Production Of Organic Matter Research Articles

Carbon cycle during the late Aptian–early Albian OAE 1b: A focus on the Kilian–Paquier levels interval

The Oceanic Anoxic Event (OAE) 1b took place over a protracted time interval during the Aptian/Albian boundary interval, at the dawn of the mid-Cretaceous climatic optimum. OAE 1b is characterized by the occurrence of several sub-events recorded by organic matter-rich levels, which can be traced on regional-to-global scale. Previous studies have highlighted that the climax of the event occurred around the Kilian – Paquier interval, with this latter sub-event being the most extended and pronounced stratigraphic interval. Numerous studies on OAE 1b have however only focused on high-precision investigations of the Kilian and/or Paquier levels, leaving vast uncertainties about the environmental changes and their drivers during the entire OAE 1b, and hence also on the mechanisms leading to the formation of the sub-events themselves. In this study, we have performed a high-resolution multi-proxy analysis of the Briers section, a well-exposed section in the Blue Marls Formation of the SE France Vocontian Basin, continuously covering the Kilian – Paquier interval. Pyrolysis analyses show that most of the organic matter in this section is immature and of continental origin, averaging 1.5% TOC. The Kilian and Paquier levels are characterized by higher TOC values and a substantial increase in the amount of marine organic matter. Comparing TOC values with changes in Al or Ti concentration (proxies for continental weathering) and Hydrogen index (HI values, tracer for the type of organic matter) reveals that the background long-term change in TOC is linked to change in the continental organic matter delivery to the Vocontian Basin tied to changes in continental weathering rates. Sporadic increases in TOC values associated with the Kilian, HN 8, and Paquier levels, are most likely the result of short-lived events of increased marine primary productivity and organic matter preservation superimposed on the background influx of continental organic matter. A high-resolution bulk organic matter carbon isotope record shows that, apart from the Paquier level, all the fluctuations observed in the carbonate carbon isotope ratios are also mirrored in the organic matter record, although with higher amplitudes. This discrepancy in amplitude can be resolved by correcting the bulk organic matter carbon isotope record for fluctuations in the type of organic matter, demonstrating that both oceanic and atmospheric reservoirs were affected by similar carbon isotope fluctuations, which were hence of global extent. The abnormal bulk organic matter carbon isotope record of the Paquier level further confirms the large geographical expansion of unusual organic matter production and/or accumulation during this peculiar event. Overall, this study suggests that Milankovitch-paced (long eccentricity) changes in monsoonal activity and their effect on the accumulation of organic matter in continental wetlands best explains the rhythmic change in the global carbon isotope record across the OAE 1b interval.

Evaluasi Tepung Kedele Terproteksi Tanin Kondensasi dari Ekstrak Daun Sengon (Albizia falcataria) terhadap Ketahanan Degradasi oleh Mikroba di Rumen

Soybean meal (SBM) is a quality feed with high protein and organic matter content but is easy to degrade by microbes in the rumen. A high degradation rate in the rumen causes potential protein loss as ammonia and energy in the form of fermentation heat, CO2 gas, and methane gas. This study aimed to determine the effect of SBM protected with condensed tannins (TK) from sengon leaves on its fermentability by rumen microbes. This study used a completely randomized design (CRD) consisting of four treatments and five replications. Treatments were of P1 = SBM unprotected with condensed tannin (CT) (control); P2 = SBM- protected 2% CT; P3 = SBM-protected 4% CT, and P4 = SBM- protected 6% CT. The amount of CT (0, 2, 4, 6%) was calculated and converted to the amount of sengon leaves equivalent to 0, 226.24, 452.49, and 678.72 g/kg SBM based on CT content in sengon leaves of 8.84%. SBM samples were weighed as much as 0.5 g, then put into a serum bottle with a capacity of 100 ml, added 40 ml of a mixture of rumen fluid and McDougall's buffer (1:4 v/v), closed with a rubber stopper, climb sealed using an aluminum seal, and incubated in an incubator for 3, 6, 9, 12, 24, and 48 hours. The variable measured was in vitro cumulative gas production (GP), methane production (CH4), dry matter degradation (DMD), organic matter degradation (OMD), metabolism energy (ME), and production of microbial protein (PMP). The results showed that the treatment of SBM protected with condensed tannins from sengon leaf extract had a significant effect (P<0.05) on reducing GP, CH4, DMD, OMD, ME, and PMP. The Treatment of P1 (control) was higher produced of GP, CH4, DMD, OMD, ME, and PMP (P<0.05) compared to P2, P3, and P4. But between P2, P3, and P4 were not significantly different (P>0.05). This study concluded that the use of condensed tannin at levelof 2% could be used to protect soybean meal from microbial degradation in the rumen.

Bacterial Control of Marine Humic‐Like Substance Production, Composition, Size, and Transfer to Sea Spray Aerosols During Phytoplankton Blooms

AbstractHumic‐like substances (HULIS) are present in every environmental reservoir, including the ocean and the atmosphere. Ocean‐derived HULIS can be transferred to the atmosphere in the form of sea spray aerosols (SSA). Little information exists on the factors controlling this transfer process or how HULIS alter SSA physicochemical properties, cloud‐forming ability, and atmospheric reactions. Here, using excitation‐emission matrix spectroscopy and isolated ocean‐atmosphere systems, we investigated how ocean biology affects HULIS sea‐to‐air transfer during multiple phytoplankton bloom experiments. We posit that bacterial enzymatic activity on phytoplankton‐derived organic matter control HULIS size, production, and chemical composition. We found that changes in fluorescence indices and shifts in the HULIS fluorescence emission spectra reveal changes in HULIS chemical composition induced by bacteria. High bacterial enzymatic activity on the proteinaceous, lipid, and phosphorus‐rich organic pools enhanced HULIS production and its transfer to SSA. Seawater HULIS consistently accumulated across all experiments. The majority of HULIS was smaller than 0.2 μm or 50 kDa. Our results suggest that enzymatic‐processing bacteria transform the composition of HULIS in seawater, degrading dissolved organic matter into diverse chemical structures that are more efficiently transferred to the atmosphere in SSA.

Effects of ethoxyquin on metabolism and composition of active marine microbial communities

Salmon culture has the potential to generate environmental impacts due to the release of organic matter and chemical products into the water column. Ethoxyquin (EQ) is a food additive widely used as an antioxidant in fish feed, but due to the scarce evidence on its safety for the environment it has been banned by the European Food Safety Authority. To evaluate and compare responses of marine microbial communities to EQ additions (10, 100 and 1000 μg L−1), we carried out 20 L seawater microcosm experiments in two distinct areas, Achao and Coliumo Bay, where the first is influenced by salmon farming. We estimated metabolic response (respiration, extracellular enzymatic activity and ECOplates) for two size fractions (< 1 μm and < 63 μm) and changes in the active microbial community diversity. The results revealed different responses associated with study sites and size fractions. For the < 1 μm fraction (bacterioplankton), the addition of EQ increased both oxygen consumption and the degradation of proteinaceus compounds, while for the entire community (< 63 μm), the addition of EQ decrease respiration and the capacity to degrade carbohydrates and lipids. The carbon substrates utilization was variable, decreasing in the 100 and 1000 μg EQ. L−1 treatments, suggesting that high EQ concentrations may limit the capacity to process different carbon sources, producing a preference for amino acids and carboxylic acids in the first hours of exposition in Achao. In the area without salmon farming (Coliumo Bay) substrates utilization, mainly carbohydrates and carboxylic acids, was stimulated by the addition of EQ. A shift was observed in the active microbial community between treatments at different taxonomic levels, especially associated with Alphaproteobacteria, which presented lower activity when exposed to EQ. Gammaproteobacteria (KI89A), Bacteroidea (NS10, NS3b clade) and MGII showed higher activity associated with EQ additions. Overall, our study indicates that EQ may generate both changes in the metabolism (respiration, enzymatic extracellular activity, carbon sources preferences) and composition of the active microbial community in the water column altering the degradation of organic matter.

Isotopic and spectral signatures unravel the sources, preservation and degradation of sedimentary organic matter in the Dongzhai Harbor mangrove estuary, southern China

Sedimentary organic matter (SOM) production and transformation processes have a prominent role in regulating biogenic element cycling in mangrove ecosystems. However, aquaculture biodeposits can substantially affect source apportionments and biogeochemical processes of SOM within mangroves. In this study, natural stable isotopes (13C and 15N), spectral techniques, and hydrogeochemical analysis were used to elucidate the sources, preservation, and degradation of SOM across the Dongzhai Harbor (DZH) estuary, southern China, where aquaculture systems are extensive. Along the estuarine salinity gradient, sediment and bottom water samples were collected from the upper fluvial mangrove zones to the lower marine endmember. Results indicated that source contributions to SOM along the estuarine gradient were spatially heterogeneous. Aquaculture-derived organic matter was the largest contributor to the Sanjiang River (44.29 %) in the upper estuary, and terrestrial sources from C3 mangrove forests were highest in the Yanfeng East River (62.87 %) near the middle estuary. Farther seaward, marine plankton sources were elevated in the Dongzhai Harbor channel (64.15 %) and Yanfeng West River (48.83 %) of the lower estuary. The terrestrial/microbial humic-like component (C1), tryptophan-like component (C2), and soil-derived fulvic acid (C3) were identified from the samples using fluorescence excitation emission matrices and parallel factor analysis (EEM-PARAFAC). Results show that in the upper and middle estuary, SOM was preserved by sedimentation due to the abundance of fine-grained aquaculture-derived biodeposits, weak hydrodynamic conditions, and the formation of Fe/Mn-humus complexes. In contrast, in the lower estuary, SOM originated from marine plankton and was rapidly degraded via aerobic respiration. Moreover, correlations between δ13C and δ15N values vs C/N ratios further suggest progressive SOM degradation from initial diagenesis to post-depositional geochemical processes. This study provides new insights into aquacultural and environmental factors controlling SOM preservation and degradation within estuaries. The findings have implications for shoreline stability and the protection and restoration of estuarine mangrove wetlands.

Forest Management Plans for Carbon Sequestration

Carbon sequestration in forest ecosystems has become an important issue in the discussion about abrupt climate change. Forestry sequestrates carbon from the atmosphere and stores it in living tree biomass, dead organic matter and wood-based products. However, it is difficult to estimate the stored carbon in a forest accurately. To address this issue, this study develops a series of models to calculate the carbon sequestration of the living tree and the additional part of the forestry carbon sequestration. The influences of four carbon sequestration pathways on total carbon sequestration are analyzed using the proposed model. The results show that the proposed model can predict future carbon dioxide and determine the cutting intensity. This study provides a feasible plan for forest management.

Mineral weathering is linked to microbial priming in the critical zone

Decomposition of soil organic matter (SOM) can be stimulated by fresh organic matter input, a phenomenon known as the ‘priming effect’. Despite its global importance, the relationship of the priming effect to mineral weathering and nutrient release remains unclear. Here we show close linkages between mineral weathering in the critical zone and primed decomposition of SOM. Intensified mineral weathering and rock-derived nutrient release are generally coupled with primed SOM decomposition resulting from “triggered” microbial activity. Fluxes of organic matter products decomposed via priming are linearly correlated with weathering congruency. Weathering congruency influences the formation of organo-mineral associations, thereby modulating the accessibility of organic matter to microbial decomposers and, thus, the priming effect. Our study links weathering with primed SOM decomposition, which plays a key role in controlling soil C dynamics in space and time. These connections represent fundamental links between long-term lithogenic element cycling (= weathering) and rapid turnover of carbon and nutrients (= priming) in soil.

Optimising biotechnological glycolate production in Chlamydomonas reinhardtii by improving carbon allocation towards the product

One of the central goals of algal biotechnology is to replace fossil fuels with autotrophic production of organic matter. Hence, numerous studies are currently focusing on improving the efficiency of algal biotechnology approaches. Based on a multidimensional analysis of the growing conditions, the resulting data allows the estimation of the energetic and economic parameters of the process control. In this paper, we present such an approach using the green alga Chlamydomonas reinhardtii for biotechnological glycolate production. Glycolate can then be used as a chemical feedstock for a variety of downstream processes. This work evaluates the effects of different cultivation conditions and reactor architectures, aiming to increase carbon allocation towards the product glycolate. Under optimised conditions, up to 7.5 g glycolate per g biomass accumulated in the medium, which demonstrates the high product yield that can be achieved with this approach.

Transport inventories and exchanges of organic matter throughout the St. Lawrence Estuary continuum (Canada)

Hypoxia (O2 &amp;lt; 2 mg/L) driven by eutrophication in estuaries and shelves is a worldwide expanding problem. The role of organic matter (OM) inputs is emerging as an important contributor to this issue, beside the well-known implication of inorganic nutrients. The St. Lawrence Estuary, one of the largest and deepest estuarine system in the world is facing strong persistent and increasing hypoxia. In this context, transport and exchange of particulate and dissolved organic matter (POM and DOM, respectively) were investigated as a first step to understand their implication in hypoxia. Tributaries and Gulf contributions were compared to St. Lawrence Estuary inventories for the spring freshet (May), the summer low-flow (August), and the fall-mixing (October). Furthermore, changes in OM ratios were examined along the estuarine gradient from the upper St. Lawrence Estuary (USLE), downstream of the maximum turbidity zone, to the lower estuary (LSLE). For the USLE, net transport was always positive and net export/loading ratios suggested that 64–90% of POM and 30–63% of DOM were either retained or transformed during its course from tributaries to LSLE. Net transport from the USLE toward the LSLE was 3–13 fold more important in May than in August or October. For the LSLE, net transport to the Gulf was generally negative meaning that OM production was the dominating proces. The extremely high net export/loading ratios in August indicate that POM production was 28.8 to 41.4 times the combined inputs of tributaries and Gulf. Net export/loading ratios remained superior to one during May and October (1.7–9.4) for the LSLE. Changes along the upstream–downstream continuum were seen for POM, with a steady increase relative to total suspended matter from 7.3% to 50.2%, but they were not observed for DOM, for which no obvious trends were detected. Our results highlight the importance of explicitly considering OM in eutrophication monitoring programs of the St. Lawrence Estuary, as the mineralisation of a portion of the large OM pool size could influence our understanding of hypoxia and acidification of the deep waters of LSLE.

Reconstructing eutrophication trends of a shallow lake environment using biomarker dynamics and sedimentary sterols

Major extractable lipid biomarkers (hydrocarbons, sterols and fatty acids) were assessed in Lake Seeburg, a shallow eutrophic lake that has increasingly been suffering from cyanobacterial blooms due to continued anthropogenic nutrient inputs over the last decades. Over the course of one year (2018/19), the distributions of these compounds were analyzed in the inflow, the lake water, and the topmost sediments (0–2 cm) to assess their origin and transfer into the lake deposits. Principal component analysis (PCA) was used to cluster the studied biomarkers into 5 groups with similar characteristics. These groups were comprised of (i) compounds delivered from external sources via the inflow, (ii) autochthonous compounds formed in the lake by eukaryotes or (iii) bacteria, (iv) compounds accumulating in the surface sediment, and (v) C27 to C29 stenols together with their degradation products, C27 to C29 5α(H)-stanols. Their seasonal partition clearly revealed that C27 stenols mainly derived from autochthonous sources within the lake, whereas C29 stenols largely reflect allochthonous material reaching the lake via the inflow. Analysis of stenol plus stanol concentrations with depth in two lake sediment cores (≈30 and 50 cm) found highest C27 to C29 ratios in surface sediments with lowest ratios at depth. These signals are interpreted to reflect the increasing trend of eutrophication of Lake Seeburg and, thus, enhanced autochthonous organic matter production in the lake over the last decades. The abundances of C27 vs. C29 stenols, summed with their respective degradation products, 5α(H)-stanols, are considered as suitable molecular indicators to qualitatively reconstruct historical eutrophication trends.

Development of Anaerobic Biodigester for the Production of Biogas Used in Semi-Continuous System Bioprocesses: An Efficient Alternative for Co-Digestion of Low Biodegradability Biomass

The objective of this work was to develop an automated anaerobic biodigester capable of operating in a semi-continuous or batch system for biogas production. Low biodegradability biomass has little efficiency in the production of biogas by anaerobic digestion processes and an efficient alternative is the use of bioprocesses in semi-continuous system. Two experiments were carried out in the same proportions but in different processes, and all control and automation parameters were tested and evaluated. For testing, mixtures of organic waste, anaerobic sludge (inoculum) and raw sewage without any treatment from the sewage treatment plant, in mesophilic phase (37 °C), were used during the 60 days of experiment. The semi-continuous system showed the greatest reduction in organic matter, expressed by the removal of 80.7% Total Solids Volatile (TVS) and the greatest volume (68.5 L) and methane percentage (78.5%). Finally, with these and other results found, it is possible to conclude that the biodigester developed for semi-continuous system, with the automation and control system, was satisfactory for the reduction in organic matter and biogas production. In addition, all operating system worked properly and with the use of current, low-cost technologies, the application and development on a larger scale becomes viable in the future.

Primary production and destruction of organic matter in Lake Arakhley (Eastern Transbaikalia, Russia)

Global climate changes affect water ecosystems. Long-term observations of climatic variables are indicative of cyclic climate changes. The fluctuations result in changes in water levels in lakes, which, in turn, alter primary production processes. Planktonic algae are the main drivers of primary production. This research continues long-term studies on hydroecology of Lake Arakhley. The lake is used for fishery and recreation. This work aims to estimate production and destruction processes in Lake Arakhley during the current transitional period between dry and wet years. To this end, we performed field studies on Lake Arakhley in August from 2016 to 2021, during the season of maximum precipitation, in the central and littoral zones of the lake. Primary production of phytoplankton in water was estimated by the oxygen light and dark bottle method. Sampling was carried out to assess physical and chemical parameters of water using a multiparameter water quality instrument. Lake Arakhley features the low level of mineralization under alkali conditions and relatively stable level of mineralization registered from 2016 to 2021. Macrophytes zone expanded after the massive flooding of the shore in 2021 hence alterating the values of such environmental factors as oxygen levels, total and mineral phosphorus, with destruction prevailing over organic matter production. Depth and transparency however contribute to significant production of organic matter in the lake. The findings can be used as the groundwork for the sustainable management of the lake.

Emerging investigator series: aqueous photooxidation of live bacteria with hydroxyl radicals under cloud-like conditions: insights into the production and transformation of biological and organic matter originating from bioaerosols.

Live bacteria in clouds are exposed to free radicals such as the hydroxyl radical (˙OH), which is the main driver of many photochemical processes. While the ˙OH photooxidation of organic matter in clouds has been widely studied, equivalent investigations on the ˙OH photooxidation of bioaerosols are limited. Little is known about the daytime encounters between ˙OH and live bacteria in clouds. Here we investigated the aqueous ˙OH photooxidation of four bacterial strains, B. subtilis, P. putida, E. hormaechei B0910, and E. hormaechei pf0910, in microcosms composed of artificial cloud water that mimicked the chemical composition of cloud water in Hong Kong. The survival rates for the four bacterial strains decreased to zero within 6 hours during exposure to 1 × 10-16 M of ˙OH under artificial sunlight. Bacterial cell damage and lysis released biological and organic compounds, which were subsequently oxidized by ˙OH. The molecular weights of some of these biological and organic compounds were >50 kDa. The O/C, H/C, and N/C ratios increased at the initial onset of photooxidation. As the photooxidation progressed, there were few changes in the H/C and N/C, whereas the O/C continued to increase for hours after all the bacterial cells had died. The increase in the O/C was due to functionalization and fragmentation reactions, which increased the O content and decreased the C content, respectively. In particular, fragmentation reactions played key roles in transforming biological and organic compounds. Fragmentation reactions cleaved the C-C bonds of carbon backbones of higher molecular weight proteinaceous-like matter to form a variety of lower molecular weight compounds, including HULIS of molecular weight <3 kDa and highly oxygenated organic compounds of molecular weight <1.2 kDa. Overall, our results provided new insights at the process level into how daytime reactive interactions between live bacteria and ˙OH in clouds contribute to the formation and transformation of organic matter.

The Effect of Beneficial Autochthonous Microorganisms (Bams) on the Chemical Quality of Agricultural Soils and Olive Production in the Wilaya of Tlemcen (Western of Algeria)

Abstract Beneficial Autochthonous Microorganisms (BAMs) are a multi-purpose technology that has already been used in Latin America and Southeast Asia but is still unknown in Africa and particularly Algeria. The aim is to examine the effect of BAMs on agricultural soils and olive fields. The study was carried out in two degraded olive fields located in the Oued Tafna basin west of Tlemcen (The Semi-arid region in Western Algeria). The objective is to evaluate the effectiveness of BAMs on the chemical characteristics of the soils, particularly in terms of organic matter (MO), pH, electrical conductivity (EC), total limestone (CaCO3), moisture, organic carbon (C) and olive production and its weight. Statistical analysis (Independent Test) between all groups (treated and controls) showed a significant difference, in conductivity (EC) where we recorded “0.214±0.03μs /cm “ in treated soils vs. “0.198±0.029μs/cm “ in control soils a different statistical significance was recorded for the other parameters, however, it was observed that there is a relative increase in these parameters in the soils of the treated groups such as carbon (C): “2.85±1.06%” organic matter (MO): “4.91± 1.83%”, “pH=7.81±0.225”, “CaCO3 27.76±4.99% and a decrease in humidity “15.11±3.77%” compared to control soils. The results of statistical analyses (Mann-Whitney Test and Suite Test) of olive production showed a clear alternation (every other year) in fruit production in the control group and a positive effect of BAMs on olive production in the treated group, with a slight increase of production (19 kg in 2019 vs. 30 kg in 2020), but without any significant difference regarding the weight of the fruit between the two sessions. However, a highly significant difference “p=0.00&lt;0.001” in fruit weight was noted between the treated groups “3.908g” and “5.70g” and the control ones “4.40g “ and “5.00g” in 2019 and 2020 respectively. The use of MAB is an interesting technique to restore the chemical properties of degraded soils, and increase olive tree production. To achieve more reproducible results (in terms of quantity and quality), sufficient doses of these BAMs and periodicals must be added to provide a good nutritional supplement and reduce farmers’ use of pesticides and mineral fertilizers.

Revendo o processamento da matéria orgânica pelas áreas úmidas

Abstract Aim Cycling processes in wetlands are highly dynamic and involve complex interactions between hydrological processes, biogeochemical transformations, and microbial communities. This review attempts to assess the interactions between elements within biogeochemical cycles and the possible routes in which organic matter is processed in waterlogged soils. Methods The input and cycling of organic matter in flooded soils were approached in this review. We used a non-systematic literature survey to indicate the possible biogeochemical routes of organic matter processing in waterlogged soils. Results We explore hydrological processes, oxygen availability, biogeochemical routes of the organic matter process, and the inputs and exports of organic matter in flooded soils from wetlands. Conclusions The anaerobic degradation of organic resources predominantly occurs within submerged soils. Under conditions of maintenance of natural rates of primary production and allochthonous detritus input, storing organic detritus in flooded soils prevails over mineralization. The importance of hydrology for the export of organic carbon is evident. In wetlands, the export of organic matter is predominantly associated with dissolved organic matter and methane production.

ВЛИЯНИЕ СОЛЕНОСТИ ВОДЫ НА РАЗВИТИЕ ПРИДОННОЙ ГИПОКСИИ И УРОВЕНЬ ПЕРВИЧНОГО ПРОДУЦИРОВАНИЯ ОРГАНИЧЕСКОГО ВЕЩЕСТВА В ТАГАНРОГСКОМ ЗАЛИВЕ

At present, the Azov Sea ecosystem exists in the context of continuously decreasing continental runoff and increasing water salinity, which reached in 2020-2021 the highest values for the entire period of observations since 1962. The increase in water salinity inevitably leads to the transformation in the composition of biological communities, which has a pronounced effect on the environment and fisheries. This paper discusses the long-term impact of water salinity on the development of near-bottom hypoxic phenomena and on the volume of primary production of organic matter by phytoplankton in the Taganrog Bay during the summer season (1962-2021). A statistical ecosystem analysis describing the contribution of the major hydrological and hydrochemical factors into the processes of hypoxia formation in the bottom water layer of the Taganrog Bay has been performed. It is shown that the desalinization of the waters of the Taganrog Bay in 1993-2008 was accompanied by the increase in the size of hypoxic zones in the bottom water layer. During the modern period of salinization extending from 2009 to the present, there has been recorded a decrease in the scale of oxygen deficiency in the Taganrog Bay. The most crucial contribution to the hypoxic processes in the Taganrog Bay is provided by the stability of water masses, water temperature, organic nitrogen concentration, and the water salinity (due to the effect of salinity on the stability of water masses). During the streaks of the Taganrog Bay salinization, the decrease in the stability of water masses and in the content of organic nitrogen and phosphorus in the water (crucial factors in the formation of hypoxic zones) has been recorded. The highest rates of the primary production of organic matter by phytoplankton in the Taganrog Bay were observed during the desalinization period of 1962-1968, and the lowest ones were recorded during the salinization periods. The results of this assessment have exposed the significant relationship: the primary production of organic matter depends on the average annual runoff of the Don River, the water salinity, and the concentration of mineral nitrogen.

Localization of production-destruction processes by distribution of phosphate in the estuaries of Uda and Usalgin Rivers (Okhotsk Sea)

The areas with prevalence of either production or decomposition of organic matter are localized in the estuaries of Uda and Usalgin Rivers (western coast of the Okhotsk Sea) on the data of chemical survey conducted in conditions of summer flood in July, 2016, interpreting patterns of non-conservative variations of inorganic phosphorus concentration (deflections of observed values from potential values determined by the river water mixing with the seawater). Sign of production-destruction balance changed along both surveyed estuaries: the organic matter decomposition prevailed in the internal estuaries but its production prevailed in the upper part of the external estuaries. Another common feature of both estuaries was active recycling: the larger portion of organics was produced with utilizing the phosphorus mineralized within the estuaries, but not the terrestrial phosphorus provided by the rivers ionic discharge. Extremely intensive recycling was observed in the Usalgin estuary that drained swampy lands.

Highly efficient transformation of slowly-biodegradable organic matter into endogenous polymers during hydrolytic fermentation for achieving effective nitrite production by endogenous partial denitrification

The utilization of slowly-biodegradable organic matter (SBOM) to provide nitrite efficiently for anaerobic ammonia oxidation (anammox) process is an essential topic. High nitrite concentration without inhibition of exogenous organic matter is optimal condition for anammox process. In this study, hydrolytic fermentation (HF) of SBOM was applied to drive an endogenous partial denitrification (EPD) process (nitrate to nitrite) during an anaerobic-anoxic operation in a starch-fed system. With a limited production of exogenous organic matter (22.3 ± 4.9 mg COD/L), 79.0% of SBOM was transformed into poly-hydroxyalkanoates (PHA) through a pathway of simultaneous HF-absorption and endogenous polymer synthesis, corresponding to a hydrolytic fermentation ratio of 86.0%. A high nitrate to nitrite transformation ratio of 85.4% was achieved under an influent carbon to nitrogen ratio of 4.8. Denitrifying glycogen-accumulating organisms (DGAOs) was enriched from 0.6% to 10.9%, with an increase from 0.7 to 1.0 of nitrate reductase genes to nitrite reductase genes ratio. Subsequently, nitrate reduction rate was 5.6-fold higher than the nitrate reduction rate. A prominent migration of exogenous complete denitrification to EPD was accomplished. Furthermore, the starch-fed system exhibited performance with significant adaptability and stability in the presence of different SBOMs (dissolved protein and primary sludge). Therefore, the HF-EPD system achieved efficient nitrite production through EPD with the addition of various SBOMs, providing a potential alternative to anammox systems for the treatment of SBOM-rich wastewater.

Effect of air mixing on high-solids anaerobic digestion of cow manure: Performance and mechanism

This study aimed to further investigate the effect of air mixing on the performance of a high-solids anaerobic digestion system and reveal its underlying mechanisms via analyses of carbon conversion, microbial communities and key functional genes. When the air mixing intensity was 12.5, 37.5 and 62.5 mL/(L‧min), compared with the anaerobic digestion without air mixing, the methane yield was increased by 6 %, 13 % and 6 %, respectively. The improved performance was partly attributed to the increased hydrolysis rate of macromolecular substances by 5 %–16 % and carbon recovery in the form of methane by 6 %–7% compared with the controls. Functional flora (Magnetospirillum, Synergistaceae) and hydrolytic metabolism-related enzymes (cellulose, α-amylase) demonstrated higher abundance under air mixing condition, thus promoting the degradation of organic matter and methane production. This work provides some new insights into the use of air mixing to improve anaerobic digestion of high-solids waste.

Natural marsh-pasture/sugarcane field transitions greatly reduced lignin-derived pyrolysis products of soil organic matter

Cultivation of marshes (Ma) to arable like pasture (Pa) and sugarcane (Sa) usually causes soil organic carbon (SOC) pool depletion within a short time. However, there are some uncertainties about which molecular composition of soil organic matter (SOM) is sensitive to land use change (LUC). In the present work, molecular components of SOM were investigated and compared to better understand the impacts of LUC on the carbon cycle from Ma to Pa or Sa in Louisiana and Florida. Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) analysis indicated that LUC greatly altered the molecular composition of SOM. More lignin, polysaccharide, and phonetic compounds were founded from Ma, and more nitrogen-containing compounds were identified from Sa. Lignin and phenolic compounds had unexpectedly the most decrease from native marsh-sugarcane/pasture transitions, showing the same trend as SOC. This meant that lignin and phenol were not as stable as expected when undergoing LUC. LUC significantly yield more molecular moieties and then resulted in higher complexities and diversities of molecular components in Pa or Sa than those in Ma. Principal component analysis implied higher contributions of old carbon to SOM in Ma, and fresh biomass input contributed more SOM in Sa. Our results implied that human activities such as LUC could not only alter carbon fluxes but also simultaneously change molecular mechanisms that drive the carbon cycle.