Distribution, Source and Cycling of Organic Carbon and Nitrogen in the Icy Soils of University Valley (McMurdo Dry Valleys of Antarctica)

Abstract

Between 2009 and 2013, 16 ice-bearing permafrost cores were collected from 10 polygons along the floor of University Valley (McMurdo Dry Valleys of Antarctica) and were subsequently analysed in order to assess the geochemical properties of the valley’s icy soils and ground ice. Elemental analysis showed that icy soils located in the seasonally non-cryotic zone (NCZ) of the valley contained (on average) twice as much organic carbon (1.19 mg/g) as the ice cemented permafrost soils sampled in its perennially cryotic zone (PCZ). It also showed that nitrogen accumulation in the icy soils was a result of atmospheric fallout and chemical weathering of mineral soils. Isotopic analysis showed that the organic matter contained in the valley’s icy soils are mostly derived from the deposition and burial of cryptoendolithic communities living in the adjacent sandstone valley walls. Dissolved organic carbon (DOC) concentration measures indicated that soils containing the highest amounts of DOC were enriched in 13CDOC relatively to soils with low DOC concentrations. This indicated that microbial activity in soils was the highest during past super interglacial periods. A soil habitability index calculation from Stoker et al. (2010) was used to establish that soils located in the NCZ were more habitable than soils sampled in the PCZ and also presumably more habitable than soils at many Mars landing sites.