Climate change events significantly impact the food production chain by damaging crops in their most fragile phenological states. Furthermore, increasing human population and excess food waste present agricultural systems with the challenge of closing the yield gap and securing food demands in the future as well as protect the soil health and biodiversity. Biostimulants are a novel alternative in agriculture that can effectively use inputs, enhance crop resilience to abiotic stresses and improve food quality. Additionally, biostimulants offer a promising and eco-friendly solution for reducing the use of chemical fertilizers, as they have the potential to increase crop nutrient use efficiency and yield. Because of their effects on plant growth, a wide range of products can be marketed as biostimulants. Presented in this review is an overview of recent literature on the use of plant growth-promoting microbes and microalgae-derived extracts obtained from either waste streams or recycled substrates. Starting from their source material, extraction technologies and application modalities, a view of their factors shaping the composition and activity of biostimulants is provided to elucidate a mechanistic model of action which leads to increased stress resilience in crops. This work further sets out to understand if the biostimulants can be used to transform waste into a valuable product that can accelerate the transition to sustainable agriculture.This article is part of the theme issue 'Crops under stress: can we mitigate the impacts of climate change on agriculture and launch the 'Resilience Revolution'?'.

Biochars, produced via pyrolysis, are gaining attention in applications ranging from soil amendments to energy storage and environmental remediation. While lignocellulosic biochars from woody biomass are well studied, algal biochars remain comparatively overlooked despite offering diverse organic and inorganic content that may broaden their applications. This study investigates how pyrolysis temperature and oxidative pretreatment affect the structure and properties of biochars derived from two macroalgae, Ulva expansa and Sargassum sp., under various pyrolysis conditions (500 to 900 degrees C). Using Raman spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, and nanoindentation, it was found that the C-O and C-N surface functional groups decreased in Ulva but the C=O and C-O-C groups increased in Sargassum upon pyrolysis. The reduced modulus ranged between 2.6 to 7.9 GPa and was governed by pyrolytic carbon content and inorganic composition. Of these two factors, the amount and type of pyrolytic carbon were determined by the heating conditions, with oxidation at 200 degrees C generally preserving more carbon than oxidation at 300 degrees C. Meanwhile, the final pyrolysis temperature dictated residual carbon content, salt formation, and carbonation. These findings highlight the potential for tailored pyrolysis to produce algal biochars with customizable structures and properties, enabling environmental and industrial applications such as carbon sequestration, filtration, and energy storage.

Fungal diseases caused by Fusarium spp. significantly threaten food security and sustainable agriculture. One of the traditional strategies for eradicating Fusarium spp. incidents is the use of chemical and synthetic fungicides. The excessive use of these products generates environmental damage and has negative effects on crop yield. It puts plants in stressful conditions, kills the natural soil microbiome, and makes phytopathogenic fungi resistant. Finally, it also causes health problems in farmers. This drives the search for and selection of natural alternatives, such as bio-fungicides. Among natural products, algae and cyanobacteria are promising sources of antifungal bio-compounds. These organisms can synthesize different bioactive molecules, such as fatty acids, phenolic acids, and some volatile organic compounds with antifungal activity, which can damage the fungal cell membrane that surrounds the hyphae and spores, either by solubilization or by making them porous and disrupted. Research in this area is still developing, but significant progress has been made in the identification of the compounds with potential for controlling this important pathogen. Therefore, this review focuses on the knowledge about the mechanisms of action of the fatty acids from macroalgae, microalgae, and cyanobacteria as principal biomolecules with antifungal activity, as well as on the benefits and challenges of applying these natural metabolites against Fusarium spp. to achieve sustainable agriculture.

Snow algae darken the surface of snow, reducing albedo and accelerating melt. However, the impact of subsurface snow algae (e.g., when cells are covered by recent snowfall) on albedo is unknown. Here, we examined the impact of subsurface snow algae on surface energy absorption by adding up to 2 cm of clean snow to surface algal blooms and measuring reflectivity. Surprisingly, snow algae still absorb significant energy across an array of wavelengths when snow-covered. Furthermore, the scale of this effect correlates with algal cell densities and chlorophyll-a concentrations. Collectively, our results suggest that darkening by subsurface snow algae lowers albedo and thus potentially accelerates snowmelt even when the algae is snow-covered. Impacts of subsurface algae on melt await assessment. This implies that snow algae play a larger role in cryosphere melt than investigations of surface-only reflectance would suggest. IMPORTANCE This study addresses a gap in research by examining the impact of subsurface snow algae on snow albedo, which affects snowmelt rates. Previous studies have focused on visible surface blooms, leaving the effects of hidden algae unquantified. Our findings reveal that snow algae beneath the surface can still absorb energy across various wavelengths, accelerating melt even when not visible to the naked eye. This suggests that spectral remote sensing can detect these hidden algae, although their biomass might be underestimated. Understanding how subsurface snow algae influence albedo and snowmelt is crucial for accurate predictions of meltwater runoff, which impacts alpine ecosystems, glacier health, and water resources. Accurate projections are essential for managing freshwater supplies for agriculture, drinking water, and other vital uses. Thus, further investigation into subsurface snow algae is necessary to improve our understanding of their role in snow albedo reduction and water resource management.

This study focuses on mitigating the socio-economic and environmental damage of the invasive macroalga Rugulopteryx okamurae and counteracting the pollution from petroleum-based plastics by using the alga as a feedstock for polyhydroxybutyrate (PHB) production. The enzymatic hydrolysis of R. okamurae, non-pretreated and hydrothermally acid-pretreated (0.2 N HCl, 15 min), was carried out, reaching reducing sugar (RS) concentrations of 10.7 g/L and 21.7 g/L, respectively. The hydrolysates obtained were used as a culture medium for PHB production with Cupriavidus necator, a Gram-negative soil bacterium, without supplementation with any external carbon and nitrogen sources. The highest yield (0.774 g PHB/g RS) and biopolymer accumulation percentage (89.8% cell dry weight, CDW) were achieved with hydrolysates from pretreated macroalga, reaching values comparable to the highest reported in the literature. Hence, it can be concluded that hydrolysates obtained from algal biomass hydrothermally pretreated with acid have a concentration of sugars and a C/N ratio that favour PHB production.

Pesticides are chemical substances that have become essential for global food production. However, their extensive use has resulted in significant environmental and health costs. Among the most widely used are diazinon and methamidophos, an insecticide and acaricide, respectively. These chemicals are classified as highly hazardous with high toxicity upon contact, ingestion, and inhalation. They are known to cause mutagenic effects, cancer, damage to the endocrine and nervous systems of humans, and their high solubility makes them likely to be found in soil, water, air, and certain foods. In this research, we evaluated the use of the microalga Chlorella vulgaris for phycoremediation of these two pesticides. The first step was to establish and optimize the growth parameters of C. vulgaris to maintain the microalgae in a state of reproduction. Favorable results were obtained at pH 7.0, a dilution ratio of 1:2 for the culture medium, and a photoperiod of 12 h of light and 12 h of darkness. Subsequently, the Minimum Inhibitory Concentration (MIC) and the Half-Maximal Effective Concentration (EC50) of the pesticides diazinon and methamidophos were evaluated. The microalga exhibited a high tolerance rate, with concentrations exceeding those naturally found in the environment. Based on these results, the conditions for assessing the biodegradation of both pesticides by the microalga were established. The outcome showed degradation percentages of 96 % for diazinon (25 mg L-1) and 100 % for methamidophos (500 mg L-1). In addition, the analysis of intermediate metabolites during the biodegradation process of both pesticides revealed the formation of less toxic compounds compared to the precursors and possibly complete mineralization as well; this given the positive response in terms of inorganic phosphate generation during the degradation. Finally, we propose biodegradation pathways for methamidophos and diazinon based on the detected metabolites and available information on biodegradation by certain bacteria.

Salvia miltiorrhiza , a widely used medicinal herb renowned for its properties in promoting blood circulation, removing blood stasis and alleviating pain, is currently facing quality degradation due to excessive heavy metal levels, posing a threat to medication safety. In order to investigate the effects of microbial inoculant, microalgae and biochar on the growth of Salvia miltiorrhiza under copper (Cu) stress, as well as its Cu absorption, antioxidant activity, active component contents and rhizosphere microbial community, a pot experiment was conducted. Salvia miltiorrhiza plants were cultivated in the soil containing 400 mg/kg of Cu for six months and treated with microbial inoculant, microalgae and biochar, either individually or in combination. Almost all soil amendment treatments led to an increase in root biomass. Notably, co -application of microbial inoculant and microalgae had the optimal effect with a 63.07 % increase compared to the group treated solely with Cu. Moreover, when microbial inoculant was applied alone or in combination with microalgae, the Cu content in plant roots was reduced by 19.29 % and 25.37 %, respectively, whereas other treatments failed to show a decreasing trend. Intriguingly, Cu stress increased the active component contents in plant roots, and they could also be enhanced beyond non -stress levels when microbial inoculant and microalgae were applied together or in combination with biochar. Analyses of plant antioxidant activity, soil properties and rhizosphere microorganisms indicated that these amendments may alleviate Cu stress by enhancing peroxidase activity, facilitating plant nutrient absorption, and enriching beneficial microorganisms capable of promoting plant growth and mitigating heavy metal induced damage. This study suggests that the combined application of microbial inoculant and microalgae can reduce Cu levels in Salvia miltiorrhiza while enhancing its quality under Cu stress.

The optical properties of snow can be strongly modified by the presence of a variety of impurities including mineral dust and snow algae. We made use of measured concentration of snow algae and mineral dust to parameterize the BioSNICAR radiative transfer model. Surficial snow samples were gathered during a field campaign on 7th July 2020 at the Presena glacier (Rhaetian Alps). We collected 18 samples of surface snow containing different amount of snow algae and mineral dust. Through radiative transfer simulations we estimated an average broadband albedo reduction of 7.4 +/- 6.1 % and 35.3 +/- 7.4 % compared to clean snow, caused by snow algae and mineral dust presence, respectively. When we considered the combined effect of snow algae and dust, we estimated a broadband albedo reduction equal to 40.8 +/- 8.4 %. We estimated an average instantaneous radiative forcing induced by snow algae, mineral dust and both impurities equals to 42.3 (+/- 36.1) W/m(2), 203.7 (+/- 45.5) W/m(2), and 211.8 (+/- 45.9) W/m(2), respectively. Using BioSNICAR simulations, we also tested a series of narrowband spectral indices to determine the concentration of mineral dust and snow algae from multi- and hyper -spectral data. Results showed that most spectral indices used for snow algae mapping are correlated also with mineral dust concentration. We found that only an index correlates uniquely with snow algae: the scaled band integral at 680 nm. A new spectral index, namely the Green Blue Normalized Index, is therefore proposed to discriminate mineral dust from snow algae when both impurities are present. The high spectral resolution of current (e.g. PRISMA, EnMAP) and future (e.g. CHIME, SBG) hyperspectral satellite missions will be fundamental to decouple the effect of mineral dust and snow algae on the optical properties of snow. In fact, from those data it is possible to calculate all narrowband indices presented in this study.

Vector-borne diseases pose a significant public health challenge in economically disadvantaged nations. Malaria, dengue fever, chikungunya, Zika, yellow fever, Japanese encephalitis, and lymphatic filariasis are spread by mosquitoes. Consequently, the most effective method of preventing these diseases is to eliminate the mosquito population. Historically, the majority of control programs have depended on chemical pesticides, including organochlorines, organophosphates, carbamates, and pyrethroids. Synthetic insecticides used to eradicate pests have the potential to contaminate groundwater, surface water, beneficial soil organisms, and non-target species. Nanotechnology is an innovative technology that has the potential to be used in insect control with great precision. The goal of this study was to test the in vitro anti-dengue potential and mosquitocidal activity of Chaetomorpha aerea and C. aerea-synthesized Mn-doped superparamagnetic iron oxide nanoparticles (CA-Mn-SPIONs). The synthesis of CA-Mn-SPIONs using C. aerea extract was verified by the observable alteration in the colour of the reaction mixture, transitioning from a pale green colour to a brown. The study of UV-Vis spectra revealed absorbance peaks at approximately 290 nm, which can be attributed to the surface Plasmon resonance of the CA-Mn-SPIONs. The SEM, TEM, EDX, FTIR, vibrating sample magnetometry, and XRD analyses provided evidence that confirmed the presence of CA-Mn-SPIONs. In the present study, results revealed that C. aerea aqueous extract LC50 values against Ae. aegypti ranged from 222.942 (first instar larvae) to 349.877 ppm in bioassays (pupae). CA-Mn-SPIONs had LC50 ranging from 20.199 (first instar larvae) to 26.918 ppm (pupae). After treatment with 40 ppm CA-Mn-SPIONs and 500 ppm C. aerea extract in ovicidal tests, egg hatchability was lowered by 100%. Oviposition deterrence experiments showed that in Ae. aegypti, oviposition rates were lowered by more than 66% by 100 ppm of green algal extract and by more than 71% by 10 ppm of CA-Mn-SPIONs (oviposition activity index values were 0.50 and 0.55, respectively). Moreover, in vitro anti-dengue activity of CA-Mn-SPIONs has good anti-viral property against dengue viral cell lines. In addition, GC-MS analysis showed that 21 intriguing chemicals were discovered. Two significant phytoconstituents in the methanol extract of C. aerea include butanoic acid and palmitic acid. These two substances were examined using an in silico methodology against the NS5 methyltransferase protein and demonstrated good glide scores and binding affinities. Finally, we looked into the morphological damage and fluorescent emission of third instar Ae. aegypti larvae treated with CA-Mn-SPIONs. Fluorescent emission is consistent with ROS formation of CA-Mn-SPIONs against Ae. aegypti larvae. The present study determines that the key variables for the successful development of new insecticidal agents are rooted in the eco-compatibility and the provision of alternative tool for the pesticide manufacturing sector.

Climate change has emerged as a challenge for soybean cultivation around the world, stimulating the development of technological alternatives that aim to mitigate the damage caused by water deficit. From this perspective, algae extract-based biostimulants have been tested to reduce water stress in several crops, but little is known about their effects on soybean. Thus, we hypothesize that a commercial biostimulant based on Ascophyllum nodosum can improve the physiological performance and water relations of Glycine max plants subjected to water deficit. To test this hypothesis, we set up an experiment in controlled conditions in a greenhouse, considering five treatments (control; application of biostimulant; water deficit (WD); WD + application of biostimulant; and WD + split application of biostimulant). The experiment was designed in completely randomized blocks with four replications per treatment and conducted in polyethylene pots containing 10 L of soil and three plants per pot. The irrigation was carried out daily; the water deficit was 50% soil moisture at field capacity, starting at the R1 stage (beginning of flowering, where there is at least one flower open at any node on the plant) and maintained for ten days. The biostimulant was applied concurrently with the onset of water deficit. We confirmed the hypothesis that foliar application of 1.0 L ha-1 of the biostimulant reduces the deleterious effects of the common water deficit at the beginning of the reproductive stage of soybean through the reduction of damage from oxidative stress (reduction of malondialdehyde synthesis by 31.2% in relation to the WD plants), maintenance of water potential and cellular homeostasis (10.2% increase in relative water content when compared with WD plants), and conservation of the contents of chlorophyll in leaves and stimulation of photosynthesis and carboxylation (68% increase in net photosynthetic rate and 49.3% increase in carboxylation efficiency in relation to WD plants). However, when applied in installments, the biostimulant was not efficient in reducing soybean water stress. Therefore, we conclude that the application of a biostimulant based on A. nodosum can help reduce the harmful effects of water deficit on soybean plants, opening up perspectives for the mass use of this extract in agricultural crops produced on a large scale.