Aquatic Sciences最新文献

Local environmental and spatial processes, in combination with surrounding land use, are considered key interacting mechanisms shaping the structure of aquatic communities. Traditional approaches have quantified the effects of environmental and spatial processes on community organization by focusing on its taxonomic facet only. The inclusion of functional traits, however, holds the potential to improve our ability to predict community responses to environmental filters, both biotic and abiotic, and major underlying spatial gradients. In this study, we evaluated the relative influence of local environmental conditions, land use and space on the taxonomic and functional composition of zooplankton communities across 47 ponds located in northwestern Spain. Variation partitioning showed that functional traits better reflected both local environmental and spatial effects on zooplankton community variation than species composition alone. Local environmental constraints were the primary source of community variation, although spatial effects also had a significant effect. However, large fractions of variation remained unexplained, a finding that is consistent with the prevalence of idiosyncratic and random stochastic events that have an effect on community structure. Land use did not play a significant role in explaining species distribution or functional trait variation, suggesting that changes in local environmental conditions may have masked the effects of land use on zooplankton community organization.

The accurate assessment of ichthyoplankton (fish eggs and larvae) diversity is frequently impeded by their small size and complex morphology. To enhance taxonomic resolution, we utilized a rigorous in silico pipeline to design and confirm the efficacy of two novel primer sets targeting the cytochrome c xidase subunit I (COI) gene. The first set, universal primers (UP), demonstrated broad taxonomic utility, achieving up to 90% successful amplification in target phyla and 75% in nontarget phyla. The second set, Chordata-specific primers (CSP), was engineered for precise targeting of this phylum, and successfully applied to an ichthyoplankton case study in Vietnam, yielding a high amplification rate of 94.41%. Comparison with traditional morphological methods showed that molecular identification, enabled by these optimized markers, increased the capacity for species detection, especially for specimens with underdeveloped features. While incomplete reference databases occasionally constrained this resolution, the study strongly advocates for the integration of genetic and morphological approaches for robust species assessment. These new COI markers offer a powerful resource for biodiversity research in complex ecosystems, holding substantial implications for conservation and fisheries management.

Organic phosphorus (P) is the predominant form of sedimentary P in many lakes; however, its role in P exchange at the sediment–water interface remains difficult to quantify. We investigated the dynamics of the organic P pool and its constituent species and their contribution to P release from the upper reactive sediment layer of a deep mesotrophic boreal lake. Using the non-carbonaceous mineral component as a reference, we estimated a 25% reduction in organic matter (OM) and a 63% decline in organic P (on the basis of sequential extraction) by 13-cm sediment depth compared with the surface. P release from the organic P pool was estimated to be at least four times higher compared with the combined pool of inorganic aluminum-, iron-, and calcium-bound P. Solid-state ³¹P nuclear magnetic resonance (NMR) spectroscopy revealed that the predominant organic P species in the studied sediment were monoester phosphates and DNA-associated P. We propose that estimating the temporal dynamics of OM and organic P pools in upper reactive sediment layers can be refined by referencing concentrations to a relatively stable sediment component, such as the mineral fraction, under the assumption of consistent inputs of both organic and mineral matter during the time span over which the studied sediment layer accumulated.

Lakes are important sources of methane (CH₄) to the atmosphere, but these water bodies are currently considered the most uncertain components of the global CH₄ budget. Here we propose a time-integrated air sampling approach to characterize the atmospheric CH₄ concentration in the periphery of a lake, as an indicator of its CH₄ emission behavior. Air samples were collected using vacuum vessels equipped with a shutoff valve and flux restrictors deployed at central buoys and peripheral sites to determine atmospheric CH₄ concentrations (AM). The AM measured at peripheral stations (AM_P) showed strong-to-moderate linear relationships with those from central buoys, as well as with CH₄ fluxes at the water–air interface (MF), particularly under predominant wind directions and low calm frequencies. Even under less favorable conditions, such as high calm or variable wind directions, the accumulated signal remained coherent, demonstrating the ability of this strategy to integrate over time and detect consistent CH₄ patterns. Multiple regression analysis showed that AM_P considering only downwind periods was significantly explained by MF and the frequency of calm events, indicating that peripheral monitoring integrates both emission intensity and atmospheric transport. The relative variation in AM_P, interpreted in the context of wind-driven variability, allows discrimination between weak and strong CH₄ emission regimes in lentic systems, with larger AM_P enrichments corresponding to periods of higher emissions. Compared with the static chamber technique, commonly used to estimate CH₄ fluxes, this approach is less labor-intensive and more easily extrapolated to the simultaneous study of multiple lakes or large-scale assessments.

Plastics are found ubiquitously in all ecosystems. The rapid urbanization of cities has resulted in high anthropogenic activities leading to the accumulation of domestic plastics in freshwater habitats. This field-based investigation of substrate-dependent periphytic microalgal diversity on natural and plastic substrates demonstrated that variations in key physicochemical parameters including electrical conductivity (120 ± 10 to 1499.33 ± 47 µS/cm), nitrate (8.64 ± 0.10 to 256.88 ± 1.95 µg/L), phosphate (16.62 ± 0.20 to 64.47 ± 1.28 µg/L), and potassium (0.87 ± 0.10 to 29.31 ± 0.11 µg/L) strongly influenced the composition and diversity of periphytic microalgal communities. The Shannon–Wiener index indicated high green algal richness (H′ = 3.067) and diatoms (H′ = 2.431) in the peripheral zone, whereas cyanobacteria (H′ = 2.625) were dominant in the contaminated urban zone. These findings highlight the ecological plasticity of microalgae in producing biofilms and forming communities on specific substrates. The periphytic potential of 14 microalgal species was confirmed through laboratory-based growth assays, demonstrating that plastic substrates provide suitable physical support for attachment and sustained growth. Species belonging to the genera Chlorococcum, Uronema, Cocomyxa, Phormidium, Nostoc, Oscillatoria, Nitzschia, and Navicula exhibited substrate specificity toward High-Density Polyethylene (HDPE), Low-Density Polyethylene (LDPE), and PolyVinyl Chloride (PVC), enabling prolonged survival on these polymer surfaces. In summary, epiplastic microalgal diversity involves interactions with plastic substrates, which have the potential to drive and shift the community structure of freshwater ecosystems in response to physiological and chemical parameters, highlighting their ecological significance and implications for freshwater ecosystem health under increasing anthropogenic pressures.

Photos and video footage can provide useful insights into the seasonal dynamics of aquatic and riparian ecosystems and can be a source of effective visuals for outreach. Here, we introduce the use of timelapse photography and underwater video to document the changes in seasons, phenology, water levels, and the use of seasonal off-channel habitats by spring spawning fishes in an inland river delta in Norway (61°N). Hourly photos and continuous video footage from a 7-month period in 2024 were condensed into a 3-min film, showing the dynamic interplay between weather, water, and fish. Timelapse photography represents a potentially useful method for ecologists interested in data collection using optical methods, such as measuring the extent, timing, and availability of seasonal habitats for fishes, whereas underwater video can document the presence of fish species. In combination, underwater video and timelapse photography can link the visual representation of life above and below the surface and offer a comprehensive visual aid for communicators interacting with broad audiences.

This study investigates the long-term changes in composition and functional role of benthic bivalve mollusks in the upper Neva Estuary (Neva Bay, eastern Gulf of Finland) on the basis of field data collected in 2022–24 and historical records spanning more than four decades. Despite sustained anthropogenic pressure, including port development and urban wastewater discharge, bivalves remain dominant in zoobenthic biomass and organic matter (OM) processing by benthic invertebrates. Currently, large unionids prevail, particularly in the southwestern bay, where they are associated with elevated phytoplankton production and contribute to pelagic–benthic coupling. In contrast, the role of small sphaeriids—once dominant in the 1980s and crucial for an estuary’s self-purification—has declined sharply. This shift reflects a transition from an allochthonous OM source, driven by improved wastewater treatment and climate-related increases in primary production. In 2022, the invasive Dreissena polymorpha was recorded in the Neva Bay for the first time, likely indicating changing trophic conditions that now support additional filter-feeding species. Our findings highlight the importance of historical baselines for understanding ecosystem change and underscore the overlooked functional value of small-bodied taxa such as Sphaeriidae, which can drive OM mineralization and secondary production. Finally, the study demonstrates the potential of using bivalves—especially metabolically active, pollution-tolerant sphaeriids—as a nature-based solution for water purification in urbanized estuaries. These insights are critical for designing effective management strategies in systems undergoing similar trophic and hydrological transformations.

Dissolved organic matter (DOM) is the largest reactive organic C pool and plays a significant role in different biogeochemical processes in river ecosystems. In recent decades, climate change and anthropogenic activities (e.g., reservoir construction and changes in land-use types) have obviously influenced the quality and quantity of DOM. However, the responses of DOM chemistry in rivers to both seasonal alteration and land-use types remain poorly understood. Here we investigated the influence of seasonal alteration and land-use types on the concentration, compositions, and sources of DOM in the Luohe River, one of the largest tributaries of the Yellow River Basin in China, using ultraviolet (UV)–visible and three-dimensional fluorescence excitation–emission matrix (3D-EEM)-parallel factor analysis (PARAFAC). The results showed that the concentration of dissolved organic carbon (DOC) in the Luohe River during the summer (8.40 ± 2.85 mg L⁻¹) was significantly higher than that during both the spring (5.36 ± 1.00 mg L⁻¹) and autumn (4.24 ± 1.33 mg L⁻¹). The absorption properties of DOM exhibited the presence of DOM composition with high hydrophilic substances and low molecular weight. The fluorescence index showed the source of DOM with both autochthonous and allochthonous sources. Three types of humic-like components (C1 + C2 + C4, Em. > 380 nm) and one type of protein-like component (C3, Em. < 380 nm) were identified using the PARAFAC model. The optical properties of DOM exhibited significant seasonal variation. The partial least squares structural equation modeling (PLS-SEM) analysis indicated that the direct effects of land use on protein-like component and humic-like component in spring were 0.2286 and −0.2593, respectively, and those in summer were 0.2241 and −0.4824, respectively. In addition, land use indirectly influenced the protein-like component by changing DOM origin (0.3455) and nutrients (0.1205) in spring, and affected the humic-like component by changing DOM origin (−0.3417) and nutrients (−0.1184) in spring. These findings suggested that both seasonality and land-use types were key drivers for the DOM sources and compositions, which are useful to understand the vital role of DOM in the biogeochemical cycle, and can provide a theoretical foundation for water quality protection.

The presence of non-native species is one of the primary drivers of biodiversity loss, disrupting the ecological processes that sustain complex interactions among organisms. Their expansion in freshwater environments is an alarming phenomenon, demanding continuous investigation to map spatiotemporal patterns, assess ecological impacts, forecast future scenarios, and identify strategic areas for intervention to prevent uncontrolled invasions. In the Triângulo Mineiro and Alto Paranaíba (TMAP) region of Minas Gerais, Brazil, non-native species pose an increasing threat. In freshwater systems such as the upper Paraná River basin, the introduction of non-native species is known to alter ecological interactions, disrupt trophic networks, and compromise the persistence of native ichthyofauna. The major tributaries of this basin in the TMAP region, the Paranaíba and Grande rivers, are potentially facing these significant ecological threats. This study investigates the occurrence patterns and spatiotemporal distribution of non-native fish species in the TMAP rivers over the past five decades. We compiled an inventory of non-native fish species in the Paranaíba and Grande rivers, whose tributaries traverse the TMAP, and analyzed geospatial patterns to identify rivers with the highest spatial densities and the temporal trends in species expansion over time. Our inventory revealed 45 non-native fish species present in TMAP rivers, with particularly high occurrences of Cichla spp. (peacock bass), Oreochromis niloticus (Nile tilapia), and Poecilia reticulata (guppy), all characterized by wide spatial distributions and high densities. Our analysis also identified invasion hotspots in key tributaries of the Paranaíba and Grande rivers. Among them, the Araguari, Uberabinha, and lower Tijuco (Paranaíba), and the Claro and São João (Grande) emerged as epicenters of invasion in the TMAP. Although historical records show fluctuations in the abundance of non-native species over the past five decades, a marked trend of rapid expansion, particularly since the 2000s, has been observed. In light of this scenario, conserving the native ichthyofauna of the TMAP requires effective control strategies for non-native species and sustained scientific monitoring in critical areas, especially in the identified invasion hotspots of the Paranaíba River Basin.

Food webs in small, forested streams rely heavily on litterfall for energy, but the role of fruitfall remains understudied. We conducted a field experiment comparing the decomposition of two fruits with hard pericarps (Astrocaryum vulgare and Bactris gasipaes) and five with soft pericarps (Genipa americana, Mangifera indica [non-native], Mauritia flexuosa, Syzygium cumini [non-native], and Talisia esculenta). Whole and cut fruits were incubated in fine- and coarse-mesh litter bags for 62 days to simulate undamaged and vertebrate-damaged fruitfall. We expected that fruits with thin pericarps or cut fruits would decompose faster than hard-pericarp fruits, because both macroinvertebrates and microbes could access the soft tissue. This expectation was partially confirmed; cut fruits generally decomposed faster and supported higher invertebrate richness, while hard-pericarp fruits resisted decomposition regardless of treatment. In the whole fruit experiment, 785 invertebrates were recorded, dominated by Endotribelos (Diptera: Chironomidae; 96%). Abundance was highest in S. cumini and lowest in A. vulgare, with higher values in coarse-mesh bags. A. vulgare had 17× more remaining mass than other fruits, with no mesh-size effects, indicating strong resistance to decomposition. In the cut-fruit experiment, 2715 invertebrates from 14 families were recorded, with A. vulgare again showing the highest remaining mass (34× more than other species). The remaining mass did not differ between mesh types, emphasizing microbial activity. Richness was highest in G. americana and A. vulgare and lowest in M. indica. Intact pericarps limited invertebrate access, as richness increased in cut fruits. Both whole and cut fruits can complement leaf litter as an energy source in Amazonian stream food webs.