Peaks in biogenic silica concentration in cores from high sedimentation areas in Lake Erie and Lake Ontario provide two potential time horizons that will be used to tests the limits of stratigraphic correlation in depositional basins. The first peak has been associated with European settlement and forest clearance in the late 1980's and the second peak has been attributed to a rapid increase after 1950 in sewered population. The causal mechanism hypothesized for both peaks is increased inputs of phosphorus and resulting increased production of diatoms until silica becomes limiting. The basic objectives of the proposed research are to determine how the biogenic silica stratigraphy changes in relation to sedimentation rate and whether nutrient accumulation (different forms of phosphorus and biogenic silica) varies with sedimentation rate. This research has important ecological implication because siliceous microfossil population structure will be analyzed to determine if time-dependent signals are present across depositional basins. In addition, the research will address questions about the relationship between phosphorous loading and diatom production which may be different than reported previously in the literature. Thus, research on biogenic silica and siliceous microfossils offers promise for developing independent time biomarkers in the sediment record and in understanding the causal mechanisms responsible for their presence.
