Search Results (385)

Marine mucilage events are intensifying in semi-enclosed seas under accelerating climate- and nutrient-driven pressures, yet their ecosystem-level consequences for aquaculture-linked coastal habitats remain insufficiently documented. This study provides an integrated spatiotemporal assessment of water quality, phytoplankton community structure, and biometric responses of Mytilus galloprovincialis during and after the 2025 mucilage outbreak in the Gulf of Erdek (Sea of Marmara, Türkiye). Mucilage accumulation was associated with sharp increases in turbidity, total suspended solids, and particulate organic matter, alongside declines in dissolved oxygen and pH. Phytoplankton assemblages exhibited marked seasonal restructuring: the mucilage period was characterized by the coexistence of mucilage-forming taxa, non-toxic bloomers, and multiple harmful algal bloom (HAB) groups, including DSP- and ASP-related species, whereas post-mucilage conditions were dominated by non-toxic diatoms with substantially reduced HAB representation. The dinoflagellate species representing the May period in terms of abundance were Noctiluca scintillans and Prorocentrum micans; the diatom species were Chaetoceros radiatus, Cylindrotheca closterium, Pseudo-nitzschia pseudodelicatissima, and Thalassiosira rotula; and the coccolithophore was Phaeocystis pouchetii. Mussel biometric analyses revealed biometric indices and condition values markedly below regional historical baselines during the mucilage event, alongside reduced meat yield, followed by pronounced compensatory growth during the post-mucilage period. Our findings demonstrate that mucilage acts as both a physical and biological stressor, driving short-term ecological shifts in phytoplankton diversity and imposing substantial but reversible physiological impacts on mussel stocks. These results underscore the need for continuous biodiversity monitoring frameworks that integrate mucilage dynamics, HAB occurrence, and aquaculture resilience in regions vulnerable to climate-enhanced organic aggregate formation. Full article

The primary objective of this research is to engineer a high-performance, sustainable material for aquatic remediation by repurposing low-cost biogenic silica into a selective hydrophobic adsorbent. By integrating the natural hierarchical porosity of Diatomaceous Earth (DE) with a tailored silanization strategy, this work aims to provide a scalable and eco-friendly solution for the efficient encapsulation and mechanical recovery of hydrocarbons from contaminated water. To overcome the inherent hydrophilicity of DE, a two-step functionalization process was developed, involving alkaline activation followed by the covalent grafting of hexadecyltrimethoxysilane (C16) in different concentrations. The resulting C16@DE hybrid materials underwent a dramatic surface energy transformation, shifting from hydrophilic behavior to robust hydrophobicity, with static contact angles reaching up to 134.8°. Optical analysis revealed a unique remediation mechanism: while pristine DE disperses homogeneously in the aqueous phase, functionalized C16@DE spontaneously organizes into discrete pellets upon contact with diesel, effectively encapsulating the fuel. Quantitative UV/vis spectrophotometry confirmed that these composites sequester approximately 55–56% of the diesel phase. Together, these results demonstrate that C16@DE materials couple intrinsic biosilica porosity with tailored hydrophobicity to achieve efficient hydrocarbon capture. By combining the natural hierarchical porosity of diatoms with engineered surface selectivity, this research positions functionalized DE as a scalable, low-cost, and eco-friendly promising solution for marine oil spill recovery and industrial wastewater treatment. Full article

Water dynamics and nutrients are widely recognized as the main triggers of phytoplankton blooms. These factors may control the stability of marine ecosystems. Penzhina Bay and the Shelikhov Gulf are famous for their high tidal dynamics in comparison with the basins of the World Ocean and for being the feeding places of Bowhead whales. Here, we study the dynamics and thermohaline structure of water; nutrients; isotopic signatures of δ¹⁵N–$\mathrm{N}{\mathrm{O}}_3^{-}$ and δ¹⁸O–$\mathrm{N}{\mathrm{O}}_3^{-}$; as well as chlorophyll a in Penzhina Bay, the Shelikhov Gulf, and the Penzhina River to understand the features of an ecosystem with intense tidal dynamics in the subpolar region. This work is based on data obtained in three cruises of the R/V “Akademik Oparin” in the period from 2023 to 2025, with speed boat observations in the Penzhina River from May to October, including the flooding peak in June. The observations covered cases with tides from 7 to 13.4 m in height. The interaction between tides and river runoff was observed to supply dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) from the sea and dissolved silicate (DSi) from the river. The “white nights” in July, combined with the increased supply of nutrients, are good conditions for phytoplankton blooms, and as a result, the concentration of chlorophyll a in the study area was observed to be up to 39 µg/L. High primary production supports the food chain, and this is probably the main reason why Bowhead whales come to feed in the summer. The DIN/DIP ratio indicates DIN as a limiting factor in most of Penzhina Bay and throughout the Shelikhov Gulf. At the same time, the DSi/DIP ratio at a significant distance from the mouth of the Penzhina River is close to 0, indicating unfavorable conditions for diatoms. The DSi limit can cause the blooming of dinoflagellates, which sometimes occurs in this region. Full article

The present study investigated the community composition and dynamics of freshwater biofouling on fiberglass inland waterway vessel (IWV) models coated with two commercial antifouling paints deployed in the Danube River (Serbia) for a total of five months. Biofouling was characterized using visual observations, in situ optical microscopy, the rapid ATP bioluminescence method, dry biomass measurements, and analyses of phototrophic and fungal communities. Based on the results, Hard Racing TecCel demonstrated the highest suppression of biofouling, with the lowest biomass accumulation and reduced algal diversity. At all stages of biofouling, diatoms dominated the phototrophic community, comprising 123 taxa. Achnanthidium minutissimum and Gomphonella olivacea were shown to be persistent hull colonizers, while Cyanobacteriophyta and Chlorophyta had reduced presence. Overall, the results highlight a slower progression of freshwater biofouling compared to marine systems and emphasize the need for the development of tailored antifouling strategies for IWVs to reduce environmental impact and operational costs. Full article

Phytoplankton is a key component of marine ecosystems and a sensitive indicator of environmental change. In this study, light microscopy (LM) and DNA metabarcoding (18S-V4, 18S-V9, and rbcL) were combined to assess differences in phytoplankton diversity and community structure across three LTER sites in the northern Adriatic Sea, and to evaluate the methodological effects on community assessment. A total of 329 genera and 527 species were recorded by integrating both the approaches. Metabarcoding (MB) revealed increased taxonomic richness than LM, particularly for dinoflagellates and small phytoflagellates, while LM was better for identifying the diatoms and coccolithophores. The rbcL marker improved the taxonomic resolution for the diatoms compared to the 18S regions. The proportion of species shared among the sites increased from 13% with LM to 33–42% with MB, suggesting that MB may effectively reduce the discrepancies observed when relying solely on LM. Cluster analysis performed on species-relative abundances grouped the samples by approaches rather than sites, showing that methodological variability exceeded the ecological differences. The relative abundance patterns differed between methods but became more comparable after applying correction factors based on the 18S rRNA gene copy numbers, particularly for the dinoflagellates. Overall, MB enhances biodiversity assessment and comparability among sites, while LM remains essential for morphological validation and for abundance assessment. Full article

Trace metals are persistent stressors in coastal ecosystems, yet most marine algal toxicity assessments still rely on freshwater model species and growth-based endpoints that provide limited mechanistic resolution. Here, we quantified the sensitivity of two ecologically contrasting marine diatoms—the benthic Cylindrotheca closterium and the planktonic Thalassiosira weissflogii—to ten environmentally relevant metals using a dual-endpoint approach that integrates chlorophyll fluorescence (photosystem function) and Nile Red-based lipid-body fluorescence (metabolic reallocation). Fluorescence-based EC₁₀ values revealed distinct species- and metal-specific patterns, with C. closterium consistently responding at lower concentrations and Hg producing the strongest inhibition in both species (EC₁₀ ≈ 0.04–0.06 mg L⁻¹). Lipid-body accumulation detected earlier metabolic disturbance for several metals, particularly Hg, As, Cr(VI), and Cd, and frequently occurred at concentrations where fluorescence remained minimally affected. These sequential thresholds indicate that pigment impairment and metabolic reallocation represent mechanistically distinct stages of the cellular stress response that differ among metals and between diatom guilds. Comparison with published toxicity data shows that the dual-endpoint sensitivities observed here fall within, or slightly above, the upper range of reported microalgal responses, underscoring the pronounced susceptibility of benthic diatoms to redox-active and thiol-reactive metals. The strong agreement between fluorescence-based EC values and traditional growth-derived benchmarks for key metals further supports fluorescence as an operationally efficient endpoint suitable for integration into emerging ISO marine algal bioassays. Overall, this study demonstrates that pairing a rapid functional marker with a mechanistically informative metabolic biomarker enables metal-specific toxicity fingerprinting and provides an ecologically grounded basis for incorporating benthic diatoms into coastal metal risk assessment frameworks. Full article

Phaeodactylum tricornutum was cultivated in a 1000 L photobioreactors using f/2 medium. The resulting algal biomass contained 24.5% lipids, 37.8% protein, 19.4% carbohydrates, and had a gross energy content of 19.8 MJ/kg. These components were sequentially extracted. The ultra-high performance liquid chromatography-high resolution mass spectrometry (UHPLC-HRMS) analysis of lipids revealed 35 triacylglycerols, a wide range of galactolipids and phospholipids including a novel sulfoquinovosyl diacylglycerol (SQDG), namely SQDG(C16:1/C24:0), characterized by mass fragmentation analysis. Additionally, three sulfoquinovosyl monoacylglycerols (SQMGs) with C14:0, C16:0, and C16:1 fatty acyl chain were detected in P. tricornutum for the first time. Fatty acid analysis further confirmed that P. tricornutum is an excellent source of ecosapentaenoic acid, which is predominantly present in triacylglycerol and glycolipid forms. CombiFlash chromatography allowed for the separation of monogalactosyldiacylglycerols, digalactosyldicylglycerols, SQDGs and phosphatidycholines, and their structure were confirmed by NMR spectral analysis. Fucoxanthin was the major carotenoid, and the study showed all essential amino acids required for humans and fish were present in it. A two-phase in vitro gastric/pancreatic digestibility assay showed high protein digestibility for both whole biomass (89%) and protein isolate (77%). Monosaccharide analysis showed that polysaccharides extracted by EtOH precipitation after alkaline extraction and by hot water extraction contained similar monomers with different relative intensities. Protein isolates and polysaccharides exhibited antioxidant properties. Full article

We evaluated the algicidal properties of Bacillus Ba3 fermentation broth combined with clay for harmful algae bloom (HAB) control through in situ enclosure experiments in Suao Bay, China. It was indicated by the results that the combination significantly reduced HAB abundance, turbidity and phosphorous in water without affecting zooplankton and small fish. The treatment achieved 99.8% (Phase 1) and 100% (Phase 2, with sediment) removal rates for harmful dinoflagellates, primarily Prorocentrum donghaiense and Karenia mikimotoi, while demonstrating high taxonomic selectivity, allowing beneficial diatom populations such as Chaetoceros spp. to remain resilient. This synergy is attributed to clay acting as a physical carrier that brings adsorbed algicidal metabolites into direct, prolonged contact with algal membranes. This method shows promise for prolonged dinoflagellate control and may offer an economical and environmentally sound approach to HABs. More research is needed to establish its action on a wider scale in marine environments. Full article

Malignant melanoma is skin cancer arising from genetically altered melanocytes. Recently, a complex relationship between melanoma and chronic inflammation has been highlighted, representing an excellent condition for tumor development. Microalgae have been shown to be a promising source of bioactive compounds for drug discovery. In this study, we investigated Halamphora sp. (BEA0050) to identify possible compounds with immunomodulatory activity. The most active fraction (fraction D) showed anti-inflammatory activity against human melanoma cancer cells (A2058) stimulated using lipopolysaccharide (LPS) to induce an inflammatory phenotype. Chemical profiling of the bioactive fraction using chromatography and high-resolution mass spectrometry (UHPLC-HR-MS) revealed hydroxypheophorbide a, a breakdown product of chlorophyll a. In order to investigate the mechanism of action, the TNF-α release was detected through ELISA sandwich assays in A2058 cells and through confocal microscopy in LPS-stimulated HaCaT cells. Gene expression of principal pro-inflammatory cytokines and pathways was detected through real-time PCR, which showed the down-regulation of the inflammatory pathway in LPS-induced A2058 and HaCaT cells treated with 12.5 µg/mL of fraction D. This study reports for the first time the anti-melanoma and anti-inflammatory activities of Halamphora sp., identifying protein mediators and highlighting its biotechnological potential. Full article

Background: Nano- and microplastics (N/MPs) are widespread pollutants in aquatic ecosystems and may interfere with the physiology of diatoms. However, the underlying molecular mechanisms remain poorly understood. Methods: Cultures of the diatom species Skeletonema marinoi, a key contributor to marine primary production and biogeochemical cycles, were exposed for 10 days to polyethylene (PE) N/MPs (25 and 75 µg/mL). Growth, morphology, and cell viability were monitored, while gene expression of stress, inflammation, programmed cell death (PCD), and extracellular polymeric substance (EPS) biosynthesis markers was assessed by RT-qPCR. Results: Growth was not significantly affected. Gene expression showed biphasic regulation of antioxidant enzymes, induction of HSP70/90, transient modulation of prostaglandin-related genes, and dose- and time-dependent activation of PCD markers. Selected CAZymes possibly involved in EPS synthesis were downregulated at early stages, suggesting impaired aggregation potential. Conclusions: Exposure to PE N/MPs elicited subtle yet multifaceted effects in S. marinoi, including oxidative stress, inflammatory-like responses, modulation of EPS pathways, and PCD activation. Despite apparent growth resilience, the molecular alterations observed may impact bloom dynamics and carbon export. Full article

Temperate seagrass meadows are foundation habitats, but their communities are hard to census. Here, I provide a first COI environmental DNA (eDNA) metabarcoding snapshot from seawater at a Zostera marina meadow in the Vostok Bay marine reserve (Peter the Great Bay, Sea of Japan). In September 2021, eDNA from two 900 mL replicates of water were filtered, isolated, amplified for the 313 bp COI fragment with dual-index PCR (multiple replicates), and sequenced on Illumina NovaSeq. I obtained 53,666 reads for 176 operational taxonomic units (OTUs). Eukaryota dominated (154 OTUs; 93.7% of reads), while 22 bacterial OTUs comprised 6.3%. The assemblage was largely photosynthetic microeukaryotes, especially diatoms (61 OTUs; 49% of reads), consistent with late-summer productivity. Metazoan detections included a strong signal of the phoronid Phoronopsis harmeri (7511 reads; 14%), diverse invertebrates, and few vertebrate reads (0.5%), indicating limited fish sensitivity of universal COI assays. One abundant OTU was initially assigned to the giant kelp Macrocystis pyrifera but was rejected after additional BLAST and phylogenetic checks, illustrating database-driven misassignments. COI eDNA offers rapid, low-impact screening for marine protected area monitoring, but robust use requires seasonal replication, multi-marker assays, and a curated regional reference library. Full article

Algal carotenoids play a promising role in handling chronic diseases due to their diverse bioactive properties, including anti-inflammatory, antioxidant, and anticancer effects. This study assesses the activity of the antioxidant xanthophyll diatoxanthin (Dt), derived from marine diatoms, against triple-negative breast cancer (TNBC) cells using in vitro models, gene expression evaluation, and explores its role in potentiating the cytotoxic effect of chemotherapy. Dt exhibited selective activity against MDA-MB-231 and BT-549 TNBC cells at concentrations ≥12.5 ng/mL, with maximal effects observed at 25 ng/mL while sparing human umbilical vein endothelial cells (HUVECs) at these doses. When combined with doxorubicin (0.1–0.5 μM), Dt enhanced the anti-tumor efficacy in both TNBC cell lines, further reducing cell viability compared with doxorubicin alone (p < 0.05–0.001). Dt also exerted its activity in inhibiting migration and chemotaxis by approximately 30–50% compared with the controls (p < 0.01) and suppressing 3D-tumor spheroid growth at day 12 (up to >50% reduction, p < 0.001). Notably, secretome analysis revealed Dt-induced changes in inflammatory, oxidative and angiogenic mediators, highlighting its ability to modulate the TNBC microenvironment. Dt also downregulated key pro-survival, pro-angiogenic and pro-tumorigenic genes in both TNBC cell lines, supporting its role in disrupting oncogenic pathways. Angiogenesis-related genes were significantly reduced. Dt also decreased the expression of angiogenic mediators in HUVECs, supporting Dt’s role in inhibiting tumor vascularization. Results on gene expression regulation were also confirmed by RNA-Seq analysis. These findings pose Dt as a promising chemopreventing candidate in the challenging fight against TNBC, a well-known type of cancer that is aggressive and resistant to conventional therapies, targeting critical pathways for tumor survival, such as inflammation, angiogenesis, tumor cell growth, and cell migration. Given its selective activity against TNBC cells, ability to enhance chemotherapy efficacy, and modulation of the tumor microenvironment, Dt holds promise as a complementary drug for cancer prevention and interception. Future studies should focus on validating these effects in vivo and exploring Dt’s potential in combinatorial treatment strategies for cancer. Full article

Classifying optical water types (OWTs), particularly concerning different phytoplankton bloom types, is critically important because dominant phytoplankton groups govern key marine ecosystem functions and biogeochemical processes, including nutrient cycling and carbon export. This study refines a recent OWT classification method developed for the Second-Generation Global Imager (SGLI), which was originally proposed to discriminate dinoflagellate and diatom blooms. By employing binary logistic regression (bLR) with independent in situ data from Karenia selliformis (dinoflagellate) blooms off the Kamchatka Peninsula and Skeletonema spp. (diatom) blooms in Tokyo Bay, this study establishes more robust and statistically meaningful boundaries between OWTs. The analysis confirms the diagnostic spectral shapes from SGLI data: a trough at 490 nm for K. selliformis blooms and a peak at 490 nm for diatom blooms, validating the consistency of this spectral criterion. The updated method reliably identifies waters dominated by coloured dissolved organic matter and different phytoplankton functional types in mesotrophic waters, and successfully detected a Karenia mikimotoi bloom in the Gulf St. Vincent, South Australia, demonstrating its potential for the global monitoring of red tides. By providing a reliable, satellite-based tool to distinguish between ecologically distinct phytoplankton groups, this refined OWT classification offers a valuable data product to improve the accuracy of marine ecosystem and carbon cycle models, moving beyond bulk chlorophyll-a parameterizations. Full article

Benthic marine diatoms are speciose but vastly underexplored eukaryotic microbes. Diatoms are identified by their intricately ornamented silica cell walls known as frustules, following removal of all organic matter with acid or strong oxidants. When living samples of diatom communities are examined, it is impossible to detect all the species present, as rare ones are easily obscured among the other materials present, and taxonomic identification of living diatoms can be uncertain or impossible, even with isolated cells. These features of diatom taxonomy have important consequences for biogeography, which we illustrate and discuss using new observations from two species. Despite being the mainstay for diatom descriptions, species described by light microscopy (LM) alone may conflate two species or (as in the case presented) lead to spurious new species; both need ultrastructural study to ascertain taxonomic and geographical boundaries. The species studied with scanning electron microscopy (SEM) over the last 45 years by Stephens & Gibson, Pennesi et al., and Lobban under the name of Mastogloia hustedtii is shown to be synonymous with M. grunovii. The former became known in the SEM era to bear both pseudoconopea (longitudinal flaps parallel to the sternum, invisible in LM) and silica plaques on the inner margins of the partecta (chambers on the valvocopulae), with the latter supposedly bearing neither, but there is a single, pantropical/Mediterranean species encompassed in the original description of M. grunovii. A new ultrastructural feature for the genus is reported from this species: marginal chambers formed by laminae over the mantle areolae and the first 2–3 areolae on the valve face. The second species studied, M. meisteri, had been reported a few times from one region based on very rare frustules, which do not meet the first criterion for biogeography: where did they live? Although we, too, did not observe living cells, the number of specimens present is evidence for a living population epiphytic on a Virgin Islands coral reef. The ultrastructure of this species is also shown for the first time. Because absence of evidence is overwhelming in microbial biogeography, the best we can say is that this species is potentially a regional endemic. Full article

Heterotrophic bacteria and microalgae are key regulators of marine biogeochemical cycles. The phycosphere, a nutrient-rich microenvironment surrounding microalgae, serves as a crucial interface for bacterial–algal interactions. Our previous work identified Opacimonas immobilis LMIT016^T, a phycosphere isolate from the diatom Actinocyclus curvatulus that possesses the smallest genome within the Alteromonadaceae family. However, its adaptation mechanisms to the phycosphere remain unclear, particularly given its extensive genome streamlining, a process involving the selective loss of non-essential and energetically costly genes to enhance fitness in nutrient-specific niches. Here, the co-cultivation experiments demonstrated significant mutual growth promotion between LMIT016^T and its host microalgae, with the bacterium forming dense attachments on diatom surfaces. Genomic analysis revealed that in addition to loss of motility-related genes, the strain exhibits a substantial reduction in c-di-GMP signaling components, including both synthases and receptors. Conversely, LMIT016^T harbors numerous genes essential for extracellular polysaccharide (EPS) biosynthesis and adhesion, supporting long-term attachment and biofilm formation. Other retained genes encode pathways for nutrient acquisition, stress response, and phosphate and nitrogen metabolism, reflecting its adaptations to the nutrient-rich phycosphere. Furthermore, the genome of LMIT016^T encodes two polysaccharide utilization loci (PULs) targeting laminarin and α-1,4-glucans, whose functions were experimentally validated by the transcriptional induction of the corresponding carbohydrate-active enzyme genes. These findings indicate that this strain counterbalances genome reduction by enhancing its attachment capabilities and metabolic specialization on algal polysaccharides, potentially facilitating stable association with diatom cells. Our results suggest that genome streamlining may represent an alternative ecological strategy in the phycosphere, highlighting a potential evolutionary trade-off between metabolic efficiency and niche specialization. Full article