Nutrient Characteristics of Well-mixed Coastal Waters off Perth, Western Australia

Seasonal cycles and horizontal distribution of temperature, salinity and dissolved nutrients over a 3-year period are described for coastal waters off Perth, Western Australia. Adjacent oceanic nutrient concentrations are low and there is little terrestrial runoff. The coastal waters contain nutrients in low concentrations, yet support highly productive benthic macrophyte communities. The waters are well mixed and characterized by summer maxima of phosphate and salinity and winter maxima of silicate and nitrate. Horizontal differences in nitrate concentrations within a semi-enclosed lagoon during autumn and winter appear to be due in part to a decrease with depth in the ability of benthic communities to reduce nitrate concentrations in the overlying water.