Hypolithic communities shape soils and organic matter reservoirs in the ice-free landscapes of East Antarctica

Abstract

The soils of East Antarctica have no rhizosphere with the bulk of organo-mineral interactions confined to the thin microbial and cryptogamic crusts that occur in open or cryptic niches and are collectively known as biological soil crust (BSC). Here we demonstrate that cryptic hypolithic varieties of BSC in the Larsemann Hills of East Antarctica contribute to the buildup of soil organic matter and produce several types of continuous organogenous horizons within the topsoil with documented clusters of at least 100 m2. Such hypolithic horizons accumulate 0.06–4.69% of organic carbon (TOC) with isotopic signatures (δ13Corg) within the range of −30.2 – −24.0‰, and contain from 0 to 0.38% total nitrogen (TN). The properties of hypolithic organic matter alternate between cyanobacteria- and moss-dominated horizons, which are linked to the meso- and microtopography patterns and moisture gradients. The major part of TOC that is stored in hypolithic horizons has modern or centenary 14C age, while the minor part is stabilized on a millennial timescale through shallow burial and association with minerals. Our findings suggest that hypolithic communities create a “gateway” for organic carbon to enter depauperate soils of the Larsemann Hills and contribute to the carbon reservoir of the topsoil at a landscape level.

Exopolysaccharides from Marine Microbes: Source, Structure and Application

“…Joseph et al reported that the EPS produced by the marine psychrophilic bacterium Colwellia psychrerythraea strain 34H could affect the carbon cycle and nutrient transfer in the deep sea [ 161 ]. In the Antarctic environment, the EPS promote the accumulation of soil organic matter at the landscape level in depauperate Antarctic soil [ 79 , 162 ]. Antarctic green algae sequester 479,000 tons of carbon each season [ 163 ].…”

Extracellular polymeric substances in Antarctic environments: A review of their ecological roles and impact on glacier biogeochemical cycles

“…In such regions, sediment binding by EPS builds the physical structure of the soil, stabilizing the soil, retaining moisture and protecting it from erosion (Büdel and Colesie, 2014). Carbon and nitrogen fixing activities within the biocrust also helps improve its fertility and contributes to the carbon reservoir of the topsoil at a landscape level (Jung et al, 2018;Mergelov et al, 2020).…”

“…In the Antarctic environment, where decomposition rates are low, biocrusts also act as an important CO 2 sink continuously enriching the soil with organic carbon contributing between 7 and 17 % total organic carbon in the top soil (Jung et al, J o u r n a l P r e -p r o o f 2018). They therefore facilitate the build up of soil organic matter at a landscape level in depauperate Antarctic soils (Mergelov et al, 2020). Some of the organic carbon fixed by the autotrophic communities is eventually utilized by heterotrophic microbes and CO 2 is released back into the atmosphere through community respiration (Stibal et al, 2012).…”

Novel Lichen-Dominated Hypolithic Communities In the Namib Desert

“…In contrast, the ventral surfaces of translucent pebbles (mainly quartz or marble) often harbor hypolithic communities that constitute substantial standing biomass [2,3,4]. Indeed, hypolithic microbial communities are considered hot-spots of primary productivity and organic matter accumulation in hyper-arid deserts [5]. Under these translucent rocks, microbial communities exist in microrefugia with less stringent environmental conditions than open soils, where the overlying lithic substrate provides protection against high incident UV fluxes, generates thermal buffering and enhances moisture availability [6].…”