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Platinum nanoparticles (PtNPs) are one of the widely used NPs, which contribute to potential risks to the aquatic ecosystem. However, PtNPs toxicity in phytoplankton remains inadequately understood, with significant gaps in knowledge regarding their biochemical bases and species-specific responses. Herein, we investigated the impact of PtNPs on two cyanobacterial species (Anabaena laxa and Nostoc muscorum) to explore the harmful pathways triggered by PtNPs in cyanobacteria, which may help in selecting appropriate biomarkers for PtNPs pollution in aquatic environments. We studied the effect of PtNPs on growth, oxidative stress markers, and antioxidant defense systems of the two species. The obtained results showed that PtNPs reduced the level of chlorophyll. Furthermore, they induced dose-dependent oxidative stress to the two species, expressed by significant increases in H 2 O 2 , malondialdehyde (MDA), and protein oxidation (p < 0.05). Stress-induced oxidative damages were more pronounced in N. muscorum , yet the two cyanobacterial species showed higher levels (p < 0.05) of antioxidant metabolites and antioxidant enzymes to combat oxidative stress. Compared to N. muscorum , A. laxa invested more in the induction of antioxidant metabolites including FRAP, polyphenols, flavonoids, and glutathione (GSH), as well as in antioxidant enzymes such as POX, CAT, GR, and GPX. Overall, A. laxa species could be exploited as efficient biomarkers for monitoring PtNPs-induced ecotoxicology. Further investigation of bio-absorption and uptake of PtNPs by microalgae is recommended for developing algae-based bioremediation technologies. [Display omitted] • Impact of PtNPs on two cyanobacterial species was investigated. • PtNPs reduced the levels of chlorophylls in cyanobacterial species. • PtNPs induced dose-dependent oxidative stress to the two cyanobacterial species. • Stress-induced oxidative damages were more pronounced in N. muscorum. • A. laxa can be used as a biomarker for monitoring PtNPs-induced toxicology. [ABSTRACT FROM AUTHOR]

Heavy metals such as beryllium (Be) have been identified as toxic for plants with a negative impact on plant growth. Therefore, there is an urgent need for environmentally friendly techniques to reduce Be toxicity on plant growth and productivity. To this end, arbuscular mycorrhizal fungi (AMF) are widely applied to induce plant growth and stress tolerance. However, how AMF-plant symbiosis can support plants under Be stress has not been studied. Accordingly, we investigated the physiological and biochemical responses of AMF inoculated ryegrass and chickpea plants to Be stress. The associated changes in Be uptake and accumulation, photosynthesis, oxidative stress, carbon and nitrogen metabolism were studied. Soil contamination with Be induced higher Be accumulation, particularly in ryegrass, which consequentially reduced plant growth and photosynthesis. However, photorespiration and oxidative damage (H 2 O 2 accumulation, lipid oxidation, and LOX activity) were increased, mainly in ryegrass. In both plant species, AMF inoculation reduced Be accumulation and mitigated growth inhibition and oxidative damage, but to a more extent in ryegrass. This could be explained by improved photosynthesis as well as the upregulation of osmoprotectants i.e., sucrose and proline biosynthesis pathways. The increase in proline level was consistent with higher nitrogen (N) metabolism as reflected by N level and nitrate reductase. Species-specific responses were recorded and supported by principal component analysis. This study provided insight into the mechanism of AMF's impact on Be-stressed ryegrass and chickpea plants. Hence, the current research suggested that AMF inoculation could be used as a viable strategy to mitigate Be phytotoxicity in ryegrass and chickpea plants. [Display omitted] • Ryegrass was more tolerant than chickpea to Be stress. • Inoculation with AMF reduced Be phytotoxicity and enhanced photosynthesis of both plants. • AMF inoculation reduced Be accumulation and mitigated growth inhibition and oxidative damage. • Sucrose and proline biosynthesis pathways were upregulated under Be stress. • Nitrogen level and nitrate reductase activity were induced by AMF under Be stress. [ABSTRACT FROM AUTHOR]

Aluminum (Al) toxicity limits crops growth and production in acidic soils. Compared to roots, less is known about the toxic effects of Al in leaves. Al subcellular compartmentalization is also largely unknown. Using rye (Secale cereale L.) Beira (more tolerant) and RioDeva (more sensitive to Al) genotypes, we evaluated the patterns of Al accumulation in leaf cell organelles and the photosynthetic and metabolic changes to cope with Al toxicity. The tolerant genotype accumulated less Al in all organelles, except the vacuoles. This suggests that Al compartmentalization plays a role in Al tolerance of Beira genotype. PSII efficiency, stomatal conductance, pigment biosynthesis, and photosynthesis metabolism were less affected in the tolerant genotype. In the Calvin cycle, carboxylation was compromised by Al exposure in the tolerant genotype. Other Calvin cycle-related enzymes, phoshoglycerate kinase (PGK), glyceraldehyde 3-phosphate dehydrogenase (GAPDH), triose-phosphate isomerase (TPI), and fructose 1,6-bisphosphatase (FBPase) activities decreased in the sensitive line after 48 h of Al exposure. Consequentially, carbohydrate and organic acid metabolism were affected in a genotype-specific manner, where sugar levels increased only in the tolerant genotype. In conclusion, Al transport to the leaf and compartmentalization in the vacuoles tolerant genotype's leaf cells provide complementary mechanisms of Al tolerance, protecting the photosynthetic apparatus and thereby sustaining growth. [Display omitted] • Al within cell leaves is mobilized to organelles in a genotype specific manner. • Differential Al compartmentalization in vacuoles is a key to enhanced Al tolerance in rye. • Photosynthetic apparatus was more compromised in the sensitive genotype. • Al inhibited pigment biosynthesis and photosynthesis metabolism in a genotypic-specific manner. [ABSTRACT FROM AUTHOR]

The genus Gracilaria is an economically important group of seaweeds as several species are utilized for various products such as agar, used in medicines, human diets, and poultry feed. Hence, it is imperative to understand their response to predicted ocean acidification conditions. In the present work, we have evaluated the response of Gracilaria foliifera and Gracilaria debilis to carbon dioxide (pCO 2) induced seawater acidification (pH 7.7) for two weeks in a controlled laboratory conditions. As a response variable, we have measured growth, productivity, redox state, primary and secondary metabolites, and mineral compositions. We found a general increase in the daily growth rate, primary productivity, and tissue chemical composition (such as pigments, soluble and insoluble sugars, amino acids, and fatty acids), but a decrease in the mineral contents under the acidified condition. Under acidification, there was a decrease in malondialdehyde. However, there were no significant changes in the total antioxidant capacity and a majority of enzymatic and non-enzymatic antioxidants, except for an increase in tocopherols, ascorbate and glutathione-s-transferase in G. foliifera. These results indicate that elevated pCO 2 will benefit the growth of the studied species. No sign of oxidative stress markers indicating the acclimatory response of these seaweeds towards lowered pH conditions. Besides, we also found increased antimicrobial activities of acidified samples against several of the tested food pathogens. Based on these observations, we suggest that Gracilaria spp. will be benefitted from the predicted future acidified ocean. [Display omitted] • Seawater acidification improved primary productivity, pigments, and carbon storage. • No sign of oxidative stress under acidification • Improved antimicrobial activities in acidified samples • Possible benefits in the future high pCO 2 conditions [ABSTRACT FROM AUTHOR]

The removal of heavy metals combined with biodiesel production by microalgae in a cost-effective way is a promising approach. Herein, we grew two green microalgal species, Chlorella sorokiniana and Scenedesmus acuminatus, in media contaminated with Cu2+ (3.2 ppm) or Zn2+ (65.4 ppm) to investigate their growth and full metabolic profile. Furthermore, to integrate the potential economic impact of biodiesel production with heavy metals removal efficiencies. Although acute exposure to heavy metals, on the other hand, reduced growth and increased removal efficiencies of Cu2+ (59.4, 98.1%) and Zn2+ (72.4, 98.2%) in C. sorokiniana and S. acuminatus , respectively. Besides, Cu2+ and Zn2+ increased primary metabolites, particularly lipids (49, 47% in S. acuminatus , 27, 26% in C. sorokiniana), with a significant induction in the unsaturation levels. Indicating that C. sorokiniana and S. acuminatus are excellent phycoremediators for industrial drainage and future sustainable algal-biofuels platform. Economic assessment of daily 1000-tonne biodiesel production from S. acuminatus grown on highly polluted wastewater via Na 4 SiO 4 transesterification catalysis has all been assessed with an accuracy of ± 10% for the price of the diesel of US$ 1000/tonne and for the cost of the evaluated algal biomass of US$ 430/tonne. The daily 1000 T algal diesel business was viable, with a return on high investment (16.4%) and a payback period of 5 years. According to break-even and sensitivity analyses, the algal diesel cost that makes this business viable should be greater than US$ 147/barrel, while the biomass cost should not exceed US$ 462/tonne. Brent Crude Oil Spot exceeds US$ 95/barrel indicating promising prospects for algal fuel industrialization. Furthermore, the protein and amino acids-based waste biomass may serve as a sustainable biorefienry platform for various biofuel industries through biomass conversion technologies. [Display omitted] • Scenedesmus acuminatus is a promising biomass-derived biodiesel feedstock. • S. acuminatus experienced high Cu2+ and Zn2+ removal & lipid accumulation. • Cu2+ and Zn2+ increased amino acids & unsaturated fatty acids in S. acuminatus. • Techno-economic analysis of green-diesel project indicated 1000 T daily production rate. • Diesel business using S. acuminatus is feasible when algae oil content ˃ 41.1% and BCO exceeds US$ 95/ barrel. [ABSTRACT FROM AUTHOR]

Propiconazole (PCZ), a triazole broad spectrum fungicide has been frequently detected in agricultural water webs. This emerging contaminant imposes a serious toxic impact on soil and aquatic microbiota. Thus, we aimed to investigate the potential of the microalgae as PCZ phycoremediator. To this end, its toxicity, degradation and detoxification mechanisms by Scenedesmus obliquus and Nostoc muscorum were studied. Over a week, both species were exposed to mild (5 mg/L) and high (10 mg/L) PCZ concentrations. Results showed a dose-dependent accumulation of PCZ typically higher in S. obliquus than in N. muscorum. Moreover, S. obliquus degraded PCZ into a less toxic environmental product; 1-[2-(2,4-dichlorophenyl)− 4-(hydroxypropyl)− 1,3-dioxolan-2ylmethyl]− 1,2,4-triazole and 1-(2,4-dichlorophenyl)− 2-(1,2,4-triazol-1-yl) ethanone. The metabolic pathway assumed cellular dehydroxylation and side chain breakdown in S. obliquus. The high PCZ dose significantly decreased cell growth, chlorophyll a content and inhibited photosynthesis activity and machinery (PEPC and RuBisCo) in both species but, to lesser extend in S. obliquus. Additionally, the exposure to high concentration of PCZ caused a serious oxidative damage especially in N. muscorum. This damage is evident by increased lipid peroxidation, H 2 O 2 level, protein oxidation and NADPH oxidase activity. The two species experienced differential antioxidant and detoxification mechanisms using glutathione-S-transferases, phytochelatins and metalothionine to alleviate PCZ-oxidative stress. This study represented S. obliquus as an efficient PCZ phycoremediator and provided new data on the PCZ toxicity, environmental fate and risk of PCZ to aquatic environment. [Display omitted] • S. obliquus accumulated considerable level of propiconazole (PCZ). • PCZ was detoxified and decomposed by S. obliquus to less-hazardous compounds. • PCZ inhibited photosynthesis & evoked oxidative damage, especially in N. muscorum • Antioxidants induction in S. obliquus explained its resistance to PCZ. • S. obliquus is introduced as a PCZ phycoremediator. [ABSTRACT FROM AUTHOR]