What does a Trophic State Index (TSI) Number Mean?
The Trophic State Index is a classification system designed to “rate” individual lakes based on the amount of nitrogen, phosphorus and chlorophyll in the water. Using the index we can compare how productive lakes are is by its assigned TSI number. Classifications range from 1 to 100 and are generally described as follows: • Lakes with TSI values ranging from 0 to 49 are considered to be at the lowest end of the biological productivity scale. In other words: because there are fewer nutrients available in the water, these lakes tend to support less algae, aquatic plants, birds, fish, insects and other wildlife. • TSI values ranging from 50 to 59 are considered to be moderately productive • TSI values ranging between 60 and 69 are considered to have fairly high productivity • Lkes with TSI values ranging from 70 to 100 are the most productive have the highest nutrient concentrations, and have the potential to support the highest level of biological productivity (i.e.
