Abstract
This study presents and discusses the result of research on the chemical composition of bottom sediments of throughflow lakes located in Drawieński National Park. Basic hydrochemical indicators of the studied sediments are discussed: total organic carbon (Corg), total nitrogen (Ntot), and the Corg/Ntot ratio, which shows the rate of organic matter mineralization. The research and the analysis of the results show that the quality of the studied sediments changed with their distribution in the lake basin. The highest Corg and Ntot values were noted in sediments accumulated in the maximum depth of each lake, and at the inflow and outflow from the first lake in the whole cascade of throughflow lakes. Low Corg/Ntot ratios indicate that most of the sedimentary organic matter in the throughflow lakes comes from aquatic organism production, but the small participation of land-plant organic matter delivered to the lakes is also shown.