Snow cover, the extensive terrestrial habitat in Antarctica, sometimes exhibits vivid coloration, yet the structure and function of its microbial communities remain poorly characterized. Using metagenomic sequencing of red snow (RS) and green snow (GS) from the Fildes Peninsula, we found that bacterial, eukaryotic, and archaeal relative abundances were 85.82

Riverine nutrient pollution is intensifying under climate warming and anthropogenic loading, yet the mechanisms that generate spatial decoupling between nitrogen (N) and phosphorus (P) across large river networks remain insufficiently resolved. Here, we analyzed 101,576 monthly hydrochemical observations from 3149 monitoring sites across 319 Chinese cities to evaluate whether dissolved oxygen (DO) is associated with spatially divergent responses of riverine N and P to climatic and anthropogenic forcing. N and P showed pronounced spatial decoupling: N accumulated mainly in northern and central water-limited rivers, whereas P hotspots clustered in eastern coastal urban agglomerations. Geographically weighted regression explained 61% and 65% of the spatial variability in N and P, respectively, indicating spatially non-stationary relationships between nutrient concentrations and their climatic, anthropogenic, and oxygen-related predictors. Warming-associated deoxygenation was linked to constrained aerobic N transformation and removal, whereas hypoxia was associated with enhanced redox-sensitive release of legacy P from sediments. These oxygen-associated patterns were spatially concentrated in northern high-N systems and eastern high-P clusters, but were less pronounced in southern high-flow rivers with greater metabolic buffering capacity. Our findings suggest that DO is closely associated with spatially non-stationary nutrient-driver relationships, and that climate-resilient river management should prioritize nutrient-load reduction while using oxygen-state management as a targeted, system-specific complement where technically and ecologically feasible.

Nutrient dynamics in inland waters are shaped by climate change, yet how climate shifts reorganize nitrogen (N) and phosphorus (P) distributions across waters remains poorly resolved. Here, a dataset encompassing 117,212 validation grade monthly observations captured across 3646 unique monitoring stations from January 2021 to December 2023, combined with geostatistical mapping and climate-nutrient models, was used to assess seasonal nutrient patterns across China's rivers, reservoirs, lakes, and estuaries to project their responses under mid- and late-century SSP2-4.5 climate scenarios. Results showed the mean N and P concentrations were 2.57 ± 2.66 mg L-1 and 71 ± 66 μg L-1 respectively, with strong varying among water-body types; estuaries had the highest mean concentrations of both N and P, whereas lakes had the lowest Nand reservoirs had the lowest P. Moreover, N concentrations were higher in winter than in summer, whereas P concentrations peaked in summer. Across paired monitoring sites, the median molar N:P ratio was 53% higher in winter than in summer, and national monthly mean N and P concentrations were strongly inversely correlated (ρ = -0.85). Extreme spatial hotspots were also distinct: only 31.6% of the sites in the upper decile of N concentrations were simultaneously in the upper decile of P concentrations. Under SSP2-4.5, projected decreases in N and increases in P reduced seasonal molar N:P ratios by approximately 19-36% by the mid- and late-century periods. These temporal, spatial, and stoichiometric metrics demonstrated that climate-conditioned N-P decoupling reflects divergent redistribution patterns rather than merely opposite mean concentration trends. It was deduced that regionally differentiated management strategies rather than uniform national nutrient targets control strategies were required in the future.

Harmful algal blooms (HABs) threaten freshwater ecosystems and are linked to nutrient cycling. We conducted a metagenomic investigation in Yuqiao Reservoir, which experiences filamentous cyanobacterial blooms (Pseudanabaena and Cylindrospermopsis), to elucidate microbial mechanisms driving nitrogen and phosphorus cycling during HABs. 28 genes for both nitrogen-cycling and phosphorus-cycling showed significantly different abundances between bloom and non-bloom periods. Bloom periods exhibited unified, energy-efficient metabolic strategies, featuring upregulated genes for nitrogen uptake via ammonia assimilation (gltB/D) and enhanced inorganic phosphorus uptake, including high-affinity phosphate transporters (pstA/B/C) and polyphosphate storage genes (ppk1, phoU), supporting rapid microbial proliferation. Conversely, non-bloom periods showed a metabolic transition to diversified nitrogen acquisition, including upregulation of nitrate assimilation, nitrification, denitrification, coupled nitrification-denitrification, and nitrogen fixation. Organic phosphorus mineralization genes became predominant. Concurrently, significant restructuring occurred in both nitrogen- and phosphorus-cycling communities. Although composed predominantly of Actinobacteria, Cyanobacteria, and Proteobacteria in both periods, keystone taxon analysis revealed a critical functional shift from an "autotrophic cyanobacteria-driven" pattern during blooms to a "heterotrophic bacteria-mediated metabolism" in non-bloom phases. Microbial co-occurrence network analysis indicated that the algal bloom triggered a fundamental community reorganization, from a broadly cooperative and stable structure to a more partitioned and potentially specialized state, reflecting strong niche partitioning due to altered environmental conditions. Partial least squares path modeling confirmed that algal blooms govern functional gene abundance by driving microbial community restructuring. Our findings demonstrate that microbial metabolic pattern mediated by algal blooms determined the unification of nitrogen and phosphorus cycling genes, revealing the mechanisms of HABs' ecological impacts.

Nanoplastics (NPs) in aquatic environments raise concerns as carriers that alter the bioavailability of co-occurring pollutants, such as cadmium (Cd), affecting combined toxicity. Precision toxicology now demands single-cell assessments to provide novel insights into pollutant interactions. In this study, we utilized a 3D-printed droplet microfluidic platform integrated with time-resolved analysis (TRA)─inductively coupled plasma mass spectrometry (ICP-MS)─to investigate the uptake behavior of single algal cells exposed to Cd and Eu-containing polystyrene (PS) NPs. 3D printing enables rapid prototyping and design flexibility for optimized microfluidic chips, while the monolithic structure eliminates assembly errors, reduces dead volume, and supports large-scale production. The droplet platform offers high-throughput single-cell encapsulation; coupled with TRA-ICP-MS, it minimizes cross-contamination and enhances sensitivity for multielement single-cell analysis. Single-cell analysis revealed that coexposure increased both the proportion of Eu/Cd-containing cells and the uptaken Eu/Cd content. The adsorption of Cd2+ imparted a more positive surface charge to PS NPs. This promoted heterogeneous aggregation between algal cells and PS NPs, thereby enhancing the bioavailability of PS/Cd2+ to the algae. Complementing these single-cell measurements, bulk-cell assays were conducted to evaluate the toxicological impacts of coexposure to Cd and PS NPs on microalgae. The results demonstrate that coexposure to PS NPs and Cd2+ resulted in synergistic effects, including enhanced growth inhibition, photosynthetic impairment, membrane damage, and increased secretion of extracellular polymers. These findings highlight the increased ecological risks posed to aquatic organisms by the coexposure to PS NPs and Cd2+, emphasizing the need for comprehensive assessments of nanoplastic-pollutant interactions in aquatic ecosystems.

Phycoerythrin (PE) is a high-value fluorescent pigment-protein with broad applications in food, diagnostics, and therapeutics, yet its conventional production from marine algae faces challenges of unstable yield, high cost, and ecological concerns. This narrative review systematically evaluates the potential of freshwater microalgae as sustainable platforms for PE production within a circular economy framework. A structured literature search was conducted across Web of Science and Google Scholar using keywords related to freshwater algae, PE biosynthesis, genetic engineering, wastewater bioremediation, and biorefinery. Key findings demonstrate that specific Cyanobacteria and Cryptophyta strains (e.g., Anabaena fertilissima: 475 mg/g dry weight; Cryptomonas pyrenoidifera: 345 mg/g dry weight) exhibit yields comparable or superior to those of traditional marine sources. Genetic engineering strategies—including promoter engineering (e.g., psbA modification increasing expression 3.7-fold), heterologous expression (achieving 96.7% chromophorylation), and CRISPR-Cas9-mediated metabolic flux redirection—offer robust tools for enhancing PE yield and stability. Wastewater cultivation enables efficient removal of nutrients (>90% N/P) and emerging contaminants (e.g., >95% heavy metals, 50% pharmaceuticals, >84% microplastics) alongside biomass production. High-value PE applications—as fluorescent probes (quantum yield 0.98), photosensitizers in photodynamic therapy, and photocatalysts for pollutant degradation (>90% removal)—provide economic drivers. A SWOT-TOWS analysis identifies strategic pathways addressing cost, scalability, and regulatory barriers. We propose an integrated biorefinery model coupling wastewater treatment, multi-product cascading (PE, lipids, biochar, biofertilizers), and policy instruments (carbon credits, purity standards) to accelerate sustainable commercialization of freshwater algae-derived PE.

Abstract Metabolite movement into chloroplasts is essential for sustaining chloroplast anabolic metabolism and cellular growth, and yet how the specific factors/transporters that enable import and support metabolism under heterotrophic conditions (in the dark in the presence of fixed carbon) remain poorly understood. Here, we identify CreTPT10, a chloroplast envelope-localized transporter in the unicellular green alga Chlamydomonas reinhardtii (Chlamydomonas throughout) that, of the substrates tested, has the highest specificity for xylulose 5-phosphate (X5P). We also demonstrated that the loss of CreTPT10 caused a pronounced reduction in growth and respiratory activity in the dark, whereas no growth defects were observed in the tpt10 mutants when they were maintained in the light or under nutrient-limiting conditions. Furthermore, dark-grown tpt10 mutants exhibited markedly reduced levels of lipids, nucleotides, isoprenoids, and aromatic secondary metabolites, accompanied by coordinated repression of genes encoding enzymes associated with chloroplast-localized biosynthetic pathways. This metabolic suppression extended beyond the chloroplast, as genes associated with the mitochondrial respiratory chain and cell cycle progression were markedly downregulated in darkness. Together, these findings indicate that X5P import via CreTPT10 is critical for sustaining chloroplast anabolic metabolism and functionally coordinates chloroplast and mitochondrial energy metabolism to support heterotrophic growth.

Dissolved organic matter (DOM) composition plays a critical role in disinfection byproducts (DBPs) formation, yet the molecular mechanisms governing the formation of highly toxic nitrogenous DBPs (N-DBPs) remain unclear, particularly under seasonally varying conditions. This study conducted continuous monthly fixed-point sampling for 1 year at a large drinking water source lake in Taihu, and simulated chlor(am)ination disinfection of the water samples. A total of 16,383 molecular formulas were identified, while seasonal variations were reflected by changes in the abundance and distribution of specific molecular groups. Protein-like and nitrogen-containing compounds were enriched in summer, whereas lignin-like and more aromatic compounds dominated in winter. Despite moderate total DBPs levels, winter samples exhibited the highest Chinese hamster ovary (CHO) cell LC50 values, with HANs contributing over 60% of toxicity. Molecular-level analysis revealed that HANs formation was not directly associated with nitrogen-containing DOM, but instead strongly correlated with lignin-like CHO compounds. Combined with positive relationships between HANs and ammonia nitrogen (p < 0.05), these results suggest a potential carbon-nitrogen coupling mechanism underlying the formation of nitrogenous disinfection byproducts, in which lignin-derived carbon structures act as key reactive precursors, while nitrogen availability regulates the incorporation pathways leading to N-DBPs. This mechanism explains the decoupling between total DBPs concentration and toxicity and highlights the critical role of DOM molecular composition and nutrient conditions in controlling DBPs risks. The study also reveals that targeted control measures for DBPs in drinking water and risk assessment are necessary in different seasons.

Against the backdrop of increasing extreme weather events (EWEs) due to global climate change, and given the limited research on their impact on aquatic ecosystems, this study investigated the effects of floods and blizzards on periphytic algal communities in seven water bodies in the Shennongjia Forestry District, China. We hypothesized that EWEs would reduce periphytic algal diversity, weaken community stability. Results revealed that EWEs significantly decreased periphytic algal biomass (by 92.9% ± 2.9%), richness (1.3% ± 0.2%), evenness (21.5% ± 4.0%), and Shannon diversity (7.0% ± 1.4%) (P < 0.05). Additionally, these events destabilized the co-occurrence networks by reducing node connectivity, centrality, and complexity, resulting in structural simplification that diminished the system’s ability to withstand disturbances. Floods specifically increased water velocity (58.1%) and created shading, leading to a decline in algal diversity. In contrast, blizzards drastically reduced water temperature (69.5%), posing severe survival challenges to the algal communities. It was concluded that EWEs reduced community’s diversity by altering habitat heterogeneity and weakened network stability through changing in species’ adaptation and community shifts. Water temperature and velocity were identified as key drivers of community composition changes during EWEs. This research provided insights into the mechanisms of climate change affecting periphytic algal communities.

Chromochloris zofingiensis is recognized as a promising resource for the production of carotenoids. However, current knowledge regarding its capacity for zeaxanthin accumulation remains limited, which restricts its potential for commercial application. The development of high-yielding strains and an understanding of the underlying metabolic and regulatory mechanisms are critical to advancing large-scale zeaxanthin production. In this study, a novel zeaxanthin-enriched mutant CZ-Z12 was obtained using ethyl methyl sulfonate (EMS). CZ-Z12 displayed a rapid growth rate when cultivated heterotrophically. On Day 6, zeaxanthin content and total fatty acid (TFA) content reached 0.229

Cadmium pollution posed a serious threat to eco-environmental security, but molecular variation in microalgae induced by cadmium remains unknown. To address this, we screened the molecular dynamics in Synechocystis sp. PCC 6803 exposed to an environmentally relevant Cd2+ concentration (0.05 mg L-1) over 0-144 h. Differential express genes/proteins (DEGs/DEPs) and expression levels divided the exposure process into two stages. The response phase (0-24 h) was characterized by the rapid, transient, and highly specific gene/protein activation; the top uniquely DEGs/DEPs included nrsA (cation-efflux), PsbA1/T (Photosystem II protein) and Ssl1911 (glutamine synthetase) were defined as stage-specific molecular signatures. Their expression peaked before 24 h and showed no significant change thereafter. The adaptive phase (24-144 h) was characterized by the sustained and synergistic proteomic dynamic regulation, 145 co-expressed DEPs were identified, cadmium influx-associated transporters (MntCAB/FeoB) were suppressed, efflux systems (Slr0944/ZiaA) were induced coupled with enhanced central carbon metabolism (carbon fixation, oxidative phosphorylation, TCA cycle) and elevated antioxidant enzyme activity (Slr1516). It was concluded DEGs/DEPs involved in photosynthetic processes and antioxidant defense changed significantly within 24 h. These changes were followed by adaptive mechanisms, including down-regulating inward Cd2+ transporters while simultaneously up-regulating efflux pumps, as well as enhancing energy metabolism and antioxidant capacity. This dynamic pattern provided insight into the interaction between cyanobacterial cells and cadmium ions.

Diatoms play a crucial role in aquatic ecosystems, yet the mechanisms underlying their long-term dominance remain poorly understood. This study investigated the relationship between diatom ecological persistence and their phycosphere bacterial communities by comparing the long-term dominant species Cyclotella atomus with the short-term dominant species Ulnaria ulna. 16S rRNA gene sequencing combined with predictive functional profiling revealed that the bacterial community associated with C. atomus was more diverse, stable, and interconnected than that associated with U. ulna. Taxonomic analysis identified key bacterial taxa such as Gemmatimonas, Sphingobium, and Pseudorhodoferax enriched in C. atomus. Co-occurrence network analysis demonstrated higher microbial interaction complexity in C. atomus, enhancing functional redundancy and ecosystem stability. Functional predictions indicated significant enrichment in carbohydrate metabolism (glycosaminoglycan degradation, pentose/glucose interconversion) and stress response pathways (betaine biosynthesis, xenobiotic metabolism by cytochrome P450) in the C. atomus microbiome, supporting a mutualistic relationship in which diatom-derived extracellular polymeric substances sustains specialized bacteria that reciprocate with vitamin B12, phytohormones, and chemical defenses. Based on these results, a mutually reinforced symbiotic cycle model was proposed to illustrate how the diatom and its phycosphere microbiome established a resilient holobiont capable of prolonged ecological dominance. The bacterial community associated with each diatom species exhibited host specificity and contributed to the maintenance of host dominance. These findings highlight the critical role of microbial partnerships in diatom success, offering new insights for predicting phytoplankton community dynamics and managing aquatic ecosystems.

Understanding the effects of a hydrological regime on the eco-environment of a tributary in a river-type reservoir is essential because reservoir regulations substantially change the freshwater ecosystem in the tributary. The construction of cascade reservoirs upstream of the Yangtze River has significantly altered the water regime and impacted reservoir ecosystems. However, the effects of water level rising (WLR) on the temperature-nutrient-phytoplankton aspects lack research. A three-dimensional model, covering the Three Gorges Reservoir (TGR) and one of its tributaries, the Xiangxi River (XXR), was built based on the Environmental Fluid Dynamics Code (EFDC). The model was calibrated and validated using measured data during 2018 and 2019 and adopted to determine the associations between reservoir operation and the tributary eco-environment. The spatiotemporal distributions of hydrodynamics, temperature, nutrients, and phytoplankton biomass were numerically analyzed under various WLR scenarios during the flood season. The results indicated that WLR intensified mid- and bottom-layer reversed-density currents, decreased water temperature, and, hence phytoplankton biomass, which increased total nitrogen (TN) and total phosphate (TP). 5-m WLRs of 15-day duration reduced Chl-a concentrations by up to 6.18, 2.53, and 0.83 μg/L, in June, July, and August, respectively. Higher magnitudes and shorter durations enhanced the reduction effect of WLR on Chl-a. A 1-m WLR over 15 days resulted in a 0.72 μg/L reduction. These findings suggest WLR as a viable strategy for phytoplankton biomass regulation and algal bloom control in river-type reservoirs.

The global rise in CO2 concentration is having a profound impact on the structure and function of aquatic ecosystems. However, little information is available on the responses of odor-producing cyanobacteria to the increase in CO2 concentration. In this study, the effects of different CO2 concentrations on 2-methylisoborneol (MIB)-producing Pseudanabaena and non-2-MIB-producing Pseudanabaena under monoculture and co-culture conditions were investigated. Results show that the specific growth rate of Pseudanabaena gradually increased with the rise in CO2 concentration, and for the 2-MIB-producing strain, this increase was significantly higher than the non-2-MIB-producing strain. Under co-culture conditions, the proportion of non-2-MIB-producing Pseudanabaena was significantly higher than that of 2-MIB-producing Pseudanabaena, suggesting a superior competitive ability of non-2-MIB-producing Pseudanabaena over 2-MIB-producing Pseudanabaena. Under monoculture conditions, the total 2-MIB production at the 300-µg/g CO2 concentration was significantly higher than that at 600- and 1 200-µg/g CO2 concentrations. The 2-MIB concentration produced by Pseudanabaena decreased with the increasing in CO2 concentration. Therefore, we believe that with the future increase in CO2 concentration, 2-MIB concentration would be decreased and so would the risk of 2-MIB outbreaks.

Global climate change has led to periphytic algal overgrowth in water diversion canals, causing clogging issues and water quality deterioration. Flushes with high water velocity can effectively detach periphytic algae, but little information can be found on the association of flush–periphyton interactions. To fulfill the gap, flush experiments were carried out at the different colonization stages of periphytic algal community (Stage 1: initial colonization stage, Stage 2–1: early community formation stage, Stage 2–2: late community formation stage, and Stage 3: primary succession stage) with varied flushing time (0 d, 2 d, 4 d). The results demonstrated that periphytic algal community at Stage 2–1 had weak resistance to flushing-flows and the lowest biomass accumulation ability after the flush. Besides, flush suppressed the growth of periphytic filamentous algae at Stage 2–1, reducing clogging issues. Short-term (less than 2 days) flushing-flows with high velocities (v = 0.8 m/s) inhibited algal proliferation and reduced species diversity with temporary scour effects. The algal species (Navicula, Achnanthes, and Fragilaria) with strong scouring resistance became dominant species and proliferated extensively after the flush. This study laid the groundwork for hydraulic regulation, and the flushing strategy would reduce the threat of periphytic algae in the water transportation canals.

Cadmium threatens eco-environmental security and human health, but the interaction between cadmium and microalgae cells remains unknown. This research examined the molecular detoxification mechanism of Synechocystis sp. to cadmium. The results indicated that cadmium stress significantly inhibited chlorophyll a content and maximum photochemical quantum yield (Fv/Fm), with EC50 of 0.50 mg L-1. The differentially expressed genes/proteins (DEGs/DEPs) were significantly enriched in pathways of two-component system, translation, nucleotide metabolism, ribosome, photosynthesis and chlorophyll synthesis. 1073 DEGs and 338 DEPs were identified, and 84 DEGs/DEPs with consistent expression trends were obtained. Foldchange of Sll1725 ranked fourth in DEGs/DEPs but its function was unexplored. Phylogenetic analysis and 3D structure identified Sll1725 as an ABC transporter and molecular simulation determined its cadmium-efflux function. Under 0.50 mg L-1 cadmium stress, Δsll1725 had lower growth and Fv/Fm values than the wild-type. Meanwhile, the intracellular cadmium in Δsll1725 was higher, indicating that Sll1725 mitigated cadmium toxicity by efflux. The duckweed with overexpressed sll1725 exhibited cadmium tolerance. It could be deduced that Sll1725, belonged to ABC transporters, which played an important detoxification mechanism. These mutants might possess the potential for bioremediation. This study provides a basis for applying algal genetic resources in cadmium pollution treatment.

High-ammonium wastewater can be simultaneously remediated and valorized through phototrophic cultivation of stress-resilient microalgae. This study evaluated the growth performance of 16 microalgae strains (specific growth rate μ = 0.108–0.217 day−1) from different terrestrial habitats, recognizing that there is a high diversity of terrestrial microalgae, which could harbor species with unique metabolites and properties, among which Tribonema arborum HJX, Cephaleuros virescens LST0102, and Cephaleuros virescens 42.85 exhibited high biomass productivity, reaching up to 190.6 mg L−1 day−1. Tribonema arborum HJX demonstrated the highest production of lipids and carotenoid, with a total of 46.9 and 2.51 mg L−1 day−1, respectively. The tolerance of these strains to ammonium and low pH, along with their performance in a 10-L panel PBR, was then assessed. The results revealed that filamentous algae isolated from terrestrial habitats have significant potential for the co-production of lipids and carotenoids, as well as robust growth capabilities under high-ammonium and low-pH environmental stress. This study highlights the potential of terrestrial filamentous algae in co-producing high-value chemicals with high-ammonium wastewater.

Eutrophication management in aquatic ecosystems is crucial for maintaining water quality and biodiversity. As a green and environmentally friendly treatment agent with sustained-release properties, calcium peroxide (CaO2, CP) has been widely applied in eutrophication management, particularly for its ability to inhibit algal growth and improve water quality, but its effects in different waters with varying degrees of eutrophication level remain to be thoroughly investigated. To fulfill this gap, this study was conducted to screen the short-term effects of CP treatment on waters with different levels of eutrophication. The results showed that CP significantly reduced algal biomass and improved water quality by increasing dissolved oxygen (DO) and pH, while decreasing total nitrogen (TN) and total phosphorus (TP) concentrations. Moreover, CP's impact on zooplankton exhibited a gradient response to eutrophication: selective elimination of sensitive species in lightly eutrophic waters, whereas in moderately to highly eutrophic waters, synergistic stress led to comprehensive community collapse, amplifying ecological risks through combined toxicity and environmental degradation. Concurrently, CP altered the bacterial community structure, reducing the relative abundance of dominant species and decreasing the complexity and stability of the bacterial community network. Furthermore, cyanobacterial cell density was confirmed to be a key factor limiting the selective adjustment of CP on phytoplankton communities. As the degree of eutrophication intensified, the disposal effects varied: accelerated pH elevation, reduced H2O2 release, and shortened DO persistence, coupled with increased dissolved organic carbon (DOC), constrained the overall effectiveness of CP on water quality, bacterial, and phytoplankton communities. These research findings provided a basis for the practical application of CP in eutrophication management.