Benthic dissolved organic carbon fluxes and distribution in Lake Baikal sediments

Dissolved organic matter (DOM) simultaneously with dissolved inorganic carbon (DIC), dissolved total carbon (TC) and cations (Na+, K+, Ca2+, Mg2+, Fe2+ and Mn2+) in sediment pore waters from Lake Baikal was investigated. That is the first detailed study of a relatively highly resolved DOC profile in benthic pore water profile from the Lake Baikal. We quantified DOC fluxes under different redox conditions in surface bottom sediment, which changed direction twice at the redox boundaries. Shown, that mobilization of DOC in oxygen-free sediments closely links to reductive dissolution of ferric minerals. Oxidized surface sediments are an efficient DOC trap where DOC is bound to ferric minerals. Redox conditions appears to be the primary regulator of the DOC exchange, resulting in sedimentary uptake of DOC (83 mol m-2d-1) under oxic conditions, and Lake Baikal sediment is a sink of DOC. The results of this study offer significant insight into the nature and properties of DOM in freshwater ecosystems.