Search Results (29)

Baiyangdian Lake, the largest freshwater lake in North China, plays a critical role in the ecological security of the Beijing–Tianjin–Hebei urban agglomeration. This study conducted systematic monitoring of Baiyangdian Lake from April 2023 to November 2024. Utilizing the Trophic State Index (TSI) and principal component analysis (PCA), we elucidated the impact mechanisms of extreme precipitation events on the water quality of shallow lakes. The results indicate that: (1) During the study period, Baiyangdian Lake exhibited moderate to severe eutrophication. The average total nitrogen (TN) concentration was 2.13 mg/L, exceeding the Class V threshold of the national surface water quality standard. The average total phosphorus (TP) concentration was 0.05 mg/L, far surpassing the recognized eutrophication threshold for freshwater lakes. (2) The average TSI was 49.6 ± 4.0, indicating the lake is in a transitional state from mesotrophy to eutrophy, with 64% of sampling sites classified as eutrophic. Nitrogen was identified as the primary limiting nutrient. (3) The 2023 extreme precipitation event exerted a significant three-phase impact on water quality: “dilution–legacy–restoration”. A clear dilution effect was observed from the pre-flood to the flood period (TN decreased from 1.52 to 1.04 mg/L). A pronounced legacy effect emerged post-flood, with the TN concentration sharply increasing to 4.22 mg/L in September 2023, the highest value recorded during the study. (4) PCA identified two major pollution sources: agricultural non-point source pollution (PC2, contribution: 25.4%) and domestic sewage/livestock farming (PC1, contribution: 27.6%). Correlation analysis further revealed that the flood event significantly altered the intrinsic relationships among parameters like nitrogen and phosphorus, reinforcing the dominance of agricultural non-point source pollution. (5) Source analysis suggests that external inputs are the primary contributors, while the internal loading from sediments is relatively limited. This study enhances the understanding of how shallow lakes respond to extreme climatic events and provides a scientific basis for lake management in the Beijing–Tianjin–Hebei region. Full article

Microcystin (MC) contamination of surface waters threatens ecosystems and public health. Nature-based solutions such as Multi-Soil-Layering (MSL) systems have been used for MC remediation. However, the biological mechanisms controlling MC degradation remain unclear. The present study investigates microbial community responses in two MSL systems with different clay contents (8% and 54%) exposed to MC-contaminated inputs (well water and eutrophied lake water). Samples were analysed before and after treatment using quantitative PCR (qPCR) to quantify the mlrA gene (encoding microcystinase) and its bacterial hosts. Next-generation sequencing (NGS) was used to assess microbial diversity, while the FAPROTAX database was used to predict functional characteristics. Results showed that MC was mainly adsorbed in pozzolan layers, while mlrA gene abundance and MC-degrading bacteria were higher in soil mixture layers. The presence of mlrA and associated bacteria was most pronounced in lake inflow samples, indicating intrinsic MC Biodegradation potential. Taxonomic analysis revealed dominant phyla including Proteobacteria, Actinobacteriota, Firmicutes, Chloroflexi and Bacteroidota. Functional analysis identified dominant traits such as chemoheterotrophy and aerobic metabolism. These findings provide new insights into microbial interactions in MSL systems and contribute to the optimisation of water treatment strategies for MC-contaminated environments. Full article

Background/Objectives: Frailty is a common geriatric syndrome associated with adverse outcomes such as disability, hospitalization, and mortality. This study aimed to assess the association between body mass index (BMI) trajectories over ten years and frailty among community-dwelling older adults in Brazil. Methods: This population-based longitudinal study used data from the COMO VAI? cohort, conducted with individuals aged ≥60 years in Pelotas, southern Brazil. Frailty was defined in 2024 using Fried’s phenotype, which evaluates weight loss, exhaustion, low physical activity, slowness, and weakness. BMI categories were defined as underweight (BMI < 22.0 kg/m²), eutrophy (22.0–27.0 kg/m²) and overweight (>27.0 kg/m²). BMI trajectories were identified using group-based trajectory modeling for 789 participants with data from at least two of three assessments (2014, 2019, 2024). Only trajectory groups comprising at least 5% of the sample were retained. Associations of baseline BMI and BMI trajectories with frailty were analyzed using Poisson regression with robust variance, adjusted for confounders and calf circumference. Results: Baseline underweight and overweight prevalence were 9.2% and 56.2%, respectively. Trajectory modeling identified three BMI groups: eutrophic (31.6%), overweight (56.4%), and obesity (12.0%). Obesity emerged as a distinct longitudinal trajectory rather than a baseline BMI category. Underweight did not emerge as a distinct BMI trajectory due to its low prevalence over time. Frailty prevalence in 2024 was 36.5%. Overweight trajectory participants had lower frailty prevalence after ten years (PR = 0.73; 95% CI: 0.54–0.99), while baseline underweight was associated with higher frailty ten years later (PR = 1.73; 95% CI: 1.05–2.84), consistent with the known risk of underweight and the potential protective effect observed in overweight older adults. Conclusions: Baseline underweight increased frailty risk, whereas an overweight trajectory showed a potential protective effect, consistent with the “obesity paradox” in older populations. Full article

Cultural eutrophication caused by human activity significantly impacts benthic ecosystems. This study investigated how different phytobenthic components—rhodophyte germlings, mesoalgal and macroalgal assemblages, and Ulva cf. lactuca—respond to nutrient enrichment in a tidal channel system in San Antonio Bay, Argentina. Two experiments were conducted: one in spring examined the interaction between nutrient enrichment (N + P, N + P + Fe) and grazing pressure on early and established algal communities, and the other in autumn assessed nutrient effects on assemblages and Ulva cf. lactuca. Results showed that early successional stages, such as germlings and mesoalgae, responded most strongly to nutrient inputs, while mature macroalgae remained largely unaffected. Significant growth of mesoalgae, with increased pigment concentrations (chlorophyll a, c, and carotenoids), occurred at the eutrophied SAO Channel in spring. Nutrient additions increased rhodophyte germlings but eventually reduced diatom-dominated mesoalgal growth. Mature macroalgae showed site-specific differences but did not respond to fertilization. Grazing effects were evident in treatments with protective cages, suggesting herbivory influences early-stage algal development. Overall, the study emphasizes the importance of the successional stage, grazing pressure, and environmental nutrient history in shaping benthic algal responses to eutrophication, offering key insights into the dynamics of coastal ecosystems under increasing nutrient stress. Full article

The littoral zones of lakes are potential hotspots for local algal blooms and biogeochemical cycles; however, the microbial communities within the littoral sediments of eutrophic plateau lakes remain poorly understood. Here, we investigated the taxonomic composition, co-occurrence networks, and potential functional roles of both abundant and rare taxa within bacterial and archaeal communities, as well as physicochemical parameters, in littoral sediments from Erhai Lake, a mesotrophic lake transitioning towards eutrophy located in the Yunnan–Guizhou Plateau. 16S rRNA gene sequencing revealed that bacterial communities were dominated by Proteobacteria, Bacteroidetes, and Chloroflexi, while Euryarchaeota was the main archaeal phylum. Co-occurrence network analysis revealed that keystone taxa mainly belonged to rare species in the bacterial domain, but in the archaeal domain, over half of keystone taxa were abundant species, demonstrating their fundamental roles in network persistence. The rare bacterial taxa contributed substantially to the overall abundance (81.52%), whereas a smaller subset of abundant archaeal taxa accounted for up to 82.70% of the overall abundance. Functional predictions highlighted a divergence in metabolic potentials, with abundant bacterial sub-communities enriched in pathways for nitrogen cycling, sulfur cycling, and chlorate reduction, while rare bacterial sub-communities were linked to carbon cycling processes such as methanotrophy. Abundant archaeal sub-communities exhibited a high potential for methanogenesis, chemoheterotrophy, and dark hydrogen oxidation. Spearman correlation analysis showed that genera such as Candidatus competibacter, Geobacter, Syntrophobacter, Methanocella, and Methanosarcina may serve as potential indicators of eutrophication. Overall, this study provides insight into the distinct roles that rare and abundant taxa play in the littoral sediments of mesotrophic plateau lakes. Full article

Wildfires significantly influence the environmental distribution of various elements through their fire-induced input and mobilization, yet little is known about their effects on the forest floor in Siberian forests. The present study evaluated the effects of spring wildfires of various severities on the levels of major and minor (Ca, Al, Fe, S, Mg, K, Na, Mn, P, Ti, Ba, and Sr) trace and ultra-trace (B, Co, Cr, Cu, Ni, Se, V, Zn, Pb, As, La, Sn, Sc, Sb, Be, Bi, Hg, Li, Mo, and Cd) elements in the forest floors of Siberian forests. The forest floor (Oi layer) samples were collected immediately following wildfires in Scots pine (Pinus sylvestris L.), larch (Larix sibirica Ledeb.), spruce (Picea obovata Ledeb.), and birch (Betula pendula Roth) forests. Total concentrations of elements were determined using inductively coupled plasma–optical emission spectroscopy. All fires resulted in a decrease in organic matter content and an increase in mineral material content and pH values in the forest floor. The concentrations of most elements studied in a burned layer of forest floor were statistically significantly higher than in unburned precursors. Sb and Sn showed no statistically significant changes. The forest floor in the birch forest showed a higher increase in mineral material content after the fire and higher levels of most elements studied than the burned coniferous forest floors. Ca was a predominant element in both unburned and burned samples in all forests studied. Our study highlighted the role of wildfires in Siberia in enhancing the levels of geochemical elements in forest floor and the effect of forest type and fire severity on ash characteristics. The increased concentrations of elements represent a potential source of surface water contamination with toxic and eutrophying elements if wildfire ash is transported with overland flow. Full article

The study investigates water quality in a small water body in an agricultural catchment in a zone of temperate climate (East Poland). The pond is affected by annual mass cyanobacterial blooms, limiting its use. The improvement of the state of water quality involved the application of underwater aerating reactors. The economic analysis of their application was also an important issue. The analysis of the effectiveness of the proposed solution was conducted from February to October 2021. The results from the analysis of water from the pond showed that the nutrient content and phytoplankton structure conformed to the trophic status of eutrophy–hypertrophy. The primary factors causing excessive eutrophication of the pond included nutrient supply from the river, sediments, and fallen tree leaves. No development of cyanobacterial scum was observed in the water body, a phenomenon which was interpreted as the effect of the operation of the aerators ensuring additional water circulation in the pond and promoting its aeration. It was found that permanent improvement of the water quality in the studied water body is largely dependent on limiting the nitrogen and phosphorus supply to the pond. This should involve the application of systems combining traditional hydrotechnical infrastructure with Nature-Based Solutions (NBS). The economic analysis of the use of underwater aeration reactors confirmed the validity of searching for alternative solutions to power them, e.g., a photovoltaic installation. When designing a reactor system with a photovoltaic installation, it is necessary to choose the correct dimensions to reduce construction costs and, thus, increase the profitability of the potential investment. Full article

The current state of aquatic ecosystems was assessed for lakes in two river–lake systems: Święta Struga (Święte and Ocypelek) and Kałębnica (Czarne Południowe and Kałębie). Trophic states were determined using the Vollenweider, Nürnberg, and Carlson methods. Additionally, shoreline changes were analyzed for all lakes concerning their natural character, and physicochemical parameters were utilized as auxiliary elements in the assessment of the ecological state following the guidelines of Directive 2000/60/EC. Supplementary to these methods, the ecological evaluation of the littoral zone utilized meiobenthic organism grouping as an indicator. The results indicate significant differences among the studied reservoirs. Lake Święte is a reservoir bordering mesotrophy and eutrophy, with the ecological state of the littoral zone showing ongoing trophic development. Lake Ocypelek exemplifies a eutrophic reservoir undergoing progressive degradation. The lakes in the Kałębnica system also exhibit advanced trophic conditions, with Lake Kałębie being a eutrophic reservoir. Its shoreline has been significantly altered due to the development of the direct catchment area. In contrast, Lake Czarne Południowe serves as an example of a mesotrophic reservoir, with a substantially changed shoreline. Considering physicochemical elements and chlorophyll a concentration, the water quality for all examined lakes was found to be below the good category. The diagnosis of the condition of lake aquatic ecosystems requires an individualized approach to each of them. Therefore, employing various methods for their assessment, encompassing physico-chemical, biological, and morphological parameters, provides the opportunity to initiate potential remedial actions that will effectively contribute to their improvement. Conducting low-cost research involving a multidisciplinary approach to diagnose the state of aquatic ecosystems is becoming a crucial element in lake monitoring. Full article

Reservoirs are increasingly valuable worldwide as potable source waters, yet in many geographic regions, their limnology and trophic status are poorly known. We characterized 14 drinking water reservoirs and their watersheds across the warming temperate/subtropical southeastern USA. Selected reservoirs had at least three years of accessible summer water quality data during 2010–2020, including Secchi depth, nutrients, and algal biomass as chlorophyll a, and depth profiles for temperature and dissolved oxygen. Most watersheds, including lands within a 10-km radius of the reservoirs, had sustained substantial urbanization and/or intensive industrialized animal production, in some cases including the discharge of partially treated human sewage or livestock slaughterhouse wastes near or into the reservoirs. Five reservoirs were assessed as mesotrophic; the others were eutrophic. Most were stratified, but ephemeral near-surface thermoclines were common, and many were too shallow (median depth 5.0 m) to maintain uniform temperatures in the relatively warm hypolimnia. Bottom-water hypoxia/anoxia occurred throughout the summers but, surprisingly, in 8 of 14 reservoirs hypoxia commonly extended to surface waters. In the Southeast as in many regions, drinking water reservoirs are poorly protected and degrading as livestock production and/or urban development increasingly characterize their watersheds. The eutrophication trajectory of these valuable resources should be used as an indicator of ecosystem health and water quality in developing more protective management and policy actions. Full article

The creation of man-made reservoirs has become more common globally and provides many important technical, biological, and socio-economic functions. The study focused on abiotic–biotic and trophic interrelations responsible for ecological potential and biodiversity in potentially stabilized conditions of the aquatic ecosystem. Therefore, the analyses concerned 2014–2015 and 2018–2019, assuming repeatable hydrochemical conditions, in three chambers (C1–C3) of the Kamień sedimentation pond supplied through opencast mine drainage. The studies indicated eutrophic levels and at least good ecological potential. Phytoplankton were quite abundant at an average biomass of 10.0 mg L⁻¹, while zooplankton and planktivorous fish were estimated at 0.51 mg L⁻¹ and 74.3 g m⁻², respectively The general order of the growth level in chambers was C-1 > C-2 > C-3, C-1 < C-2 < C-3, and C-1 < C-3 < C-2 for phytoplankton, zooplankton, and planktivorous fish, respectively, and indicated clear differences. Both mechanisms of the top-down and bottom-up effects were revealed in all chambers. Some significant differences between abiotic and biotic (i.e., fish density and biomass, phytoplankton density) factors were recorded on a temporal scale, whereas the density and biomass of planktivorous fish were significantly differentiated on a spatial scale. The stabilized conditions concerned relatively high biodiversity but quite abundant phytoplankton and lower zooplankton abundances, trophic efficiency, and eutrophy under the maximum ecological potential. Full article

This research concerns the restoration of the strongly eutrophied Lake Łajskie (Masurian Lake District, Poland) that received pollutants from the agricultural catchment. It is a shallow (max depth 7.4 m) and small (area 48 ha) reservoir with a wide profundal zone characterized by complete deoxidation in summer. Due to its important natural and social role, the lake has undergone a restoration process. Artificial oxygenation is the main method of improving water quality. Due to unfavorable morphometric conditions, the necessity to use multi-point aeration was assumed. An experimental installation based on eight reactors selectively oxygenating only the over-bottom waters was launched in 2019. In 2021, spatial studies of the effectiveness of aerators’ work were carried out at 96 measuring points grouped into 12-test fields around each reactor. The investigations were performed three times during the summer season. It was shown that, in the water of the deepest layers of Lake Łajskie, the oxygen concentration around all reactors increased to an average level of 1–2 mg L⁻¹. The oxygenation efficiency was varied and related to the distance from the aerator and the location in relation to the direction of oxygenated water outflow. The results of the research indicate the legitimacy of designing multi-point oxygenation systems in the restoration of waterbodies degraded as a result of the impact of agriculturally transformed catchments. Full article

Under the Convention on Long-Range Transboundary Air Pollution (CLRTAP) of the UN Economic Commission for Europe, UNECE, to which Germany acceded in 1982, the harmful effects of air pollutants on the environment are to be steadily reduced and ultimately limited to a level that is compatible with nature. The ICP Modelling & Mapping (ICP M&M) under the Working Group on Effects (WGE) of CLRTAP maps critical loads for the entire Convention area and calculates the exceedance risks and associated risks to vegetation and biodiversity. A current data request was made in November 2015 with the aim of submitting new or updated ecosystem-specific critical loads for protection against acidification and eutrophication. For this task, critical loads were determined by the authors for one third of the territory of Germany using the simple mass balance (SMB) method according to the ICP Mapping Manual. The permissible eutrophying nitrogen input into the ecosystem CLnut(N), as well as the acidifying sulphur input CLmaxS, can be described as the setting of the equilibrium between substance inputs and outputs, provided that specific critical limits are met. The BERN database—created by the authors—serves as the basis for modelling vegetation-specific critical limits as a complement to the SMB model. The BERN database contains near-natural plant communities with clearly definable site constancy. The 25,600 German and a further 24,600 European vegetation records dating back to before 1960 were evaluated to determine the good ecological status of the plant communities. The results of the critical load calculation show that about half of the receptor areas have critical loads for eutrophying nitrogen below 10 kg ha⁻¹ a⁻¹ and critical loads for acidifying sulphur were below 1500 eq ha⁻¹ a⁻¹. It could be demonstrated that the BERN–SMB-modelled critical loads for eutrophying nitrogen inputs show lower values on average throughout Germany than those calculated using only the previous critical limits according to the ICP Mapping Manual. These values are closer to the empirical critical loads than the critical loads without BERN data. For the goal of the German National Biodiversity Strategy by 2007 and 2020 to define ecosystem-related impact thresholds for pollutants that describe the effects on biodiversity, the BERN/SMB critical loads for the protection of ecosystems provide a precautionary scientific basis. Full article

Allelopathy is an interaction that releases allelochemicals (chemicals that act allelopathically) from plants into the environment that can limit or stimulate the development, reproduction, and survival of target organisms and alter the environment. Lemna minor L. contains chemicals that are allelopathic, such as phenolic acids. Chemical compounds contained in L. minor may have a significant impact on the development and the rate of multiplication and lead to stronger competition, which may enhance the allelopathic potential. Allelopathic potential may exist between L. minor and C. glomerata (L) Kütz. because they occupy a similar space in the aquatic ecosystem, have a similar preference for the amount of light, and compete for similar habitat resources. L. minor and C. glomerata can form dense populations on the water surface. Allelopathy can be seen as a wish to dominate one of the plants in the aquatic ecosystem. By creating a place for the development of extensive mats, an interspecific interaction is created and one of the species achieves competitive success. It is most effective as a result of the release of chemicals by macrophytes into the aquatic environment. Therefore, allelopathy plays a significant role in the formation, stabilization, and dynamics of the structure of plant communities. Full article

Here, we examine the geobiological response to a whole-lake alum (aluminum sulfate) treatment (2016) of Base Mine Lake (BML), the first pilot-scale pit lake established in the Alberta oil sands region. The rationale for trialing this management amendment was based on its successful use to reduce internal phosphorus loading to eutrophying lakes. Modest increases in water cap epilimnetic oxygen concentrations, associated with increased Secchi depths and chlorophyll-a concentrations, were co-incident with anoxic waters immediately above the fluid fine tailings (FFT) layer post alum. Decreased water cap nitrate and detectable sulfide concentrations, as well as increased hypolimnetic phospholipid fatty acid abundances, signaled greater anaerobic heterotrophic activity. Shifts in microbial community to groups associated with greater organic carbon degradation (i.e., SAR11-LD12 subclade) and the SRB group Desulfuromonodales emerged post alum and the loss of specialist groups associated with carbon-limited, ammonia-rich restricted niches (i.e., MBAE14) also occurred. Alum treatment resulted in additional oxygen consumption associated with increased autochthonous carbon production, watercap anoxia and sulfide generation, which further exacerbate oxygen consumption associated with on-going FFT mobilized reductants. The results illustrate the importance of understanding the broader biogeochemical implications of adaptive management interventions to avoid unanticipated outcomes that pose greater risks and improve tailings reclamation for oil sands operations and, more broadly, the global mining sector. Full article

Zooplankton as an essential component in the pelagic food web are directly linked to pelagic ecosystem functioning. Therefore, comprehension of zooplankton functional diversity (FD) and its responses to environmental changes is crucial for ecosystem-based view. To identify FD responses to environmental drivers, we analysed 25 years of summer data on the brackish mesozooplankton community (including rotifers, cladocerans, copepods, and meroplankton) from the eutrophied, shallow Gulf of Riga (Baltic Sea). We established that within the Gulf of Riga, open waters are notably different from coastal regions based on the dynamics of hydrological conditions (temperature, salinity), cyanobacterial dominance, abundance of mesozooplankton functional groups, and mesozooplankton FD indices. Competition over resources in combination with hydrodynamic features and predation by adult herring were seemingly the central structuring mechanism behind the dynamics of FD metrics (richness, evenness, divergence, and dispersion) within coastal mesozooplankton communities. Whereas predation by young herring was an important driver only for the mesozooplankton communities in the open waters. Cyanobacterial dominance, used as a proxy for food quality and availability, had no effect on summer mesozooplankton FD metrics. Full article