Aquatic Sciences最新文献

Predicting fish trajectories in fishways is potentially useful for fishway design and optimization. However, few models are able to address the prediction errors associated with traditional fish trajectories. A hybrid model combining a convolution neural network (CNN) and gated recurrent units (GRUs) can successfully integrate hydraulic and fish movement features, resulting in lower prediction errors. We therefore conducted fish swimming and flow simulation experiments in the laboratory to obtain fish movement and hydraulic environmental features such as the x-coordinate, y-coordinate, speed, angle, velocity, vorticity, and turbulent kinetic energy of Schizothorax wangchiachi in a fishway. We then established a fish trajectory dataset on seven hydraulic features and divided it into two sets: a training and a test set, respectively. We ran the hybrid CNN-GRU model to determine the optimal hyperparameters through comparative experiments and then performed a single-step and multistep trajectory predictions to verify the accuracy by inputting the test set into the trained model. Our results showed that, compared with the multilayer perceptron, CNN, recurrent neural network, long short-term memory, and GRU models, the proposed CNN-GRU model achieved superior performance in terms of both the x- and y-coordinate predictions. Specifically, it resulted in reductions in the mean absolute error, root mean square error (RMSE), and mean absolute percentage error, along with an increase in the coefficient of determination (R²). As the prediction time step increased, the prediction errors for all of the models also increased; however, the CNN-GRU model always resulted in the lowest prediction errors. Our results suggest that the proposed CNN-GRU model meets the requirements for predicting fish trajectories in fishways and serves as a valuable tool for the design and optimization of fish passage facilities in regulated river systems.

Lake Geneva (Léman), the largest lake in Western Europe, is a vital freshwater ecosystem that supports a range of essential services, including water supply, fisheries, navigation, and recreational activities. However, like many other freshwater systems, it faces numerous threats that jeopardize its ecological integrity. These threats not only endanger the lake’s biodiversity but also impact the ecosystem’s overall functioning and the services it provides. One potential significant threat is the occurrence of algal blooms, particularly those involving toxic species such as pelagic cyanobacteria. These blooms can disrupt vital ecological processes and pose serious risks to animal and human health, local fisheries, and the regional economy. This article reviews the history of algal blooms in Lake Geneva over the last 70 years, aiming to identify the species involved and the services impacted, examine the common and unique factors driving these proliferations, and propose potential future scenarios in the context of both local and global changes. The ultimate goal is to inform effective management strategies to mitigate the impacts of these blooms.

The Golden Mahseer Tor putitora, is an endangered, migratory freshwater fish of ecological, commercial and cultural importance that inhabits foothill rivers in the Himalayas. This transboundary fish occurs across Bangladesh, Bhutan, India, Pakistan and Nepal, and is facing increasing pressures from multiple stressors including resource extraction and the rapid development of hydropower dams. The DRIFT ecosystem-based model was used to guide Environmental Flows assessments of a several hydropower dams in this region, with Golden Mahseer as a key indicator. Countless other hydropower dams continue to be developed in Golden Mahseer habitat without sufficient assessment of their impacts on this flagship species, thereby threatening its long-term survival. This study uses the decades of iterative work encapsulated in three DRIFT ecosystem-based models to calculate the contributions of individual causal mechanisms hypothesized to influence Golden Mahseer abundance in response to variations in natural resource management and hydropower operations. The resulting ranking of contributing mechanisms showed that the major mechanisms predicted to drive future change in Golden Mahseer abundance were those related to unsustainable levels of fishing, hydropeaking and barriers to migration. These impacts were assessed to be individually severe and cumulative such that focusing on one aspect without due consideration of the others was ineffective. On the basis of these findings five rules for hydropower are proposed to support Golden Mahseer conservation.

This study explores the primary drivers influencing dissolved inorganic carbon (DIC) dynamics in the intermittent streams of the Munnar Critical Zone Observatory in the Western Ghats, India. Seasonal sampling was conducted in seven small hilltop streams, their downstream large streams, and groundwater from surrounding areas. Stream waters were oxygenated (dissolved oxygen percentage = 30–136), favouring aerobic remineralisation of organic matter within the streams. DIC concentrations varied seasonally, ranging from 6 to 2838 µM in small streams and 44 to 2165 µM in large streams, with HCO₃⁻ identified as the dominant DIC species. In intermittent streams, DIC levels were primarily regulated by carbonate rock weathering, as indicated by ΔDIC/ΔCa²⁺ ratios, with evidence for enhanced weathering during the post-monsoon period. DIC concentrations were largely independent of stream size. Analysis of concentration-discharge relationships revealed chemostatic behaviour during the monsoon and chemodynamic patterns during the dry season. Isotopic analysis (δ¹³C-DIC) in large streams during the post-monsoon period highlighted significant DIC inputs from aerobic organic matter respiration, driven by terrestrial C₃ plant material and sewage. These findings underscore the complex interplay of hydrological, geochemical, and biogeochemical processes governing DIC dynamics in tropical mountainous catchments. Continuous, high-resolution monitoring is recommended to further elucidate the factors controlling stream water DIC in these sensitive ecosystems.

Alpine landscapes are being rapidly transformed, being fueled by ongoing environmental change and glacial recession. Glacial recession has caused emergence of new stream channels as well as changes in the physico-chemistry of surface waters embedded in glaciated landscapes. Our research examined temporal changes in the physico-chemistry and macroinvertebrates during (1) the elongation of a glacial stream and (2) among different alpine lake networks (inlets, outlets, and downstream sites) over the last 24/25 years. The glacial stream study revealed rapid colonization of the emergent stream following deglaciation as well as colonization of previous sites by novel taxa (some from lower elevations). The water physico-chemical data revealed changes in the habitat template of sites over the study period, especially in respect to water temperature and turbidity. The lake network study also showed changes in macroinvertebrate assemblages over the observation period as well as differences on the basis of lake location and type. Here, lake outlet water temperatures increased more over time at northern than southern Alpine lakes. Further, kryal and rhithral lake outlets differed in response regarding water physico-chemistry and macroinvertebrate diversity. Both studies highlight the importance of monitoring alpine surface waters for better understanding of abiotic and biotic responses to landscape transformation resulting from ongoing and rapid environmental change, especially in relation to glacial recession.

Migratory fish species are highly vulnerable to stream fragmentation. Potamodromous golden perch (Macquaria ambigua) inhabit the barrier-laden Murray–Darling Basin (MDB), Australia’s largest river system, and its lifecycle includes a requirement for uninterrupted stretches of flowing water habitat. Owing to these barriers, large-scale connectivity in many regions is limited to periods of high flow events that facilitate barrier drown-out. We undertook a 3-year (2021–2024) study using telemetry to quantify the movements of 150 adult golden perch from the Barwon–Darling River over a period that encompassed numerous high flow events and flooding. Approximately 75% of tagged golden perch undertook movements > 50 km, with > 90% of movements in an upstream direction, extending up to 1500 km and associated with increased river discharge. Tributary entries were detected on multiple occasions, with an apparent preference for specific tributaries. Ten fish migrated > 1000 km upstream across multiple flow events. The results of this study (1) highlight the importance of the Barwon–Darling River and tributaries as a key migration conduit for adult golden perch, (2) demonstrate that multiple flow events are required to achieve large-scale dispersal and (3) provide quantitative flow-movement relationships that can be used to support inter-regional management actions. These management actions might include barrier removal, the construction of fishways and protection of tributary–mainstem flow events.

Aquatic ecosystems worldwide are under severe pressure from climate change. However, studies on climate change effects on stream biota mainly focus on indicator or vulnerable species, leaving unanswered how more resilient species cope with elevated temperatures and drought, and the long-term consequences for these populations. This study therefore aims to determine the long-term population responses of a common, apparently less sensitive, aquatic insect to climate change-induced heat and drought and to unravel the mechanisms underlying its persistence under such harsh conditions. The long-term population responses of the stonefly Nemoura cinerea (Plecoptera: Nemouridae) to heat and drought are assessed by linking antecedent seasonal meteorological data to 42 years of abundance data from streams in the Netherlands. The mechanisms of resilience that enable N. cinerea to withstand these stressors during its transition from juvenile to adult stages are studied in a microcosm experiment on late-stage nymphs. Results from modelling long-term population responses to antecedent climate variables and observed responses in experimental microcosms show that temperature, and to a lesser extent drought, have negative impacts on N. cinerea fitness and abundance. Nonetheless, the species’ abundance has still modestly increased over the last four decades. This discrepancy may result from general water quality improvements, an increase in intermittent sites or altered biotic interactions due to increased intermittency, reducing competition and predation by less resilient species. Thus, even species apparently less sensitive to climate change experience harmful effects, though these appear to be offset by altered biotic and abiotic conditions.

As land use pressures intensify across watersheds, understanding how landscape features affect stream water quality has become increasingly urgent for effective environmental management. By integrating hierarchical linear modeling (HLM) with geographically weighted regression (GWR), this study captures both broad-scale trends and localized spatial variability in the relationship between water quality (biochemical oxygen demand [BOD], total nitrogen [TN], and total phosphorus [TP]), land use, and watershed topography—addressing the limitations of traditional statistical models that assume uniform effects and overlook spatial hierarchy. Our findings indicate that urban and agricultural land use were positively associated with elevated BOD and TP concentrations, but that these effects were generally weaker in areas with steeper topography. BOD interacted significantly with watershed slope in both urban and agricultural areas, while TP showed a significant interaction only in agricultural watersheds. In contrast, TN showed no significant interaction with watershed slope, suggesting that nitrogen dynamics are primarily influenced by hydrological processes and land management practices rather than topography. These results highlight the importance of multilevel modeling in water quality assessments, demonstrating that watershed characteristics can amplify or constrain land use impacts on stream ecosystems. Covering the entire national territory of South Korea, our findings provide valuable insights for land-use planning, watershed management, and national water quality policies, supporting more effective and targeted pollution control strategies.

The Yiluo River, as the largest tributary downstream of the Xiaolangdi Reservoir in the middle reaches of the Yellow River, is a critical water conservation area within the Yellow River Basin. Understanding the trophic structure of macroinvertebrate communities across different land use types in this basin is essential for maintaining ecological balance and promoting sustainable development. In October 2020 and April 2021, field investigations were conducted in the Yiluo River Basin, collecting 11,894 macroinvertebrate specimens from river sections with varying land use types. These specimens represented 143 species across 4 phyla, 7 classes, 22 orders, and 75 families. The study revealed significant variations in aquatic environments among different land use types. Macroinvertebrate density and biomass were highest in agricultural land reach, followed by forest land reach, and lowest in building land reach. Dry plant weight was the most significant environmental factor influencing the structure of functional feeding groups, followed by land use types at both near- and far-affected areas. Building land reach had the most pronounced impact on functional feeding groups at near-affected areas, while forest land reach was most influential at far-affected areas. The trophic structure of macroinvertebrate communities was most complex in agricultural land reach, followed by forest land reach, and least complex in building land reach. This study provides scientific insights for land use planning and ecological conservation in the Yiluo River Basin.

Periphytic biofilms are rich in essential biomolecules, such as fatty acids (FAs), which play a critical role in supporting metabolic functions, including growth and reproduction. There has been increased interest in using biofilm FAs as a proxy for characterizing food webs, dietary sources, energy transfer, trophic relationships within ecosystems, and stream integrity assessment. However, new knowledge is required to validate the use of fatty acids as biomarkers of water quality. The objective of this study was to determine whether stream water quality degradation, in particular nutrient enrichment, affects the fatty acid composition of periphytic biofilms. We conducted a large-scale field study in 56 natural streams across Southern Quebec (Canada) in the summers of 2019 and 2020. The studied streams represented a water quality gradient as indicated by 5-year historical physico-chemistry data collected during the summer seasons. Overall, we did not observe strong relationships between nutrients or general water quality indices and periphytic biofilm fatty acid composition. However, proportions of total polyunsaturated FAs (PUFAs) and long-chain PUFAs (LC-PUFAs) gradually increased with nutrients and as a function of general water quality degradation. In addition, we observed decreased proportions of heterotrophic marker fatty acids and increased proportions of diatom marker fatty acids with increased nutrient concentrations and general water quality degradation. Our results suggest nutrient enrichment and water quality may shape stream periphytic biofilm fatty acid composition and thereby have an impact on the nutritional quality of the basal resources in natural streams. However, our findings suggest that, although periphytic fatty acid composition may represent a valuable tool to explore changes in the nutritional quality of basal resources as a response to stress, nutrient effects on FA composition may be masked or affected by interactions with multiple environmental factors. More research is thus required to effectively account for natural environmental variations before recommending and/or considering FAs as a complementary tool for routine stream biomonitoring.