Phosphorus export from coastal plain drainage into the Peel-Harvey estuarine system of Western Australia

Abstract

Excessive growth of the benthic alga Cladophora aff. albida in the Peel-Harvey estuarine system has coincided with greatly increased inputs of phosphorus from rivers over the last 20-25 years. At present, about 90%, of phosphorus input is derived from rural coastal plain catchments, where use of superphosphate increased fourfold over the period 1945-1975. The present export of phosphorus from these catchments was found to be positively correlated with rates of superphosphate application, dairy farming, and presence of alluvial clay soils, and negatively correlated with beef farming. Reduction of phosphorus input to the estuary from the coastal plain, therefore, could be achieved by reducing or modifying the present use of superphosphate, and reducing runoff from dairy farms into waterways.