The changes in 33 factors in 8 shallow lakes and theircatchmentareas were studied over a 40 year period. Large-scale changesinecological conditions were indicated for the studied region:thedisappearance of about 30% of wetlands, a reduction in thesurfacearea of lakes by about 15% and increased forest cover in oftheregion by about 26%. Six lakes indicate increasingtransparencyand nutrient concentration, while two changed in the oppositedirection. Various reactions were observed in zooplankton andzoobenthos.Generally, individual patterns for the reactions of lakeecosystemswere indicated, even in very similar lakes. The character ofsomechanges might indicate on modulus (non-linear) types ofbiocoenosisreactions. The character and the rate of the overgrowing oftheopen waters of lakes depends to a the high degree of thespeciescomposition and the predominating structure of the plants inthelake and its drainage basin.To avoid incorrect interpretation of the reactions of lakeecosystems it is recommended that multifactor analysis be usedfordrainage basins over long periods of time.