SEDIMENT-PHOSPHORUS RELATIONSHIPS IN THREE NORTHCENTRAL OKLAHOMA STREAMS

Abstract

Sediment characteristics related to their potential for P uptake and buffering capacity were examined in threeadjacent Oklahoma streams in order to determine if stream sediments were the dominant controllers of water column Pand if benthic sediments were capable of buffering growing P loads to these systems. Sediment and water samples werecollected from Council Creek, Feather Creek and Little Stillwater Creek in northcentral Oklahoma. Particle sizedistribution, equilibrium phosphate concentration (EPC0), phosphorus sorption index (PSI), and exchangeable-P weremeasured for a single date for benthic sediments from each site. There were no detectable differences in particle sizecomposition; however, sediment attributes related to P varied significantly among sites. Sediments from Little StillwaterCreek had higher exchangeable P content and EPC0 relative to the other two sites. There were no consistent relationshipsbetween exchangeable P and sediment or water characteristics, while EPC0 was significantly correlated with percent silt.Sediment and water phosphate pools were in equilibrium at only one site. At the other two sites, either the sediment/waterbalance was temporarily in disequilibrium, or sediments were not the major determinant of water column P. In contrast tothe other sediment metrics, PSI did not vary among sites. Total sorption potential was attributed to both abiotic and bioticuptake, with biotic removal becoming increasingly important for sediments with high PSI values. Disequilibrium betweensediment and water column P and the relative importance of biotic sorption to PSI measurements suggest that factorsother than, or in addition to, physical and geochemical processes associated with benthic sediments, are important incontrolling streamwater P concentration and retention.