BIOAVAILABILITY OF SEDIMENT PHOSPHORUS INPUTS TO THE LOWER GREAT LAKES (BIOASSAY, EUTROPHICATION, KINETICS)

In this study, river water samples were collected from several major tributaries to the Lower Great Lakes (Maumee R., Sandusky R., Honey Cr., Cuyahoga R., Genesee R., and Cattaraugus Cr.) during storm runoff events in the spring and early summer of 1980 and 1981. Suspended sediments from these samples were subjected to a chemical fractionation sequence of NaOH-CDB-HCl, as well as algal bioassay analyses of sediment P bioavailability using the Dual Culture Diffusion Apparatus (DCDA) technique of DePinto (1982).; NaOH-extractable P was the largest of the chemical fractions measured for the Ohio tributaries. HCl-P was the largest fraction for New York river sediments, reflecting a geology higher in apatite minerals. The release of sediment P in the presence of P-starved Selenastrum capricornutum followed approximately first-order kinetics. The mean percentages of total sediment P (T-Sed-P) determined by the bioassay method to be ultimately available (Pult) were: Maumee R. - 25.0%; Sandusky R. - 21.4%; Cuyahoga R. - 33.9%; Honey Cr. - 24.9%; Genesee R. - 19.3%; and Cattaraugus Cr. - 7.7%. The rate of sediment P release showed relatively little variation between tributaries, and averaged 0.182 day('-1) for all river sediment samples analyzed.; Sediments from several of the bioassay experiments were reconcentrated and subjected to the chemical fractionation sequence. P released during the bioassays was found to be associated predominately with the reactive NaOH-P fraction (R-NaOH-P).; The model expressions currently used to describe P release from suspended sediments in models of Great Lakes trophic status overpredicted the bioassay data for tributary sediments by a considerable amount after a period of about 7 days. Coefficients were calculated for two different models that more accurately described the bioassay results. In one model, P(,ult) was considered to be released at a single first-order rate, while in the other, P(,ult) was separated into rapidly and slowly released components.; Several other forms of P inputs to the Lower Great Lakes were also analyzed for chemical composition and/or bioavailability. These include Detroit River suspended sediments, Lake Erie bottom sediments, shoreline erosion (bluff) sediments, soluble P in tributaries, and an indirect point source of P.