MATHEMATICAL-MODELING OF THE EVOLUTION AND CURRENT CONDITIONS OF THE LADOGA LAKE ECOSYSTEM

This work presents a new ecosystem model of Ladoga Lake. This model co ntains a more detailed description of phytoplankton than in previous m odels constructed by the authors. In the new model, phytoplankton are presented as three ecological groups. It is allowed to reproduce more adequately, the process of Ladoga Lake eutrophication. The presented m odel allows calculation of the 3D spatial distribution of three groups of phytoplankton, dissolved organic matter, detritus, as well as nutr ients. mineral phosphorus and dissolved oxygen. The model was used for reproducing year-round functioning of the basin's ecosystem, which co rresponded to the condition of phosphorus loading, averaged over the p eriod 1984-1991. The constructed model also was used in reproducing th e lake's ecosystem evolution since 1962, which is when antropogenic lo ading started to increase. The latter circumstance lead to the beginni ng of, and to the development of, the eutrophication process in the ba sin. The phosphorus loading changes and weather instability were taken into account during the evolution reproduction. The results of these computational experiments show that it is possible to use this model i br forecasting the consequences of the phosphorus loading changes. (C) 1998 Elsevier Science B.V. All rights reserved.