Variations in stream water and sediment phosphorus among select ozark catchments

Stream sediments play a large role in the transport and fate of soluble reactive phosphorus (SRP) in stream ecosystems, and equilibrium P concentrations (EPC0) of benthic sediments at which P is neither adsorbed nor desorbed are often related to stream water SRP concentrations. This study evaluated (i) the variation among water chemistry and sediment-P interactions among streams draining catchments that varied in the land use; (ii) the relations between SRP concentration, sediment EPC0, and other measured abiotic factors (e.g., particle size distribution, solpe of linear sorption isotherms, etc.) in the streams sediments; and (iii) the use of the traditional Mehlic-3 (M3) soil extraction on stream sediments. Stream water and sediments were sampled at 22 selected Ozark streams in northwest Arkansas during fall 2003 and spring 2004. Nitrate-N concentrations in the water column (r = 0.69) and modified P saturation ratios (PSRmod) of the benthic sediments (r = -0.56) and Mehlich-3-extractable P (M3P) content (r = -0.47) decreased with an increase in the percent forested area. Soluble reactive P concentrations in the stream water were positively correlated to sediment EPC0 (r = 0.51), although sediment EPC0 was generally greater than SRP. The M3 soil extraction was useful in identifying abiotic factors related to SRP concentrations were positively correlated to M3P contents (r = 0.50) and PSRmod (r = 0.71) of the benthic sediments. Thus, M3P and EPC0 estimates from stream sediments may be valuable yet simple indicators of whether benthic sediments act as sinks or sources of P in fluvial systems, as well as estimating changes in stream SRP concentrations.