Evaluación de la degradación de materia orgánica mediante técnicas de visión artificial y sensores

Organic matter (OM) decomposition has been shown to vary across ecosystems, suggesting that variation in local ecological conditions influences this process. A better understanding of the ecological factors driving OM decomposition rates will allow to better predict the effect of ecosystem changes on the carbon cycle. While temperature and humidity have been put forward as the main drivers of OM decomposition, the concomitant role of other ecosystem properties, such as soil physicochemical properties, and local microbial communities, remains to be investigated within large-scale ecological gradients. To address this gap, we measured the decomposition of a standardized OM source – green tea and rooibos tea – across 24 sites spread within a full factorial design including elevation and exposition, and across two distinct bioclimatic regions in the Swiss Alps. By analyzing OM decomposition via 19 climatic, edaphic or soil microbial activity-related variables, which strongly varied across sites, we identified solar radiation as the primary source of variation of both green and rooibos teabags decomposition rate. This study thus highlights that while most variables, such as temperature or humidity, as well as soil microbial activity, do impact decomposition process, in combination with the measured pedo-climatic niche, solar radiation, very likely by means of indirect effects, best captures variation in OM degradation. For instance, high solar radiation might favor photodegradation, in turn speeding up the decomposition activity of the local microbial communities. Future work should thus disentangle the synergistic effects of the unique local microbial community and solar radiation on OM decomposition across different habitats.

<p>Microbial breakdown of organic matter (OM) is slowed down by different environmental conditions in peatlands, such as low pH, low oxygen availability and presence of phenolic compounds, leading to their recognized carbon storage function (Freeman et al. 2001, Kang et al. 2018). Peatlands are worldwide distributed with environmental conditions and biogeographical legacy varying among regions, which determine different controlling factors of microbial OM degradation and affect carbon cycling and greenhouse gas (GHG) emissions from peat soils. Here, we present the results of a study aimed at investigating the structure and function of microbial communities involved in the OM decomposition in moss-dominated peatlands of tropical (Andes-Paramo, Colombia), temperate (Wales, UK), and arctic (Svalbard, Norway) regions. Prokaryote community, extracellular enzyme activity, and GHG (carbon dioxide, methane, and nitrous oxide) production were assessed in peat soil (first 10 cm depth) collected in one sampling campaign by region (summer north hemisphere). Results showed contrasting prokaryote communities among regions and a clear link between microbial composition and OM degrading metabolism. Arctic peatlands in Svalbard were shallow, circumneutral, with the highest prokaryote diversity (aerobic and anaerobic), an active lignin degradation, production of carbon dioxide, and nitrous oxide. In Wales, peatlands exhibited the lowest pH, an intermediate diversity of prokaryotes, with aerobic and anaerobic groups, and very low OM degrading activity and GHG production. Finally, in the Paramo’s peatlands, the oxygen level was the lowest and consequently prokaryote community was dominated by anaerobic groups with an active anaerobic OM degradation and methane production. Our study is the first, to the extent of our knowledge, giving a comparative view of microbial OM decomposition in peatlands from contrasting and remote regions. Our results highlight the great global diversity of prokaryotes and microbial metabolism and give new lights on the relationship between microbial composition and microbial carbon cycling in peatlands.</p><p> </p><p><strong>References</strong></p><p>Freeman, C., Ostle, N., Kang, H. 2001. An enzymic “latch” on a global carbon store. Nature 409:149.</p><p>Kang, H., Kwon, M. J., Kim, S., Lee, S., Jones, T.G., Johncock, A. C., Haraguchi, A., Freeman, C. 2018. Biologically driven DOC release from peatlands during recovery from acidification. Nature Communications 9:1–7.</p>

Science-based dating in archaeology

Importance of hydrogenotrophic, aceticlastic and methylotrophic methanogenesis for methane production in terrestrial, aquatic and other anoxic environments: A mini review

Chapter 13 - Whispering Gases

Sources, distribution and decomposition of soil organic matter based on an effective biomarker in the pastoral areas of Zoige Plateau, China

Evolution of surface acidity during smectite illitization: Implication for organic carbon cycle

Arctic climate warming is causing permafrost thaw and erosion, which may lead to enhanced inputs of terrestrial organic matter into Arctic Ocean shelf sediments. Degradation of terrestrial organic matter in sediments might contribute to carbon dioxide production and bottom water acidification. Yet, the degradability of organic matter in shallow Arctic Ocean sediments, as well as the contribution of terrestrial input, is poorly quantified. Here, potential organic matter degradation rates were investigated for 16 surface sediments from the Kara Sea, Laptev Sea, and the western East Siberian Sea and compared with physicochemical sediment properties including molecular biomarkers, stable and radioactive carbon isotopes, and grain size. Aerobic oxygen and carbon dioxide fluxes, measured in laboratory incubations of sediment slurry, showed high spatial variability and correlated significantly with organic carbon content as well as with the amount and degradation state of terrestrial organic matter. The dependency on terrestrial organic matter declined with increasing distance from land, indicating that the presence of terrestrial organic matter is likely a constraining factor for organic matter degradation in shallow shelf seas. However, sediment oxygen consumption rates, measured in incubations of intact sediment cores, also exhibited substantial spatial variability but were not related to organic carbon content or terrestrial influence. Oxygen consumption of intact sediments may be more strongly influenced by in situ redox conditions. Together with previous observations, our findings support that terrestrial organic matter is easily degradable in shelf sea sediments and might substantially contribute to aerobic carbon dioxide production and oxygen consumption.

<p>Oxic-anoxic interfaces serve as hotspots of organic matter decomposition, regulating soil and sediment carbon storage and nutrient cycling. Oxic-anoxic interfaces present along redox gradients, which are ubiquitous in soil and sediment environments, also serve as hotspots of reactive Mn(III) formation and Mn(III)-mediated organic matter degradation. Reactive manganese represents an important control on organic matter degradation in soil and sediment environments, impacting both greenhouse gas emissions and carbon storage. Mn(III) formation at redox interfaces depend not just on soil redox conditions, but also on microbially-mediated Mn redox cycling across the redox gradient. However, the extent to which microbially-mediated Mn(III) formation and subsequently Mn(III)-driven organic matter oxidation depends on Mn availability remains largely unknown. In this study, we quantified how variations in Mn bioavailability affects the microbial pathway and rates of Mn(III)-driven organic matter degradation across redox interfaces. To achieve this, we established redox gradients within forest soils using diffusion reactors and varied Mn availability in the anoxic zone, thereby controlling Mn(II) mobilization to the oxic-anoxic interface. We quantified changes in microbial activity and function in relation to Mn(III) formation and organic matter degradation across the redox gradient over a 12-week incubation period. Metatranscriptomics revealed Mn(II)-oxidizing enzymes responded strongly to Mn bioavailability at the redox interface, while qPCR showed that shifts in microbial community composition coincided with Mn(III) formation. Wet-chemical extractions combined with Mn XANES indicated that Mn(III) formation at the redox interface peaked after 4 weeks of incubation and was most pronounced with increasing M availability. Bioassays, combined with soil respiration measurements and carbon NEXAFS indicated organic matter degradation increased with increasing Mn availability, coinciding with the formation of Mn(III) at redox interfaces. Combined, our results show that redox gradients and oxic-anoxic interfaces serve as hotspots for Mn(III) formation and subsequent organic matter degradation and are driven by enhanced Mn availability. Our work highlights the critical role of Mn redox cycling within microbial hotspots may have in regulating carbon dynamics in terrestrial environments. </p>

<p>The project BIOMUD, part of the scientific network MUDNET (www.tudelft.nl/mudnet), investigates the decomposition of sediment organic matter (SOM) in the Port of Hamburg. The microbial turnover of sediment organic matter under reducing conditions leads to the formation of methane, carbon dioxide and others gases causing a change in the sediment rheological parameters. BIOMUD is aiming to explain the effect of organic matter lability on the rheological properties impacting the navigable depth of the harbour.</p><p>Samples of freshly deposited material were taken in 2018 and 2019 at nine locations in a transect of 30 km through the Port of Hamburg. Analyses included abiotic parameters (among others grain size distribution, standard pore water properties, standard solid properties, stable isotopes, mineral composition) and biotic parameters (among others anaerobic and aerobic organic matter degradation, DNA, protein and lipid content, microbial population). At four locations, physical density fractions and chemical organic matter fractions were analysed.</p><p>The quality of organic matter was described by normalising carbon released from microbial degradation under both aerobic and anaerobic conditions to the share of total organic carbon (mg C/g TOC). Organic matter pools with different degradation rates were used to quantify the lability of organic matter. The share of faster degradable (more labile) pools correlated strongly with the size of the hydrophilic DOC fraction, confirming results of Straathof et al. (2014) who investigated dissolved organic carbon pools in compost. The hydrophilic DOC fraction was closely correlated to the polysaccharide concentration, explaining the input of easily degradable organic matter. Moreover, the amount of organic carbon present in the sediment’s light density fraction < 1.4 g/cm<sup>3</sup> strongly correlated with the hydrophilic DOC fraction and, less strongly, with organic matter lability. High organic matter quality, i.e. the labile, easily degradable fraction, was further related to the chlorophyll concentration in the water column but also the ammonium concentration in the sediment’s pore water.</p><p>It was hypothesised that the observed toposequence of decreasing organic matter quality from upstream to downstream could be explained by a chronosequence of increasing degradation and therefore ageing of organic matter as the sediment passes through the harbour area. Further, it was hypothesized that the harbour received organic matter of higher degradability, originating from phytoplankton biomass, from the upstream part of the Elbe river, whereas the input from the tidal downstream area provided organic matter of lower quality (degradability).</p><p>This study was funded by Hamburg Port Authority.</p>

Salt marshes are among the most efficient blue carbon (C) sinks in the world, partly due to the slow decomposition of their plant-derived organic matter (OM) in the soil. The fate of this C sink under sea-level rise is still uncertain due to limited knowledge about the processes controlling OM decomposition under different inundation levels. In an in-situ manipulative experiment, we compared salt marsh OM decomposition and quality across simulated sea-level scenarios and litter types (absorptive root, fine transportive root, leave, and rhizome of the shrubby C3 halophyte Halimione Portulacoide) for 170 days. The OM decomposition rate varied only between the longest and shortest inundation treatments, that was lower than the mean inundation of our site. The OM decomposition and C loss rates varied strongly across litter types. Fine absorptive was the slowest to decay, releasing up to 40% less C than the other litter types. Changes in lignin composition varied across litter types, but were unaffected by sea-level rise scenarios. Our study suggests that 1) the assessment of soil C dynamics in salt marshes based on aboveground litter or bulk belowground litter patterns is inadequate because of a marked difference in OM decomposition across litter types; 2) belowground litter lignin quality could be a good proxy for OM decomposition in salt marshes; and 3) sea-level rise is unlikely to decrease OM decomposition under current sea-level rise projections.

Kinetics and fractionation of carbon and oxygen isotopes during the solid-phase transformation of biogenic aragonite to calcite: The effect of organic matter

Experiments were performed in tubes in Lake 303 at the Experimental Lakes Area to determine the effects of arsenate and arsenite on microbial degradation of organic matter, and to determine rates of reduction and oxidation of inorganic arsenic. Under winter ice, 40 μmol∙L−1 arsenate or arsenite inhibited microbial degradation of organic matter by 50%. Rates of oxidation of arsenite were about 2 μmol∙L−1∙d−1 under aerobic conditions, and rates of reduction of arsenate were about 1 μmol∙L−1∙d−1 under anaerobic conditions. During the ice-free season, arsenate and arsenite had little apparent effect upon rates of degradation of organic matter in lake tubes enriched with nutrients. Rates of formation of particulate phosphorus, and rates of planktonic uptake of dissolved phosphorus were depressed in the presence of arsenic. The observed rate of oxidation of arsenite in summer was similar to the winter value. Arsenate reduction rates ([Formula: see text]30 μmol∙L−1∙d−1) were very rapid under short periods of anaerobiosis. In the presence of large nutrient (N, P) concentrations, As did not inhibit the development of high algal biomass.Based on these experiments, we predict that addition of domestic sewage to arsenate-polluted Kam Lake (near Yellowknife, N.W.T.) will result in a state of restrained eutrophication. Degradation of organic matter will not be inhibited by As in summer, and dissolved phosphorus concentrations will remain high, due to As inhibition of P uptake by the plankton. During the summer, growth of algal blooms may be moderated by As, and more dissolved phosphorus will flow out of the lake to downstream waterbodies.Key words: arsenic, bacteria, algae, organic matter decomposition, eutrophication

The process of organic matter degradation is an integral part of the ecosystem cycle, which converts complex organic compounds into simpler forms through the activity of microorganisms. Microorganisms, such as bacteria, fungi, and actinomycetes, play an important role in the decomposition of organic matter, whether from household waste, crop residues, or organic industrial waste. This process involves various biochemical mechanisms, such as hydrolysis, fermentation, and oxidation, which are triggered by exocellular enzymes produced by microbes. Environmental factors, such as pH, temperature, humidity, and oxygen content, affect the efficiency of degradation by microorganisms. Several microorganisms, especially those that have the ability to decompose lignin, cellulose, and hemicellulose, have been widely applied in organic waste management technologies such as composting, bioremediation, and biogas production. Research on the role of microorganisms in organic matter degradation is not only important for understanding ecosystem dynamics, but also has the potential to support efforts to manage organic waste that are more environmentally friendly and sustainable. This abstract provides a review of the role, mechanisms, and factors that influence organic matter degradation by microorganisms, as well as their applications in environmental technology.

Decades of conflicting results have fueled a debate about how O2 affects organic matter (OM) degradation and carbon cycling. In a laboratory study, using both OM taken directly from a humic lake and chemically isolated fulvic acid, we monitored the mineralization of dissolved OM in freshwater under purely oxic and anoxic conditions, under oxic then anoxic conditions, and under anoxic then oxic conditions, for 426 d. Between 5% and 24% of the initial OM was mineralized, with most extensive mineralization occurring under purely oxic and anoxic—oxic conditions. A sequential change in the O2 regime did not result in greater overall degradation, but initially anoxic conditions favored subsequent oxic mineralization. A substantially greater fraction of the OM was degraded than in previous shorter studies, with as much as 50% of the total OM degradation occurring after 147 d into the experiment. Three fractions of the degradable OM were identified: OM degraded only under oxic conditions (68–78%), OM degraded more rapidly under anoxic conditions than under oxic conditions (16–18%), and OM degraded at equal rates under both oxic and anoxic conditions (6–14%). The degradation patterns of natural dissolved OM from a humic lake and chemically isolated fulvic acid were very similar, which indicates a similar level of bioavailability. The difference between anoxic and oxic degradation was greater in our long‐term studies than in previous short‐term experiments, which indicates that the oxic and anoxic degradation potentials vary with increasing overall OM recalcitrance and that similar oxic and anoxic degradation rates can be expected in short‐term experiments in which <30% of the long‐term degradable OM is allowed to decompose.