Total Phosphorus

Total phosphorus is indicative of too much phosphorus in the water. Phosphorus is an essential nutrient for all plants and animals. However, too much phosphorus in the water causes algae to grow in large, dense blooms, which deplete oxygen for fish and other aquatic organisms. Phosphorus enters rivers and lakes when it is washed off the land, particularly from agricultural lands that have been fertilized.


How is it scored?

Total phosphorus (TP) was used as an indicator in both the watershed and lake analysis. Year-round data for 2018 were analyzed. For each TP sample, the measurement was compared to the threshold on a pass/fail basis. Site scores were averaged into an overall region total phosphorus score.

The total phosphorus threshold used for the western Lake Erie basin analysis was the U.S. EPA threshold 0.015 mg/L.

The total phosphorus threshold used for the western Lake Erie watershed analysis was the U.S. EPA ecoregion threshold 0.07635 mg/L.

A boat on Lake Erie floats a cloud of green algae. Photo by Jeff Reutter via Flickr CC BY