SPATIAL AND TEMPORAL HETEROGENEITY OF SEDIMENT PHOSPHORUS IN THE PEEL-HARVEY ESTUARINE SYSTEM

A retrospective study was carried out on sediment data collected from 1982 to 1989 in the Peel-Harvey Estuarine System, Western Australia. T here was a distinct pattern of sediment phosphorus distribution, chara cterized by (1) higher concentrations in Harvey Estuary than in Peel M et; (2) in Harvey Estuary, the highest concentrations were along the c entral, 1.5 m depth contour and were higher along the western shore th an the eastern shore. Sediment phosphorus and organic matter are enric hed in the top few centimetres. In general, sediment total phosphorus and organic matter increased in winter when river flow was high, and i n summer-autumn. The within-year distribution of total phosphorus in t he surface sediment was related to seasonal changes in macrophyte biom ass. Between-year comparisons (1982-1989) suggested unusually high org anic-sedimentation and total P in 1983, corresponding to an unusual in crease in algal biomass in that year. There were no significant annual variations in sediment P after 1983, suggesting high sediment bufferi ng capacity. Within the sediments, the major components water content, organic content and the forms of phosphorus) were strongly and positi vely 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 pote ntial for sediment to act as a nutrient source, stimulating algal biom ass production during low flow periods. (C) 1998 Academic Press.