Spatial and Temporal Heterogeneity of Sediment Phosphorus in the Peel-Harvey Estuarine System

Abstract

A retrospective study was carried out on sediment data collected from 1982 to 1989 in the Peel-Harvey Estuarine System, Western Australia. There was a distinct pattern of sediment phosphorus distribution, characterized by (1) higher concentrations in Harvey Estuary than in Peel Inlet; (2) in Harvey Estuary, the highest concentrations were along the central, 1·5m depth contour and were higher along the western shore than the eastern shore. Sediment phosphorus and organic matter are enriched in the top few centimetres. In general, sediment total phosphorus and organic matter increased in winter when river flow was high, and in summer–autumn. The within-year distribution of total phosphorus in the surface sediment was related to seasonal changes in macrophyte biomass. Between-year comparisons (1982–1989) suggested unusually high organic-sedimentation and total P in 1983, corresponding to an unusual increase in algal biomass in that year. There were no significant annual variations in sediment P after 1983, suggesting high sediment buffering capacity. Within the sediments, the major components (water content, organic content and the forms of phosphorus) were strongly and positively correlated. About 35–52% of the sediment total P was potentially bioavailable, and was sensitive to various environmental conditions (e.g. bottom oxygen depletion, pH and temperature). There is a high potential for sediment to act as a nutrient source, stimulating algal biomass production during low flow periods.