Sediment weight loss on ignition was analyzed with an electric muffle furnace (SNOL 8,2/1100, Utena, Lithuania). Crucibles were weighed without sample (WC), and samples were dried in crucibles overnight at 105 °C. After cooling, crucibles with dry samples were re-weighed (WS). For determination of the organic matter content, samples were combusted in the furnace at 500 °C for four hours. After cooling in a desiccator, the samples were reweighed (WA). Loss on ignition (LOI)