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 (R² = 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 (R² = 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.

Keywords:

• Diatoms
• Great Lakes
• water quality index

Acknowledgments

With this work we honor the memory of John Kingston. We also acknowledge the work of the many people involved with the Great Lakes Environmental Indicators project who contributed to this work including: G. Stoermer who provided taxonomic expertise; N. Andresen who assisted with diatom identification and enumeration; J. Hennick, J. Reed, and J. Ameel, who performed water chemistry analysis; as well as the students and summer help who aided in the data-collection effort. We also acknowledge the contributions of R. Kreis and J. Thompson who provided Environmental Protection Agency (EPA) oversight to the project. This research was funded by a U.S. EPA Science to Achieve Results (STAR) grant to the Great Lakes Environmental Indicators project, US EPA Agreement EPA/8286750. The document has not been subjected to the agency's peer and policy review and therefore does not necessarily reflect the view of the Agency, and no official endorsement should be inferred. This is contribution number 436 of the Center for Water and the Environment, Natural Resources Research Institute, University of Minnesota, Duluth.

Notes

∗Deceased.