Algal-Available Phosphorus in Suspended Sediments from Lower Great Lakes Tributaries

Suspended sediments collected from five tributaries to the lower Great Lakes were chemically analyzed for several forms of phosphorus and bioassayed under aerobic conditions to measure the release of algal-available phosphorus. The bioassay data for all samples, interpreted through a first-order model of available phosphorus release, showed an average of 21.8 percent of the total paniculate phosphorus ultimately was available to Selenastrum capricornutum, and available phosphorus was released at an average rate of 0.154 day^?1. Amounts of available phosphorus varied considerably between tributaries with the Ohio tributaries (Maumee, Sandusky, and Cuyahoga Rivers) showing generally greater amounts than those in New York (Cattaraugus and Genesee Rivers). Non-apatite fractions of inorganic phosphorus (base-, and reductant-extractable) correlated well with levels of available phosphorus in the suspended sediment samples; however, the first-order release coefficients showed little dependency on the paniculate phosphorus characteristics. The results indicate that prediction of phosphorus dynamics in the lower Great Lakes may be made with greater accuracy than current models allow by considering available phosphorus to be released from an ultimately-available fraction of the total paniculate phosphorus during residence in the water column.