A diatom quality index from a diatom-based total phosphorus inference model

Abstract

A diatom quality index to assess diatom community impairment in the nearshore wetlands of the Laurentian Great Lakes was developed from a diatom-based total phosphorus (TP) weighted average inference model. The index is calculated with a weighted average equation using species optima standardized to a 1–10 scale and species tolerance standardized to a 1–3 scale. Multiple regression analysis revealed a moderate fit (R 2 = 0.63) between site scores of the selected index and GIS derived watershed characteristics (agriculture, soils, and industrial facilities). These index scores more closely fit watershed characteristics than the diatom inferred TP (R 2 = 0.59). In a regression tree analysis, soil permeability separated higher index scores from lower scores identifying this variable as an important interaction factor in the analysis. The diatom quality index can be a powerful tool for analyzing habitat quality in the Great Lakes and can communicate the link between quantifiable diatom assemblage response with watershed-level disturbance.