The Main Factor Determining the Dynamics of the Lake Ecosystem under Excessive Nutrient Loading (A Case Study of the Naroch Lakes)

The system of the Naroch lakes, which includes the eutrophic Lake Batorino, the mesotrophic Lake Myastro, and the oligo-mesotrophic Lake Naroch, serves as a model object for the study of the factors initially influencing the state of a particular lake ecosystem affected by variable nutrient loading. Throughout the 1970s–2000s, these lakes have been going through the stages of anthropogenic eutrophication, deeutrophication, and benthification. A set of continuous data based on the seasonal means ​​of the eight parameters from each lake for the period 1978–2015 has been analyzed by Principal Component and Singular Spectrum Analysis (SSA, or Caterpillar). In addition, we consider the dynamics of the trophic index of each lake, which had been calculated earlier at the same data set. The first main component is the stability of the lake ecosystem under variable nutrient loading, which is inversely related to the trophic state of the water body. This component determines the condition of the Batorino, Myastro and Naroch lakes by 63, 65, and 43% respectively.