PARTITIONING OF TOTAL SUSPENDED PARTICULATES IN THE WESTERN BASIN OF LAKE ERIE AND SANDUSKY BAY BY LASER PARTICLE SIZE ANALYSIS

Suspended particulates represent one of the principle classes of non-point source pollution in Lake Erie and comprise both lithogenic and biogenic particles. Our objective was to partition the suspended particulates into biogenic and lithogenic components to explore the pattern of co-variation associated with the two classes of particles. We collected 1L surface water samples from 10 to 20 stations during a series of five day cruises (July 13, 20, 29; Aug 14, and 21, 2004) aboard the R/V Gibraltar III in the western basin of Lake Erie and the mouth of Sandusky Bay. Volume concentration and laser particle size spectra were generated for each sample using a Malvern Mastersizer 2000 laser particle size analyzer. Comparison of the Malvern volume concentration measurements (a proxy for total particulate concentration) with in situ turbidity measurements from a HydroLab CTD equipped with a turbidity meter indicate that the Malvern provides an accurate means of estimating total suspended particulates in this environment. Samples collected in the mouth of Sandusky Bay, the plumes of the Toussaint and Portage Rivers and at the boundary of the Western and Central basins exhibited the greatest temporal variability in volume concentration. The grain size spectra of coretop sediment collected from the lake bottom at each sampling location indicated very little variation in the distribution of sediment grain size for the western basin of Lake Erie and Sandusky Bay. Comparison of the particle size spectra for the surface water samples with the particle size spectra of the coretop sediment indicates that stations with the greatest concentration of suspended sediment were located in Sandusky Bay or in the vicinity of the plumes of the Toussaint and Portage Rivers, while samples furthest from the shoreline exhibited the lowest concentration of suspended sediment.