Variability in fluvial suspended and streambed sediment phosphorus fractions among small agricultural streams

Abstract

Agriculture is a major source of sediment and particulate phosphorus (P) inputs to freshwaters. Distinguishing between P fractions in sediment can aid in understanding its eutrophication risk. Although streams and rivers are important parts of the P cycle in agricultural catchments, streambed sediment and especially fluvial suspended sediment (FSS) and its P fractions are less studied. To address this knowledge gap, seasonal variations in FSS P fractions and their relation to water quality and streambed sediment were examined in three Swedish agricultural headwater catchments over 2 yr. Sequential fractionation was used to characterize P fractions in both streambed sediment and FSS. All catchments had similar annual P losses (0.4–0.8 kg ha–1), suspended solids (124–183 mg L–1), and FSS total P concentrations (1.15–1.19 mg g–1). However, distribution of P fractions and the dominant P fractions in FSS differed among catchments (p