Search Results (1,958)

Some Sacoglossa sea slugs are capable of stealing and maintaining functional intracellular chloroplasts—kleptoplasts—from their macroalgal prey for periods of up to several months, a process known as kleptoplasty. Although the cultivation of these marine invertebrates under laboratory conditions is crucial for research in various fields (e.g., endosymbiosis, animal physiology, discovery of new marine natural products), rearing protocols are scarce. This study presents a standardized protocol for the laboratory rearing of large numbers of the sacoglossan tropical sea slug Elysia crispata. The detailed protocol successfully facilitated embryonic development, larval metamorphosis, and juvenile-to-adult transition, allowing the rearing of multiple generations. Two groups, characterized by acquiring different kleptoplasts, were obtained by feeding the sea slugs with two different prey macroalgae: Bryopsis sp. and Acetabularia acetabulum. Usually referred to as lettuce sea slug among marine aquarium hobbyists, E. crispata is a highly valued organism for its striking appearance and ability to control nuisance algal growth in reef aquariums. This protocol allows experimental reproducibility and access to specimens under different development stages, potentially boosting research on kleptoplasty while also contributing to reducing the impact of the marine aquarium trade on natural populations. Full article

Mesozooplankton play a pivotal role in marine pelagic food webs, mediating energy and matter transfer between primary producers and higher trophic levels. Daya Bay, a semi-enclosed bay located in the northern South China Sea, has undergone significant environmental changes due to anthropogenic activities, such as thermal discharge from nuclear power plants and eutrophication. This study examined the mesozooplankton community structure, feeding preferences, and food web organization through four seasonal cruises (May 2022, February 2023, August 2023, and November 2023), employing stable isotope analysis and a Bayesian Isotopic Mixing Model. Results indicate that mesozooplankton abundance and diversity were lower in regions affected by thermal discharge, suggesting a suppressive effect of elevated temperatures. Seasonal shifts in dominant species were observed: Penilia avirostris and Dolioletta gegenbauri dominated the community in spring, while Noctiluca scintillans blooms occurred in summer and winter. Isotopic analysis revealed distinct trophic strategies: copepods exhibited omnivorous habits, whereas cladocerans and tunicates showed stronger herbivorous tendencies. N. scintillans functioned as a high-trophic omnivore, preying on copepod larvae and competing for food resources. Overall, the mesozooplankton community was characterized by an omnivory-dominated trophic network, which enhanced resilience yet remains sensitive to anthropogenic disturbances. This study clarifies how human-induced environmental changes reshape trophic pathways in subtropical coastal waters, providing a valuable reference for long-term monitoring and ecosystem management in Daya Bay. Full article

Biofouling communities are usually managed as pests in aquaculture, yet their natural proliferation in fish farms makes them also promising IMTA extractive components. The growth and biomass production of four dominant macrofoulers, Mytilus galloprovincialis (mussels), Sabella spallanzanii (polychaete worms), Phallusia mammillata and Styela plicata (ascidians), were evaluated under a novel IMTA system in the Ionian Sea (southern Italy). Coconut-fiber ropes (10 m) were deployed around fish cages in October 2022 and monitored over a 1-year cycle. Monthly density, length-frequency and cohort analyses combined with species-specific length-weight relationships were used to estimate target species’ growth and biomass. Mytilus and Sabella showed single-cohort dynamics, with densities steadily declining over time, whereas ascidians displayed continuous recruitment allowing for additional rope-deployment windows. Specific growth rates in length were significantly higher in Phallusia and Sabella (≈25% month⁻¹) than in Mytilus and Styela (≈17 and 22% month⁻¹). Total macrofouling biomass (live weight) increased from ≈350 kg in May to a peak of ≈2500 kg in August, remaining as high in October. Mytilus and Sabella accounted for 60–80% of total biomass while ascidians contributed 20–40%. Beyond environmental restoration, this multispecies biomass offers several potential commercial opportunities and could be further valorized through biorefinery-based cascading extraction, including final conversion into bioenergy. Overall, IMTA could leverage traditionally undesired fouling organisms as multifunctional crops, enhancing bioremediation while supporting circular blue-bioeconomy principles. Future research should focus on optimizing rope deployment timing, harvesting strategies, and biomass valorization pathways to fully exploit the emerging potential of integrating multispecies fouling biomass within IMTA systems. Full article

The Jiangsu Coastal Thermal Front (JCF), a persistent feature in Chinese marginal seas, plays a significant role in modulating phytoplankton dynamics and carbon cycling. However, the multi-scale spatiotemporal variability of the persistent JCF and the underlying mechanisms driving its ecological effects remain limited. Using satellite observations and reanalysis data, this study systematically investigates the JCF’s distribution and its regulatory impact on phytoplankton chlorophyll-a (Chla) and particulate organic carbon (POC). Results show the persistent JCF is most active in summer and winter, primarily in Haizhou Bay and the Jiangsu Shoal. In summer, stratification-induced nutrient limitation within the Haizhou Bay thermal front decreases Chla and POC (by ~−20% and ~−40%, respectively), whereas nutrient-replete non-frontal waters support higher biomass. In the Jiangsu Shoal, the thermal front blocks the southward transport of POC, helping to maintain stable POC levels in the nearshore non-frontal region; meanwhile, the shift from southward to northward transport leaves the offshore non-frontal area without sufficient replenishment, resulting in a ~35% decrease in POC. In winter, the Haizhou Bay thermal frontal barrier effect restricts suspended particulate matter, alleviating light limitation inside the front and enhancing Chla (up to 15%) while reducing POC due to diminished resuspension. We elucidate that the JCF shapes ecological patterns through two primary pathways: by directly acting as a barrier to material transport and by interacting with ancillary processes like upwelling. These findings advance the mechanistic understanding of frontal impacts on coastal ecosystems and provide a mechanistic basis for understanding synergistic coastal carbon sinks. Full article

As an important component of waters constituent that affects ocean color and the underwater ecological environment, the accurate assessment of Chromophoric Dissolved Organic Matter (CDOM) is crucial for observing the continuous changes in the marine ecosystem. However, remote sensing estimation of CDOM remains challenging for both coastal and oceanic waters due to its weak optical signals and complex optical conditions. Therefore, the development of efficient, practical, and robust models for estimating the CDOM absorption coefficient in both coastal and oceanic waters remains an active research focus. This study presents a novel algorithm (denoted as DQAAG) that incorporates ultraviolet bands into the inversion model. The design leverages the distinct spectral absorption characteristics of phytoplankton versus detrital particles in the ultraviolet (UV) region, enabling improved discrimination of water color parameters. Furthermore, the algorithm replaces empirical formulas commonly used in semi-analytical approaches with an artificial intelligence model (deep learning) to achieve enhanced inversion accuracy. Using IOCCG hyperspectral simulation data and NOMAD dataset to evaluates Shanmugam (2011) (S2011), Aurin et al. (2018) (A2018), Zhu et al. (2011) (QAA-CDOM), DQAAG, the results indicate that the a_g(443) derived from the DQAAG exhibit good agreement with the validation data, with root mean square deviation (RMSD) < 0.3 m⁻¹, mean absolute relative difference (MARD) < 0.30, mean bias (bias) < 0.028 m⁻¹, coefficient of determination (R²) > 0.78. The DQAAG algorithm was applied to SeaWiFS remote sensing data, and validation was performed through match-up analysis with the NOMAD dataset. The results show the RMSD = 0.14 m⁻¹, MARD = 0.39, and R² = 0.62. Through a sensitivity analysis of the algorithm, the study reveals that R_rs(670) and R_rs(380) exhibit more significant characteristics. These results demonstrate that UV bands play a crucial role in enhancing the retrieval accuracy of ocean color parameters. In addition, DQAAG, which integrates semi-analytical algorithms with artificial intelligence, presents an encouraging approach for processing ocean color imagery to retrieve a_g(443). Full article

Commercial smooth-hound sharks of the genus Mustelus are commonly landed and consumed in Mediterranean fisheries, raising concerns about potential human exposure to persistent contaminants. This study investigated the occurrence of organochlorine compounds (OCs), including hexachlorobenzene (HCB), dichlorodiphenyltrichloroethane (DDT) and its metabolites, and polychlorinated biphenyls (PCBs), together with per- and polyfluoroalkyl substances (PFAS), in muscle and liver tissues of Mustelus mustelus and Mustelus punctulatus collected in the waters of the Egadi Archipelago (central Mediterranean Sea). OCs were detected in all analyzed samples, with total PCB concentrations reaching higher values in liver compared to muscle tissues, reflecting tissue-specific accumulation and detoxification processes. PFAS were detected in all analyzed muscle samples (1.10–58.5 ng/g w.w.), with PFOS, PFOA and PFNA generally below current European regulatory thresholds, although isolated exceedances were observed. Stable isotope analysis (δ¹³C and δ¹⁵N) highlighted differences in trophic ecology between the two species and suggested that feeding habitat and trophic position may influence contaminant exposure patterns, particularly in M. punctulatus. The human health risk assessment, conducted as a screening-level evaluation, indicated potential concern associated with PCB concentrations in liver tissue, while risks associated with muscle consumption were generally lower. Overall, the integration of contaminant analysis and stable isotopes provides insights into organismal exposure pathways and supports the use of smooth-hound sharks as sentinels of contaminant presence in Mediterranean coastal ecosystems. Full article

The Strait of Messina (Central Mediterranean Sea) has always been known for the stranding of marine organisms, especially during the spring. We came across an extraordinary event of mass stranding in April 2025, with 453 specimens of Macroramphosus sp. found through a single night. A total of 571 post-larvae and juvenile individuals stranded between February and May 2025 were examined for this study. Clear morphological differences related to the size, especially in post-larvae, were highlighted. The relationship between Body Length (BL) and other morphometric measurements, such as Dorsal Spine Length (DSL), Snout Length (SNL), and Body Height (BH), were studied, with the aim of identifying without any doubt the species Macroramphosus gracilis. A slightly negative allometric relationship between length and weight shows that it grows faster in length and slower in weight. This study aims to improve the state of knowledge on slender snipefish M. gracilis, and particularly on the somatic features of different post-larval development stages, such as the presence of spinules in various parts of the body. All these morphological changes could give us a hint at the ecological adaptation to the habit shift, as relates to development. Full article

Dissolved organic matter (DOM) is central to biogeochemical cycles in estuarine-coastal zones, with its source-sink dynamics linking regional ecological functions to global carbon budgets. As a typical semi-enclosed bay in southern China, Zhanjiang Bay (ZJB) features intense tidal mixing and significant seasonal runoff variations, making it a representative system for understanding DOM dynamics in complex land–sea interaction zones. The migration of dissolved organic carbon (DOC) is crucial for bay carbon budgets, yet its estimation is constrained by land–water interface dynamics and in situ observation limitations. To clarify the regulation of DOM’s fate and exchange flux in ZJB, this study integrated in situ observations, ultraviolet spectroscopy, and three-dimensional fluorescence techniques to analyze DOM tidal dynamics and net DOC exchange flux. Results indicated terrestrial runoff dominated rainy-season DOC sources, resulting in slightly higher concentrations (1.86 ± 0.46 mg·L⁻¹) compared to the dry season (1.82 ± 0.20 mg·L⁻¹). Terrestrial inputs endowed rainy-season DOM with high molecular weight and aromaticity, with microbial humic substances (C2) accounting for 36%. Tidal fluctuations affected DOC via water exchange: ebb tides diluted concentrations with low-DOC open-ocean seawater, while flood tides increased them through high-DOC bay water discharge. Dry-season DOM relied on in situ biotransformation, characterized by low molecular weight and aromaticity, with the protein-like fraction (C4) accounting for 24.3%. Fluorescence index (FI = 1.77–1.79) confirmed DOM as a mixture of allochthonous and autochthonous sources, with significant in situ contributions and weak humification. Net DOC exchange flux, regulated by terrestrial runoff, was 3.6–4.6 times higher in the rainy season, decreasing from the estuary to the coast. In conclusion, the joint regulation of terrestrial runoff-driven seasonal dynamics and tidal water exchange governs ZJB’s DOM dynamics, providing valuable insights for biogeochemical research in semi-enclosed bays. Full article

Microorganisms, as the foundation of deep-sea ecosystems, are crucial for maintaining the structure and stability of polymetallic nodule field environments. To investigate the community structure and distributional patterns of benthic microorganisms in such environments, this study used high-throughput sequencing to analyze the composition, diversity, and environmental correlations of bacteria, archaea, and fungi in the BPC (Beijing Pioneer Hi-tech Development Corporation Ltd., Beijing, China). Furthermore, microbial communities from BPC were compared with those from UK-1 (UK Seabed Resources, Southampton, UK) in terms of community structure and co-occurrence network characteristics. The results revealed that in the BPC, the bacterial communities were dominated by Proteobacteria and Chloroflexi, while Crenarchaeota represented the overwhelmingly dominant group. Fungal communities were primarily composed of Ascomycota and Basidiomycota. Correlation Analysis suggested that water depth, TOC (Total organic carbon), TN (Total nitrogen), and δ¹⁵N emerged as the key environmental drivers of microbial community variation. Comparative analysis showed microbial groups exhibited certain similarities but also some differences at the phylum, class, and order levels, with the differences becoming increasingly pronounced at finer taxonomic resolutions between BPC and UK-1. Co-occurrence network analyses indicated the microbial networks with higher density and node connectivity in the BPC, whereas the UK-1 exhibited greater modularity and clustering coefficients. Microbial interactions were weaker in the UK-1, but its resilience to benthic disturbance was expected to be higher than in the BPC. Full article

The identification of mRNA isoforms in biological samples is crucial for studying tissue- and cell-specific isoform expression, activity of tissue-specific promoters, alternative splicing events, and alternative polyadenylation signals in genes. For single or several genes, expressed mRNA isoforms can be found using RT-PCR and RT-qPCR. Available transcriptome short-read archives deposited in GenBank or as laboratory data can be used to identify mRNA isoforms instead of or prior to wet analysis by other methods in eukaryotic organisms with annotated genomes. However, isoform expression analysis requires advanced bioinformatics skills and may be time-consuming. In addition, this analysis generates a large amount of unnecessary data. To detect mRNA isoforms encoded by one gene of interest, screening of expressed mRNAs in NGS data can be simplified by mapping NGS short reads to a single-gene or transcript sequence. Using single-gene/transcript mapping, we analyzed the expression of the Otx gene at the mRNA isoform level in some embryonic and adult tissue mRNA libraries of the sea urchin Strongylocentrotus purpuratus available in GenBank. The presence of expressed Otx mRNA isoforms was confirmed by RT-qPCR in the same tissues and at the same developmental stages of the closely related species Strongylocentrotus intermedius. We showed that single-gene/transcript mapping is a suitable approach for qualitative evaluation of the expression of mRNA isoforms and recognition of at least two expressed isoforms in the same biological sample. Full article

Highly pathogenic avian influenza (HPAI) A(H5N1) clade 2.3.4.4b has recently emerged as a major threat to wildlife, agriculture, and public health due to its expanding host range and the increasing frequency of spillover into mammals. In July–August 2023, the mass death of over 3500 northern fur seals (Callorhinus ursinus) and at least one Steller sea lion (Eumetopias jubatus) was recorded on Tyuleniy Island in the Sea of Okhotsk, Russia. Two HPAI A(H5N1) viruses were isolated from fur seal carcasses and designated A/Northern_fur_seal/Russia_Tyuleniy/74/2023 and A/Northern_fur_seal/Russia_Tyuleniy/75/2023. Both viruses exhibited high pathogenicity in chickens (IVPI 2.7–3.0) and mice (MLD₅₀ 1.9–2.5 log₁₀EID₅₀/mL), with distinct differences in disease progression, histopathology, and organ tropism. Experimental infection of mice revealed that strain A/74/2023 induced more severe pulmonary and neurological lesions than A/75/2023. Whole-genome sequencing and phylogenetic analysis demonstrated close relatedness to HPAI H5N1 strains circulating in the Russian Far East and Japan from 2022 to 2023, with several mutations associated with mammalian adaptation, including NP-N319K and, in one isolate, PB2-E627K. According to our findings, northern fur seals (Callorhinus ursinus) on Tyuleniy Island acted as spillover hosts for the highly pathogenic avian influenza (HPAI) H5N1 virus of clade 2.3.4.4b. Furthermore, the high population density of fur seals and the extensive mortality observed during the outbreak highlight these animals’ potential role as another vessel for the evolution of avian influenza viruses. This study represents the first documented case of HPAI H5N1 in pinnipeds in the North Pacific region and supports previous reports indicating that pinnipeds, including northern fur seals, are highly susceptible to HPAI H5N1 clade 2.3.4.4b viruses. Full article

Sustainable fertilization strategies are increasingly required to enhance crop performance while reducing dependence on synthetic inaputs. In this study, the effectiveness of sea-derived organic amendments, Posidonia oceanica compost and mussel shell powder, was evaluated in Salvia officinalis (sage) cultivation. A pot experiment was conducted in Istron Kalou Xoriou (Crete), using three nitrogen rates (0, 40 and 80 kg ha⁻¹) in combination with four rates of mussel shell powder (0, 50, 100 and 200 g/pot). A total of 9 treatments were set up, each replicated 3 times, resulting in 27 pots. Growth parameters (plant height, total and leaf fresh-dry weight), nitrogen content in plant tissues, nitrogen uptake, and nitrogen use efficiency (NUE) were assessed across three harvest periods. The results indicated that both P. oceanica compost and mussel shell amendments significantly improved soil properties and plant performance. The treatment receiving 200 g/pot of mussel shell powder combined with 80 kg ha⁻¹ fertilization (PH200) consistently produced the highest values for biomass (223.99–383.58 g/plant), nitrogen plant concentration (1.967–2.117%), and nitrogen uptake (1.762–3.248 g/plant). The application of mussel shells effectively increased soil pH, thereby enhancing nutrient availability and promoting nitrogen assimilation. Furthermore, NUE values showed a progressive increase with rising amendments rates. Overall, sea-derived organic amendments demonstrated strong potential as sustainable fertilization materials, contributing to sage productivity improvement while supporting circular management of coastal waste resources. Full article

The introduced red king crab Paralithodes camtschaticus holds significant commercial value in the Barents Sea. This species is recognized as a host for a wide variety of symbiotic organisms, including polychaetes. In July 2015 and 2025, a total of 12 specimens of the marine terebellid polychaete Amphitrite cirrata were discovered inhabiting the gills of two red king crabs in Dalnezelenetskaya Bay, Barents Sea. This study represents the first documented occurrence of an association between these benthic species. Colonization of the red king crab by Amphitrite cirrata offers several advantages to the polychaetes by providing access to suitable feeding conditions, increased mobility, and protection from potential predators. However, this association poses disadvantages to the host crabs, as it results in tissue damage and an elevated concentration of sand particles within their gills. Full article

Using MODIS-Aqua satellite observations, this study analyzes the spatiotemporal distribution characteristics of particulate organic carbon (POC) in China’s marginal seas from 2003 to 2024. The statistical relationships between various marine environmental variables, including sea surface temperature (SST), nutrients, and primary production (PP), and POC concentrations are explored using partial least squares path modeling (PLS-PM). Finally, a box model approach is conducted to assess the POC budget in the study area. The results indicate that the POC concentration in the marginal seas of China generally exhibits a characteristic of being high in spring and low in summer. The highest concentration of POC is observed in the Bohai Sea, followed by the Yellow Sea, and the lowest in the East China Sea, with coastal waters exhibiting higher POC concentrations compared to the central areas. The spatial distribution and seasonal changes in POC are jointly influenced by PP, water mass exchange, resuspended sediments, and terrestrial inputs. Large-scale climate modes show statistical associations with POC concentration in the open waters of China’s marginal seas. PP and respiratory consumption are identified as the predominant input and output fluxes, respectively, in China’s marginal seas. This study enriches the understanding of carbon cycling processes and carbon sink mechanisms in marginal seas. Full article

Deep-sea cages are highly susceptible to biofouling due to long-term seawater immersion, which promotes the attachment and growth of marine organisms on nets, significantly reducing fish survival. To address this issue, this study explores the use of low-pressure abrasive water jets (LPAWJs) for cage fouling removal through numerical simulation. Based on a Box-Behnken response surface design, nozzle inlet pressure X₁, nozzle outlet diameter X₂, and target distance X₃ were selected as optimization parameters. The peak jet impact force Z₁, stable jet impact force Z₂, peak abrasive water jet velocity Z₃, and peak abrasive particle velocity Z₄ were chosen as evaluation indicators to characterize the jet’s instantaneous impact ability, sustained action ability, and dynamic particle behavior. Using the entropy method, weights for each indicator were determined, and the jet’s overall removal capability was calculated. A regression model was developed by integrating numerical simulation with the response surface methodology (RSM), and the optimal parameter combination was identified as X₁ = 4.5 MPa, X₂ = 10 mm, and X₃ = 205.396 mm. Compared with the poorest experimental condition (Condition 1), the jet’s overall removal capability obtained under the optimal parameter combination increases by 101.35%. Experimental validation further confirms that the optimized parameters yield the best oyster-removal performance of the low-pressure abrasive jet, with the average removal rate improving by 100.55% relative to Condition 1. The methodology and results of this study provide a theoretical foundation and technical reference for the design and optimization of automated net-cleaning systems or net-cleaning robots equipped with low-pressure abrasive jets. By integrating the proposed model and operating parameters, future robotic systems will be able to predict and dynamically adjust jet conditions according to fouling characteristics, thereby improving the efficiency, cost-effectiveness, and sustainability of maintenance operations in marine aquaculture. Full article