Carbon and nitrogen stable isotope fractionation in the sediment of Lake Bled (Slovenia)

Stable isotope composition of carbon and nitrogen in the sediment and pore water of a eutrophic freshwater lake was studied. Based on changes in the δ11C and δ15N values of dissolved components and sediment fraction. possible processes involved in the decomposition of sedimentary organic matter are outlined. The relative importance of acetate fermentation and CO2 reduction was estimated using known mathematical models, and ammonia assimilation by methanogenic bacteria is hypothesised to be the main process governing the isotope fractionation of dissolved nitrogen in pore water.