Reconstructing phosphorus levels using models based on the modern diatom assemblages of 55 lakes in southern Quebec

Abstract

This study shows how modern diatom assemblages, obtained from the surface sediments of 55 deep and shallow lakes in southern Quebec and representing a gradient in trophic state and specific conductivity, can be used to reconstruct the historical water column concentrations of total phosphorus (TP) over time. Inference models were developed with the aid of regression analyses based on weighted means. The TP models demonstrate statistical performances equal to or superior to TP models developed in the past for other regions in Canada and elsewhere in the world. A reconstruction of TP values, based on fossil diatom assemblages of Lac Nairne (Charlevoix, QC), was conducted. Comparing the TP inferred values with the measured values and those estimated using export coefficients, the reliability of the model was proven. In addition, the comparison of the results obtained from reconstructions performed with two inference models (Quebec and Ontario lakes) also revealed that models predicted TP and not a collinear variable.