Search Results (745)

The impact of nitrogen on harmful algal blooms (HABs) and functions of biota in marine ecosystems under eutrophication is a topical issue of growing importance. The article aimed at describing the diversity of planktonic bloom-forming dinoflagellates in the SW Baltic Sea coastal waters under variable eutrophication. The analysis of 44 year-long database revealed 82 dinoflagellate species and demonstrated diversity patterns of ten common bloom-forming species, including seven mixotrophs from the genera Prorocentrum, Dinophysis, and Ceratium, under variable eutrophication evaluated using total nitrogen (TN) content in water. Based on the Intermediate Disturbance Hypothesis (IDH), we presumed those coastal waters with total nitrogen concentrations that are optimal to dinoflagellates to host greater taxonomic diversity compared to areas with non-optimum TN content. The results showed that the highest dinoflagellate species richness was associated with much lower TN concentrations than the optimum values for these species. Thus, our findings disagreed with the IDH. We suggested and discussed possible reasons of this inconsistency, including algal growth rates and disturbance frequency. We also updated the classification of eutrophication levels in the Baltic Sea based on the distribution of TN content and diversity of HAB-forming dinoflagellates. The results can contribute to predictive assessment of HABs under growing eutrophication. Full article

Incorporating microalgae into integrated biotechnologies facilitates rational resource management. Cultivation of microalgae in various types of wastewater offers a number of advantages: safe disposal of liquid waste, restoration of water resources, and the production of valuable products. This study presents a comparative analysis of the growth and biomass productivity of various algal strains in an unsterilized fish processing plant wastewater. Desmodesmus sp. EE-M8 demonstrated the most efficient growth, with a biomass yield of 2.21 ± 0.09 g L⁻¹. The average biomass yield obtained during the growth of Chlorella vulgaris SB-M4, Chlorella sp. EE-P5, Micractinium inermum EE-M2, and Tetradesmus obliquus EZ-B11 ranged from 1.42 to 1.96 g L⁻¹. Ammonium, phosphate, and sulfate ions were completely utilized from the wastewater during algal growth. In addition, the bacterial community structure of wastewater was found to change drastically toward the dominance of Alphaproteobacteria during the microalgal growth. The algal strains (in combination with bacterial partners) used to determine their biostimulant potential demonstrated a positive effect on the germination of garden cress seeds. These findings demonstrate that incorporating algae into the wastewater purification process will reduce the negative impact on the environment and produce valuable biomass for various purposes. Full article

Rapid industrialization has generated large volumes of acidic wastewater that, without adequate treatment, pose serious environmental and public health risks. Traditional remediation processes, such as chemical neutralization, ion-exchange, and membrane filtration, are effective but costly, energy-intensive, and generate toxic secondary waste. In contrast, acidophilic microalgae offer a sustainable, cost-effective, and eco-friendly alternative. Algae rely on their cellular structure and metabolism to adsorb, absorb, bioaccumulate, and transform toxic metals while simultaneously neutralizing wastewater with minimal secondary waste production. Although acidophilic algae tolerate highly toxic and low pH conditions, their growth rate and biomass productivity, key drivers of algae-based bioremediation, are often compromised under such conditions. Thus, identifying robust species and evolving strains to thrive in these wastewaters without compromising productivity will facilitate adoption of algae-based bioremediation on a large scale. Integrating algal wastewater remediation with biofuel and biofertilizer production can contribute to the circular economy. In this review, we synthesize mechanisms employed by acidophilic algal strains when exposed to acidic and metal-enriched environments to remediate wastewater. We highlight recent studies applying these strains to acidic wastewater remediation and biogas upgrading and discuss current biotechnological tools aimed at enhancing strain performance for future use in commercial systems. Full article

This study uses high-frequency monitoring across a river–barrier lake–reservoir continuum in the upper Minjiang River, southwestern China, to quantify the spatiotemporal dynamics and drivers of aquatic CO₂ partial pressure (pCO₂) and to identify the dominant controls under contrasting lotic and lentic conditions. River reaches were CO₂-supersaturated throughout the year, with higher pCO₂ in the wet season (mean 521 ppm) than in the dry season (421 ppm), indicating persistent CO₂ evasion to the atmosphere. In contrast, the downstream canyon-type reservoir showed a pronounced seasonal reversal. During the wet season, surface-water pCO₂ averaged 395 ppm, about 24% lower than that of the river and below atmospheric levels (~419 ppm); more than 55% of observations were undersaturated, with minima as low as 141–185 ppm, indicating temporary CO₂-sink behavior. In the dry season, mean pCO₂ increased to 563 ppm, exceeding both riverine and atmospheric levels and returning the reservoir to a CO₂ source. The reservoir pCO₂ variability was governed by the interaction of hydrology and metabolism: rising water levels and longer residence times likely enhanced CO₂ accumulation from the decomposition of inundated organic matter, while warm temperatures, high light and monsoon-driven nutrient inputs promoted phytoplankton growth that removed dissolved CO₂ and elevated dissolved oxygen, producing temporary sink behavior. In the river, short residence time and strong turbulence limited in-stream biological regulation, and pCO₂ variability was mainly driven by catchment-scale carbon inputs along the elevation gradient. Overall, our results demonstrate that dam construction and impoundment can substantially modify carbon cycling in high-mountain rivers. Under specific conditions (warm water, sufficient nutrients, high algal biomass), lentic environments may strengthen photosynthetic CO₂ uptake and temporarily transform typical riverine CO₂ sources into sinks, with important implications for carbon-budget assessments and reservoir management in mountainous basins. Full article

Astaxanthin, a high-value keto-carotenoid with potent antioxidant and health-promoting properties, has gained global attention as a sustainable nutraceutical and biotechnological product. The green microalgae Haematococcus pluvialis and Chromochloris zofingiensis represent two promising natural producers, yet they differ markedly in physiology, productivity, and industrial scalability. This review provides a focused comparative analysis of these two species, emphasizing their quantitative performance differences. H. pluvialis can accumulate astaxanthin up to ~3–5% of dry biomass but typically reaches biomass densities of only 5–10 g L⁻¹, whereas C. zofingiensis achieves ultrahigh biomass concentrations of 100–220 g L⁻¹ under heterotrophic fed-batch fermentation, although its astaxanthin content is much lower (~0.1–0.5% DW). While H. pluvialis remains the benchmark for natural astaxanthin due to its exceptionally high cellular content, its thick cell wall, slow growth, and strict phototrophic requirements impose major cost and operational barriers. In contrast, C. zofingiensis exhibits rapid and flexible growth under heterotrophic, mixotrophic, or phototrophic conditions and can achieve ultrahigh biomass in fermentation, though its ketocarotenoid flux and astaxanthin accumulation remain comparatively limited. Meanwhile, a rapidly growing patent landscape demonstrates global technological competition, with major portfolios emerging in China, the United States, and Europe, spanning chemical synthesis, microbial fermentation, algal metabolic engineering, and high-density cultivation methods. These patents reveal clear innovation trends—ranging from solvent-free green synthesis routes to engineered microalgae and yeast chassis for enhanced astaxanthin production—which increasingly shape industrial development strategies. By synthesizing recent advances in metabolic engineering, two-stage cultivation, and green extraction technologies, this review identifies key knowledge gaps and outlines a practical roadmap for developing next-generation astaxanthin biorefineries, with an emphasis on scalable production and future integration into broader biorefinery frameworks. The findings aim to guide future research and provide actionable insights for scaling sustainable, cost-effective production of natural astaxanthin. Full article

The paper assesses brown seaweed diversity following the catastrophic events of the 2010 Deepwater Horizon (DWH) oil spill in offshore deep bank habitats at 45–90 m depth in the northwestern Gulf of Mexico, and their potential regeneration and recovery in the region. Innovative approaches to expeditionary and exploratory research resulted in the discovery, identification, and classification of brown seaweed diversity associated with rhodoliths (free-living carbonate nodules predominantly accreted by crustose coralline algae). Whereas the rhodoliths collected in situ at our research sites pre-DWH were teeming with brown algae growing on their surface, post-DWH they looked dead, bare, and bleached. These post-DWH impacts appear long-lasting, with little macroalgal growth recovery in the field. However, these apparent “dead” rhodoliths collected post-DWH at banks offshore Louisiana showed macroalgal regeneration starting within three weeks when placed in microcosms in the laboratory, with 19 brown algal species emerging from the bare rhodoliths’ surface. Some taxa corresponded to new records for the GMx (genus Cutleria and Dictyota cymatophila). Padina vickersiae is resurrected from synonymy with P. gymnospora. Reproductive sori evidence is presented for Lobophora declerckii. A detailed nomenclatural list, morphological plates, and phylogenetic/barcoding trees of brown seaweed that emerged from rhodoliths’ surfaces in laboratory microcosms are provided. These findings provide key molecular and morphological insights that reinforce species boundaries and highlight the significance of mesophotic rhodolith beds as previously overlooked reservoirs of cryptic brown algal diversity. Full article

The accelerating pace of global population growth, urbanization, and industrialization is exerting considerable pressure on freshwater resources. In developing countries, where infrastructure constraints often hinder the adoption of advanced treatment technologies, cost-effective and efficient wastewater solutions are essential. Algal–bacterial bioremediation represents a promising, eco-friendly method for removing organic pollutants through biological processes. This study evaluates a hybrid treatment system composed of three ponds: a covered anaerobic pond for organic matter digestion, a microalgal pond equipped with rotating biological contactors (RBCs) that facilitate interactions between heterotrophic bacteria and diatoms, and a final settling pond. Granular activated carbon embedded within the RBC enhances biofilm formation by attracting heterotrophic bacteria, thereby increasing treatment efficiency. Under optimal conditions—10 g of activated carbon and 1.7 d hydraulic retention time—the system achieved removal efficiencies of 95.8% for total suspended solids (TSS), 96.3% for turbidity, 85% for biological oxygen demand (BOD), and 99.9% for Escherichia coli. Bacteriological analysis showed complete removal of fecal coliform and total coliform. The characteristics of the outflow treated wastewater are 3 mg/L, 0.9 NTU, and 3.2 mg/L for TSS, turbidity, and BOD, respectively, while E. coli detection is under detection limit. The treated effluent complies with Category A for the reuse of treated wastewater in the Egyptian code for the reuse of treated municipal wastewater for agricultural purposes, offering a scalable and sustainable solution for wastewater management in resource-constrained regions. Full article

Fatty acid desaturase (FAD) is a key enzyme that catalyzes the biosynthesis of polyunsaturated fatty acids (PUFAs) and is widely present in animals, plants and microorganisms. In this study, Phaeodactylum tricornutum was used as the material. Bioinformatics methods were employed to identify the FAD gene family within the entire genome of P. tricornutum. The genomic distribution, gene structure, conserved domains, phylogenetic relationships, and physicochemical properties of proteins were systematically analyzed. The results showed that a total of 15 FAD genes were identified in the genome of P. tricornutum, which could be classified into 4 subfamilies. These genes are unevenly distributed on the 11 chromosomes. Motif analysis predicted that motif1 and motif2 are not only highly conserved but also play a key role in the synthesis of unsaturated fatty acids. To verify the gene function, we transferred the exogenous Ptd5α gene into P. tricornutum. Through screening and verification, we successfully obtained three transgenic algal strains (5D1, 5D2, 5D3). Compared with the wild algal strain (WT), overexpression of the Ptd5α gene did not have a significant impact on the growth and development of P. tricornutum. Moreover, the total fatty acid content of the transgenic algal strain was significantly increased, and the proportion of EPA in the total fatty acids could be raised to over 30%. The results of this study lay an important foundation for in-depth analysis of the biological functions of the FAD gene family in P. tricornutum, and also provide experimental and theoretical basis for the large-scale industrial production of EPA using model microalgae. Full article

This study presents the effects of using pyrite aggregate in field concretes on the mechanical, surface performance, and algal growth tendency of concrete. The substitution of pyrite influences the process of hydration, as the gradual release of its iron- and sulfur-bearing components shifts the reaction mechanism, leading to differences in phase formation and some modification in the pore structure of the cement matrix. Three different concrete mixes (PB0, PB2.5%, and PB7.5%) were designed by replacing 0%, 2.5%, and 7.5% of the total weight of sand and crushed sand with ground pyrite as a fine aggregate. Prismatic specimens of 80 × 100 × 200 mm were produced from these mixtures and mechanical properties such as flexural, splitting tensile, and abrasion were investigated after 28 days of curing. Then, to determine the effect of pyrite on concrete surface properties, pyrite was substituted on the surface of three concrete specimens produced in 50 × 240 × 500 mm dimensions at rates of 0, 1, and 3 kg/m². These specimens were divided into two groups: one group was exposed to clean water drops at a constant flow rate in a closed environment, and the other group was exposed to dirty water in an open environment, and observed for 2 months. At the end of the process, sections of 50 × 80 × 200 cm³ were taken from the specimens and friction, abrasion and flexural tests were carried out. The results of the study demonstrate that a 7.5% pyrite substitution improves both flexural and shear strength by 38%. At the same time, pyrite substitution prevented algal growth on the surface of field concrete under clean water and delayed its formation in those under contaminated water. Finally, it was observed that pyrite, when used in concrete mix and surface applications, optimizes mechanical performance and environmental durability. Full article

Composting seaweed biomass reduces environmental impacts while supporting circular-economy strategies in coastal areas, where seaweed removed for recreational management is commonly treated as waste. This approach aligns with regional and EU policies on circular bioeconomy and coastal ecosystem restoration. This study evaluated the effects of Mar Menor seaweed compost applied at 0%, 15% and 35% on lettuce cultivation. Two nitrogen supply levels (100% and 60%) were also used to assess interactive effects on plant growth and nutrient dynamics. The optimal rate of 15% compost enhanced lettuce growth by 25.1% under 100% N irrigation and by 32.2% under 60% N irrigation, indicating that reduced nitrogen availability did not limit biomass accumulation. Indeed, irrigation nitrogen level did not affect total biomass. Compost addition also improved nutrient content and increased phenolic compounds in leaves. When nitrogen was reduced, the combination with compost further boosted phenolic accumulation, by 39.6% with 15% compost and 34.7% with 35%, suggesting a synergistic response. Overall, seaweed compost improves crop performance and nutritional quality while lowering dependence on synthetic fertilisers. Environmentally and economically, it provides coastal municipalities a sustainable option for managing excess seaweed by converting waste into valuable agricultural inputs and mitigating impacts of algal overgrowth. Full article

The present study systematically explored the purification effects and response of submerged plants, Ceratophyllum demersum and Myriophyllum spicatum, on toxic and non-toxic strains of Microcystis aeruginosa via indoor co-culture experiments. The results showed that: (1) Both plants significantly inhibited the growth of Microcystis and reduced the concentration of chlorophyll-a (Chla) in the water by rapidly absorbing nutrients such as nitrogen and phosphorus, with no significant differences in the inhibition between toxic and non-toxic strains, indicating that nutrient competition might be the dominant mechanism for algal suppression. (2) C. demersum had higher nitrogen and phosphorus removal efficiency than M. spicatum, but the microcystins (MCs) released by toxic M. aeruginosa inhibited the nutrient removal capacity of both plants. (3) The plants promoted cell lysis of toxic M. aeruginosa and reduced extracellular MCs in the water while accumulating MCs internally, with C. demersum showing stronger MC accumulation and removal ability. (4) Microcystis stress activated the plants’ antioxidant defense systems, increased activities of SOD (Superoxide Dismutase) and CAT (Catalase), and caused membrane lipid peroxidation, increased content of MDA (Malondialdehyde), with toxic M. aeruginosa inducing stronger oxidative stress, and M. spicatum being more severely affected. (5) Plant species and algal toxicity jointly drove changes in the attached microbial community structure. The rhizosphere of M. spicatum specifically enriched Bdellovibrionota, suggesting a potential microbial predation pathway for algal suppression, while C. demersum was more associated with Bacillus and other microbes with allelopathic potential. In summary, C. demersum performed better in nutrient removal, toxin accumulation, and physiological tolerance. This study provides further theoretical support for using submerged plants to regulate cyanobacterial blooms and remediate eutrophic water bodies. Full article

Microcystis aeruginosa formed in natural water bodies grow in aggregate particles, while Microcystis aeruginosa commonly used in scientific research grow in a single-celled discrete state during cultivation. To elucidate the factors and mechanisms of Microcystis aeruginosa entering the “cell-aggregate” survival state in the natural environment, we focused on studying the influence of biological factors in their living environment (coexisting bacteria) on the aggregation behavior and growth characteristics of Microcystis aeruginosa. The bacterial strain A20, which can promote the aggregative behavior of Microcystis aeruginosa, was isolated from the water of Taihu Lake, where a cyanobacterial bloom broke out. A20 was identified as Priestia megaterium. Results showed that A20 could significantly drive Microcystis aeruginosa to form sac-like aggregate structures and promote the increase of aggregate particle size from 3–7 μm to 180 μm. The coexistence of bacteria and algae exhibited a dynamic stage adaptation strategy, with A20 promoting the transition of Microcystis aeruginosa from “high-chlorophyll, low-photochemical efficiency growth and proliferation” to “stable survival and maintenance of chlorophyll and photochemical efficiency in fluctuating changes” adaptation strategies. The coexistence of bacteria and algae significantly intensified the release of humic acid-like, fulvic acid-like, and protein-like substances from Microcystis aeruginosa, with the most significant increase in small-molecule fulvic acid-like substances. This is probably related to the endogenous metabolic stress response of Microcystis aeruginosa during A20 invasion, as well as the utilization and transformation of autotrophic Microcystis aeruginosa metabolites by heterotrophic bacteria A20. This study contributes to the study of microbial interactions underlying bloom outbreaks and can be useful for developing community-targeted algal control technologies. Full article

Nitrated monoaromatic hydrocarbons (NMAHs) are emerging air pollutants commonly found in biomass burning (BB) and anthropogenic aerosols (AA). Despite their frequent deposition into aquatic systems, their ecotoxicity is still poorly understood. This study evaluates the toxicity of BB and AA aerosol extracts and their main NMAH constituents (nitrocatechols, nitrophenols, and nitrosalicylic acids) using in vitro (cellular uptake, cytotoxicity) and in vivo (algal growth inhibition, zebrafish embryo development) bioassays. Polar aerosol extracts showed higher toxicity than nonpolar ones, with stronger interaction via zebrafish organic anion Oatp1d1 than organic cation Oct1 transporter, indicating selective uptake. NMAHs and their relevant mixtures showed similar toxicity patterns as BB water extract, so NMAHs were identified as contributors to aerosol toxicity. Nitrocatechols stand out for their toxicity, showing the highest chronic toxicity in algae (IC₅₀: 0.6–1.1 mg/L) and acute cytotoxicity in fish cells (IC₅₀: 2.0–4.1 mg/L), possibly because they dominated the NMAHs composition of aerosols (BB: 80.6%; AA: 79.8%). Sublethal NMAH concentrations caused developmental disorders and altered lipid homeostasis in zebrafish embryos, indicating early physiological stress on higher organisms. These findings reveal NMAHs as significant ecotoxic components of BB and AA emissions which may pose an increasing threat to aquatic ecosystems following atmospheric deposition. Full article

The identification and development of novel antimicrobials is a crucial challenge in the face of increasing antibiotic and antimycotic resistance. As such, there is growing interest in exploring the chemical diversity of natural sources, such as invasive seaweeds such as Asparagopsis armata. The valorization of such sources can further contribute to the development of bio-based industries, aligning with societal goals for environmental and economic sustainability. Therefore, a solid-liquid extraction method was performed using ethanol, and the obtained extract was studied for chemical composition elucidation, bioactivity, and toxicity evaluation. Analysis by GC-MS revealed some major chromatographic peaks, including floridoside (2-α-O-D-galactopyranosyl glycerol), glycerol, and oleamide. Also, several other smaller peaks were tentatively attributed to Low Molecular Weight Carbohydrate Derivatives, including isosaccharino-1,4-lactone, which had only been reported once in nature. The extract demonstrated significant antioxidant activity as measured by Ferric Reducing Antioxidant Potential and Oxygen Radical Absorption Capacity, but not by Lipid Peroxidation Inhibitory Potential assays, which is in line with its polar nature. The extract exhibited antimicrobial activity against various microorganisms, with a MIC of 2 mg/mL observed for Staphylococcus epidermidis, Vibrio parahaemolyticus, and the three yeast strains tested. Moreover, the extract inhibited the growth and phenotypic changes in filamentous fungi, which may result in reduced virulence. Specifically, the extract inhibited sporulation in Aspergillus fumigatus and orange pigmentation in Fusarium graminearum, possibly by a reduction in the production of aurofusarin, rubrofusarin, and mycotoxins. In vitro cell viability assays in 3T3, RAW264.7, and HaCaT demonstrated the extract was not cytotoxic or presented low cytotoxicity at concentrations up to 0.1 mg/mL, but a strong cytotoxic effect was observed at 1 mg/mL. At non-cytotoxic concentrations, the ethanol extract inhibited up to 48% of NO production in LPS-stimulated RAW264.7. This may indicate that anti-inflammatory activity may add to the antimicrobial activity in human and animal systemic and topical applications of the extract. In this work, new molecules were reported in A. armata, and the bioactivities reported were novel for this extract and algal species—especially through the choice of uncommon but very relevant pathogens to study. Our findings are a valuable contribution to addressing challenges in human and animal health, food and feed technology, as well as animal husbandry and agriculture. Full article

Nutrient cycling has barely been studied in acidic environments and may have an important influence on the evolution of the microbial communities. In this research, we studied nutrient sources and fluxes in acidic metal-mine pit lakes to evaluate their relationship with the lakes’ microbial ecology. Nutrient concentrations (including phosphorus, nitrogen, and dissolved inorganic carbon) increase with depth in all the studied pit lakes. Phosphorus comes mainly from the leaching of the host rock and is rapidly scavenged from the aqueous phase in the oxygenic and Fe(III)-rich mixolimnion due to adsorption on ferric precipitates (schwertmannite, jarosite), which leads to an important P-limitation in the photic zone. Below the chemocline, however, the sum of phosphorus inputs (e.g., settling of algal biomass, desorption from the ferric compounds, microbial reduction of Fe(III)-sediments) sharply increases the concentration of this element in the anoxic monimolimnion. Nitrogen is very scarce in the host rocks, and only a limited input occurs via atmospheric deposition followed by N-uptake by algae, N-fixation by acidophilic microorganisms, sedimentation, and organic matter degradation in the sediments. The latter process releases ammonium to the anoxic monimolimnion and allows some nitrogen cycling in the chemocline. Soluble SiO₂ in the mixolimnion is abundant and does not represent a limiting nutrient for diatom growth. Differences in phytoplankton biomass and extent of bacterial sulfate reduction between relatively unproductive lakes (San Telmo) and the more fertile lakes (Cueva de la Mora) are likely caused by a P-limitation in the former due to the abundance of ferric iron colloids in the water column. Our results suggest that phosphorus amendment in the photic zone could be an efficient method to indirectly increase acidity-consuming and metal-sequestering bacterial metabolisms in these lakes. Full article