Biomass Composition Research Articles

Denitrification efficiency and accumulation characteristics of residual organics for the main compositions in woody biomass using a carbon source

Denitrification efficiency and accumulation characteristics of residual organics for the main compositions in woody biomass using a carbon source

Dairy Wastewaters to Promote Mixotrophic Metabolism in Limnospira (Spirulina) platensis: Effect on Biomass Composition, Phycocyanin Content, and Fatty Acid Methyl Ester Profile

This study explores the mixotrophic cultivation of Limnospira platensis using dairy byproducts, specifically scotta whey (SW), buttermilk wastewater (BMW), and dairy wastewater (DWW), to promote biomass production and enhance the composition of bioactive compounds. By assessing various concentrations (1%, 2%, and 4% v v−1) of these byproducts in a modified growth medium, this study aims to evaluate their effect on L. platensis growth, phycocyanin (C-PC) content, and fatty acid methyl ester (FAME) profiles. The results show that the optimal biomass production was achieved with 2% scotta and dairy wastewater, reaching maximum concentrations of 3.30 g L−1 and 3.19 g L−1, respectively. Mixotrophic cultivation led to increased C-PC yields, especially in buttermilk and dairy wastewater treatments, highlighting the potential for producing valuable pigments. Additionally, the FAME profiles indicated minimal changes compared to the control, with oleic and γ-linolenic acids being dominant in mixotrophic conditions. These findings support the viability of utilizing dairy byproducts for sustainable L. platensis cultivation, contributing to a circular bioeconomy while producing bioactive compounds of nutritional and commercial interest.

Removal of antibiotics and their impact on growth, nutrient uptake, and biomass productivity in semi-continuous cultivation of Auxenochlorella protothecoides.

The prevalence of antibiotics in wastewater poses risks to human and animal health, contributing to antimicrobial resistance. Although various antibiotic removal methods exist, microalgae-based technology presents a cost-effective and eco-friendly alternative; however, limited research on its long-term integration in semi-continuous wastewater treatment trials hinders our understanding of its potential effectiveness. This investigation explored the antibiotic removal capabilities of the microalga Auxenochlorella protothecoides in photobioreactors with synthetic wastewater under semi-continuous conditions over one month. Additionally, the study assessed the impact of seven commonly used antibiotics (ciprofloxacin, clarithromycin, erythromycin, metronidazole, ofloxacin, sulfamethoxazole, and trimethoprim) on the microalgal system regarding growth, nutrient removal, and biomass productivity. The microalga effectively removed antibiotics, achieving maximum removal efficiencies ranging from 45.8% to 70.1% over 3-4 days of exposure. Remarkably, antibiotics stimulated algal growth, resulting in an 11.0% increase in biomass. Nutrient removal also improved significantly; ammonium removal rose from 78.0% to 86.4%, and phosphate removal increased from 85.1% to 90.3%. Furthermore, the biomass composition showed notable enhancements, with increases in pigments (12.9%), lipids (20.6%), proteins (45.8%), and carbohydrates (50.6%). These findings highlight the potential applicability of A. protothecoides as a valuable addition to conventional wastewater treatment plants. The study emphasises the importance of considering antibiotic presence in microalgae-based wastewater treatment technologies, as these compounds can have a stimulatory effect that enhances both growth and nutrient removal efficiency. Overall, this research contributes to the development of more effective strategies for managing antibiotic pollution in wastewater.

Testing the Purity of Limnospira fusiformis Cultures After Axenicity Treatments.

Contaminations are challenging for monocultures, as they impact the culture conditions and thus influence the growth of the target organism and the overall biomass composition. In phycology, axenic cultures comprising a single living species are commonly strived for both basic research and industrial applications, because contaminants reduce significance for analytic purposes and interfere with the safety and quality of commercial products. We aimed to establish axenic cultures of Limnospira fusiformis, known as the food additive "Spirulina". Axenicity is strived because it ensures that pathogens or harmful microorganisms are absent and that the harvested biomass is consistent in terms of quality and composition. For the axenic treatment, we applied sterile filtration, ultrasonication, pH treatment, repeated centrifugation, and administration of antibiotics. For testing axenicity, we considered the most common verification method plate tests with Lysogeny Broth (LB) medium, which indicated axenicity after treatments were performed. In addition, we included plate tests with Reasoner's 2A (R2A) agar and modified Zarrouk+ medium, the latter comparable to the biochemical properties of L. fusiformis' cultivation medium. In contrast to LB plates, the other media, particularly Zarrouk+, indicated bacterial contamination. We conclude that LB-agar plates are inappropriate for contamination screening of extremophiles. Contamination was also verified by cultivation-independent methods like flow cytometry and 16S rRNA genome amplicon sequencing. We detected taxa of the phyla Proteobacteria, Bacteriodota, Firmicutes and to a lesser extent Verrucomicrobiota. Contaminants are robust taxa, as they survived aggressive treatments. Sequencing data suggest that some of them are promising candidates for in-depth studies to commercially exploit them.

Non-Thermal Plasma-Activated Water Enhances Nursery Production of Vegetables: A Species-Specific Study

Non-thermal plasma technology (NTP) has found widespread applications across several fields, including agriculture. Researchers have explored the use of NTP to improve plant growth and increase agricultural product quality using plasma-activated water (PAW). This technology has shown potential benefits in boosting seed germination, promoting plant growth, as an effective defense against plant pathogens, and increasing systemic plant resistance. An experiment was set up over three different cultivation cycles to investigate the benefits of PAW administration on nursery production. Plasma-activated water was generated using two NTP intensities (PAW-HI = 600 mV; PAW-LI = 450 mV; CTR = tap water control) and manually applied to plants under greenhouse conditions. The species considered in the current study were tomato (Solanum lycopersicum L.), Swiss chard (Beta vulgaris L.), cabbage (Brassica oleracea L.), basil (Ocimum basilicum L.), and lettuce (Lactuca sativa L. var. Longifolia). The following morphological traits were measured at the end of each cycle and for each species: plant height (PH, cm), collar diameter (CD, mm), biomass (g), nutritional status (SPAD index), dry matter (DM, %), and chemical composition. The sturdiness index (SI) was determined by the PH-to-CD ratio. Results indicated a species-specific response to both PAW treatments compared to CTR. The plant height significantly increased in tomato (+11.9%) and cabbage (+5%) under PAW-HI treatment. In contrast, PAW-HI treatment negatively affected the PH in lettuce and basil (−18% and −9%, respectively). Swiss chard showed no significant response to either PAW-LI or PAW-HI treatments. Regarding DM, no significant differences were observed between the PAW treatments and CTR. However, an increase in total N content was detected in plant tissues across all species, except for basil, where no change was observed. The results suggest that PAW treatment has the potential to enhance vegetable nursery production, with species-specific responses observed in crops.

Biotechnological transformation of giant miscanthus biomass into bacterial nanocellulose

Biotechnological transformation of plant materials constitutes one of the most promising industrial processes for obtaining high-value products from inexpensive plant materials. The article analyzes the biotransformation of giant miscanthus (Miscanthus × giganteus) into high-value bacterial nanocellulose from the feedstock to the final product, i.e., presents the complete cycle of plant material processing. First, the chemical composition of giant miscanthus biomass was determined, and the content of cellulose was found to be 54%. After that, biotransformation was performed in three stages: in the first stage, the giant miscanthus biomass was pretreated using four methods; then, the obtained substrates were subjected to enzymatic hydrolysis under the same conditions, and carbohydrate growth media were obtained; in the final stage, bacterial nanocellulose was biosynthesized in the obtained growth media using Medusomyces gisevii Sa-12 symbiotic culture. The chemical pretreatment with dilute solutions of nitric acid and sodium hydroxide was found to be extremely effective and increase the reactivity to enzymatic hydrolysis by 28–31 times as compared to native miscanthus. It is shown that for the production of bacterial nanocellulose from giant miscanthus, biomass should undergo one-stage pretreatment with a dilute nitric acid solution. In this case, the substrate yield from the feedstock (for subsequent hydrolysis) amounts to 50%, the extraction of reducing sugars from miscanthus biomass is maximum (65.2%), and the yield of bacterial nanocellulose is 1.1–1.3 times higher than for the other three biomass pretreatment methods.

Utilization of the aqueous phase of the hydrothermal liquefaction process as a substrate for microalgae cultivation

The article presents the culturing of nine microalgae strains from the IPPAS collection of IFR RAS using components of the aqueous phase of the excessive activated sludge hydrothermal revitalization process as a substrate. In order to select the most promising cultures, their growth characteristics and efficient removal of NH4+ ions, PO43- and organic compounds were studied. All the studied cultures are shown to be able to utilize components of the aqueous phase as a nutrient substrate. The highest specific growth rate of 0.92 day-1 was observed in the strain Chlorella sp. IPPAS C-1210. However, the Parachlorella kessleri IPPAS C-9 and Chlorella minutissima IPPAS C-123 strains were also promising in terms of their efficiency of pollutant removal from the medium: efficiency of ammonium nitrogen assimilation was 78 and 81%, while phosphate ion assimilation was 89 and 91%, respectively. The biomass composition of C-9 and C-123 cultures was investigated, mainly consisting of polysaccharides – at 41 and 44% – and proteins – at 31 and 25% of the total mass, respectively. A high degree of neutralization of the medium was additionally achieved as a result of consecutive two-stage purification of the aqueous phase of the process of hydrothermal revitalization of excessive activated sludge with the use of microorganisms-destructors (Paenarthrobacter nicotinovorans and Comamonas testosteroni) and the studied microalgae cultures. During 17 days of the purification process, the concentration of ammonium ions decreased from 289.8±14.9 to 51.1±2.2 mg/dm3, phosphates from 116.3±8.1 to 11.3 mg/dm3; the overall efficiency of the process of pollutants removal from the aqueous phase was up to 90%.

Impact of Eastern Redcedar (Juniperus virginiana L.) Canopy Diameter and Stand Canopy Cover on Aboveground Biomass and Composition in the Northern Great Plains Mixed-Grass Prairie

Eastern redcedar (ERC) (Juniperus virginiana L.) trees are invading prairies throughout the Great Plains. This encroachment poses a threat to native plant communities in terms of their production, regeneration, and diversity. The objectives of this study were to determine how ERC canopies impact herbaceous biomass production and composition. Square quadrats (0.25 m2) were placed in four cardinal directions underneath canopies of ERC trees ranging from 0.1–10 m in diameter and at grassland control locations. We collected herbaceous foliar cover by species and biomass estimates underneath 326 ERC trees and at 240 grassland control locations among two sites totaling 1381 samples overall. We found herbaceous biomass production underneath ERC canopies decreased exponentially with increasing ERC canopy diameter with 63–97% reduction under trees with canopies larger than 2 m. Also, biomass decreased linearly with increasing ERC stand canopy cover (%) at nearly a 1:1 ratio. Mean foliar cover for all species, Floristic Quality Index, species richness, and native species richness decreased as individual ERC canopy diameter increased. Results indicate that ERC encroachment is not only reducing herbaceous biomass production, but it is also altering the composition of plant communities. This highlights the importance of ERC control on grasslands and provides landowners with data that can be applied to their individual operation. To maintain or restore native grasslands, we suggest the removal of ERC through prescribed fire and/or mechanical removal every 5–10 years. Following these management strategies should maintain a healthy grassland system.

Multiple stressor effects act primarily on microbial leaf decomposers in stream mesocosms.

At the global level, stream ecosystems are influenced by multiple anthropogenic stressors such as eutrophication, habitat deterioration, and water scarcity. Multiple stressor effects on stream biodiversity are well documented, but multiple stressor effects on stream ecosystem processes have received only limited attention. We conducted one mesocosm (stream channel) and one microcosm (feeding trial) experiment to study how combinations of reduced flow, increased nutrient concentrations, and increased fine sediment coverage would influence fungal and macroinvertebrate decomposer assemblages and their active contribution to leaf decomposition. In the stream channels, increased fine sediment coverage significantly reduced fungal biomass, occurrence frequencies of most aquatic hyphomycete species, and microbial leaf decomposition rates compared to untreated controls. Macroinvertebrate-induced leaf decomposition rates were mainly correlated to total fungal biomass and community composition. Neither increased nutrient concentrations, nor reduced flow conditions significantly influenced leaf decomposer communities or decomposition rates. The feeding trials revealed significantly reduced leaf consumption in the freshwater amphipod Gammarus pulex when feeding on leaf material from treatments with increased fine sediment coverage in the mesocosm experiment. When offered a food choice between sterile, unconditioned leaf material and leaf material from treatments with increased fine sediment coverage, G. pulex foraged mainly on sterile material. This study showed that increased fine sediment coverage can alter the flux of energy and material in the detrital food chain through bottom-up regulation of leaf conditioning by fungal decomposers. Our results suggest that increasing attention should be given to mitigating fine sediment transport and deposition in stream systems to preserve ecosystem functioning within the detrital food chain.

Evaluating the efficacy of various types of guarding nets in minimizing bycatch in a Mediterranean trammel net fishery

Static nets, like trammel nets, may have less environmental impact than towed gear, but they often result in high discard rates. Trammel nets targeting the common cuttlefish Sepia officinalis in Thermaikos Gulf (N. Aegean) were shown to display a discard rate of 40.2% with the vast majority of discarded catch consisting of invertebrate species, such as muricid gastropods, sea urchins, and spider crabs. In addition to the environmental impact, capturing some of these species can be a substantial difficulty for small-scale fishers, leading to delays in their fishing operations and damage to their gear. This research examined the effectiveness of different types of guarding nets, namely short gillnets positioned between the main trammel net and the footrope, in terms of biomass and species composition in commercial catches and discards. All tested gears significantly reduced the capture rate of crustaceans, notably spider crabs. However, the results for the other groups of organisms varied. The only gear modification that had no significant effect on cuttlefish catches was the addition of a well-rigged guarding net with a smaller mesh (20mm instead of 40mm). On the other hand, when the guarding net was loosely attached to the main net or had a greater mesh size, the biomass of cuttlefish and the abundance of demersal teleosts decreased. Our study showed that, despite the added cost, putting a guarding net during the period when species like crabs are at their seasonal height may benefit fishers in avoiding delays in disentanglement and damage to their fishing gear.

Harnessing deep eutectic solvent for enhanced inulinase production from agricultural via submerged fermentation with Aspergillus niger.

This study aimed to enhance inulinase production from agricultural biomass pretreated with deep eutectic solvents (DES) using Aspergillus niger A42 (ATCC 204447). Barley husk (BH), wheat bran (WB), and oat husk (OH) were selected as substrates and were pretreated using different molar ratios of choline chloride: glycerol (ChCl: Gly) and choline chloride: acetic acid (ChCl: AA). DES pretreatment was followed by dilute sulfuric acid hydrolysis. The fermentable sugar content (FSC), sugar profiles, and inhibitory components in the hydrolysates were analyzed. DES pretreatment improved the FSC in all substrates, with wheat bran showing the highest FSC of 72.54g/mL. Considering the fermentable sugar contents, ChCl: Gly (1:2) was selected as the most suitable DES. The analysis of biomass composition after pretreatment indicated a reduction in extractives and lignin, along with an increase in cellulose content. Subsequently, inulinase fermentation using Aspergillus niger A42 has demonstrated that DES-pretreated wheat bran was the most effective substrate, yielding 416.05U/mL inulinase activity (Iase) and 486.22U/mL invertase-type (Sase) activity. The enzyme solution was partially purified via Spin-X UF membranes (50kDa cut-off), resulting in Iase activity of 769.93U/mL and Sase activity of 566.69U/mL. The purification coefficients were 1.88 and 0.92 for inulinase and invertase-type activity, respectively. In conclusion, DES pretreatment was successfully applied to produce inulinase enzyme from BH, WB, and OH. Among the materials studied, WB emerged as the most suitable biomass for producing inulinase from Aspergillus niger A42.

Growth of Picochlorum celeri in produced water from the Permian Basin (US)

Produced water generated from hydraulic fracking is a waste stream that, on one hand, demands remediation, and, on the other hand, can be used as a water source to support a circular economy. In this study, we aimed to assess the ability of Picochlorum celeri to grow in two different sources of raw, untreated produced water collected in New Mexico, USA. The produced water had initial salinities of 110 and 140 PPT. Picochlorum was screened, with additional algae, on two different sources of produced water supplemented with nitrogen and phosphorus. The strain was able to grow on 25 % and 50 % produced water and achieve biomass densities between ~40 and 100 % of those demonstrated by control cultures. To separate the effects of high salinity stress from toxicity of the produced water samples, we conducted a bioassay with produced water under isotonic conditions of 60 PPT. When controlling for salinity, the contaminants associated with the two sources of produced water did not affect growth of the algae. This study provides justification to consider P. celeri as a candidate for remediation of and biomass production on produced water. Foundational studies are necessary to assess remediation potential and characterize the growth, biomass accumulation, and biomass composition of P. celeri grown on a variety of produced water streams.

Nitrogen uptake and associated pH changes influence growth and biomass composition in microalgae from a polluted river

Nitrogen uptake and associated pH changes influence growth and biomass composition in microalgae from a polluted river

Performance of Individual Tree Segmentation Algorithms in Forest Ecosystems Using UAV LiDAR Data

Forests are crucial for biodiversity, climate regulation, and hydrological cycles, requiring sustainable management due to threats like deforestation and climate change. Traditional forest monitoring methods are labor-intensive and limited, whereas UAV LiDAR offers detailed three-dimensional data on forest structure and extensive coverage. This study primarily assesses individual tree segmentation algorithms in two forest ecosystems with different levels of complexity using high-density LiDAR data captured by the Zenmuse L1 sensor on a DJI Matrice 300RTK platform. The processing methodology for LiDAR data includes preliminary preprocessing steps to create Digital Elevation Models, Digital Surface Models, and Canopy Height Models. A comprehensive evaluation of the most effective techniques for classifying ground points in the LiDAR point cloud and deriving accurate models was performed, concluding that the Triangular Irregular Network method is a suitable choice. Subsequently, the segmentation step is applied to enable the analysis of forests at the individual tree level. Segmentation is crucial for monitoring forest health, estimating biomass, and understanding species composition and diversity. However, the selection of the most appropriate segmentation technique remains a hot research topic with a lack of consensus on the optimal approach and metrics to be employed. Therefore, after the review of the state of the art, a comparative assessment of four common segmentation algorithms (Dalponte2016, Silva2016, Watershed, and Li2012) was conducted. Results demonstrated that the Li2012 algorithm, applied to the normalized 3D point cloud, achieved the best performance with an F1-score of 91% and an IoU of 83%.

Shear stress controls prokaryotic and eukaryotic biofilm communities together with EPS and metabolomic expression in a semi-controlled coastal environment in the NW Mediterranean Sea

While waves, swells and currents are important drivers of the ocean, their specific influence on the biocolonization of marine surfaces has been little studied. The aim of this study was to determine how hydrodynamics influence the dynamics of microbial communities, metabolic production, macrofoulers and the associated vagile fauna. Using a field device simulating a shear stress gradient, a multi-scale characterization of attached communities (metabarcoding, LC–MS, biochemical tests, microscopy) was carried out for one month each season in Toulon Bay (northwestern Mediterranean). Shear stress appeared to be the primary factor influencing biomass, EPS production and community structure and composition. Especially, the transition from static to dynamic conditions, characterized by varying shear stress intensities, had a more pronounced effect on prokaryotic and eukaryotic beta-diversity than changes in shear stress intensity or seasonal physico-chemical parameters. In static samples, mobile microbe feeders such as arthropods and nematodes were predominant, whereas shear stress favored the colonization of sessile organisms and heterotrophic protists using the protective structure of biofilms for growth. The increase in shear stress resulted in a decrease in biomass but an overproduction of EPS, specifically exopolysaccharides, suggesting an adaptive response to withstand shear forces. Metabolite analysis highlighted the influence of shear stress on community dynamics. Specific metabolites associated with static conditions correlated positively with certain bacterial and algal groups, indirectly indicating reduced grazer control with increasing shear stress.

Computational Modeling of Biomass Fast Pyrolysis in Fluidized Beds with Eulerian Multifluid Approach

This study investigated the fast pyrolysis of biomass in fluidized-bed reactors using computational fluid dynamics (CFD) with an Eulerian multifluid approach. A detailed analysis was conducted on the influence of various modeling parameters, including hydrodynamic models, heat transfer correlations, and chemical kinetics, on the product yield. The simulation framework integrated 2D and 3D geometrical setups, with numerical experiments performed using OpenFOAM v11 and ANSYS Fluent v18.1 for cross-validation. While yield predictions exhibited limited sensitivity to drag and thermal models (with differences of less than 3% across configurations and computational codes), the results underline the paramount role of chemical kinetics in determining the distribution of bio-oil (TAR), biochar (CHAR), and syngas (GAS). Simplified kinetic schemes consistently underestimated TAR yields by up to 20% and overestimated CHAR and GAS yields compared to experimental data (which is shown for different biomass compositions and different operating conditions) and can be significantly improved by redefining the reaction scheme. Refined kinetic parameters improved TAR yield predictions to within 5% of experimental values while reducing discrepancies in GAS and CHAR outputs. These findings underscore the necessity of precise kinetic modeling to enhance the predictive accuracy of pyrolysis simulations.

Epoxy resin‐based biomass composites based on modified corn stalks: Preparation, properties, and toughening mechanism

AbstractIn this study, a series of sustainable eco‐friendly epoxy resin (EP)‐based biomass composites (DSA‐CS/EP) were prepared using bisphenol A EP as matrix, 2‐methylimidazole as curing agent, and corn stalk (CS) esterified with dodecene succinic anhydride (DSA) as filler. The static contact angle test results showed that the hydrophobicity of CS after esterification with DSA (DSA‐CS) was enhanced, which results in the compatibility of DSA‐CS with EP matrix was improved. And then, the DSA‐CSs were dispersed homogeneously in the matrix without agglomerating. The morphology and properties of the biomass composites were studied and analyzed in order to elucidate the toughening mechanism of CS and DSA‐CS. When the content of DSA‐CS is 15 wt%, the tensile strength and impact strength of DSA‐CS/EP reached a maximum value of 30.39 MPa and 3.34 KJ/m2, which were increased by 128.49% and 81.52% compared with pure EP. Finally, it is deduced that the possible toughening mechanism is that DSA‐CS can not only share part of the external stress but also a mutual solute region is formed between DSA‐CS and EP matrix.Highlights Corn stalks esterified by DSA were used as reinforcement filler for epoxy resin. The cellulose in CS was mainly esterified. The tensile and impact strength of DSA‐CS 15/EP reached a maximum value. A mutual solute region is formed between filler and matrix.

Beeswax waste improves the mycelial growth, fruiting body yield, and quality of oyster mushrooms (Pleurotus ostreatus).

Heilongjiang Province has the third largest bee population in China, producing over 2,000 tons of beeswax waste (BW) each year. Most of this BW is discarded or burned. Therefore, we urgently need to find sustainable applications of BW. Pleurotus ostreatus mushrooms, commonly referred to as oyster mushrooms, are cultivated for both food and medicine. The substrate used to grow P. ostreatus mushrooms often contains wheat bran as a nitrogen source. The goal of this study was to explore the feasibility of substituting this wheat bran with BW to cultivate P. ostreatus mushrooms. Five treatments were established, with BW making up 0%, 3%, 5%, 7%, and 9% of the total substrate, and the effects on the mycelial growth and development, biological efficiency (BE), and yield were evaluated along with changes in the chemical biomass composition of the fruiting bodies. Adding BW increased the number of days needed for primordia initiation and the number of days between flushes of P. ostreatus mushrooms. With increasing BW, the total fresh weight of P. ostreatus mushrooms first increased and then decreased. The 5% BW treatment resulted in the highest yield and biological efficiency (BE) of 1,478.96 ± 9.61 g bag-1 and 92.43 ± 0.60%, respectively, which exceeded the values of the control by 4.14% (control: 1,420.15 ± 9.53 g bag-1 and 88.76 ± 0.60%, respectively). The 5% BW treatment also resulted in the highest mushroom crude protein content (23.47 ± 0.18 g 100 g-1), which was 28.18% higher compared with the control (18.31 ± 0.05 g 100 g-1). The 9% BW treatment resulted in the highest crude polysaccharide content (10.33 ± 0.76 g 100 g-1), which was 2.42-fold that of the control (4.26 ± 0.30 g 100 g-1). This study suggests that BW could serve as an effective source of nitrogen to cultivate P. ostreatus. BW is a promising, cost-effective, and efficient additive to mushroom substrate, improving the yield and quality of P. ostreatus mushrooms while providing a sustainable use for an otherwise difficult to dispose of waste product.

Physiological responses of the alien macroalga Rugulopteryx okamurae (Phaeophyceae, Heterokontophyta) to changes in nutrients and temperature.

The Asian brown macroalga Rugulopteryx okamurae has invaded the oligotrophic areas of Mediterranean coasts since 2015, with drastic impacts on environmental conditions and socioeconomic activities in coastal areas in Europe. Therefore, it is intriguing how this species is able to grow and expand at the observed rates. In this context, the physiological responses of R. okamurae to changing nutrient concentrations and temperature were analyzed. Two experiments were conducted, evaluating six combinations of nitrate and phosphate concentrations and their potential interaction with temperature. Nutrient uptake efficiency (NUE) and rates (NUR), photosynthetic responses, growth rates, and biomass composition were evaluated. Photosynthesis parameters, soluble proteins, and -NUR increased with increasing N:P ratio; however, -NUR was very similar in all treatments. The species showed high capacity for nitrate assimilation, which was rapidly modulated by its external concentration and temperature (more than 90% of NO3-NUE after 5 days in treatments with N:P rations of 5, 10, 16, 25, and 40 N to 1 P). Consequently, N-nutrients were removed from the water by R. okamurae and likely stored inside the cells. This process will allow the alga to maintain high growth rates if thalli are moved to oligotrophic areas, favoring its spreading to many marine environments. Additionally, fucoxanthin was the predominant carotenoid in this species, although its content was lower than in other brown macroalgae species (mean value of 0.51 ± 0.05 mg · g-1 DW). However, since a huge amount of R. okamurae is observed recurrently on beaches, the use of this biomass might be proposed to compensate partially for its impacts.

The name of the compound and allelopathic effect of metabolites produced by common ragweed (Ambrosia artemisiifolia L.)

Purpose. To identify the phytochemical composition of the aboveground biomass of Ambrosia artemisiifolia L., the effect of its root exudates on major crops within agroecosystems, and the competitiveness of this weed species compared to other plants. Methods. Allelopathic, chemical, physiological-biochemical, analytical, and statistical methods. Results. The biomass of A. artemisiifolia contains a high concentration of essential physiologically active components, with coumarins being the most prevalent at 2.97%. The roots of A. artemisiifolia release protocatechuic acid, n-hydroxybenzoic acid, vanillic acid, syringic acid, n-coumaric acid, and ferulic acid into the rhizosphere. Phytotoxic extracts from the vegetative organs of A. artemisiifolia reduced seed germination in winter pea by an average of 37–50%, in maize by 27–40%, in sorghum by 17–22%, and in sugar beet by 12–28%. Root phytotoxic extracts and rhizosphere soil extracts significantly decreased seed germination in the studied crops: in winter pea by 71% and 78%, respectively, in maize by 42% and 38%, respectively, in sugar beet by an average of 26%, and in sorghum by 33% and 16%. Sunflower demonstrated the highest resistance, with seed germination reduced by only 7%, 5%, and 4% when treated with phytotoxic extracts from the stems, leaves, and inflorescences of A. artemisiifolia, respectively. Phytotoxic extracts from the soil and roots reduced sunflower seed germination by 11% and 6%, respectively. The highest competitiveness against the allelopathically active components of the weed species was exhibited by yellow mustard (Sinapis alba), sorghum, and creeping couch grass (Elymus repens), as their phytotoxic soil extracts reduced A. artemisiifolia seed germination by 75%, with creeping couch grass and sorghum extracts reducing germination by 88% and 68%, respectively. Conclusions. Water extracts from the vegetative and generative organs of A. artemisiifolia contain significant amounts of physiologically active components that impact the quality of seed germination in the studied crops. It was found that sunflower seeds are resistant to the allelopathically active substances of the A. artemisiifolia. Yellow mustard, sorghum, and creeping couch grass demonstrate resistance to the phytotoxic components of A. artemisiifolia, due to their high levels of phytochemical compounds capable of inhibiting seed germination of this highly allelopathic weed.