*3.2.2 Trophic states*

Various indicators are used to measure the degree of this phenomenon, and one of the best indicators is the use of Nurenberg's classification [64]. This classification is based on the concentration of total phosphorus and nitrogen and chlorophyll a (**Table 2**) [65, 66].

The concept of trophic state is complex and lacks a precise definition. In the past, the trophic state was mainly related to the amount of nutrients in a lake. However, it now also takes into account biological factors that can cause changes in the lake's morphology. The term "eutrophic state" is not only applicable to lakes with high nutrient levels, but also to shallow wetlands and places where aquatic plants grow, even if nutrient levels are not high. Lakes are classified into four groups based on their trophic state: "oligotrophic," "mesotrophic," "eutrophic," and "hypertrophic."
