Catchment soil characteristics predict organic carbon, nitrogen, and phosphorus levels in temperate lakes

English. Allochthonous supply of dissolved organic matter (DOM) and nutrients from the catchment have a sub-stantial impact on the physical and chemical properties of lake water. Transport of DOM and nutrients is affectedby different catchment characteristics, e.g., catchment area, soil and land cover, and population density. The aim ofthis study was to relate geological, hydrological, land-cover, and soil characteristics of 52 temperate catchments inEstonia to variability in DOM (measured as dissolved organic carbon [DOC]), total organic nitrogen (TON), andtotal phosphorus (TP) in lakes and to assess the relative importance of different land-cover and soil types as sourcesof these substances. DOC, TON, and TP were very diverse in the studied lakes. Strong positive correlation betweenDOC and TON indicated that these substances had similar concentration patterns and sources. Catchment soil coverwas the best predictor of DOC, TON, and TP levels in lakes, explaining up to 43.8% of their variabilities. This obser-vation can partly be explained by different soil organic carbon (SOC) content: soils with higher SOC were associatedwith higher lake DOC and TON, whereas soils with low SOC corresponded to lower DOC and TON. Similar to othertemperate lakes, bogs and peat soils were a major source of DOM in our studied lakes. DOC, TON, and color werepositively associated with percentages of peat soils in the catchment. On the other hand, TP increased with the pro-portion of urban areas in the catchments, indicating the importance of human impact on its concentration. Under-standing the impact of different catchment characteristics on DOC, TON, and TP in temperate lakes is crucial fordeveloping transport models used for predicting future levels of DOM and nutrients under changing climate and landuse.

English. This study was funded by the Estonian Research Council grants PUTJD954, PRG709, and PRG1167, by the European Regional Development Fund through Estonian University of Life Sciences ASTRA project “Value-chain based bio-economy”, and by the European Union H2020 WIDESPREAD grant 951963 (TREICLAKE). The Estonian Ministry of Environment and the Estonian Environment Agency supported data collection in the national monitoring program.

English. Received 23 December 2020; Accepted 23 August 2021; Published online 30 November 2021. Associate Editor, Janice Brahney.

English. This study was funded by the Estonian Research Councilgrants PUTJD954, PRG709, and PRG1167, by the European Regional Development Fund through Estonian University of LifeSciences ASTRA project “Value-chain based bio-economy”, andby the European Union H2020 WIDESPREAD grant 951963(TREICLAKE). The Estonian Ministry of Environment and theEstonian Environment Agency supported data collection in thenational monitoring program.