Search Results (4)

Mofettes or natural CO₂ springs release large amounts of geogenic CO₂ at ambient temperature, leading to long-term soil hypoxia in these extreme ecosystems. Thus, they can serve as natural long-term experiments in ecology and evolution and other environmental studies, providing stable long-term changes in abiotic factors that are most pronounced in mofette soils. This paper reviews basic research on rhizosphere processes, soil microbial communities, and microbial diversity in mofettes, focusing on reports describing the effects of altered soil gas regimes on root respiration and the diversity and community structure of archaea, bacteria, and fungi in soil. Furthermore, an insight into possible applications of mofette ecosystems is given. For more than 20 years, mofettes have provided new insights into the importance of long-term changes in abiotic environmental factors in regulating soil biodiversity, serving as a model for extreme ecosystems. Mofettes provide an innovative approach to the study of many ecological processes that occur slowly and, therefore, require extensive and lengthy observations and experiments, acting as a space-for-time substitution. Previous studies in mofettes around the world have determined plant responses to elevated CO₂ concentrations over multiple generations, described new species of collembolans and yeasts, and identified stable patterns in microbial communities describing specific acidophilic and methanogenic consortia of soil archaea and bacteria, as well as stable communities of plant symbiotic arbuscular mycorrhizal fungi. As the development of high-throughput molecular techniques has accelerated rapidly in the last decade, mofettes now serve more than ever as a natural long-term experimental system to study soil and rhizosphere ecology and contribute to further research on long-term ecological and evolutionary processes that are crucial for understanding past evolutionary events, managing future ecosystems, and predicting ecological responses to global change. Some recent developments target the specific geological and biological characteristics of these extreme ecosystems, including in terms of applications related to environmental impact assessment of carbon capture and storage systems, as well as conservation status, tourism, culture and education, i.e., broader ecosystem services of mofettes, which are addressed in this review together with basic research on soil biodiversity. Full article

High levels of carbon dioxide are known to inhibit the growth of microorganisms. A total of twenty strains of filamentous fungi and yeasts were isolated from habitats with enriched carbon dioxide concentration. Most strains were derived from modified atmosphere packed (MAP) food products or mofettes and were cultivated under an atmosphere of 20% CO₂ and 80% O₂. The influence of CO₂ on fungal cell membrane fatty acid profiles was examined in this study. Major changes were the increase in linolenic acid (C_18:3 cis 9, 12, 15) and, additionally in most strains, linoleic acid (C_18:2 cis 9, 12) with a maximum of 24.8%, at the expense of oleic (C_18:1 cis 9), palmitic (C_16:0), palmitoleic (C_16:1 cis 9) and stearic acid (C_18:0). The degree of fatty acid unsaturation increased for all of the strains in the study, which consequently led to lower melting temperatures of the cell membranes after incubation with elevated levels of CO₂, indicating fluidization of the membrane and a potential membrane malfunction. Growth was reduced in 18 out of 20 strains in laboratory experiments and a change in pigmentation was observed in several strains. Two of the isolated strains, strain WT5 and strain WR1, were found to represent a hitherto undescribed yeast for which the new genus and species Stenotrophomyces fumitolerans (MB# 849906) is proposed. Full article

Mofettes are gas emission sites where high concentrations of CO₂ ascend through conduits from as deep as the mantle to the Earth’s surface and as such provide direct windows to processes at depth. The Hartoušov mofette, located at the western margin of the Eger Graben, is a key site to study interactions between fluids and swarm earthquakes. The mofette field (10 mofettes within an area of 100 m × 500 m and three wells of 28, 108, and 239 m depth) is characterized by high CO₂ emission rates (up to 100 t/d) and helium signatures with (³He/⁴He)_c up to 5.8 Ra, indicating mantle origin. We compiled geological, geophysical, geochemical, and isotopic data to describe the mofette system. Fluids in the Cheb basin are mixtures between shallow groundwater and brine (>40 g/L at a depth of 235 m) located at the deepest parts of the basin fillings. Overpressured CO₂-rich mineral waters are trapped below the mudstones and clays of the sealing Cypris formation. Drilling through this sealing layer led to blow-outs in different compartments of the basin. Pressure transients were observed related to natural disturbances as well as human activities. External (rain) and internal (earthquakes) events can cause pressure transients in the fluid system within hours or several days, lasting from days to years and leading to changes in gas flux rates. The 2014 earthquake swarm triggered an estimated excess release of 175,000 tons of CO₂ during the following four years. Pressure oscillations were observed at a wellhead lasting 24 h with increasing amplitudes (from 10 to 40 kPa) and increasing frequencies reaching five cycles per hour. These oscillations are described for the first time as a potential natural analog to a two-phase pipe–relief valve system known from industrial applications. Full article

In a 1.140 km² study area of the volcanic West Eifel, a comprehensive investigation established the correlation between red wood ant mound (RWA; Formica rufa-group) sites and active tectonic faults. The current stress field with a NW-SE-trending main stress direction opens pathways for geogenic gases and potential magmas following the same orientation. At the same time, Variscan and Mesozoic fault zones are reactivated. The results showed linear alignments and clusters of approx. 3,000 RWA mounds. While linear mound distribution correlate with strike-slip fault systems documented by quartz and ore veins and fault planes with slickensides, the clusters represent crosscut zones of dominant fault systems. Latter can be correlated with voids caused by crustal block rotation. Gas analyses from soil air, mineral springs and mofettes (CO₂, Helium, Radon and H₂S) reveal limiting concentrations for the spatial distribution of mounds and colonization. Striking is further the almost complete absence of RWA mounds in the core area of the Quaternary volcanic field. A possible cause can be found in occasionally occurring H₂S in the fault systems, which is toxic at miniscule concentrations to the ants. Viewed overall, there is a strong relationship between RWA mounds and active tectonics in the West Eifel. Full article