Search Results (343)

Interactions between cyanobacteria and eukaryotic algae are traditionally viewed as favoring cyanobacteria, which are often the dominant competitors in freshwater ecosystems. However, increasing evidence suggests that eukaryotic algae also possess effective chemical defenses capable of suppressing cyanobacterial proliferation. In this study, the anti-cyanobacterial potential of a methanolic biomass extract of the green microalga Chlorella vulgaris against the bloom-forming cyanobacterium Microcystis aeruginosa was investigated. Optical density measurements revealed the inhibition of cyanobacterial growth, with extract concentrations of 0.4–1.6 mg mL⁻¹ significantly reducing biomass accumulation. The lowest concentration (0.2 mg mL⁻¹) stimulated the accumulation of phycobiliproteins, whereas concentrations of 0.8–1.6 mg mL⁻¹ significantly decreased phycobiliprotein content, indicating progressive physiological impairment. The results suggest that the highest extract concentration applied may also cause alteration in phosphate acquisition. Lipid profiling of the Chlorella biomass showed that 97% of the extractable lipids consisted of methanol-soluble fatty acids, with C18 fatty acids predominating among the 20 identified compounds. These metabolites are reported to possess allelopathic activity and therefore represent plausible contributors to the observed inhibition. These findings support that anti-cyanobacterial activity may represent a widespread ecological trait of Chlorella and potentially other green microalgae, providing a promising foundation for environmentally friendly cyanobacterial bloom management. Full article

Invasive algal taxa represent an emerging but poorly quantified threat to Iraq’s freshwater ecosystems. Drawing on floristic surveys, recent molecular detections, and regional literature, this review synthesizes the current evidence regarding the occurrence of Didymosphenia geminata and Hydrodictyon reticulatum and identifies Leptolyngbya benthonica and Nostoc paludosum as cryptogenic cyanobacterial taxa requiring further ecological assessment. A preliminary qualitative risk evaluation identifies D. geminata and H. reticulatum as high-priority taxa for monitoring based on their documented invasion history elsewhere, potential ecological effects, and likelihood of introduction and spread. In contrast the cryptogenic cyanobacteria Leptolyngbya benthonica and Nostoc paludosum should be interpreted cautiously because they are recently detected taxa whose origin and ecological behavior remain uncertain. Potential ecological risks include competitive displacement of native periphyton, disruption of benthic food webs, oxygen depletion during decomposition, and habitat alteration through the formation of dense mats. Major knowledge gaps include the absence of baseline distribution data, continued reliance on morphology-based identifications, limited application of molecular tools, and the lack of standardized national risk-assessment frameworks. Addressing these gaps would improve Iraq’s ability to detect, monitor, and manage algal invasions, thereby safeguarding vital water resources under escalating climatic and anthropogenic pressures. Full article

Sediment internal nutrient loading is a major cause of surface water eutrophication. Adding organic amendments to dredged sediments can improve reuse potential but risks enhancing nutrient leaching. This column study investigated the effect of adding compost (25% v/v), freshwater algae suspension (2.5% v/v), or their combination (22.5% compost + 2.5% algae) to reservoir bottom sediments on the leaching of orthophosphate (PO₄³⁻) and nitrate nitrogen (NO₃-N) under three simulated weekly rainfall events. Unamended sediment served as the control. Compost-amended sediment showed the highest PO₄³⁻ concentrations in the leachates, but these levels stabilized over time, whereas NO₃-N concentrations decreased rapidly. Algae alone reduced both PO₄³⁻ and NO₃-N leaching compared to the control. The combination of compost and algae enhanced the retention of several elements, though it did not fully mitigate phosphorus leaching. Furthermore, this combination effectively decreased overall leachate volume; it was a direct result of the progressive hydration of the organic material, which increased the mixture’s water-holding capacity and thereby reduced percolation. Chemically, compost promoted nitrogen transformation processes (e.g., immobilization or denitrification), while algae likely facilitated nutrient uptake. We conclude that organic amendments play a dual role: compost increases phosphorus availability but stabilizes its release, whereas algae reduce the leaching of both nutrients. The choice of amendment should therefore align with specific water quality targets. Longer-term and field-scale studies are needed to confirm these trends. Full article

This work aimed to evaluate the combined effects of an antibiotic (erythromycin, ERY) and an herbicide (metolachlor, MET), at environmentally relevant concentrations, on the physiology of the freshwater microalga Raphidocelis subcapitata. For this purpose, firstly, the alga was exposed to each toxic compound to determine the respective effect concentrations after 72 h (72h-EC values). Subsequently, the alga was exposed to mixtures composed of 72h-EC₁₀, 72h-EC₂₅, and 72h-EC₅₀ values of each toxicant, and interaction analysis was conducted using the independent action (IA) model. Overall, the mixtures of ERY and MET inhibited algal growth synergistically. Regarding photosynthetic performance, exposure to the mixtures of toxicants, generally resulted in a reduction of the maximum photochemical efficiency of photosystem II (PSII) (F_v/F_m), the effective photochemical yield of PSII (Φ_PSII), and the electron transport rate (ETR). However, MET antagonizes the negative effects of ERY on photosynthesis, particularly at lower concentrations of the antibiotic (72h-EC₁₀ and 72h-EC₂₅). The exposure to ERY–MET mixtures resulted in an overall increase in photosynthetic pigments (chlorophyll a and carotenoids), likely reflecting a compensatory response by the alga to counterbalance impaired photosynthetic function. Nonetheless, overall pigment analysis indicated an antagonistic interaction between the two toxicants, as the magnitude of this increase was lower than predicted by the IA model. The results presented here provide new insights into the toxicological interactions between ERY and MET in microalgae and contribute to addressing the critical knowledge gap regarding the ecotoxicity of pharmaceutical–herbicide mixtures in aquatic environments. Full article

The production of Nitrocellulose (NC) generates wastewater containing insoluble fines which can be solubilized via alkaline hydrolysis (AH). However, this process yields effluents with high NO₂-N and NO₃-N concentrations (3:1 ratio), opening the possibility of further treatment and nutrient recovery. This study investigated the ecotoxicity and algae-based treatment potential of post-AH liquor as a proof of concept for wastewater management. Ecotoxicity assessments such as microalgal and Microtox^® bioassays showed 30% toxicity (corresponding to 240–270 mg NO₂-N/L and 100 mg NO₃-N/L) and a 15 min EC50 of 331–399 mg NO₂-N/L and 133–146 mg NO₃-N/L, respectively. Additional studies on toxicity identified nitrite (NO₂⁻) as the primary toxicant, inhibiting the freshwater microalga Scenedesmus obliquus at concentrations higher than 60 ± 5 mg N/L. Furthermore, higher toxicity was observed in the presence of sodium and nitrate. Consequently, growth screening tests using synthetic liquors (20–300 mg TN/L, with NO₂-N:NO₃-N ratio 3:1) compared S. obliquus against the marine microalga Nannochloropsis salina, revealing that S. obliquus thrived at concentrations below 160 mg N/L, whereas N. salina performed poorly. System efficiency was shown to be highly dependent on the initial nitrogen load; S. obliquus achieved 60% removal at 200 mg/L total nitrogen (3:1 NO₂-N:NO₃-N), whereas efficiency reached 99% at concentrations less than or equal to 100 mg/L within seven days. Nitrogen removal rates peaked at 15 mg/(L·day) (at <160 mg TN/L), a result validated through scale-up experiments using both monoculture and a consortium with post-AH liquor. These preliminary findings demonstrate a promising two-step chemical and biological treatment strategy for NC wastewater, which assimilates hazardous inorganic nitrogen into valuable algal biomass for potential energy production. Full article

Daphnids, commonly known as water fleas, are freshwater planktonic microcrustacean species used as model organisms in ecotoxicology, particularly in regulatory frameworks that adhere to OECD and ISO standards. Mortality is the most common endpoint in toxicity testing; however, more sensitive indicators are required to assess sublethal acute effects of pollutants. The use of feeding impairment as a toxicity phenotypic endpoint in daphnids is considered a cost-effective approach that aligns with the 3Rs principle (Replace, Reduce, Refine) and is more physiologically and environmentally relevant. Current feeding methods are inefficient due to the large test volumes and extended incubation periods required. In this paper, we present a miniaturised protocol to assess feeding behaviour following exposure to chemicals in daphnids. The method is based on the consumption of algae, which is measured with chlorophyll fluorescence. The optimised protocol is more robust and rapid, and results can be obtained in 30 min and in a 96-well plate. Responses in feeding rate were investigated using this miniaturised protocol following exposure to a range of prevalent pollutants, which include two metals and, as a more realistic sample, a leachate from smoked cigarette filters. All three pollutants were tested at sublethal concentrations. This method provides an efficient approach to assess the toxicity of chemicals and water quality. Full article

This study evaluated locally available dry feed formulations (FFs) as practical alternatives to fresh Chlorella sp. for culturing the freshwater fairy shrimp Streptocephalus sirindhornae. Seven dietary treatments were evaluated, including fresh Chlorella sp. at 1 × 10⁶ cells mL⁻¹ (FF1; control) and six mixed dry diets (FF2–FF7) formulated from spirulina powder, commercial shrimp feed, fish meal, and rice bran. Fairy shrimp were cultured for 20 days in a completely randomized design with three replicates per treatment at a stocking density of 30 individuals L⁻¹. Growth performance (body length and wet body weight) and survival were assessed across three developmental stages (1–5, 6–10, and 11–20 days post-hatch). Across all developmental stages, FF2 (50% spirulina powder + 50% commercial shrimp feed) consistently supported culture performance comparable to that of the control treatment. During the early developmental stage (1–5 days post-hatch), shrimp fed FF2 exhibited growth and survival rates comparable to those of the control group and significantly higher (p < 0.05) than those observed in several other dry diet treatments. During the late developmental stage (11–20 days post-hatch), survival of shrimp fed FF2 (62.45 ± 5.28 percent) did not differ significantly from that of the control group (61.85 ± 4.25 percent) but was significantly higher (p < 0.05) than survival in the other dry diet treatments. In addition, shrimp biomass produced with FF2 showed greater protein, lipid, carotenoid, and amino acid contents than shrimp fed fresh Chlorella sp. Protein, lipid, and amino acid contents were determined using standard AOAC methods, and carotenoid content was analyzed by HPLC. These findings suggest that FF2 may serve as a practical algae-independent diet for maintaining growth and survival of S. sirindhornae under controlled hatchery conditions. Full article

This study aims to resolve the genetic origin of crude oils accumulated in the D Subsag and to assess the potential cross-sag hydrocarbon migration from the adjacent Haizhong Sag. The D Subsag, situated on the western margin of the Weixinan Sag in the Beibuwan Basin, is a significant petroleum province with proven reserves exceeding 10 million tons in the Weizhou Oilfield. However, the origin of these oils and the contribution from the Haizhong Sag source kitchen remain poorly constrained, hindering accurate resource assessment. To address this, we integrated organic geochemical analyses of nine source rock samples from the Haizhong Sag (Well H1) and eight crude oil samples from the D Subsag reservoirs. Bulk geochemical and biomarker signatures reveal distinct organic facies within the Paleogene succession. Type III kerogen, characterized by terrigenous higher plant input (high C₁₉₊₂₀ tricyclic terpanes and C₂₉ regular steranes, Pr/Ph > 2.5) deposited under oxic freshwater conditions, dominates source rocks from the third member of the Weizhou Formation (EWZ₃). In contrast, the second and third members of the Liushagang Formation (Els₂ and Els₃) contain mixed Type II₂-III kerogen with elevated contributions from lacustrine algae and aquatic organisms (elevated C₂₃ tricyclic terpanes and C₂₇ regular steranes). Thermal maturity assessment (with T_max of 436 to 448 °C) confirms that all source intervals are within the oil generation window. Two genetically distinct oil groups are identified in the EWZ₃ reservoirs. Group 1 oils (Well W4) exhibit a lacustrine algal signature (C₂₇/C₂₉ sterane > 1.15; low Pr/Ph 1.54–1.68) that does not correlate with the analyzed Haizhong Sag source rocks, suggesting localized, intra-sag source contributions. In contrast, Group 2 oils (Wells W6 and W6-2) display strong geochemical affinities with the Els₂ and Els₃ source rocks, evidenced by mixed terrestrial/aquatic signatures (∑nC₂₁⁻/∑nC₂₂⁺ < 1.0). These findings confirm that fault systems acted as conduits for long-distance migration from the Haizhong Sag, while also highlighting a previously unrecognized contribution from local source intervals. This refined petroleum system model provides critical constraints for delineating remaining hydrocarbon potential and reducing exploration risk in the Beibuwan Basin. Full article

Poterioochromonas is a typical mixotrophic chrysophyte that plays an important ecological role in natural aquatic environments and has received particular attention from morphological and ecological perspectives over the last few decades because of its peculiar mode of feeding and relevance for practical applications. However, the taxonomic classification of this genus remains controversial, and the true extent of its diversity remains largely unknown. Here, we use a complementary approach of culturing, morphological and phylogenetic analyses, and sequence database mining to address this issue. We collected 16 cultures of Poterioochromonas to determine the essential morphological characteristics and clarify the taxonomy and phylogeny of the genus. Our results confirmed that all Poterioochromonas strains produce lorica, which is the diagnostic character for the genus. We suggest that the shape of the lorica cup and the morphology of the cyst could be used as diagnostic characteristics to differentiate different species within the genus. Molecular phylogenetic analysis based on the SSU rDNA and rbcL gene sequences confirmed the monophyly of Poterioochromonas, which is subdivided into heterotrophic and mixotrophic clades. Comparative analysis of six molecular markers revealed that the COI gene is the most sensitive for distinguishing both inter- and intraspecific relationships. An exhaustive screening of the NCBI GenBank database and publicly available amplicon sequencing datasets revealed 100 SSU rDNA gene sequences for Poterioochromonas. The results showed that many soil-derived environmental sequences grouped with heterotrophic Poterioochromonas and indicated that the heterotrophic representatives of the genus are abundant in the soil environment. The results also revealed that many environmental sequences did not group with any reference sequences of known species, indicating that the genus Poterioochromonas is much more diverse than previously thought. This study contributes to a clearer taxonomic and distributional framework for Poterioochromonas, thereby facilitating future basic and applied research on this genus and similar mixotrophic chrysophytes. Full article

Algae rarely occur as solitary phototrophs in nature or engineering; instead, they are embedded in complex bacterial consortia that control their physiology, productivity and ecological performance. The phycosphere, a microscale niche rich in algal exudates, promotes extensive metabolic exchange and chemical signaling, defining these associations. Bacteria capitalize on the dissolved organic carbon released by algae, providing growth supporting molecules such as vitamins, trace metals, and siderophores, as well as regenerated inorganic nutrients. Bidirectional beneficial interactions range from obligate mutualism to facultative commensalism and antagonism, depending on environmental context and community membership. Bacterial partners can stimulate algal growth, morphogenesis, and stress tolerance, as well as modulating defense and programmed cell death during the decline and bloom succession of algae resulting from algicidal taxa. Metabolic cooperation, QS signaling, extracellular enzyme activity, and chemically induced gene expression produce the exometabolome in the phycosphere, which in turn reprograms gene expression in all partners. Recent advances in multi-omics toolboxes, single-cell isotopic analyses, and microfluidics have greatly enhanced our understanding of the functional and spatiotemporal orientation of algal microbiomes. Ecologically, algal–bacterial interactions manage the phytoplankton community structure, control HABs, and modulate carbon and nutrient fluxes in both marine and freshwater realms. Biotechnologically, engineered algal–bacterial consortia are a promising tool for enhancing biomass production, stabilizing large-scale cultivation, improving wastewater treatment, and upgrading biofuels and fine chemicals. Despite these notable research advances, the context- and species-dependent complexity of multispecies interactions remains a major obstacle to their practical modeling and scalable implementation. Integrative research frameworks that combine molecular, ecological, and bioengineering approaches are urgently needed to unlock the full potential of sustainable applications in the future. Full article

Predicting algal proliferation in freshwater systems is crucial for effective water quality management and ecological sustainability. This study proposes a novel data-driven framework that integrates correlation-based feature ranking with a concatenation-enhanced artificial neural network (ANN) architecture to improve algae prediction accuracy. The analysis was conducted through a systematic evaluation of parameter relationships, employing Pearson’s correlation coefficient and standardized coefficients (Beta) to determine feature importance. Based on the magnitude of these coefficients, the input variables were progressively grouped into six feature sets, enabling a comparative assessment of predictive performance. The ANN models were trained and validated using root mean squared error (RMSE), mean absolute error (MAE) and Normalized Nash–Sutcliffe Efficiency (NNSE) as evaluation metrics. The results demonstrate that the fourth feature set, including chlorophyll-a, temperature, dissolved oxygen, total dissolved solids, and ammonia (NH₃), identified through combined Pearson and Beta analysis, achieved the lowest prediction errors and superior generalization performance. These findings highlight the effectiveness of feature selection guided by correlation and standardized coefficients in enhancing ANN performance for algae prediction. The proposed framework offers valuable insights for improving the predictive modeling of algal dynamics, thereby supporting proactive water quality monitoring and the sustainable management of aquatic ecosystems. Full article

Aquatic environments, whether freshwater, brackish, or marine, are increasingly disrupted, in terms of frequency, extent, geographic distribution, and duration, by the massive, worldwide proliferation of harmful and/or nuisance algae, the so-called Harmful algal blooms (HABs), which are a global phenomenon that poses a major threat to human and animal health and ecosystems [...] Full article

Bodanella lauterborni W.M. Zimmermann and Heribaudiella fluviatilis (Areschoug) Svedelius are members of brown algae (Phaeophyceae) that exclusively inhabit freshwater habitats. Heribaudiella fluviatilis is the most frequently reported freshwater brown alga, widely distributed in the Northern Hemisphere. In contrast, B. lauterborni, one of the rarest algae globally, has been reported in only four glacial Alpine lakes and has not been observed in nature for nearly 50 years. Since 2019, the species has been considered locally extinct at its type locality, and its presence in the other three lakes is also questionable. Here, we report the occurrence of B. lauterborni in three springs on the Vlasina Plateau (Southeast Serbia), being the first finding of the species in Southeast Europe and the fifth discovery globally in environmental conditions not previously described for the species. We also provide detailed data on the morphology, ecology, and biogeography of B. lauterborni and H. fluviatilis. Additionally, we report the non-obligate association Hildenbrandio rivularis-Heribaudielletum fluviatilis discovered in two rivers. Our findings significantly expand the known ecological and geographical range of phaeophytes, highlighting Southeast Europe as a refugium for freshwater Phaeophyceae biodiversity. Full article

As a representative large shallow freshwater lake in China, Lake Taihu has suffered from persistent cyanobacterial blooms for a long time. Although intensive restoration actions have been carried out and caused visible improvements, the long-term evolution path and inner driving mechanisms of its ecosystem are still not fully made clear. Based on long-term monitoring data during 2011 to 2024, this study aims to characterize temporal dynamics of the aquatic environment, find out key drivers that shape community succession, and offer a scientific foundation for effective lake management. A series of data about hydrometeorological factors, physicochemical water quality indexes, and biological community data was analyzed by using the Mann–Kendall trend test, Pettitt change-point test, Redundancy Analysis, and correlation heatmaps. The results show that the Taihu ecosystem has experienced a notable regime shift in the past 14 years. First, nitrogenous nutrients reacted quickly to external emission reductions, showing a notable monotonic decline; in comparison, Total Phosphorus and Cyanobacterial Density followed a non-linear “U-shaped” path, with a notable shift happening in 2020, which marks the change from a “deterioration phase” to a “recovery phase.” Second, correlation analysis has confirmed that the lake is mainly phosphorus-limited, and a clear “decoupling” between nitrogen levels and algal outbreaks has taken place. Third, the “10-year Fishing Ban” (initiated in 2020), together with sustained phosphorus control, reduced the competitive exclusion of phytoplankton by cyanobacteria, promoting the recent rebound in biodiversity. This study points out that Lake Taihu has passed a tipping point of ecological restoration, shifting from a turbid “algae-dominated state” to a stable state with higher biodiversity. Future management strategies should put first the mitigation of internal phosphorus loading and adaptive management against extreme climatic events. Full article

Palynological analysis of seventy-seven cutting samples from six boreholes in the Marañón Basin (northeastern Peru) has identified five distinct Neogene marine incursion events (ME-1 to ME-5), challenging existing models that depict them as short-lived episodes. The diverse palynological assemblages, comprising spores, pollen, freshwater algae, and critical marine indicators—including dinoflagellate cysts, foraminiferal test linings, and copepod eggs—reveal that these incursions were protracted and recurrent, each associated with a maximum flooding surface and bounded by intervals of continental sedimentation. The stratigraphic record shows the earliest event ME-1 (Aquitanian to Late Burdigalian, 23.03–17.7 Ma) identified across all studied wells. ME-2 (latest Burdigalian to Middle Langhian, 17.0–16.1 Ma) is also recorded basin-wide. ME-3 (latest Burdigalian to earliest Langhian 16.5–15.7 Ma) registered in two wells. ME-4 (Late Langhian to latest Serravallian, 14.6–11.62 Ma) registered in only two wells and ME-5 (Early Tortonian, 11.6–10 Ma) is documented exclusively in the southernmost well, culminating in Zanclean (~5.5–3.6 Ma) mangrove development. We interpret the ingress routes for ME-1 to ME-3 to be westward via the Marañón Portal or northward from the Caribbean, associating them with the Proto-Pebas and Pebas systems. In contrast, ME-4 would also be from Amazon trunk or Paraná Portal associated with the Pebas Phase, and ME-5 likely originated from the south through the Paraná Portal, linking it to the Acre Phase. These results demonstrate that Miocene marine incursions into western Amazonia were not brief episodes but represented prolonged periods of marine influence, facilitated by sustained subsidence in the Marañón retro-arc foreland basin. This history reveals a dynamic connectivity throughout the Neogene, with marine conditions acting as persistent biogeographic barriers that critically shaped the region’s Miocene biodiversity patterns. This refined chronology provides a comprehensive regional framework, significantly advancing our understanding of Amazonian paleogeography. Full article