Search Results (329)

The understanding of coastal ecosystems regarding variability and resilience under climatic and anthropogenic forcing is reliant upon long-term ecological records. We examined the Helgoland Roads time series (1968–2017), which includes temperature, salinity, nutrients (nitrate, phosphate), and biological parameters (diatoms and Acartia spp.). We applied autocorrelation, multi-taper spectral analysis, and wavelet and cross-wavelet transforms to identify dominant temporal patterns and scale-dependent interactions. Sea surface temperature shows consistent long-term warming, and subdecadal (2–3-year) and decadal (7–8-year) oscillations reflect coherent patterns with the North Atlantic Oscillation and Arctic Oscillation. Salinity varied in anti-phase to Elbe River discharge at 6–7-year scales, reflecting control of seasonal, riverine freshwater, and salinity scenarios. Nutrients, as declining long-term trends (particularly phosphate), are associated with seasonal to multi-year variability linked to episodic discharge events. Biological parameters had strong annual periodicities reflective of bloom cycles but also variability above the annual limit. Diatoms responded to climatic, nutrient, and biological responses at the 3–5-year scale associated with this ecological context, particularly nitrate and phosphate; Acartia (spp.) respond to temperature, salinity, and resource availability (diatoms), reflecting climate/nutrient/trophic linkages. This study indicates that Helgoland Roads is represented as a multi-scale, non-stationary system, in which climate variability, riverine input, and ecological linkages are cascaded down to physical and chemical processes that structure biological communities. Spectral methods reveal scale-dependent synchrony and highlight the risks of trophic mismatch under climate change, emphasizing the importance of sustained high-frequency monitoring. Full article

An unknown species of the diatom genus Ulnaria was identified during the study of freshwater environments in Mongolia. Monoclonal strains of the unknown species were obtained and subjected to molecular analysis. The strains were investigated through light and scanning electron microscopy, coupled with molecular analysis of SSU rRNA and rbcL gene sequences. The features of sexual reproduction of the cultured specimens were studied, and traits previously unknown to representatives of Ulnaria were demonstrated. Based on the results of morphological comparison against similar species from the Ulnaria ulna species complex and data from the two-gene molecular analysis, a description of Ulnaria williamsii sp. nov. was provided. Analysis of the features of sexual reproduction—gametogenesis, the mating system, and gamete movement—allowed us to discuss the species dispersion and evolution within the genus Ulnaria. Full article

The bioproduction of high-value molecules offers a sustainable and cost-effective alternative to traditional extraction and chemical synthesis, particularly for complex metabolites like cannabinoids (CBs), which have therapeutic potential for neurodegenerative diseases. The marine diatom Phaeodactylum tricornutum presents a promising chassis for CB biosynthesis due to its high lipid content, essential building blocks to biosynthesize CBs. In this study, we explored the feasibility of producing olivetolic acid (OA), the key CB precursor, using a hybrid-type polyketide synthase, SteelyA, from Dictyostelium discoideum. Unlike the native Cannabis sativa enzymes—tetraketide synthase and olivetolic acid cyclase—which exhibit low productivity and stability in diatoms, SteelyA was expected to offer an alternative biosynthetic route. Heterologous production in P. tricornutum resulted in a C-terminal fragment of the SteelyA enzyme, suggesting partial expression or processing of the very high-molecular-weight (352 kDa) SteelyA protein over six months without affecting cellular growth. However, HPLC-MS analysis did not detect intracellular OA or its derivatives in vivo and in vitro, suggesting enzymatic inactivity or metabolic limitations. These negative findings highlight the need for further investigation into the metabolic and proteomic requirements for CB precursor biosynthesis in diatoms, guiding future optimization strategies for sustainable cannabinoid production. Full article

Fucoxanthin is the predominant carotenoid in diatoms, playing a central role in light harvesting and photoprotection, and is increasingly valued for its potential in pharmaceutical, nutraceutical, and cosmetic applications. In this study, we investigated the influence of high nitrate supplementation, low-light exposure, and combined treatment, on fucoxanthin content and on the expression of key genes involved in its biosynthetic pathway in the marine diatom Thalassiosira rotula. Fucoxanthin content was quantified using HPLC-based and spectrophotometric methods. Control culture at the exponential growth phase showed a fucoxanthin content of 4.7 mg g⁻¹ DW, reaching 5.2 mg g⁻¹ DW under low-light conditions at the late exponential phase. Gene expression analysis revealed condition-dependent modulation of major biosynthetic genes (PSY, PDS, ZCIS, CRTISO, ZEP, VDL, DDE). Early biosynthetic genes, PSY and PDS, were upregulated under low light, whereas ZCIS and CRTISO responded to high nitrate availability. ZEP exhibited treatment-specific induction and VDL isoforms showed differential regulation, highlighting distinct xanthophyll cycle gene expression patterns across treatments. These results demonstrate that both light and nitrate availability modulate fucoxanthin content and biosynthetic gene expression in T. rotula, providing insights into the regulatory mechanisms underlying carotenoid metabolism in diatoms and proposing T. rotula as a potential candidate for fucoxanthin production. Full article

The Arieș River, in the Apuseni Mountains of Romania, has been historically impacted by gold mining, resulting in elevated concentrations of metal trace elements. This study assessed the river’s ecological status between 2022 and 2024 by integrating physico-chemical parameters at four sites and diatom-based bioindicators at the same sites in 2024 across monitoring sectors. Key results showed strong mining influence downstream of Baia de Arieș, with episodic acidification (pH down to 5.7), elevated conductivity (>400 μS/cm), and notable exceedances in metal trace elements, particularly Cu (up to 237 μg/L) and Cd (up to 4.18 μg/L). Analysis showed a dominance of α-mesosaprobic taxa (e.g., Amphora ovalis, Navicula cryptocephala, Nitzschia inconspicua), including teratological forms, at polluted sites, while sensitive species persisted upstream. Multivariate analyses indicated that metal trace elements and nutrients are the main drivers of chemical and biological patterns. These findings highlight diatoms as sensitive bioindicators of mining-related impacts. Incorporating diatom-based monitoring into management strategies can support early detection of pollution and more effective protection of freshwater ecosystems. Full article

Human activities in the Apuseni Mountains region, Romania, especially in the Roșia Montană mining area, have significantly impacted water quality in the Arieș River tributaries. This study assessed the main physico-chemical and salinity parameters, along with the contents of trace elements (As, Cd, Co, Cr, Cu, Fe, Mn, and Ni) dissolved in water, as well as in the Abrud, Ștefanca, Valea Seșii, and Sârtaș rivers, the main tributaries of the Arieș River. Maximum concentrations of trace elements were observed in Valea Seșii (e.g., Zn up to 716 µg/L, Fe up to 562 µg/L), while Abrud and Sartăș showed moderate contamination. Diatom analysis revealed a high prevalence of Achnanthidium minutissimum and Planothidium lanceolatum, with teratological forms of A. minutissimum being the most frequent, indicating stress from pollutants. Saprobic index values ranged from 1.21 to 1.91, reflecting water quality from good to moderately impacted. The integration of chemical and biological data highlights the cumulative effects of mining and agricultural activities, demonstrating the utility of combined monitoring for effective freshwater management. Our results showed that numerous diatom taxa are currently present in samples collected from various watercourses within the Aries River basin, reflecting both the biological diversity and the variable influence of environmental factors on aquatic communities. Full article

The efficiency of wetlands in removing nutrients from streams and rivers can be accurately evaluated using diatom-inferred total phosphorus (DI-TP), as DI-TP integrates the effects of various environmental factors. However, studies assessing the efficiency of an extensive set of wetlands at multiple scales and under different levels of human disturbance activities (HDA) in removing DI-TP from streams and rivers are sparse. A national-scale dataset from the U.S. EPA’s 2008–2009 National Rivers and Streams Assessment survey provides a unique opportunity to answer this question. Our results showed that, compared to watershed-scale wetlands, local-scale wetlands performed better at removing DI-TP from streams and rivers. Additionally, wetlands performed better at removing DI-TP under lower levels of HDA, suggesting that high levels of HDA could alter the structure and function of wetlands enough to affect their ability to remove nutrients. Interaction analysis revealed there was a significant positive relationship between HDA and local-scale wetlands. We conclude that DI-TP is a valuable metric for evaluating the effectiveness of wetlands at removing nutrients from streams and rivers. To support freshwater management, both the spatial scale of wetlands and the level of HDA on wetlands, along with their cross-scale interactions, should be considered. Full article

In this purely analytical analysis, we have investigated the effects of a point-like defect in a continuous medium on a diatomic molecule under the influence of small oscillations arising from the Lennard-Jones potential. In the search for bound-state solutions, we have shown that the allowed values for the lowest energy state of the molecule are influenced by the presence of the defect. Furthermore, another quantum effect was observed: the stability radial point of the diatomic molecule depends on the system’s quantum numbers; it is quantized. Full article

A new species, Fragilaria longwania sp. nov. from Sihailongwan Maar Lake in northeastern China is described on the basis of observations made using light microscopy (LM) and scanning electron microscopy (SEM) that reveal the distinctive features that separate this new taxon from the other species currently placed in the genus Fragilaria. Fragilaria longwania sp. nov. has relatively short valve length, high stria density, spindle-shaped valves with a swollen, and sometimes deformed central area and capitate valve apices, short spines and weakly developed apical pore fields. This combination of character was found to be unique when the new species was compared with morphologically similar taxa. This species was found in various samples collected from Sihailongwan Maar Lake between 2003 and 2017. The analysis of the diatom assemblages collected in the sediment trap samples allowed an assessment of the cell size variation, seasonal occurrences and ecological requirements of this species. Fragilaria longwania appears to be a planktonic diatom most often associated with the spring season. Full article

This study examines fish communities in the heavily impacted Bistrița River, located in the Eastern Carpathians of Romania, where diffuse pollution from mining, domestic wastewater, agricultural and forestry activities emerged as the most severe pressures. Fish sampling was conducted at twenty sites across two Natura 2000 protected areas. Results showed that species richness and diversity were higher downstream (Z1–Z5), indicating improved ecological conditions compared to the upstream section (B1–B15). The fish-based Index of Biological Integrity (IBI) suggested overall good biological integrity, with excellent conditions (class I) recorded in 70% of sites. Redundancy analysis (RDA) further revealed that elevation and conductivity significantly shaped community structure, while the site-specific impact score had only marginal effects. To assess water quality and biotic integrity based on different communities, as required by the Water Framework Directive (WFD), five sites were selected for parallel sampling of diatoms and benthic invertebrates. Among these, zoobenthos proved the most sensitive to water quality degradation, with biotic indices indicating classes I to III. These findings demonstrate that assessments based solely on fish may underestimate ecological impacts, underscoring the need for complementary approaches that account for multiple biotic communities when monitoring riverine ecosystem health. Full article

Phytoplankton serves as the primary producer in estuarine ecosystems, with its community structure and dynamics being directly influenced by the concentration and ratio of nitrogen (N) and phosphorus (P) nutrients. This study utilized raw water from the Yangtze Estuary to establish a series of ocean microcosm systems, setting up gradients of dissolved inorganic nitrogen (DIN) and reactive phosphate (SRP) concentrations to explore the reaction of phytoplankton communities over 30 days. The results indicated that total phytoplankton abundance significantly increased under prolonged exposure to high concentrations of DIN and SRP. However, the community diversity indices exhibited a declining tendency, indicating a simplification and increased instability of the community structure. Diatoms and dinoflagellates, the predominant phytoplankton taxa, differed in their response to DIN and SRP. Diatom abundance rose at elevated DIN concentrations and initially increased and then decreased at high SRP concentrations, while dinoflagellate abundance diminished at high DIN concentrations and persisted in increasing at elevated SRP concentrations. An ecological threshold is the critical point at which the structure or function of an ecosystem undergoes significant changes when subjected to external disturbances or internal changes. The Threshold Indicator Taxa Analysis (TITAN) was employed to identify indicator species within the microcosm systems, revealing that the ecological response thresholds of phytoplankton communities to DIN and SRP were 0.50 mg/L and 0.030 mg/L, respectively. This study quantitatively analyzed the environmental exposure concentrations of DIN and SRP at the community level and calculated the ecological response thresholds, providing fundamental data and a scientific basis for nitrogen and phosphorus management in estuaries. Full article

The sediments of shallow basins formed on along the coast of the Baltic Ice Lake in the Late Glacial are a valuable source of information for reconstructing the paleoenvironment. A detailed diatom analysis, along with chronological and lithological studies, was performed for the sediments of one of these paleoreservoirs, uncovered in the Kulikovo section (Sambian Peninsula, Kaliningrad Region of the Russian Federation) and dated to 14,000–12,500 calBP. As a result of this study, the essential diversity of Late Glacial diatoms was revealed and 204 species were found. Among them, benthic and epiphytic species belonging to the group of oligohalobous indifferents predominate. The most typical species are Pseudostaurosira brevistriata, Staurosirella ovata, Gyrosigma attenuatum, G. acuminatum, Amphora affinis, Epithemia adnata and Cymbopleura inaequalis. A comparison with available regional data showed that the mass development of pioneer epiphytic diatoms of the Fragilariaceae in the Allerød is common to most of the paleoaquatic ecosystems. A local feature of the Kulikovo paleoreservoir, along with a wide range of ecological diatom groups, is the episode of massive development of Gyrosigma spp., benthic diatoms capable of living in streaming water, in the first half of the Allerød. The Kulikovo diatom assemblages reacted sensitively, not only to the main environmental shifts of the Allerød and Younger Dryas, but also to smaller-scale climatic events, such as Herzensee Oscillation (GI-1b) and changes in hydrological regimes (water level fluctuations, flow rate) caused by local environmental transformations. Full article

Sea cucumbers, important members of the phylum Echinodermata, play a crucial role in sediment mixing and nutrient cycling on the seafloor. They also hold significant economic value, particularly in Asian food and pharmaceutical markets. In the Mediterranean Sea, the harvesting of sea cucumbers has recently intensified, often without regulation, threatening both species populations and the health of benthic ecosystems. This study investigated the potential of using fatty acid (FA) profiles as ecological biomarkers to trace the different origin and feeding ecology of two sea cucumber species, Holothuria polii and H. tubulosa, collected from ten coastal sites in Italy. A total of 285 individuals were analyzed through lipid extraction and characterization from their body walls using gas chromatography (GC-FID and GC-MS). Key fatty acids identified included arachidonic acid, eicosapentaenoic acid, eicosenoic acid, palmitic acid, palmitoleic acid, stearic acid, and nervonic acid. Principal Component Analysis (PCA) revealed patterns consistent with geographic origin, suggesting that FA profiles can reflect site-specific trophic conditions. The analysis also indicated that sea cucumbers primarily feed on diatoms, bacteria, and blue-green algae, with notable regional variation. This study is the first to successfully apply FA-based trophic markers to differentiate Italian populations of these species, providing insights for ecological monitoring and fishery management. Full article

Silica-based materials are recognized as effective functional materials across diverse industrial fields, including biomedicine (e.g., drug delivery systems (DDS), biosensors, and tissue engineering), owing to their excellent stability and physicochemical characteristics. Among them, diatom biosilica (DB), which constitutes a major part of aquatic biomass, recently gained significant attention as a valuable biomaterial following breakthroughs in its innovative surface structure, superior biocompatibility and multifunctionality. Therefore, DB is emerging as an alternative to synthetic materials used in the biomedical field. This review comprehensively examines the diverse biological properties of DB, followed by an analysis of harvesting and purification strategies. Then, the current application status of DB in two principal biomedical domains, DDS and biosensors, is evaluated. Furthermore, the convergence of these domains into theragnostic applications addresses a significant unmet clinical need for simultaneous therapeutic intervention and diagnostic monitoring, positioning DB as a transformative biomaterial solution. The unique combination of natural hierarchical architecture, tunable surface properties, and excellent biocompatibility make DB promising candidates for next-generation integrated biomedical platforms to address the growing demand of personalized medicine and precision healthcare solutions. Full article

The depletion of water resources caused by climate change and human activities is a pressing global issue. Lake Ereen is one of the ten natural landmarks of the Gobi-Altai of western Mongolia is included in the list of “important areas for birds” recognized by the international organization Birdlife. However, the construction of the Taishir Hydroelectric Power Station, aimed at supplying electricity to the western provinces of Mongolia, had a detrimental effect on the flow of the Zavkhan River, resulting in a drying-up and pollution of Lake Ereen, which relies on the river as its water source. This study assesses the pollution levels in Ereen Lake and determines the feasibility of its rehabilitation by redirecting the flow of the Zavkhan River. Field studies included the analysis of water quality, sediment contamination, and the composition of flora. The results show that the concentrations of ammonium, chlorine, fluorine, and sulfate in the lake water exceed the permissible levels set by the Mongolian standard. Analyses of elements from sediments revealed elevated levels of arsenic, chromium, and copper, exceeding international sediment quality guidelines and posing risks to biological organisms. Furthermore, several species of diatoms indicative of polluted water were discovered. Lake Ereen is currently in a eutrophic state and, based on a water quality index (WQI) of 49.4, also in a “polluted” state. Mass balance calculations and box model analysis determined the period of pollutant replacement for two restoration options: drying-up and complete removal of contaminated sediments and plants vs. dilution-flushing without direct interventions in the lake. We recommend the latter being the most efficient, eco-friendly, and cost-effective approach to rehabilitate Lake Ereen. Full article