Search Results (308)

Gut microbial community assembly involves a critical bioenergetic trade-off, yet the gut microbes with roles in influencing intestinal metabolic homeostasis remain poorly understood in pelagic ecosystems. A central unresolved question is whether microbiome structure is primarily governed by stochastic geographic drift or by deterministic metabolic filters imposed by diet. Here, we test the metabolic release hypothesis, which posits that access to high-quality prey physiologically “releases” the host from obligate dependence on diverse fermentative symbionts. By integrating δ15N analysis with 16S rRNA metabarcoding in the anchoveta from the South Pacific waters (Engraulis ringens), we reveal a profound, diet-induced restructuring of the gut ecosystem. We demonstrate that trophic ascent triggers a deterministic collapse in microbial alpha diversity (rs = −0.683), driven by the near-complete competitive exclusion of fermentative bacteria (rs = −0.874) and the resulting dominance of a specialized proteolytic core. Mechanistically, the bioavailability of zooplankton-derived protein favors efficient endogenous hydrolysis over costly microbial fermentation, rendering functional redundancy obsolete. Crucially, we find that while metabolic function converges, taxonomic identity remains geographically structured (r = 0.532), suggesting that local environments supply the specific taxa to fulfill universal metabolic roles. These findings establish a link between δ15N as a nutritional physiology proxy of anchoveta and its gut for microbial functional state, bridging the gap between nutritional physiology and ecosystem modeling to better inform the management of global forage fish stocks. 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

Background: Galectin-10 (Gal-10), the main constituent of Charcot–Leyden crystals, is a recognized marker of eosinophilic inflammation, yet its role in nasal mucosal remodeling in Seasonal Allergic Rhinitis (SAR) remains poorly defined. Methods: Gal-10, IL-5, MUC5AC, and IFN-γ were analyzed in Nasal lavage (NL) samples from children with SAR by ELISA. Unsupervised clustering and discriminant analyses were applied. The functional effects of Gal-10 were investigated ex vivo using a 3D epithelial–mesenchymal trophic unit (EMTU) model stimulated with NL containing high, low, or depleted Gal-10 levels. EMT (epithelial–mesenchymal transition) markers (vimentin, E-cadherin, SNAIL1) and MUC5AC secretion were assessed by immunohistochemistry, Western blot, and ELISA. Results: Gal-10 levels in NL positively correlated with IL-5 and MUC5AC and inversely with IFN-γ. Clustering analysis identified distinct SAR endotypes, with Gal-10 showing the highest discriminative power. In the 3D EMTU model, high Gal-10 NL induced increased vimentin and SNAIL1 expression and enhanced MUC5AC secretion, effects attenuated after Gal-10 depletion. Conclusions: Gal-10 is associated with Th2-type inflammation, mucus hypersecretion, and early epithelial–mesenchymal transition in pediatric SAR, supporting its role as a mediator of nasal mucosal remodeling and a potential therapeutic target Full article

Amphibians are among the most threatened vertebrate groups globally, with over 40% of species at risk of extinction. However, a gap remains in understanding how to effectively develop and implement amphibian conservation strategies at local and global scales to minimize extinction risk. This review synthesizes multidisciplinary evidence to frame amphibian conservation as a priority not only for species preservation but for safeguarding ecosystem functioning and human well-being. Drawing on ecological, physiological, biomedical, and technological literature, we highlight the foundational roles amphibians play in various biomes: regulating invertebrate populations, mediating nutrient and energy flows, modifying physical habitats, and supporting biodiversity through trophic interactions. Their dual aquatic–terrestrial life cycles and highly permeable skin make them highly sensitive to environmental change, positioning them as bioindicators for ecosystem health. We further explore emerging tools and concepts such as environmental metabolomics, remote sensing, and citizen science for monitoring population trends and environmental stressors. Additionally, we discuss conservation challenges in relation to land-use change, climate disruption, invasive species, emerging diseases, and institutional underinvestment. We argue for the recognition of amphibians as ecological allies and the increased integration of amphibian conservation into broader frameworks such as ecosystem service valuation, climate resilience planning, and public health policy improvement. Finally, we identify key research gaps and suggest future directions to remedy these oversights, including the incorporation of traditional knowledge, socio-cultural engagement, and technological innovations for sustainable amphibian conservation. Realizing this vision will require globally coordinated, locally grounded strategies that fuse scientific insight, inclusive governance, and long-term investment—ensuring that amphibian conservation advances ecosystem stability and benefits both nature and society. Full article

Understanding trophic ecology is fundamental for the conservation of threatened species with specialist trophic strategies, such as the short-tailed chinchilla (Chinchilla chinchilla), a critically endangered rodent whose diet in the wild is poorly understood. This study presents the first integrated annual characterization of the dietary habits, trophic niche, and resource selection patterns of a high-Andean population. Plant availability was assessed, and dietary composition was analyzed via seasonal microhistological analysis of fecal samples. Diversity (Shannon-Wiener, H′), overlap (Schoener, PS), and resource selection (Manly’s selection index) metrics were calculated. The results indicate a diet of very low diversity (H′ < 0.1), stable throughout the year (PS > 0.99), and dominated (>77%) by grass Pappostipa frigida, with significant positive selection in all seasons. Shrub species, such as Adesmia frigida, were consistently avoided. This high degree of specialization reflects low functional plasticity and highlights the high vulnerability of C. chinchilla to environmental changes and habitat loss, underscoring that the conservation and restoration of P. frigida grasslands are imperative for the species’ survival. Microhistological methodology is confirmed as a key tool for identifying critical trophic relationships and supporting conservation plans based on essential resources. Full article

Fish communities undergo climate-induced shifts; it is crucial to study the trophic interactions of various fish species in order to understand the extent to which fish trophic niches overlap and the degree of competition between them. We investigated the food web structure, feeding habits, and trophic positions of common fish in the subarctic Lake Imandra. Two methods were used: SCA (stomach content analysis) and SIA (stable isotope analysis). Perch (Perca fluviatilis) and whitefish (Coregonus lavaretus, large sparsely rakered morph) had similar trophic positions (TP = 3.69 ± 0.55 and 3.67 ± 0.55, respectively; p > 0.05); both species were generalists. The diet similarity (the index of relative importance of food items in stomach contents) of perch and whitefish was 48%, with aquatic insects (Trichoptera) being common items in both fish. According to carbon isotope values (δ¹³C), vendace (Coregonus albula), smelt (Osmerus eperlanus), and burbot (Lota lota) were more closely related with pelagic food sources (δ¹³C ranged from −27 to −25‰), whereas perch, whitefish, and ruffe (Gymnocephalus cernua) were more fuelled by benthic food web compartments (δ¹³C ranged from −24 to −21‰). The highest average nitrogen values (δ¹⁵N) were found in smelt and ruffe, 15.0 ± 0.7‰ and 14.2 ± 1.9‰, respectively. Perch and whitefish overlap significantly in their isotopic composition (δ¹³C and δ¹⁵N), demonstrating 36% overlap in the combined 40% ellipses (according to Stable Isotope Bayesian Ellipses in R) of the isotopic space. This study confirms the existence of distinct food competition between these two species in a subarctic lake. Full article

The Yangtze River Estuary is one of the most productive estuarine ecosystems in the western Pacific, supporting diverse fish communities that sustain ecosystem functioning. This study investigated the seasonal patterns and community structure of intertidal fish assemblages to provide a baseline for future habitat assessments. Seasonal surveys conducted from May to December 2024 recorded 47 fish species belonging to 10 orders, 18 families, and 37 genera. Cyprinidae contributed the highest proportion of species (42.55%). Dominant species identified by the index of relative importance-including Cynoglossus gracilis, Coilia nasus, and Lateolabrax japonicus—characterized the seasonal assemblage structure. The assemblages were dominated by sedentary species (82.98%), and demersal fishes accounted for 48.94% of the species. Carnivorous taxa (57.45%) dominated the trophic guilds. Diversity indices indicated moderate diversity (H′: 1.797–2.441; C: 0.788–0.892; D: 1.724–4.770; J′: 0.6318–0.8642). Similarity analysis based on Jaccard’s index (Cj) showed the highest overlap between spring and summer (Cj = 0.5000) and the lowest between spring and winter (Cj = 0.1714); spring–autumn and summer–autumn were approximately 0.30, indicating moderate overlap. ABC curves yielded slightly negative W values in spring and summer and positive values in autumn and winter (W = −0.066 to 0.276), indicating moderately disturbed assemblages in spring–summer and less disturbed communities in autumn–winter. Overall, the study provides a seasonal baseline of intertidal fish assemblages in nearshore waters of the southern branch of the Yangtze River Estuary, which can provide useful ecological context for future assessments of nursery and feeding habitats of juvenile Chinese sturgeon (Acipenser sinensis). Full article

Τhe trophic ecology of Pterois miles in the Mediterranean Sea was performed by integrating data from stomach contents (SCA) and stable isotopes analyses (SIA), based on samples caught off the Greek island of Rhodes, SE, Aegean Sea, for the first time. This combined approach provides information on ingested (SCA) and assimilated (SIA) food and thus allows for the depiction of predator–prey relationships. Specimens of devil firefish, including both juveniles and adults (total length of analyzed specimens spanned from 11.40 to 31.50 cm), were collected from different sites around Rhodes. Their diet consisted of bony fish, cephalopods, crustaceans, and gastropods. The δ¹³C and δ¹⁵N values ranged from −18.0 ‰ to −14.4 ‰ and from 7.2 ‰ to 9.2 ‰, respectively. SIA data allowed for the estimation of the trophic position of devil firefish from Rhodes Island, which showed a mean value of 3.1 ± 0.6 and confirms that the species primarily relies on a benthic baseline. Further, our isotopic values approach those obtained in North Carolina and Bermuda, confirming its role as a mesopredator in the Mediterranean benthic food webs. Although preliminary, such results can provide an important baseline for future investigations on the species and the potential impact on the Mediterranean food webs. Full article

Fast-running flies (Diptera: Hybotidae) play an important role as predators in agricultural landscapes. This semi-field study examined the effects of pesticides on Hybotidae communities and their role in natural pest control in three winter wheat management systems (organic, conventional, and hybrid (no chemical synthetic pesticides with optimized use of nitrogen fertilizers)) in Brandenburg, Germany. To evaluate the impact of management practices, sweep netting and eclector trapping were carried out over three years (2020–2022) at the plot scale. Hybotidae abundance fluctuated across the management systems and collection methods, with no consistent trend linked to pesticide use. However, an increase in the abundance of Hybotidae in 2022, especially in eclector trapping, indicated that year-to-year fluctuations were pronounced and likely driven by environmental factors, such as climate and soil moisture, rather than management practices. The community structure showed a high degree of similarity among all management systems, but species diversity displayed pronounced interannual variation, suggesting complex ecological interactions. Sweep netting collections indicated positive predator–prey associations in every management system, pointing to a generally stable trophic structure. The study also demonstrates that using multiple insect collection methods is crucial for accurately assessing insect diversity and abundance. Further research is needed to fully understand species diversity, predator–prey dynamics, and their implications for sustainable agriculture. Full article

The trophic status of coastal environments is largely controlled by nutrient inputs, particularly nitrogen and phosphorus, whose excess may lead to eutrophication. The northern Adriatic Sea has historically been affected by these processes, with notable impacts on water quality. This study analyses a time series (2015–2024) collected at six offshore sites in the Gulf of Trieste within the Marine Strategy Framework Directive (MSFD) Descriptor 5. Dissolved Inorganic Nitrogen (DIN) showed marked spatial variability, with 19.9% of samples exceeding the threshold of 6.85 µM. Phosphate concentrations were low (mean 0.17 µM), indicating strong P-limitation (mean N:P ratio = 277). Chlorophyll a concentrations (mean 0.9 ± 0.1 µg L⁻¹) reflected oligotrophic conditions, although 17% of samples exceeded 1.5 µg L⁻¹. Time-series analyses revealed a significant warming trend (+0.1 °C yr⁻¹; p = 0.022) and a significant decrease in chlorophyll a (p = 0.038), while no significant trends were observed for nutrients, dissolved oxygen or TRIX. TRIX values (0.8–6.9) indicated overall good to high ecological status. A trophic–hydrological gradient highlighted the positive influence of river inputs and precipitation on nutrient availability and trophic conditions. These results provide a solid quantitative baseline for MSFD assessments and underscore the role of hydrological and meteorological forcing in shaping trophic variability in the Gulf of Trieste. Full article

Vegetation degradation in the alpine meadows is becoming increasingly severe under global change, with species loss frequently linked to changes in plant functional groups (PFGs). Changes in PFGs alter plant-derived carbon inputs, which significantly influence soil organic carbon (SOC) sequestration and soil communities. However, the impact of specific PFG removal on soil carbon fractions and nematode trophic groups remains underexplored. In this study, above-ground removal of PFGs was carried out for five consecutive years in the Qinghai–Tibet Plateau alpine meadow, with five treatments: (1) no removal of PFGs (CK); (2) keep non-legume forbs (remove graminoids and legumes, Forbs); (3) keep graminoids (remove legumes and non-legume forbs, Graminoids); (4) keep legumes (remove non-legume forbs and graminoids, Legumes); (5) remove all PFGs (All-plants-removed). Root properties, nematode community, and soil carbon fractions were measured. We found that the Graminoids treatment significantly increased root biomass, whereas the All-plants-removed treatment led to a significant decrease. Nematode abundance was highest under the Legumes treatment, primarily due to increased omnivores-predators. Meanwhile, the soil particulate organic carbon (POC) varied significantly between PFG types, being the highest in the Forbs and CK treatments. Correlation analysis revealed a significant positive relationship between SOC and bacterivore abundance, suggesting that higher SOC enhances bacterivore populations and subsequently influences carbon cycling. We conclude that PFG removal alters soil nematode community structure and POC, underscoring the role of PFGs in below-ground biodiversity and soil carbon sequestration. Full article

The widespread dispersion of microplastics (MPs) has been recognized as a pervasive and persistent environmental contaminant in worldwide freshwater ecosystems, and although relative studies have skyrocketed, there are still significant knowledge gaps in areas like southern Europe. This study assesses the microplastic pollution in seven Greek inland aquatic ecosystems which vary in morphology, trophic status, and anthropogenic pressure. Surface and vertical samples were taken with 200 μm plankton nets. MPs were present in all samples, with fibers being the dominant form, having an abundance range between 0.47 and 149.4 items/m³ with fragments between 0.08 and 9.17 items/m³. Fibers and fragments had greater abundance in the vertical than in the surface samples. There were no significant abundance differences between lakes and lagoons, and among the sampling sites in each ecosystem. Blue and transparent were the colors that prevailed, and most of the fibers and fragments were smaller than 1 mm. Four types of MPs were recorded, with PET (polyethylene terephthalate) being the most frequent. The use of the novel Relative Anthropogenic Pressure (RAP) index resulted in positive correlations between certain sociological parameters and the microplastics’ abundance, efficiently reflecting the impingement of human populations on the inland aquatic ecosystems. Full article

The longevity, site fidelity, and trophic position of freshwater turtles have led to their increasing recognition as useful bioindicators of environmental contamination. Mauremys leprosa (n = 25) shells from a Northern African wetland system were examined for trace element concentrations in order to assess shell composition as a non-invasive biomonitoring method. Micro x-ray fluorescence (μXRF) method was used to measure the shell concentrations of 17 elements, including Ca, P, Fe, Zn, Mn, Sr, Pb, Sb, and Al. As would be expected from the structural composition of bony tissues, calcium and phosphorus were the predominant constituents. In addition to bulk concentrations, micro-XRF elemental mapping revealed heterogeneous spatial distributions of essential and toxic elements within the shells, providing visual evidence of bioaccumulation patterns and supporting the use of shells as non-invasive bioindicators. There were statistically significant sex-related differences in the levels of trace elements, with males exhibiting higher concentrations of Mg, Mn, Sb, Pb, and Al (p < 0.05). Spearman correlations revealed strong associations between certain shell elements (e.g., Fe, Mn, Ti, Zn) and morphometric parameters. Comparisons with environmental samples (water and sediment) showed moderate to strong correlations, particularly with sediment metal concentrations, supporting the utility of shell chemistry as an integrative exposure matrix. Nonetheless, there were significant percentages of censored or missing values for certain metals (Cu, Ni, and As). This study emphasizes how viable turtle shells are as non-lethal markers of bioaccumulation and stresses how crucial it is to take environmental matrices, element-specific variability, and sex into account when assessing contamination. Longitudinal monitoring, physiological biomarkers, and isotopic analysis should all be used in future studies to bolster the causal relationships between environmental exposure and turtle health. Full article

The majority of research on food webs has focused on temperate lakes, and little is known about the food web of lakes in polar regions. Subarctic lakes are particularly sensitive to climate change, which affects their stability. Therefore, the trophic structure of the food web in such lakes was considered as the object of this study. We studied a clear-water oligotrophic lake located in the subarctic region of Eurasia, specifically in northern Karelia and the White Sea coast of Russia. The study examined both open water periods (summer–autumn) and ice-covered periods (winter–spring) in this lake. Stable isotope analysis of carbon (¹³C/¹²C ratio or δ¹³C value) and nitrogen (¹⁵N/¹⁴N, δ¹⁵N) in producers and consumers was applied and revealed significant seasonal variations in the structure of the food web. The results indicate the presence of both pelagic and littoral/benthic food web compartments, with a notable contribution of autochthonous carbon derived from benthic sources. Omnivorous fish (perch, Perca fluviatilis; vendace, Coregonus albula; nine-spined sticklebacks, Pungitius pungitius) and some benthic invertebrates (mayfly, Ephemera vulgata; bivalves, Sphaerium corneum) had intermediate δ¹³C values, integrating these compartments by obtaining resources from both. Planktonic invertebrates had significantly depleted ¹³C, with the lowest δ¹³C value reaching −41.7‰, indicating an important contribution of methane-derived carbon. The study also revealed close trophic relationships between lake invertebrates and cyanobacteria, namely with planktonic Dolichospermum lemmermannii and benthic Phormidium sp. Seasonal changes in δ¹⁵N values and in trophic position have been observed among predacious omnivorous fish and crustaceans (amphipods, Gammaracanthus loricatus, and copepods, Cyclops scutifer), which are capable of a generalist feeding strategy depending on food availability. Using the example of this lake, it can be concluded that polar lake ecosystems are characterized by different seasonal intakes of allochthonous organic carbon from wetland catchment (humic compounds) and nitrogen because of nitrogen fixation in the air by cyanoprocaryotes. Alternative energy sources, such as carbon derived from methane, can also contribute to the energy balance of lake ecosystems. This study contributes to our understanding of energy flow and connectivity between producers and consumers in high-latitude lakes. Full article

Understanding the feeding mechanisms and interspecific coexistence of sharks is crucial for effective conservation. This study conducted stable isotope analysis on muscle and liver samples from 449 individuals of eight common bycatch shark species collected via bottom trawling in the northern South China Sea (NSCS). Results revealed significant differences in δ¹³C and δ¹⁵N values among species and tissue types. Scoliodon laticaudus exhibited the highest trophic position (TP_muscle = 4.60 ± 0.33; TP_liver = 4.53 ± 0.29), while Apristurus platyrhynchus had the lowest (TP_muscle = 2.97 ± 0.44; TP_liver = 2.75 ± 0.53). Muscle and liver isotopic signals were consistent, but δ¹³C differences indicated distinct carbon sources, with Carcharhinus sorrah linked to deep-sea organic matter and S. laticaudus to coastal inputs. Significant correlations between δ¹³C/δ¹⁵N and body length in A. platyrhynchus and Cephaloscyllium fasciatum suggest ontogenetic shifts in diet and habitat toward deeper waters. Trophic niche analysis using corrected standard ellipse area (SEAc) showed Halaelurus burgeri with the widest trophic niche (SEAc > 1.7‰²), reflecting a broad diet, while C. fasciatum had the narrowest (SEAc < 0.3‰²), indicating specialized feeding. Additionally, H. burgeri and C. sarawakensis exhibited significant niche differentiation, reducing interspecific competition, whereas C. fasciatum and Squalus megalops showed high niche overlap, suggesting intense resource competition. The narrower liver niche of C. sarawakensis may reflect recent habitat constriction due to bottom trawling. This study elucidates the feeding ecology and habitat resource utilization of NSCS sharks, providing a scientific basis for effective conservation strategies for shark populations in the region. Full article