ID:02 Biogeochemistry of permafrost ecosystems and global change

21 February 2023 | 16:00 - 18:00 (GMT+1)

Open Session - HYBRID

 

Room: Hörsaal 1

 

Session Conveners: Nicolas Valiente Parra (University of Vienna, Austria); Oriol Grau Fernandez (University of Antwerp, Belgium); Victoria Sophie Martin (University of Vienna, Austria)

 

Session Description: 

Global change alters climate patterns on regional, continental and hemispheric scales. Permafrost ecosystems are among the most sensitive ones to such impacts. Permafrost soils and permafrost-affected peatlands cover ~25 % of the terrestrial surface and hold the world's largest soil organic carbon and global nitrogen pools. Gradual deepening of the active layer due to rising temperatures impacts manifold biogeochemical and ecological processes. Yet, in ice-rich landscapes, thaw can result in substantial impacts even noticeable to the human eye, such as thermokarst processes including ground collapse or the emergence of thermokarst lakes. When permafrost thaws, newly available organic matter is available for microbial decomposition. Microbial activity drives all biogeochemical cycles but is anticipated to be considerably modified in a way to turn these climate susceptible ecosystems from sinks to sources of greenhouse gases with inevitable consequences for global climate. This session invites contributions focusing on microbial activity and biogeochemical cycling within all kinds of terrestrial permafrost affected systems in the wake of a changing climate. We encourage submissions involving studies on organic and inorganic carbon, nitrogen, phosphorus and other elements based on laboratory experiments, field observations or modelling work.

 

Presentations: 

• unfold_more16:05 - 16:20: When cool microbes warm up

  Victoria Sophie Martin¹; Andreas Richter¹, Carolina Urbina Malo¹, Julia Horak¹, Rachele Lodi², Julia Wagner³, Niek Speetjens⁴, Gustaf Hugelius³, Willeke A'Campo³, Luca Durstewitz³, George Tanski⁴, Michael Fritz⁵, Hugues Lantuit⁵, Cornelia Rottensteiner¹, Moritz Mohrlok¹,
  ¹University of Vienna; ²Ca' Foscari University of Venice; ³Stockholm University; ⁴Vrije Universiteit Amsterdam; ⁵Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research

  Abstract:

  Arctic ecosystems outpace global rates of temperature increase. Permafrost soils store vast amounts of organic C and their fast thaw raises concerns about their role in fuelling a positive feedback via the release of greenhouse gases. This feedback occurs due to warming induced stimulation of mass-specific growth and respiration rates, that do not acclimate over time. Our mechanistic understanding of microbial C cycling in permafrost soil under warming is still vague. The high spatial heterogeneity of Arctic landscapes adds complexity in addition. In the following study we investigated how microbial activity changes in different soil horizons and polygonial landscape units of a lowland tundra. Under controlled laboratory conditions, we subjected samples to warming and measured microbial respiration weekly, as well as microbial biomass, growth and potential enzymatic activities after 8 weeks of incubation. The temperature response (Q10) of permafrost microbial communities was high in all investigated soils. While differences between horizons in the respiratory Q10 values were prevalent in the beginning of the incubation, all response rates converged to similarly high values (2.4-3) at its end. Since microbial biomass was unaffected but mass-specific growth was enhanced in all soil layers and landform units, a higher turnover is suggested. In consent, we also observed elevated potential extracellular activities involved in C, N and P acquisition.

  Our results corroborate that short-term warming strongly stimulated the activity of permafrost microbes without indications for physiological acclimation. Yet, the temperature response of different soil horizons and landform units seems more similar than anticipated.

• unfold_more16:20 - 16:35: Don’t look down: permafrost microbes and soil organic matter in times of global warming

  Cornelia Rottensteiner¹; Andreas Richter¹; Victoria Sophie Martin¹; Hannes Schmidt¹; Moritz Mohrlok¹; Leila Hadžiabdić¹; Rachele Lodi²; Julia Wagner³; Niek Speetjens⁴; Gustaf Hugelius³; Julia Horak¹; Carolina Urbina Malo¹; Willeke A'Campo³; Luca Durstewitz³; George Tanski⁴; Michael Fritz⁵; Hugues Lantuit^{5
  1}University of Vienna; ²Ca' Foscari University of Venice; ³Stockholm University; ⁴Vrije Universiteit Amsterdam; ⁵Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research

  Abstract:

  The Arctic warms four times faster than the global average, leading to widespread permafrost thaw. Organic matter that was stored in permanently frozen soil layers for centuries and millennia is no longer occluded from microbial decomposition. However, our current knowledge about the composition of soil organic matter (SOM) and microbial community composition in permafrost soils is limited, particularly regarding their spatial variability. The objective of the present study was to analyze (1) SOM composition and (2) microbial community composition within the permafrost soil profile and in different landscape types and (3) to investigate their interaction in explaining observed temperature responses. We examined permafrost soils from 4 different layers within 3 landscape types from 2 sites in arctic Canada. We used pyrolysis-GC-MS fingerprinting to characterize SOM and amplicon sequencing (16S rRNA gene and ITS1 region) to analyze microbial community composition. We performed a warming experiment, incubating soils at 4 °C (control) and 14 °C (warmed) for 8 weeks to investigate the temperature response of microbial growth and respiration. Our results suggest distinct bacterial, archaeal and fungal communities established among the studied sites, polygon types and soil layers. Microbes of the active layer seem to be better adapted to changing temperatures when submitted to short-term warming than microbial communities of frozen or water-saturated soils. This pattern might be connected to the differential distribution of the main SOM compound classes (carbohydrates, lignin derivatives, lipids, N-compounds, phenols & aromatics). We will further discuss the interaction of microbial community and SOM composition.

• unfold_more16:35 - 16:50: Tracking changes in iron organic carbon interactions upon permafrost thaw

  Sophie Opfergelt¹, Arthur Monhonval¹, Maxime Thomas^{1
  1}UCLouvain

  Abstract:

  Mineral organic carbon (OC) interactions in soils and ice-rich sediments are key to stabilize OC and mitigate greenhouse gas emissions upon permafrost thaw. However, changes in soil water pathways upon permafrost thaw are likely to affect the stability of mineral OC interactions. Dissolution of mineral surfaces can release associated OC which contributes to carbon loss, whereas precipitation of new mineral surfaces can promote loci for OC interactions limiting carbon loss. Here we use radiogenic Sr isotopes to locate in situ dissolution-precipitation processes of mineral OC interactions along a gradient of permafrost thaw in soils and ice-rich sediments. In these materials, about 20% of OC is stabilized as organo-mineral associations (association between ferrihydrite and OC) and organo-metallic complexes (associations between Fe, Mn, Al, Ca polyvalent cations and organic acids). We target Sr adsorbed or occluded to metal oxides or participating in organo-metallic complexes. We hypothesize that a change in the Sr isotopic signature of such mineral OC interactions upon permafrost thaw indicates a destabilization of the binding between mineral surfaces and Sr, and hence OC. We show that it is in saturated layers that mineral OC interactions have remained undissociated and preserved since their formation. At the redox interface, the data highlight processes of dissolution and precipitation of the mineral OC interactions, supporting loci for the loss and gain in OC stabilization potential. Given the importance of stabilizing surfaces and cations involving Fe for the stabilization of OC in permafrost environments, we propose an approach to estimate at larger scale in Arctic the proportion of this “reactive iron” in permafrost soils.

• unfold_more16:50 - 17:05: Components of carbon cycle in soils of Arctic islands (Novaya Zemlya, Franz Josef Land)

  Anna Bobrik
  
  

  Abstract:

  The interaction of Arctic ecosystems with the atmosphere under conditions of global climate change is especially important for the overall development of the biosphere. Understanding the heterogenity in carbon exchange in terrestrial ecosystems is a significant step towards understanding the global carbon cycle. The aim of our study was to assess variability of soil organic carbon (CO2 efflux, content of microbial and water-extractable organic carbon) and relationship with environmental factors in the soils of typical ecosystems of the islands of the Franz Josef Land (Heys Island (80°37 N, 58°03 E) and Hooker Island (80°20 N, 52°46 E)) and Novaya Zemlya (76°56 N, 68°32 E) archipelagos. The special grids (5 m * 5 m, 25 points of measurements) have been used on all sites. Our results show that CO2 efflux by the soils of the typical ecosystems at the monitoring sites in June 2021 (Novaya Zemlya, Hayes Island, Hooker Island) varied significantly from 0 to 278 mgСО2/m2hr, 54±37 mgСО2/m2hr on average (n=75). All other investigated parameters (environmental parameters, as well as contents of the labile and microbial carbon) are characterized by high spatial variability. Active layer thickness determines the type of ecosystem in such landscapes and organic matter transformation processes. Our results emphasize the significant contribution of soil CO2 efflux to the global carbon pool.

• unfold_more17:05 - 17:20: Greenhouse gas and vegetation change beyond initial thermokarst formation in permafrost peatlands

  Hanna Lee¹; Casper Tai Christiansen²; Inge Althuizen³, Anders Michelsen²; Peter Dörsch⁴; Anja Greschkowiak¹; David Risk⁵; Sebastian Westermann^{6
  1}Norwegian University of Science and Technology; ²University of Copenhagen; ³NORCE Norwegian Research Centre, Bjerknes Centre for Climate Research; ⁴Norwegian University of Life Sciences; ⁵St. Francis Xavier University; ⁶University of Oslo

  Abstract:

  Initial thermokarst formation is expected to release large amounts of greenhouse gasses to the atmosphere, creating positive feedback to climate warming. The current understanding supports that thermokarst formation will lead to surface inundation, which leads to dominantly producing methane during the decomposition. Over time, natural succession may occur leading to decreased methane release and increased carbon uptake. We investigated how thermokarst formation and subsequent natural succession over time affect CO2, CH4, and N2O release and uptake in northern Norway (69ᵒN), where recent degradation of permafrost created thaw ponds in palsa peat plateau-mire ecosystems. We observed changes in vegetation, soil and water microclimate, biogeochemistry, and soil CO2, CH4, and N2O fluxes. We show that abrupt permafrost thaw and land surface subsidence increase net annual carbon loss. Permafrost thaw accelerated CO2 release greatly in thaw slumps (177.5 gCO2 m-2) compared to intact permafrost peat plateau (59.0 gCO2 m-2). During the growing season, peat plateau was a small sink of atmospheric CH4 (-2.5 gCH4 m-2), whereas permafrost thaw slumping and pond formation increased CH4 release dramatically (ranging from 9.7 to 36.1 gCH4 m-2). Furthermore, CH4 release continues to increase even in natural succession likely due to aerenchyma transport of CH4 from deeper soil. Beyond thermokarst formation, carbon uptake from the natural succession of vegetation, but we show that greenhouse gas emissions continue to increase beyond abrupt permafrost thaw event towards natural succession.

• unfold_more17:20 - 17:35: Mercury seasonal variation in two thermokarst lakes in the Canadian Subarctic

  Beatriz Malcata Martins¹, Holger Hintelmann², Martin Pilote³, Rute Cesário¹, Rodrigo Dias¹, João Canário¹, Audrey Laberge-Carignan⁴, Raoul-Marie Couture^{4
  1}Instituto Superior Técnico; ²Trent University; ³Environment and Climate Change Canada; ⁴Université Laval

  Abstract:

  Permafrost covers almost 25% of exposed land in the Northern Hemisphere and is considered a barrier to contaminants that can be accumulated in this type of soil during extended periods of time. One of these contaminants is mercury (Hg), recognized as a high priority contaminant over decades and under the Global Minamata Convention on Mercury. The accelerated warming of the Arctic is leading to the thawing of ice-rich permafrost resulting in a release of large amount of Hg and carbon (C) and in the formation of thermokarst lakes. These unique ecosystems are rich in organic matter, creating ideal living conditions for certain microbial communities such as methylating bacteria, one of the responsible for the formation of methylmercury (MMHg) with severe neurotoxic effects. In this presentation, it will be reported the total mercury (THg) and MMHg concentrations in water and sediments in winter and summer seasons in thermokarst lakes in the Canadian Subarctic, near the Cree and Inuit Communities of Whapmagoostui-Kuujjuarapik, Nunavik (Canada). Seasonal differences will be explored as results show that in sediments THg ranges between 73-95 ng/g and MMHg between 1.2-4.8 ng/g in winter, and THg ranges between 34-54 ng/g and MMHg between 0.08-0.2 ng/g in summer. The THg and MMHg concentration vertical profiles in the water column were also analyzed as well as possible relationships between these and other relevant physicochemical variables.

• unfold_more17:35 - 17:50: Presence of Contaminants of Emerging Concern in the Sediments of Kongsfjorden and Krossfjorden: Possible Impact of Human Activities in Arctic

  Charuvila T. Aravindakumar¹; KP Krishnan²; Usha Aravind³; Nejumal Khalid^{4
  1}Mahatma Gandhi University Kottayam; ²National Centre for Polar and Ocean Research; ³Cochin University of Science and Technology; ⁴Pusan National University,

  Abstract:

  Arctic, being one of the largest and most pristine regions of the world, its environmental conditions are always under continuous evaluation. Arctic region is susceptible to environmental pollution due to environmental diversity, absence of nutrients in the environment and extreme seasonal light variation of the region. Pollution and fate of pollutants in the Polar Regions are important topics of investigation in the last several decades. We have analysed sediment samples from Kongsfjorden and Krossfjorden, two sites from Arctic region, and detected a number of emerging contaminants (ECs) using high resolution mass spectrometry connected to UPLC (LC-Q-ToF-MS). Out of the seven sampling sites selected, bisphenol S (BPS), an identified pollutant and plasticiser, was detected and quantified in three sediment samples from Kongsfjorden (≈ 0.2 ppm). Four major surfactants (decylbenzenesulfonic acid, undecylbenzenesulfonic acid, 2-dodecylbenzenesulfonic acid and tridecylbenzenesulfonic acid) were also identified. A possible metabolite of BPS (sulfurtrioxide derivative of BPS) was identified in one of the samples. During the second sampling 2018, we found metoprolol, propranolol, lidocaine and mefenamic acid in micro gram per liter. Other identified compounds include Tetrahydrofurfuryl acrylate, Diphenyl sulfone, 2-[4-(3-hydroxypropyl)-2-methoxyphenoxy]propane-1,3-diol, Methallenestrilphenol, Tofogliflozin, Hydrocortisone acetate, p-Hexyloxybenzoic Acid, Myristamide, Palmitamide, Zingerone. It is proposed that the presence of these compounds is the result of human activities in the region for a long time.

• unfold_moreEnvironmental controls of organoprofiles in permafrost soils of North-Western Siberia: insights from metagenomics and 13C-NMR spectroscopy - Poster Presentation

  Ivan Alekseev; Aleksandr Shein; Antonina Chetverova,

  Abstract:

  Permafrost soils are the part of polar ecosystems and play a key role in accumulation, transformation, redistribution and migration of various chemical compounds and elements. Qualitative and quantitative studies of soil organic matter and soil microbial communities are crucial as the massive amount of organic carbon stored in permafrost soils might be vulnerable to priming, caused by the increasing availability of plant-derived organic compounds with rising temperatures. Our work is aimed at characterizing molecular organization soil organic matter, delineating its potential vulnerability as well as assessment of soil microbiome structure and functions in various parts of North-Western Sibeia region. We studied more than 150 samples collected from tundra and forest-tundra of Yamal and Gydan peninsula. Solid-state 13C-NMR spectrometry showed low amounts of aromatic fragments in majority of studied soils. All studied soils are characterized by predominance of aliphatic structures, and also carbohydrates, polysaccharides, ethers and amino acids. The predominance of aliphatic carbon species also reveals early stages of humification process in studied soils. This is in line with results of previous research (although occasional) on different sectors of Siberia. Soil microbiome was investigated at different locations using 16S rRNA gene pyrosequencing and revealed 48 bacterial and archaeal phyla, among which proteobacteria (27%) and actinobacteria (20%) were predominant. Principal component analysis showed that among the environmental factors affecting soil microbiome structure pH range and nitrogen accumulation are the most important ones.