title: The Sources of Carbon and Nitrogen in Mountain Lakes and the Role of Human Activity in Their Modification Determined by Tracking Stable Isotope Composition.
abstract: We studied the isotopic composition of organic matter in the sediments of eight mountain lakes located in the Tatra Mountains (Western Carpathians, Poland). The sediments of the lakes were fine and course detritus gyttja, mud, and sand. The total organic carbon content varied from 0.5 to 53 %. The C/N ratio indicated that in-lake primary production is the major source of the organic matter in the lakes located above the treeline, whereas terrestrial plant fragments are the major organic compounds in the sediments of dystrophic forest lakes. We also found that a clear trend of isotopic curves toward lower values ofδ13C andδ15N (both ~3 ‰) began in the 1960s. This trend is a sign of the deposition of greater amounts of NOxfrom the combustion of fossil fuels, mainly by vehicle engines. The combustion of fossil fuels in electric plants and other factories had a smaller influence on the isotopic composition. This trend has been weaker since the 1990s. Animal and human wastes from pastures and tourism had a surprisingly minor effect on lake environments. These data are contrary to previous data regarding lake biota and suggest the high sensitivity of living organisms to organic pollution.
authors.affiliation: Institute of Geological Sciences, Polish Academy of Sciences, Research Centre in Warsaw, Twarda St. No. 51/55, 00818 Warsaw, Poland.
authors.forename: Michał
authors.initials: M
authors.lastname: Gąsiorowski
authors.forename: Elwira
authors.initials: E
authors.lastname: Sienkiewicz
keywords: Acidification; Alpine lakes; Eutrophication; Fossil fuel combustion; Stable isotopes