Nitrogen is important to all living things. Nutrients such as nitrogen occur naturally in both freshwater and saltwater. Plants and animals need nutrients to grow and survive. But too much nitrogen in the water fuels the growth of excessive algae, creating dense blooms that block sunlight and reduce oxygen for fish and other organisms. In the lake, total nitrogen was used to assess nitrogen intensity. Total nitrogen is a sum of organic nitrogen as well as ammonia and nitrate-nitrite compounds.
How was it scored?
Total nitrogen (TN) was used as an indicator in both the watershed and lake analysis. Year-round data for 2018 were analyzed. For each TN sample, the measurement was compared to the threshold on a pass/fail basis. Site scores were averaged into an overall region total nitrogen score.
The total nitrogen threshold used for the western Lake Erie basin analysis was 0.8 mg/L, from Chaffin et al. 2014.
The total nitrogen threshold used for the western Lake Erie watershed analysis was the U.S. EPA ecoregion threshold 2.18 mg/L.