Mathematical Modeling of Trophic State and Nutrient Flows of Lake Karla using the PCLake Model

In the present article, we simulate Lake Karla, an important natural ecosystem under restoration in Greece, operating also as a reservoir. The lake trophic state is characterized as hypertrophic with the expected negative effects on biodiversity. The simulation of Lake Karla is a significant tool in terms of understanding, predicting and managing the ecosystem. We perform simulations using PCLake, a software package for shallow lakes, which provides a full set of parameters, modeling a wide range of physical, chemical and biological variables. The model is calibrated based on the time series of six variables for year 2012 and validated using data of years 2014–2015. We present the nutrient flow dynamics for year 2012 on a trimester basis, and investigate the interrelations of nutrient cycling and trophic state, through observed variables such as phycocyanin and chlorophyll-a concentrations, Carlson Trophic State Index and ratio of Dissolved Inorganic Nitrogen to Soluble Reactive Phosphorus.