Dissolved organic matter and amino acids in Ice Complex sediments of Muostakh Island (East Siberia)

• Main Author: Haack, Michaela
• Format: Thesis
• Language: unknown
• Published: 2014
• Subjects: Arctic; Laptev Sea; Climate change; Ice; laptev; permafrost; Siberia
• Online Access: https://epic.awi.de/id/eprint/35971/; https://hdl.handle.net/10013/epic.43870

The climate change in the Arctic has received more attention in the recent decades. Especially the carbon-rich permafrost has become an area of intense research. It´s ice-rich grounds are especially vulnerable to climate warming and ice-thaw. Carbon stored in permafrost can be activated and can become part of the carbon cycle. The transport of organic matter (OM) by coastal erosion of thawing permafrost is one type of permafrost degradation. In this study 23 ice complex sediment samples from a coast section of Muostakh Island (Laptev Sea, East Siberia) were analyzed. Permafrost melt water and water extractable dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) were measured. Water extractions as simulation of natural processes extracted on average between 45 % to 54 % more DOC compared to DOC in melt water. By this, a mobile fraction of organic carbon (OC) stored in ice complex sediments (~13 mg/100 g of sediment) was estimated. With DOC and TDN values C/N ratios were calculated to assess the availability of nitrogen throughout the coastal sediment profile of the coast. In the second part the amino acid content in permafrost melt waters was determined. On average, 3.64% of DOC exists in form of hydrolysable amino acids. L and D amino acid enantiomers were discriminated and the racemization states of single amino acids were determined using High Pressure Liquid Chromatography (HPLC). Amino acid enantiomers were converted into diastereomers using pre-column derivatization with o-phthaldialdehyde and N-isobutyryl-L-cysteine. The resulting fluorescent derivates were detected after separation in a reversed-phase column. Glycine and alanine were the most abundant amino acids. Highest contributions of Dforms to the total of each amino acid were found in alanine, asparagine, glutamine and serine. Based on recent estimates of sediment discharge from Muostakh Island, an annual transport of ~ 14 t DOC and ~ 0.5 t amino acids caused by coastal erosion was roughly estimated.