SEDIMENT TRAP STUDIES IN LAKE-MICHIGAN - RESUSPENSION AND CHEMICAL FLUXES IN THE SOUTHERN BASIN

The results of 4 years (1977-80) of sediment trap sample collection in the southeastern region of Lake Michigan are summarized and compared with water column and sediment characteristics. Mass flux data indicate strong seasonal patterns, with maximum fluxes recorded during the unstratified period. The large amount of winter resuspension is a mechanism which provides an intimate coupling of recent sediments and the water column. Also these trap study results indicate that there is a near-bottom (10-m-thick) benthic nepheloid layer whose chemical composition approaches that of deep water (fine grain) sediments. The amount of resuspended NaOH extractable phosphorus injected into the euphotic zone is estimated as approximately equal to the load of new phosphorus entering southern Lake Michigan. The role of resuspension in the cycling of organic carbon and contaminants associated with it appears to be important.