Molecular biogeochemistry of dissolved organic matter in the permafrost-influenced Lena Delta and the coastal Laptev Sea

Dissolved organic matter (DOM) is a ubiquitous complex mixture of organic compounds in aquatic systems. DOM is an important contributor to the global carbon cycle. The global inventory of permafrost carbon represents half of the global belowground soil carbon. The mobilization and degradation of this carbon pool would have critical implications in the Arctic. The ultra-complex mixture of organic compounds in DOM is a proxy of ecosystem metabolism and represents an imprint of past and ongoing biogeochemical processes. Ultra-high resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and statistical analyses were performed on DOM samples obtained in various expeditions to the Lena Delta and Laptev Sea. The DOM composition, reactivity and properties in the permafrost-influenced Lena Delta and coastal Laptev Sea, Siberia were characterized. The systematics of the molecular DOM composition with respect to source of natural waters, reactivity during the Lena River - Laptev Sea transition, mobilization, mineralization and turnover of permafrost-derived DOM were addressed.