HOLOCENE BIOGEOCHEMICAL AND POLLEN HISTORY OF A LAKE ERIE, OHIO, COASTAL WETLAND

A five meter sediment core was taken from Old Woman Creek National Est uarine Research Reserve and State Natural Area and Preserve along the western basin of Lake Erie, U.S.A., to determine the historical biogeo chemistry of the wetland. Analysis of pollen and sediment chemistry re vealed that the area has remained a wetland since ca. 5,500 yr BP, des pite changing lake levels. Pollen stratigraphy indicates a distinctive local succession, which has been divided into three zones. Sediments from sometime after glaciation to 5,500 yr BP were characterized by lo w concentrations of herb pollen; the next zone showed an establishment of hardwood forest vegetation. The modern local vegetation developed after deforestation (about 200 years ago), when sedimentation increase d an order of magnitude, phosphorus deposition increased, and the ecos ystem changed from a macrophyte dominated wetland to a plankton domina ted marsh. After European settlement, the wetland retained its ability to act as a sink and biotic transformer of bioavailable phosphorus; h owever, abiotic processes seemed to be more important than the biotic transformations that dominated before deforestation.