be aimed at maximising the deposition of sediment (and associated phosphorus) and minimising subsequent phosphorus release from the sediment. This might be achieved through the removal of accumulated organic sediments to retain the phosphorus adsorption capacity of the system, consideration of wind direction during periods of high (floating) plant growth (as detritus may accumulate along the up-wind edges of the wetland), incorporation of deep zones to minimise sediment phosphorus release and the inclusion of stands of M. quinquenervia. Results highlight pitfalls in the prevailing approach to wetland design, which ignore the complex functions which occur in natural wetland systems. A more holistic approach incorporating a high diversity of ecozones in wetland design is proposed, in effect mimicking natural systems. / Master of Science (Hons)