Dissolved oxygen is fundamental for chemical and biochemical processes occurring in natural waters and critical for the life of aquatic organisms. Many organisms are responsible for altering organic matter and oxygen transfers across ecosystem or habitat boundaries and, thus, engineering the oxygen balance of the system. Due to such Lemna features as small size, simple structure, vegetative reproduction and rapid growth, as well as frequent mass occurrence in the form of thick mats, they make them very effective in oxygenating water. The research was undertaken to assess the impact of various species of duckweed (L. minor and L. trisulca) on dissolved oxygen content and detritus production in water and the role of ecological factors (light, atmospheric pressure, conductivity, and temperature) in this process. For this purpose, experiments were carried out with combinations of L. minor and L. trisulca. On this basis, the content of oxygen dissolved in water was determined depending on the growth of duckweed. Linear regression models were developed to assess the dynamics of changes in oxygen content and, consequently, organic matter produced by the Lemna. The research showed that the presence of L. trisulca causes an increase in dissolved oxygen content in water. It was also shown that an increase in atmospheric pressure had a positive effect on the ability of duckweed to produce oxygen, regardless of its type. The negative correlation between conductivity and water oxygenation, obtained in conditions of limited light access, allows us to assume that higher water conductivity limits oxygen production by all combinations of duckweeds when the light supply is low. Based on the developed models, it was shown that the highest increase in organic matter would be observed in the case of mixed duckweed and the lowest in the presence of the L. minor species, regardless of light conditions. Moreover, it was shown that pleustophytes have different heat capacities, and L. trisulca has the highest ability to accumulate heat in water for the tested duckweed combinations. The provided knowledge may help determine the good habitat conditions of duckweed, indicating its role in purifying water reservoirs as an effect of producing organic matter and shaping oxygen conditions with the participation of various Lemna species.

Acidophiles comprise a group of microorganisms adapted to live in acidic environments. Despite acidophiles are usually associated with an autotrophic metabolism, more than 80 microorganisms capable of utilizing organic matter have been isolated from natural and man-made environments. The ability to reduce soluble and insoluble iron compounds has been described for many of these species and may be harnessed to develop new or improved mining processes when oxidative bioleaching is ineffective. Similarly, as these microorganisms grow in highly acidic media and the chances of contamination are reduced by the low pH, they may be employed to implement robust fermentation processes. By conducting an extensive literature review, this work presents an updated view of basic aspects and technological applications in biomining, bioremediation, fermentation processes aimed at biopolymers production, microbial electrochemical systems, and the potential use of extremozymes.

Erythrina brucei has been applied as a green manure to improve soil fertility in southern Ethiopia. It has been nodulated by indigenous rhizobia. The objectives of this study were to evaluate the effects of E. brucei inoculation with microbial consortia consisted of Bradyrhizobium shewense, Acinetobacter soli and arbuscular mycorrhizal fungi (AMF)on E.brucei growth, soil nitrogen and phosphorous status after application as a green manure.A field experiment was conducted by inoculating E. Brucei with different microbial consortia. E. brucei inoculated with the microbial consortia were grown for 150 days. Its shoot length was measured at 60, 90, 120 and 150 days after planting. Then, plants were uprooted and mulched as a green manure. The soil nitrogen, available phosphorous and soil organic matter analysis were done. The experimental design was completely randomized block design with eight treatments comprised of three replications. Inoculated treatments did not show a significant (p < 0.05) difference in shoot length in the first 60 days. However, shoot length was increased between 19.1 and 41.3 %, 10.5-43.4 % and 8.7-37.6 %, respectively at 90, 120 and 150 days. The soil organic matter was improved in both inoculated and un-inoculated treatments. The improvements in the soil organic matter of un-inoculated treatments may be due to the decomposition of un-inoculated plants biomass in the soil. The B. shewense inoculation improved the soil nitrogen by 17 %. The soil phosphorous was improved in 57 % of inoculated treatments. The inoculation of E. brucei with microbial consortia enhanced its growth and improved soil fertility when applied as a green manure. Inoculating the green manure legumes with symbiotically effective rhizobia and plant-beneficial microbes can enhance the growth of E. brucei and its nutrient uptake.

In regions facing water scarcity and soil salinity, mitigating these abiotic stresses is paramount for sustaining crop production. This study aimed to unravel the synergistic effects of organic matter and phosphorus management in reducing the adverse effect of saline water for irrigation on red pepper (Capsicum annuum L.) production, fruit quality, plant physiology, and stress tolerance indicators. The study was carried out in the arid Tadla region of Morocco and involved two key experiments: (i) a field experiment during the 2019 growing season, where red pepper plants were subjected to varying phosphorus fertilizer rates (120, 140, and 170 kg of P2O5.ha-1) and saline water irrigation levels (0.7; 1.5; 3; and 5 dS.m-1); and (ii) a controlled pot experiment in 2021 for examining the interaction of saline water irrigation levels (EC values of 0.7, 2, 5, and 9 dS.m-1), phosphorus rates (30, 36, and 42 kg of P2O5.ha-1), and the amount of organic matter (4, 8, 12, and 16 t.ha-1). The field study highlighted that saline irrigation significantly affected red pepper yields and fruit size, although phosphorus fertilization helped enhance productivity. Additionally, biochemical markers of stress tolerance, such as proline and glycine betaine, along with stomatal conductance, were impacted by increasing salinity levels. The pot experiment showed that combining organic amendments and phosphorus improved soil properties and stimulated red pepper growth and root weight across all salinity levels. The integration of phosphorus fertilization and organic amendments proved instrumental for counteracting salinity-induced constraints on red pepper growth and yield. Nonetheless, caution is necessary as high salinity can still negatively impact red pepper productivity, necessitating the establishment of an irrigation water salinity threshold, set at 5 dS.m-1.

Sea spray aerosols (SSA) greatly affect the climate system by scattering solar radiation and acting as seeds for cloud droplet formation. The ecosystems in the Arctic Ocean are rapidly changing due to global warming, and the effects these changes have on the generation of SSA, and thereby clouds and fog formation in this region, are unknown. During the ship-based Arctic Century Expedition, we examined the dependency of forced SSA production on the biogeochemical characteristics of seawater using an on-board temperature-controlled aerosol generation chamber with a plunging jet system. Our results indicate that mainly seawater salinity and organic content influence the production and size distribution of SSA. However, we observed a 2-fold higher SSA production from waters with similar salinity collected north of 81°N compared to samples collected south of this latitude. This variability was not explained by phytoplankton and bacterial abundances or Chlorophyll-a concentration but by the presence of glucose in seawater. The synergic action of sea salt (essential component) and glucose or glucose-rich saccharides (enhancer) accounts for >80% of SSA predictability throughout the cruise. Our results suggest that besides wind speed and salinity, SSA production in Arctic waters is also affected by specific organics released by the microbiota.

BACKGROUND: Moonmilk represents complex secondary structures and model systems to investigate the interaction between microorganisms and carbonatic rocks. Grotta Nera is characterized by numerous moonmilk speleothems of exceptional size hanging from the ceiling, reaching over two meters in length. In this work we combined microbiological analyses with analytical pyrolysis and carbon stable isotope data to determine the molecular composition of these complex moonmilk structures as well as the composition of the associated microbiota.
RESULTS: Three moonmilk structures were dissected into the apical, lateral, and core parts, which shared similar values of microbial abundance, richness, and carbon isotopes but different water content, microbiota composition, and organic matter. Moonmilk parts/niches showed higher values of microbial biomass and biodiversity compared to the bedrock (not showing moonmilk development signs) and the waters (collected below dripping moonmilk), indicating the presence of more complex microbial communities linked to carbonate rock interactions and biomineralization processes. Although each moonmilk niche was characterized by a specific microbiota as well as a distinct organic carbon profile, statistical analyses clustered the samples in two main groups, one including the moonmilk lateral part and the bedrock and the other including the core and apical parts of the speleothem. The organic matter profile of both these groups showed two well-differentiated organic carbon groups, one from cave microbial activity and the other from the leaching of vascular plant litter above the cave. Correlation between organic matter composition and microbial taxa in the different moonmilk niches were found, linking the presence of condensed organic compounds in the apical part with the orders Nitrospirales and Nitrosopumilales, while different taxa were correlated with aromatic, lignin, and polysaccharides in the moonmilk core. These findings are in line with the metabolic potential of these microbial taxa suggesting how the molecular composition of the preserved organic matter drives the microbiota colonizing the different moonmilk niches. Furthermore, distinct bacterial and archaeal taxa known to be involved in the metabolism of inorganic nitrogen and C1 gases (CO2 and CH4) (Nitrospira, Nitrosopumilaceae, Nitrosomonadaceae, Nitrosococcaceae, and novel taxa of Methylomirabilota and Methanomassiliicoccales) were enriched in the core and apical parts of the moonmilk, probably in association with their contribution to biogeochemical cycles in Grotta Nera ecosystem and moonmilk development.
CONCLUSIONS: The moonmilk deposits can be divided into diverse niches following oxygen and water gradients, which are characterized by specific microbial taxa and organic matter composition originating from microbial activities or deriving from soil and vegetation above the cave. The metabolic capacities allowing the biodegradation of complex polymers from the vegetation above the cave and the use of inorganic nitrogen and atmospheric gases might have fueled the development of complex microbial communities that, by interacting with the carbonatic rock, led to the formation of these massive moonmilk speleothems in Grotta Nera.

Optical surrogates, derived from absorbance and fluorescence spectra, are widely used to infer dissolved organic matter (DOM) composition (molecular weight, aromaticity) and genesis (autochthonous vs allochthonous). Despite the broad adoption of optical surrogates, several limitations exist, such as context- and sample-specific factors. These limitations create uncertainty about how compositional interpretations based on optical surrogates are generalized across contexts, specifically if there is duplicative or contradictory information in those interpretations. To explore these limitations, we performed a meta-analysis of optical surrogates for DOM from diverse sources, both from natural systems and after water treatment processes (n = 762). Prior to analysis, data were screened using a newly developed, standardized methodology that applies systematic quality control criteria before reporting surrogates. There was substantial overlap in surrogate values from natural and treated samples, suggesting that the gradients governing the surrogate variability can be generated in both contexts. This overlap provides justification for using optical surrogates originally developed in the context of natural systems to describe DOM changes in engineered systems, although the interpretations may change. Absorbance-based surrogates that describe the amount of spectral tailing (e.g., E2:E3 and S275-295) had a high frequency of strong correlations with one another but not to specific absorbance (SUVA254) or absorbance slope ratio (SR). The fluorescence index (FI) and biological index (β/α) were strongly correlated with one another and to the peak emission wavelength but not to the humification index (HIX). Although SUVA254 and FI have both been correlated to DOM aromaticity in prior research, there was a lack of reciprocity between these optical surrogates across this data set. Additionally, there were patterns of deviations in the wastewater subset, suggesting that effluent organic matter may not follow conventional interpretations, urging caution in the use of optical surrogates to track DOM in water reuse applications. Finally, the meta-analysis highlights that three aspects should be captured when optical spectra are used for DOM interpretation: specific absorbance, absorbance tailing, and the extent of red-shifted fluorescence. We recommend that SUVA254, E2:E3, and FI or β/α be prioritized in future DOM studies to capture these aspects, respectively.

Soil moisture reserves are a key factor in maintaining soil fertility and all other related ecosystem services (including carbon sequestration, soil biodiversity, and soil erosion control). In semiarid blown-sand areas under aridification, water preservation is a particularly crucial task for agriculture. The international Diverfarming project (2017-2022), within the EU Horizon 2020 Program, focused on the impacts of crop diversification and low-input practices in all pedoclimatic regions of Europe. In this three-year experiment conducted in the Pannonian region, the impact of intercropping asparagus with different herbs on some provisioning and regulating ecosystem services was evaluated in the Kiskunság sand regions. Relying on findings based on a range of measured physical and chemical soil parameters and on crop yields and qualitative properties, advice was formulated for farmers. The message drawn from the experiment is somewhat ambiguous. The local farmers agree that crop diversification improves soil quality, but deny that it would directly influence farm competitiveness, which primarily depends on cultivation costs (such as fertilization, plant protection, and labour). Further analyses are needed to prove the long-term benefits of diversification through enriching soil microbial life and through the possible reduction of fertilizer use, while water demand is kept at a low level and the same crop-quality is ensured.

To date, research on the toxicity and potential environmental impacts of nanomaterials has predominantly focused on relatively simple and single-component materials, whilst more complex nanomaterials are currently entering commercial stages. The current study aimed to assess the long-term and size-dependent (60 and 500 nm) toxicity of a novel core-shell nanostructure consisting of a SiC core and TiO2 shell (SiC/TiO2, 5, 25, and 50 mg L-1) to the common model organism Daphnia magna. These novel core-shell nanostructures can be categorized as advanced materials. Experiments were conducted under environmentally realistic feeding rations and in the presence of a range of concentrations of humic acid (0.5, 2, 5, and 10 mg L-1 TOC). The findings show that although effect concentrations of SiC/TiO2 were several orders of magnitude lower than the current reported environmental concentrations of more abundantly used nanomaterials, humic acid can exacerbate the toxicity of SiC/TiO2 by reducing aggregation and sedimentation rates. The EC50 values (mean ± standard error) based on nominal SiC/TiO2 concentrations for the 60 nm particles were 28.0 ± 11.5 mg L-1 (TOC 0.5 mg L-1), 21.1 ± 3.7 mg L-1 (TOC 2 mg L-1), 18.3 ± 5.4 mg L-1 (TOC 5 mg L-1), and 17.8 ± 2.4 mg L-1 (TOC 10 mg L-1). For the 500 nm particles, the EC50 values were 34.9 ± 16.5 mg L-1 (TOC 0.5 mg L-1), 24.8 ± 5.6 mg L-1 (TOC 2 mg L-1), 28.0 ± 10.0 mg L-1 (TOC 5 mg L-1), and 23.2 ± 4.1 mg L-1 (TOC 10 mg L-1). We argue that fate-driven phenomena are often neglected in effect assessments, whilst environmental factors such as the presence of humic acid may significantly influence the toxicity of nanomaterials.

The impact of integrated nutrient management seems crucial for the sustainability of crop production as revealed by studies on long-term experiments. It provided the opportunity to monitor long-term variations in crop yields and associated factors. The impacts of various nutrient management strategies on yields and soil attributes in a rice-wheat system have been researched under a long-term experiment that has been running since 1983 at Punjab Agricultural University, Ludhiana. Further, a positive correlation has been observed between crop yields and soil properties such as soil organic carbon (SOC), nitrogen (N), phosphorus (P), potassium (K) and zinc (Zn). The negative correlation with K could be attributed to soil becoming deficient in K and necessitating the application of potassium fertilizer. The treatments receiving organic manures (green manure, farmyard manure and wheat cut straw) showed a better population of soil microorganisms in comparison to the treatments receiving chemical fertilizers, thereby proving as precursors of sustaining soil health. The best soil characteristics (water-soluble aggregates, exchangeable and non-exchangeable K, fixed and total K) after rice and wheat harvesting were found where 50 % of the recommended NPK was supplemented with farmyard manure (FYM). The build-up of trace elements particularly for Fe and Zn was also noticed. In crystalline Fe oxide bound fraction (CFeOX), Fe increased between 717.1 and 984.8 mg kg-1, while Zn increased between 2.64 and 3.08 mg kg-1. Furthermore, amorphous iron oxide (AFeOX), CFeOX, carbonate (CARB), organic matter (OM) bound and exchangeable (EXCH) Fe and Zn were higher in treatments where organic manures were supplemented with 50 and 25 % N. Farmyard manure showed an incremental trend, followed by wheat cut straw and green manure (GM). The incremental trend in soil quality was noticed with FYM followed by wheat cut straw and GM.