Search Results (663)

This study investigates the spatiotemporal dynamics of zooplankton communities in the tropical low-latitude Northwestern Pacific Ocean based on field surveys conducted in August 2021 and November 2022. Redundancy analysis identified nitrate, silicate, temperature, and salinity as the primary factors influencing community structure. The distribution of dominant zooplankton groups exhibited close correlations with key environmental gradients, showing distinct habitat preferences corresponding to different hydrographic conditions. Zooplankton abundance in August 2021 was significantly higher than that in November 2022, which is presumably attributed to eddy-induced nutrient upwelling and enhanced primary productivity. Comparisons with adjacent marine regions reveal general consistency in overall zooplankton abundance and community species composition, while the observed seasonal discrepancies are closely associated with local unique hydrographic characteristics. These results highlight the role of nutrient–temperature–salinity interactions in structuring zooplankton communities and underscore their sensitivity to environmental variability. The findings provide a scientific basis for understanding pelagic ecosystem dynamics in oligotrophic waters and for developing management strategies under changing climate and oceanographic conditions. Full article

Understanding the reproductive physiology of marine fish is critical for sustainable fisheries management, particularly under environmental variability. This study evaluated seasonal changes in body parameters (condition factor, Kn, and gonadosomatic index, GSI, as proxies for body condition and reproductive status, respectively) and biochemical composition (P, proteins; G, glucose; L, lipids; fatty acids; and bioenergetic ratios L/P, LG, all as proxy of integrated biochemical condition) of female gonads in Strangomera bentincki, a key pelagic species in the Humboldt Current System (HCS) off south-central Chile. Moreover, environmental factors (sea surface temperature and chlorophyll-a) were also analyzed to explore their influence on the FA profile of gonads. Female body parameters showed significant seasonal variations, with high values of Kn and GSI in autumn and spring, respectively. The biochemical composition also revealed significant seasonal variation in protein and glucose content, with the highest protein levels in winter and elevated glucose in autumn. While total lipid and energy content remained relatively stable across seasons, the L/P and L/G ratios presented seasonal variations. Similarly, the fatty acid composition showed pronounced seasonal differences, particularly with increased polyunsaturated fatty acids (e.g., DHA) in winter. The SST was the environmental factor with the greatest influence on the seasonal variations in the gonadal FA profile. Altogether, these findings suggest a partial capital breeding strategy in S. bentincki, where reproductive investment depends on both accumulated reserves and environmental conditions during reproduction. This study underscores the importance of incorporating reproductive biochemical indicators into ecosystem-based fisheries management models to improve assessments of stock health and reproductive potential. Full article

Reconciling hydropower development with aquatic biodiversity conservation is a central challenge for sustainable river management worldwide. Cascade dam configurations, in which multiple impoundments are arranged in series along a single channel, impose longitudinal environmental gradients that restructure biological communities across trophic levels. Whether the resulting multi-trophic responses are independently driven by shared abiotic gradients (environmental filtering) or mechanistically coupled through direct food-web interactions (trophic cascading) remains unresolved. We surveyed phytoplankton, zooplankton, and benthic macroinvertebrates simultaneously at seven stations along a 430 km gradient downstream of Danjiangkou Dam in the Hanjiang River, the largest tributary of the Yangtze River and the source of China’s South-to-North Water Diversion Middle Route, over eight seasonal campaigns (2015–2017). Variance partitioning, piecewise structural equation modeling, Mantel tests, and co-occurrence network analysis were applied to partition environmental and trophic pathways. Environmental filtering dominated community restructuring at all three trophic levels, while the biotic proxy for direct trophic interactions explained less than 0.4% of community variation, consistent with weak detectable trophic coupling at seasonal resolution. Distance from Danjiangkou Dam shaped downstream transparency and turbidity gradients that mediated trophic-level-specific responses along distinct environmental axes (pH and water temperature for phytoplankton, conductivity for zooplankton, and transparency for benthic macroinvertebrates). Benthic macroinvertebrates were systematically decoupled from the pelagic analytical framework, absent from the cross-trophic co-occurrence network and structured more by spatial configuration than by water-column variables. Hub species in the network were associated with downstream mineralized conditions, confirming that network architecture reflects shared environmental preferences rather than biotic interactions. These findings support a management shift from single-dam mitigation toward cascade-scale coordination of environmental flow regimes, sediment connectivity, and substrate restoration as integrated strategies for sustaining multi-trophic biodiversity in regulated rivers. Full article

The Black Sea is highly vulnerable to environmental degradation, making the evaluation of contaminant transfer within its food webs essential for ecosystem protection, sustainable resource management, and human health risk assessment. Marine organisms accumulate contaminants through three main processes: bioconcentration (direct uptake from the abiotic environment), biomagnification (trophic transfer through consumption of contaminated prey), and bioaccumulation, which integrates contaminants from all exposure pathways. Despite numerous studies reporting contaminant concentrations in Black Sea waters, sediments, and biota, integrated analyses of trophic transfer within both pelagic and benthic food webs in the Romanian coastal sector remain limited. This study assessed the bioamplification of heavy metals—HMs, persistent organic pollutants—POPs (OCPs, PCBs) and polycyclic aromatic hydrocarbons—PAHs along the main pelagic and benthic food webs in the Romanian coastal sector, based on concentrations measured in representative invertebrate and fish species. The results revealed a compartment-driven contamination pattern, with the benthic food web functioning as an important reservoir and transfer pathway. Heavy metals showed variable and context-dependent trophic transfer, with selective amplification for Cu and Ni in some benthic links, trophic dilution or neutral transfer for Cd and Pb, and more consistent retention for Cr. In contrast, several PCB congeners showed clear biomagnification, particularly in benthic predator–prey relationships. PAHs displayed compound-dependent trophic transfer, with more pronounced amplification in benthic pathways. Overall, biomagnification was stronger for organic pollutants, particularly PCBs, than for heavy metals. The study contributes to two United Nations Sustainable Development Goals (SDGs): SDG 14 (Life Below Water) and SDG 12 (Responsible Consumption and Production). Full article

The Black Sea waters and sediments accumulate a wide range of pollutants, which, together with natural factors, can have diverse and combined effects on marine organisms. Cellular oxidative stress (OS) is a common response to environmental stressors and thus an indicator of the physiological resilience of organisms. The present study analyzed OS in fish species from the Bulgarian part of the Black Sea. Samples of 18 fish species were obtained during monitoring trawling in the northern and southern regions of the Bulgarian Black Sea and were analyzed. The OS-specific biomarkers (lipid peroxidation, glutathione, and antioxidant enzymes) were spectrophotometrically measured in the liver and gills. The obtained results revealed pronounced variability in pro- and antioxidant responses, shaped by sampling location, species identity, and tissue type. In fish sampled from the northern part, the liver showed stronger antioxidant activation, while the gills exhibited higher lipid peroxidation. Benthic fish exhibited pronounced hepatic antioxidant responses. Pelagic species had higher gill lipid peroxidation. Generalist feeders displayed variable stress responses associated with a diverse diet and the presence of multiple contaminants in it. In conclusion, OS was most pronounced in benthopelagic and pelagic species, which were more stressed in the northern Bulgarian part of the Black Sea, while benthic or coastal fish species experienced greater environmental pressure in the southern part. Full article

Marine mesozooplankton (0.2–20 mm), as a critical trophic link between primary producers and higher trophic levels, are pivotal drivers of trophic cascades regulating pelagic ecosystem structure and function. This review synthesizes recent advances in understanding mesozooplankton-mediated trophic cascades (MMTC), with a focus on selective feeding mechanisms, and presents an original, integrated quantitative framework that fills gaps in quantification and prediction of MMTC. This framework includes the following: a dual-pathway conceptual model distinguishing density-mediated and trait-mediated cascades; a three-level grazing rate correction model addressing long-standing underestimations of mesozooplankton direct grazing rate on phytoplankton; a comprehensive Cascade Strength Index for quantifying cascade intensity; an extended numerical model—NPMZ model (Nutrient–Phytoplankton–Microzooplankton–Mesozooplankton) for simulating MMTC dynamics and their biogeochemical impacts. The review further elucidates the spatiotemporal heterogeneity of MMTC and its implications for plankton community size structure and biological carbon pump efficiency. It also systematically assess the combined impacts of global change drivers (ocean warming, acidification, eutrophication) on MMTC and their ecological consequences. This review advances the theoretical framework of marine trophic cascade research by establishing a unified quantitative paradigm for MMTC and provides mechanistic insights and predictive tools for understanding how climate change modulates pelagic food web dynamics and marine ecosystem services. Moreover, the proposed integrated research paradigm combining molecular tools, multi-factor experiments, and high-resolution numerical modeling offers a critical roadmap for future MMTC research in the Anthropocene. This provides a scientific basis for the conservation and adaptive management of marine ecosystems under global change. Full article

The round sardinella (Sardinella aurita Valenciennes, 1847) is a widely distributed migratory pelagic fish inhabiting the Mediterranean Sea and the eastern Atlantic coasts. The species is heavily exploited and represents a valuable resource for global fisheries. In the Mediterranean area, uptakes of round sardinella are particularly high in the Ionian and Levant regions, where landings have shown fluctuating yet significant peaks in recent decades. Given its migratory nature, understanding the connectivity among populations is crucial for delineating appropriate fishery management units. Previous studies employing morphometric, meristic, and molecular analyses have yielded mixed results regarding population structuring. Here, the genetic differentiation among Eastern Mediterranean S. aurita populations was investigated using a multi-marker approach: the mitochondrial cytochrome c oxidase subunit I (COI), cytochrome b (CytB), control region (CR), and 16S ribosomal RNA (16S rRNA), and seven species-specific nuclear simple sequence repeats (SSRs). Overall, the results indicate high genetic diversity coupled with weak population structuring across the Eastern Mediterranean. These analyses aim at clarifying stock boundaries towards supporting sustainable management strategies at a regional scale for this ecologically and economically important species. Full article

The recurrent influx of pelagic Sargassum spp. along Caribbean coastlines poses a significant environmental challenge while offering potential as a resource-recovery agricultural input. However, agricultural reuse of Sargassum biomass raises concerns regarding salinity and trace-metal distribution within the soil–plant–food continuum. This study evaluated the short-term elemental response to a Sargassum-Based Liquid Biofertilizer (SBLB) produced via controlled anaerobic fermentation, using tomato (Solanum lycopersicum L.) grown under greenhouse conditions. Raw biomass, fermented biofertilizer, irrigation water, soils, vegetative tissues, and fruits were chemically characterized. Elemental concentrations were quantified by ICP–OES and ICP-MS and treatment effects were analyzed using one-way and two-way ANOVA (p < 0.05). Anaerobic fermentation resulted in lower measured concentrations of sodium, arsenic, and selected trace elements in the liquid fraction relative to raw biomass. SBLB application increased soil macronutrient availability (N, P, K, Ca, Mg), while soil trace-metal concentrations remained within international reference ranges during the experimental period. Metals of concern (As, Cd, Pb, Ni, Cr) showed no detectable short-term enrichment in soils, vegetative tissues, or fruits relative to controls. In tomato fruits, arsenic, cadmium, and lead were below the limit of quantification across all treatments. Within the experimental timeframe, SBLB application was not associated with detectable trace-element accumulation in the soil–plant system. Long-term field studies and detailed soil physicochemical characterization are required to evaluate cumulative effects under repeated applications. Full article

Understanding temporal variation in population productivity is critical for effective assessment and management of pelagic fish stocks under a changing climate. In this study, we applied a stochastic surplus production model in continuous time (SPiCT) with time-varying parameters to evaluate the productivity dynamics of yellowfin tuna (Thunnus albacares) in the western and central Pacific Ocean and to examine the influence of environmental variability on productivity. Multiple time-varying parameterization scenarios were explored to characterize uncertainties in productivity estimates and associated biological reference points. Generalized additive models were subsequently used to quantify the relationships between environmental variables and time-varying productivity. Results indicate that productivity estimates exhibit consistent temporal patterns across alternative modeling scenarios, while their magnitude and associated uncertainty are sensitive to model structure. Among the environmental factors examined, the Pacific Decadal Oscillation (PDO) and mixed layer thickness (MLT) showed consistent and statistically significant associations with maximum net productivity. Higher PDO values and greater MLT were both positively associated with population productivity. Overall, the results highlight the importance of environmental variability in shaping time-varying productivity of yellowfin tuna and demonstrate the feasibility of incorporating key environmental indicators into a state-space model. This approach provides a complementary framework for interpreting stock dynamics and supports the development of ecosystem-based fisheries management strategies in the western and central Pacific. Full article

Lanternfishes (Myctophidae) dominate mesopelagic ecosystems and play a central role in pelagic food webs through their high biomass and diel vertical migration, yet detailed information on their age structure and growth dynamics remains limited in the Northwest Pacific Ocean. This study reconstructs age, growth patterns, and life-history strategies of D. gigas and D. perspicillatus using sagittal otolith microstructure analysis. Specimens were collected during oceanographic surveys conducted in 2023 and 2024, and individual ages were estimated by counting daily otolith growth increments. Somatic growth trajectories were evaluated using multiple nonlinear growth models, including the von Bertalanffy, Gompertz, and Logistic functions, and growth dynamics were further assessed through derivative-based growth speed analyses. The results reveal pronounced interspecific differences in growth strategy and longevity. D. perspicillatus exhibited rapid early somatic growth, a compressed age structure, and an early approach to asymptotic length, indicating a short-lived life-history strategy characterized by early growth deceleration and high population turnover. In contrast, D. gigas showed faster early growth, prolonged somatic development, greater inter-individual variability, and substantially larger maximum body size, reflecting delayed maturation and extended lifespan. Otolith microstructural zonation clearly corresponded to larval, juvenile, and adult growth phases in both species. The predominance of younger age classes in the catch and interannual differences in size structure were primarily attributed to ontogenetic habitat shifts, cohort composition, and sampling availability rather than intrinsic changes in growth dynamics. Full article

Small pelagic fish are nutrient-dense foods, but whether domestic cooking alters their capacity to modulate probiotic adhesion is unclear. We prepared sardines and sprats using five household techniques (raw, cooked, steamed, baked, and fried) and generated in vitro digestates using the INFOGEST method. We tested two concentrations in two intestinal co-cultures—Caco-2/HT29 and mucin-producing Caco-2/HT29-MTX. Adhesion of Lacticaseibacillus rhamnosus, Lactobacillus gasseri, and Lactobacillus brevis were quantified. Digestates altered adhesion in a probiotic strain species in a process-dependent manner. Sprat digestates from fried or baked preparations produced the strongest stimulation, exceeding 150% in Caco-2/HT29; responses in HT29-MTX were directionally similar but attenuated. In contrast, cooked or steamed sardine digestates frequently inhibited adhesion, particularly at 0.5% (e.g., L. gasseri < 50%). Raw preparations yielded divergent outcomes across models. A two-way ANOVA confirmed significant effects of processing, concentration, and their interaction, with the interaction explaining up to 21% of the observed variance. Across conditions, L. rhamnosus adhered most consistently, whereas L. brevis and L. gasseri were more environmentally sensitive. These findings suggest that standard cooking practices alter the bioactivity of fish-derived digestates and, consequently, the adhesion of beneficial lactobacilli in intestinal cell models, selecting sprats and employing dry-heat methods may favor probiotic–host interactions under in vitro conditions. Full article

Coastal ecosystems of the tropical Atlantic and the Mexican Caribbean have experienced recurrent massive influxes of pelagic brown macroalgae, Sargassum natans and Sargassum fluitans, generating severe environmental, social, and economic impacts. While the accumulation of this biomass poses a significant waste management challenge, it also represents an underexploited renewable resource aligned with circular economy and sustainability principles. This study investigated the valorisation of Sargassum spp. through comprehensive physicochemical characterisation and multiple value-added applications. The biomass collected in Tulum, Quintana Roo, Mexico, was analysed to determine its chemical composition, including lignin, holocellulose, α-cellulose, ash, and moisture content, using standardised methods of the Technical Association of the Pulp and Paper Industry (TAPPI). For mechanical testing, methods from the American Society for Testing and Materials (ASTM) were used. The biomass was subjected to controlled pretreatment and thermochemical conversion processes. Evaluated valorisation pathways included: (1) taxonomic identification and physicochemical characterisation, (2) polymer composites, (3) reinforcement in construction materials such as unfired clay bricks, and (4) biochar and activated carbon production for contaminant adsorption. The results demonstrated that Sargassum spp. biomass can be transformed from an environmental nuisance into a multifunctional, high-value biomaterial, providing scalable solutions that mitigate waste disposal challenges and contribute to climate and resource sustainability. Full article

The massive influx and subsequent anaerobic decomposition of pelagic Sargassum on Caribbean coasts release toxic gases, including hydrogen sulfide (H₂S), and pose a real public health hazard, as evidenced by thousands of reported acute exposure cases in Martinique in 2018. To effectively characterize exposure and identify at-risk areas, we utilized the interactive web-based dispersion modeling system C-PORT, representing Sargassum accumulation zones as area sources derived from recent aerial and in situ monitoring data. Inverse modeling, comparing C-PORT output against Madininair observation data from 2024 to 2025, established emission flux rates ranging from 0.45 to 3.58 mg/m² per second for H₂S, depending on Sargassum density. The resulting modeled concentrations exhibit a low average fractional bias (approx. 0.04) when compared to observations. This study demonstrates that C-PORT can be used to estimate spatially resolved concentrations for H₂S, generate health-risk maps for H₂S, evaluate options to mitigate exposure from varying Sargassum intensity levels, and serve as a crucial tool for public health agencies across vulnerable coastal regions. Full article

This pioneering study investigates bacteria isolated from marine pelagic fish, fishing vessels, and gear surfaces, focusing on the variability in biofilm formation across different substrates, media, and cultivation conditions. Bacteria from fish intestines, skin, and gills, including spoilage organisms and potential fish and human pathogens, can contaminate vessel surfaces, gear, and containers and may act as microbial reservoirs and transmission vectors. In this study, biofilm formation was evaluated at air–liquid interfaces and on submerged plastic, metal, and glass surfaces under various incubation temperatures and media. Vibrio spp. were isolated both from fishing nets and fish gills, particularly Vibrio alginolyticus, V. gigantis, and V. pelagius. Although V. harveyi was examined as a representative vibrio, it did not form a biofilm on polypropylene. Photobacterium damselae subsp. damselae, Pseudomonas fragi, P. gessardii, Psychrobacter spp., and Rothia endophytica showed a strong affinity for stainless steel. Overall adhesion regardless of media type was highest for P. gessardii, followed by P. damselae and Aeromonas veronii, which adhered strongly to steel, glass, and polypropylene; however, only P. gessardii also adhered well to polystyrene, an important finding because these are known fish and human pathogens. These results highlight species-dependent biofilm triggers and their substantial variability and provide guidance for standardized marine biofilm protocols. Full article

Cleaning, the removal of parasites and dead tissue from clients, is common in the Sea. Reef-based cleaning stations are visited by many fish clients, some by both resident and visitor pelagic species, while others are visited solely by resident species. Nonetheless, no distinction has ever been made between the potentially different cleaning stations. Here we describe two distinct categories of cleaning stations: pelagic cleaning stations (PCS) and residential cleaning stations (RCS). We suggest that the two station types differ not only in their clientele but also in the characteristics of their cleaning services. We examined the behaviour of the cleaner wrasse, Labroides dimidiatus, at six cleaning stations on isolated knolls in Palawan, the Philippines—three stations that are routinely visited by pelagic manta rays (i.e., PCS), and three stations that service only resident clients (i.e., RCS). Our results indicate that PCS have more cleaners per station and that cleaners forage at greater distances from the station’s focal point. These distinct patterns suggest functional differences between pelagic and residential cleaning stations. Our findings may aid in the identification and conservation of shark and manta cleaning stations. Full article