Level Fluctuations Research Articles

Metabolic Stress Responses in Labeo rohita Subjected to Di (2-ethylhexyl) Phthalate (DEHP), Dibutyl Phthalate (DBP), and Diethyl Phthalate (DEP)

This study investigates the stress response of glucose and cholesterol levels in Labeo rohita (Rohu) upon exposure to three widely used phthalates: Di(2-ethylhexyl) phthalate (DEHP), Dibutyl phthalate (DBP), and Diethyl phthalate (DEP). Phthalates, recognized for their endocrine-disrupting properties, are prevalent environmental contaminants. Specimens of Labeo rohita were subjected to environmentally relevant concentrations of DEHP, DBP, and DEP over a controlled period. Blood samples were collected periodically to measure fluctuations in glucose and cholesterol levels, serving as biomarkers of metabolic stress. The results indicate significant alterations in both glucose and cholesterol concentrations, with each phthalate demonstrating a distinct impact on these metabolic parameters. DEHP and DBP elicited more pronounced disruptions compared to DEP, underscoring their higher toxicity. These findings highlight the differential metabolic responses of Labeo rohita to various phthalates and underscore the ecological risks associated with phthalate contamination. The study advocates for stricter regulatory measures to mitigate phthalate pollution and protect aquatic ecosystems. This research enhances our understanding of the biochemical pathways affected by phthalate exposure and lays the groundwork for future investigations into the mechanisms underlying phthalate-induced stress in fish.

Short-Term Groundwater Level Fluctuations Drive Subsurface Redox Variability.

As global change processes modify the extent and functions of terrestrial-aquatic interfaces, the variability of critical and dynamic transitional zones between wetlands and uplands increases. However, it is still unclear how fluctuating water levels at these dynamic boundaries alter groundwater biogeochemical cycling. Here, we used high-temporal resolution data along gradients from wetlands to uplands and during fluctuating water levels at freshwater coastal areas to capture spatiotemporal patterns of groundwater redox potential (Eh). We observed that topography influences groundwater Eh that is higher in uplands than in wetlands; however, the high variability within TAI zones challenged the establishment of distinct redox zonation. Declining water levels generally decreased Eh, but most locations exhibited significant Eh variability, which is associated with rare instances of short-term water level fluctuations, introducing oxygen. The Eh-oxygen relationship showed distinct hysteresis patterns, reflecting redox poising capacity at higher Eh, maintaining more oxidizing states longer than the dissolved oxygen presence. Surprisingly, we observed more frequent oxidizing states in transitional areas and wetlands than in uplands. We infer that occasional oxygen entering specific wetland-upland boundaries acts as critical biogeochemical control points. High-resolution data can capture such rare yet significant biogeochemical instances, supporting redox-informed models and advancing the predictability of climate change feedback.

Changes in marine sedimentation patterns in the northeastern South China Sea in the past 35,000 years

In the continental margin of the northeastern South China Sea, the sea level fluctuations since the Last Glacial Maximum have profoundly impacted the sedimentary environment. Our sub-bottom profiler data show a sedimentation process change from deposition to erosion during the Last Glacial Maximum. After the widespread erosion, the sedimentation process returned depositional throughout the Holocene, probably due to the rise of the sea level. This sedimentary process results in a widespread sedimentary unconformity in the continental slope, providing a benchmark for the end of the Last Glacial Maximum. Analyzing the sediment cores, we affirm that the change in current intensity is the primary factor controlling the sedimentary environments. The current intensities strengthened during the eustatic lowstand and weakened during the highstand periods, leading to alternating erosional and depositional processes. The widespread distribution of the erosive surface represents a regional-scale change in the sedimentary environment instead of a local event.

Study on Impact of Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) on Renal Function in Postpartum Period

A prospective, observational study was conducted in the Department of Obstetrics & Gynaecology of Combined Military Hospital (CMH), Dhaka, Bangladesh, to assess pre-delivery and post-delivery (5 days after administration of NSAID) change in renal function by determining the serum creatinine levels in pregnant women. The study was conducted on 120 purposively selected patients attending for their delivery purpose in the selected hospital from January to June of 2022. Following the delivery, tablet Paracetamol 500 mg thrice a day for 5 days have been prescribed to all the respondents. Diclofenac Sodium 100 mg suppository twice a day up to for 3 days had been prescribed with dosage adjusted as required. Serum creatinine levels were evaluated on two time points: the day before delivery and 5 days after delivery. Compared to the day before delivery, 53.3% of the respondents showed increased level of serum creatinine 5 days after delivery. Acute kidney injury (AKI) was identified in 9.17% patients with a change more than 0.3 mg/dL from the pre-delivery report. The change in the serum creatinine level pre-delivery to post delivery was statistically significant, which was also dependent on the NSAIDs dose with a positive linear association. Though NSAIDs regarded as a safe choice for postpartum pain management, yet apparently healthy mothers showed fluctuations in serum creatinine level in association to dosage of NSAIDs use. CBMJ 2024 July: vol. 13 no. 02 P: 141-147

Acetylcholine and choline in honey bee (Apis mellifera) worker brood food are seasonal and age-dependent

Nursing honeybees produce brood food with millimolar concentrations of acetylcholine (ACh), which is synthesized through head gland secretions mixed with honey stomach contents. While we previously demonstrated the necessity of ACh for proper larval development, the dynamics of ACh levels throughout ontogenesis and their seasonal variations have remained unclear until now. Our HPLC analysis reveals dependencies of choline and ACh levels on larval development days (LDDs), influenced by seasonal (April–September) variations. Median ACh concentrations peak on LDD 2, declining significantly toward cell capping, while choline levels are lowest during the initial LDDs, rising markedly toward cell capping. Seasonal patterns show peak ACh levels from April to June and a low in August, paralleling choline's peak in July and low in August. This seasonality holds consistently across multiple years (2020–2022) and colonies, despite potential variations in colony performance and environmental conditions. Our analysis found no correlation between temperature, sunshine, precipitation, or favourable foraging days and ACh/choline levels, suggesting the involvement of additional factors. These findings underscore the seasonal fluctuation of ACh levels and its potential implications for the genetic programs governing winter bee development.

Modeling of water level trends and characterizing potential influencing factors in Lake Baringo in Kenya

Water plays a significant role in every sector of the ecosystem. The fluctuation of the water levels in lakes is influenced by natural and man-made factors within the water catchment. Lake Baringo, which has no visible outlet, has been rising drastically, causing panic among native communities and businesses on the shores of the lake. Using GIS and Remote Sensing, this study intends to analyze the changes in water lakes using the Automatic water extraction index (AWEI), determine the causes of the fluctuation using Land use Land cover, land surface temperature, soil erosion, and siltation in the lake basin and the lake respectively, precipitation, and later predict of the water level for the year 2030 using the MOLUSCE tool. The tool utilizes an artificial neural network and cellular automata to analyze land use and land cover conveniently. It was found that the lake’s water level has been increasing drastically over the years, and the leading causes of the fluctuations were increased rainfall and human activities within the water basin. There are visible increased human activities within the water basin, such as agriculture, deforestation, settlement, and urbanization. It was also found that there will be a further increase in water level in 2030. With all the above results, it is recommended that better policies be made to conserve the water basin effectively, and a plan should be drawn to re-delineate the new riparian buffer.

Interfacial Stresses within Droplets and Channels Influence Bacterial Physiology: A Perspective.

Bacterial cells frequently experience fluid motion in their natural environments, like water bodies, aerosols, fomites, human capillaries, etc., a phenomenon that researchers have largely overlooked. Nevertheless, some reports have suggested that the interfacial stresses caused by fluid motion inside evaporating droplets or shear flows within capillaries may trigger physiological and morphological changes in the bacterial cells. Remarkably, the virulence of bacterial cells exhibits significant alterations in response to fluctuations in stress levels and external environmental factors. The dynamics of bacterial systems are analogous to colloidal systems but with the distinction that bacterial systems exhibit responsiveness, necessitating thorough exploration in dynamic environments. In this perspective, we discuss the important issue pertaining to bacterial survival, virulence, and disease transmission. Furthermore, we delineate a pathway and underscore emerging opportunities that demand exploration to unveil new avenues in the domains of bacterial pathogenicity, drug development, and strategies for disease mitigation.

Air-stable, self-weldable, and tough alginate-based gels: A sustainable alternative to conventional plastics

The demand for innovative green materials that can viably replace environmentally harmful petrochemical plastics is escalating. To that end, novel gel materials were readily prepared in this study using a natural polymer (alginate) and a bio-friendly polyol solvent (glycerol), and then structurally characterized by Fourier-transform infrared spectroscopy and X-ray diffractometry. The optimal gel exhibited mechanical properties similar to those of common plastics (Young's modulus, ∼218 MPa; tensile strength, ∼24 MPa; work of extension, ∼17 MJ m−3; and fracture energy, ∼5130 J m−2). Additionally, a potent welding technique was devised to fuse gel fragments. The representative welded gel exhibited an exceptional adhesive strength (∼0.21 MPa) similar to cartilage–bone bonds, and was cross-sectionally analyzed by field-emission scanning electron microscopy. Importantly, the gels retained their properties even after prolonged exposure to ambient air (temperature, ∼26 °C; humidity, ∼60 %). They also exhibited a remarkable ability to withstand exposure to ultraviolet irradiation, temperature instability, and fluctuations in moisture levels. The synthesized high-performance gels could be used instead of traditional plastics in various practical settings.

Berthierine/Chamosite ooids and associated phases in Devonian deposits of the Parnaíba Basin, Brazil: Genesis and diagenetic evolution

The Parnaíba Basin Devonian deposits comprise ironstones and organic-rich sediments deposited in an epeiric sea margin under greenhouse conditions, enhanced weathering, reduction of oceanic circulation, and black shale deposition. This study aims to contribute to the understanding of the interrelation between depositional and shallow diagenetic processes of the Devonian units of the Parnaíba Basin, specifically regarding the genesis of iron minerals that constitute the ooidal ironstones of the Itaim and Pimenteiras formations. These units comprise bioturbated heterolites, ooidal ironstones, intraclastic conglomerates, and shales, deposited in a deltaic to neritic, storm-dominated platform. This research investigates drill cores from two wells in the southern part of the Parnaiba Basin, focusing on depositional and diagenetic processes. The proposed model suggests deposition of sediments originally rich in organic matter, under low siliciclastic input, and initially anoxic, transgressive conditions. Under these conditions, ferroan precursor clays were deposited, alternating with periods of reworking by storm currents, generating concentric ooids of berthierine. Bioturbation processes resulted in the concentration of previously formed berthierine ooids during intervals of low sedimentation rates. Eodiagenetic microcrystalline siderite formed along the redox boundary between oxic/bioturbated and anoxic zones. Chamosite formed by partial transformation of berthierine, upon incipient mesodiagenetic evolution of the ooidal ironstones. This study contributes to the understanding of depositional and diagenetic conditions in the Devonian section of the Parnaíba Basin, and of similar deposits, offering insights into the formation and development of berthierine ooids under the influence of sea level fluctuations, oxic/anoxic conditions, sedimentation rate, and bioturbation in sedimentary environments, providing key insights into the paleoenvironmental conditions along the northern Gondwana margin during this period.

Progress on the Effects of Permissive Hypercapnia on the CNS During the Intraoperative Period: A Narrative Review.

Previous experimental findings and clinical evidence have shown the important role of carbon dioxide (CO2) in regulating cerebral vascular tension. CO2 can affect the CNS through various mechanisms. With factors such as patient physiology or surgical interventions potentially causing increased arterial partial pressure of carbon dioxide (PaCO2) levels during mechanical ventilation in general anesthesia, it is important to explore the potential risks or benefits of intraoperative permissive hypercapnia on brain function. In November 2023, we conducted a thorough review of PubMed to establish the article outline. Articles that were non-English or repetitive were eliminated. We collected information on the year, topic, key findings, and opinions of each article. This review not only comprehensively summarizes the factors that contribute to the elevation of intraoperative PaCO2, but also explores the impact of fluctuations in PaCO2 levels on the CNS and the underlying mechanisms involved. At the same time, this article provides our understanding of the potential clinical significance of actively regulating PaCO2 levels. In addition, we propose that the aspects of permissive hypercapnia can be further studied to provide a reliable basis for clinical decision-making. The effects of permissive hypercapnia on the CNS remain a topic of debate. Further prospective randomized controlled studies are needed to determine if permissive hypercapnia can be safely promoted during mechanical ventilation in general anesthesia.

The daily costs of workaholism: A within-individual investigation on blood pressure, emotional exhaustion, and sleep disturbances.

Workaholism literature has been so far focused on individual differences in workaholic tendencies, considering the construct as a stable individual trait and highlighting its health and well-being consequences. Only recently, research has started inspecting the daily dynamics and potential consequences of state workaholism. In this preregistered study, we aimed at systematically investigating the within-individual fluctuations in workaholism levels and their potential short-term and delayed psychophysiological responses as captured by ambulatory assessment integrating subjective and objective data. Using an intensive longitudinal design over 10 workdays with 114 workers from various occupations (2,534 measurement occasions), we found higher systolic and diastolic blood pressure, emotional exhaustion, and sleep disturbances in workdays characterized by higher-than-usual workaholism symptoms. Moreover, the reactivity to state workaholism, as indexed by afternoon blood pressure, was found as a mediator of the subsequent prolonged activation indexed by bedtime blood pressure. Finally, we found evidence of a buffering effect of evening psychological detachment on the relationship between state workaholism and sleep disturbances. Overall, our results support the conceptualization of workaholism as a multilevel phenomenon that acts as an internal job-related demand by showing the typical strain reactions triggered by well-characterized external demands. This study contributes to the literature by highlighting that transient workaholism symptoms can result in significant short-term stress responses at different levels, providing new, robust, and multisource evidence that underlies the importance of effectively preventing and managing dysfunctional work investment since its early manifestation. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Multi-scale investigation on staged deterioration mechanism of sliding-zone soils induced by reservoir fluctuations

Water level fluctuations in the reservoir deteriorate soils and rocks on the bank landslides by drying-wetting (D-W) cycles, which results in a significant decrease in mechanical properties. A comprehensive understanding of deterioration mechanism of sliding-zone soils is of great significance for interpreting the deformation behavior of landslides. However, quantitative investigation on the deterioration characteristics of soils considering the structural evolution under D-W cycles is still limited. Here, we carry out a series of laboratory tests to characterize the multi-scale deterioration of sliding-zone soils and reveal the mechanism of shear strength decay under D-W cycles. Firstly, we describe the micropores into five grades by scanning electron microscope and observe a critical change in porosity after the first three cycles. We categorize the mesoscale cracks into five classes using digital photography and observe a stepwise increase in crack area ratio. Secondly, we propose a shear strength decay model based on fractal theory which is verified by the results of consolidated undrained triaxial tests. Cohesion and friction angle of sliding-zone soils are found to show different decay patterns resulting from the staged evolution of structure. Then, structural deterioration processes including cementation destruction, pores expansion, aggregations decomposition, and clusters assembly are considered to occur to decay the shear strength differently. Finally, a three-stage deterioration mechanism associated with four structural deterioration processes is revealed, which helps to better interpret the intrinsic mechanism of shear strength decay. These findings provide the theoretical basis for the further accurate evaluation of reservoir landslides stability under water level fluctuations.

Unsteady flow in a compound channel during flooding: Insights from a combined two-dimensional and three-dimensional numerical simulation

Natural channels often take the form of compound channels during flooding events. The unsteadiness of floods is crucial for flood management and river-floodplain ecosystems. However, the impact of unsteady flow on three-dimensional hydrodynamic processes within compound channels remains poorly understood. This study employed a validated two-dimensional/three-dimensional numerical model to examine how unsteady features influence key hydrodynamic indicators of compound channels, such as velocity distribution, turbulence characteristics, and discharge partitioning between the main channel and floodplain. A definitive positive correlation was found between water level fluctuation amplitudes and integrated discharge during unsteady events, as well as between mean water levels and mean discharges. The proportion of discharge conveyed by the main channel relative to the total was directly linked to the water depth ratio. The exchange at the main channel–floodplain interface exhibits a dual-layer flow pattern: surface waters spill into the floodplain, while deeper waters are siphoned into the main channel. Unsteady conditions principally modulate the intensity of these exchanges, altering hydraulic interactions and water transfer between areas. Pronounced wall shear stresses were detected at the main channel–floodplain interface due to swift channel flows and momentum exchange at the floodplain margin, with maxima adjacent to the floodplain edge correlating with peak flow velocities. Under deep conditions, cross-sectional flow across the compound channel's mixing layer was essentially two-dimensional. These findings elucidate the complex hydrodynamics inherent to unsteady overbank flows while holding implications for enhancing floodplain management and advancing the understanding of unsteady fluvial hydraulics.

An overview of Upper Pleistocene coastal deposits on Mallorca island

This review paper delves into the geological history of Mallorca, focusing on the Middle to Late Pleistocene period and its impact on the landscape and climate of the island. The Quaternary, particularly, the Last Interglacial, represents a relatively short timeframe on the global chronological scale, yet it is notable for its climatic instability and complex alternation of glacial and interglacial phases, leading to fluctuations in sea levels. During the last interglacial, millennial-scale fluctuations, known as Dansgaard–Oeschger and Heinrich events, occurred. Aeolianites are thought to have formed during periods of sparse vegetation cover and abundant sediment availability from the sea bed or platform (Heinrich events), while colluvial deposits and paleosols are believed to represent periods of reduced sediment supply and enhanced pedogenesis (Dansgaard–Oeschger events). These different deposits reflect climatic shifts and sea-level changes, offering insights into the environmental history of the island. Fossil evidence, including Strombus bubonius (currently known as Thetystrombus lauts) or “Senegalese hosts,” reveals past warm climatic fluctuations, particularly during the Last Interglacial. Myotragus balearicus exemplifies evolutionary adaptation and isolation on the island, offering a unique perspective on its paleontological legacy. The integration of stratigraphic characteristics and literature research on Optically Stimulated Luminescence (OSL) dating techniques provides a comprehensive temporal framework, spanning from Marine Isotope Stage 6 (MIS 6) to Marine Isotope Stage 2 (MIS 2), enabling the precise dating of geological events and a stratigraphic correlation.

Hydrologic Model Prediction Improvement in Karst Watersheds through Available Reservoir Capacity of Karst

This study aimed to enhance flood forecasting accuracy in the Liangfeng River basin, a small karst watershed in Southern China, by incorporating the Available Reservoir Capacity of Karst (ARCK) into the HEC-HMS model. This region is often threatened by floods during the rainy season, so an accurate flood forecast can help decision-makers better manage rivers. As a crucial influencing factor on karstic runoff, ARCK is often overlooked in hydrological models. The seasonal and volatile nature of ARCK makes the direct computation of its specific values challenging. In this study, a virtual reservoir for each sub-basin (total of 17) was introduced into the model to simulate the storage and release of ARCK-induced runoff phenomena. Simulations via the enhanced model for rainfall events with significant fluctuations in water levels during 2021–2022 revealed that the Nash–Sutcliffe efficiency coefficient (NSE) of the average simulation accuracy was improved by more than 34%. Normally, rainfalls (even heavy precipitations) during the dry season either do not generate runoff or cause negligible fluctuations in flow rates due to long intervals. Conversely, relatively frequent rainfall events (even light ones) during the wet season result in substantial runoff. Based on this observation, three distinct types of karstic reservoirs with different retaining/releasing capacities were defined, reflecting variations in both the frequency and volume of runoff during both seasons. As a real-time environmental variable, ARCK exhibits higher and lower values during the dry and rainy seasons, respectively, and we can better avoid the risk of flooding according to its special effects.

Extended analysis on peripheral blood cytokines correlated with hepatitis B virus viral load in chronically infected patients - a systematic review and meta-analysis.

Hepatitis B Virus (HBV) can affect life quality. Monitoring and understanding the fluctuations of the HBV level of viremia related to the intricate immune activity of the host helps in the development of new treatment strategies and evaluation patterns. This meta-analysis presents the correlations between cytokines and the level of viremia in chronic HBV patients for a better comprehension of the immune mechanisms behind this infection. We used PRISMA guidelines for this meta-analysis. The databases assessed were PUBMED, WEB OF SCIENCE, SCOPUS, and Cochrane Library. ZOTERO and PlotDigitizer helped the systematic research process. We extracted information related to the correlations between cytokines and the HBV-DNA level. Effect measures included comparisons between standardized mean differences and correlation coefficients. We evaluated retrieved articles with the Newcastle-Ottawa Quality Assessment Scale (NOS). The R 4.2.2 software displayed the statistical calculation and graphical representations. From 58,169 records, we extracted 16 articles with 32 different cytokine determinations. The main interleukins included in detection panels were IL-10 and IL-21. The meta-correlation analysis comprised 1,199 chronic HBV patients. The standardized mean difference between cytokine levels in HBV patients and healthy controls was 0.82 (95% CI = [-0.19, 1.84], p = 0.11). We observed a significant, fair, pooled correlation coefficient between IL-10, IL-9, and the viral load (r = 0.52, 95% CI = [0.19, 0.85]). This meta-analysis brings novelty because it gives a first rigorous systematic look at multiple studies with many cytokines. Our research approaches a debatable issue and gives a possible solution for settling controversies. Future studies can arise towards understanding the immune disruption in HBV and the development of new, improved assays for prognosis.

Groundwater level prediction for excessive agricultural irrigation to achieve SDGs: Vulnerability assessment using field-based empirical method

Excessive over-drafting and unsystematic management of groundwater brings different geo-environmental problems; thus precise prediction of groundwater (GW) status in large scale becomes prime concern for efficient GW management. This present study primarily focused on estimating the current groundwater status of agro-rich Murshidabad district using a GIS-based empirical approach including trend analysis of groundwater depth (2001–2021) by using Modified Mann Kendall test (MMKT) and Sen's slope estimator; the most prominent water level fluctuation (WLF) method employed in the estimation of groundwater recharge scenario of the last three decades. The groundwater recharge potential zone (GWRPZ) also delineated through widely used logistic regression (LR) method. The current research depicts that eight CD Blocks and twenty-five CD Blocks out of twenty-six CD Blocks are facing notable declining trend in groundwater depth in pre-monsoon and post-monsoon period accordingly, with a 95% confidence level; the lowering down of groundwater recharge (GWR) also alarming, the recharge amount in 2001, 2011 and 2021 was 210958.70 ham, 240168.80 ham and 201921.90 ham respectively due to variability in rainfall; the predicted GWRPZ shows that 674 (12.6%) Km2 and 1392 Km2 (26.02%) come under very high and high recharge zone which is predominantly found in the eastern and south-eastern part of this study region, validated through most reliable method Receiver Operating Characteristics (ROC) and Area Under Curve (AUC) with 0.954 value. Unsystematic over-drafting of groundwater and intense cropping intensity are severely responsible for this alarming condition. Thus, sustainable groundwater management is essential to fulfil SDG-6 by ensuring SDG-2 and policymakers and planners will be benefited from this study in formulating the proper mitigation measures for this agronomic Murshidabad district.

Water Resources Monitoring in a Remote Region: Earth Observation-Based Study of Endorheic Lakes

In the western Andes, climate changes have led to drastic ecological changes during the Pleistocene and Holocene. Given the debate surrounding precipitation pattern changes and the lack of research on lakes in the Chilean Altiplano, this study aims to assess recent climate changes. The paper presents an innovative methodology based on Google Earth Engine (GEE), utilizing fluctuations in water levels in endorheic lakes as natural precipitation indicators. Three lakes (Chungará, Miscanti, and Miniques) in isolated drainage systems were studied, where changes in water levels directly reflect rainfall variations. Data from Landsat-OLI 8, Landsat-ETM+, Landsat-TM 5, and MODIS spanning 31 years were processed using the Google Earth Engine platform. The shapes of the water bodies were extracted using hue saturation value (HSV) composites. The surface areas of the lakes were compared with precipitation data from national meteorological stations and the Tropical Rainfall Measuring Mission (TRMM) using linear regression analyses. Both lake area and rainfall volume showed a decrease over time, with varying trends depending on environmental conditions. However, the analysis consistently indicates a reduction in the area and volume of Chilean lakes corresponding to observed rainfall patterns over the past three decades.

Lake level fluctuations and varve preservation – The sediment record from Lake Suminko (Poland) reflects European paleoclimatic changes

We present a reconstruction of Holocene lake-level fluctuations at Lake Suminko, a eutrophic hardwater lake in northern Poland. The lake contains annually laminated (varved) sediments, forming a unique archive of past hydroclimatic variability. Employing a combination of sedimentological and geochemical methods, we demonstrate that sediment core sections with well-preserved varves and lower Ca/Fe ratios correspond to periods of higher water levels associated with colder and wetter climatic conditions. We identify twelve periods of lake level high stands, consistent with other lake sediment records from western Poland and Europe, as well as with North Atlantic IRD events. Pollen data and geochemical proxies confirm negligible human impact on the lake during most of the Holocene, except for the last 500 years when accelerated soil erosion related to landscape opening and agricultural activities occurred. Therefore, we conclude that Holocene lake-level fluctuations at Lake Suminko are primarily controlled by climatic conditions regulating water availability and groundwater supplies to the lake. Our study also highlights the potential of varve preservation as a useful indicator of lake-level changes.

Combined measures in lake restoration – A powerful approach as exemplified from Lake Groote Melanen (the Netherlands)

Controlling lake eutrophication is a challenge. A case-specific diagnostics driven approach is recommended that will guide to a suite of measures most promising in restoration of eutrophic lakes as exemplified by the case of the shallow lake Groote Melanen, The Netherlands. A lake system analysis identified external and internal nutrient load as main reasons for poor water quality and reoccurring cyanobacterial blooms in the lake. Based on this analysis, a package of restoration measures was implemented between January 2015 and May 2016. These measures included fish removal, dredging, capping of peat rich sediment with sand and an active barrier (lanthanum-modified bentonite), diversion of two inlet streams, reconstruction of banks, and planting macrophytes. Dredging and sand capping caused temporarily elevated turbidity and suspended solids concentrations, while addition of the lanthanum-modified clay caused a temporary exceedance of the Dutch La standard for freshwaters. Diversion of inflow streams caused 35 % less water inflow and larger water level fluctuations, but the lake remained water transporting with strongly improved water quality as was revealed by comparing five years pre-intervention water quality data with five years’ post-intervention data. Total phosphorus concentration in the water column was reduced by 93 % from 0.47 mg P l-1 before the intervention to 0.03 mg P l-1 after the intervention, total nitrogen by 66 % from 1.27 to 0.21 mg N l-1, total chlorophyll-a by 75 % from 68 to 16 µg l-1, cyanobacteria chlorophyll-a by 88 % from 32 to 4 µg l-1. Turbidity had declined by 58 % from 23.5 FTU to on average 9.9 FTU. No cyanobacteria blooms were recorded over the entire post-intervention monitoring period (2016–2021). Submerged macrophytes increased from complete absence before intervention to around 10 %–15 % coverage after intervention. Repeated fish removal lowered the fish stock to below 100 kg ha-1 with 12 % of bream and carp remaining. Hence, the package of cohesive measures that was based on a thorough diagnosis resulted in rapidly, strongly and enduringly improved water quality. This case provides evidence for the power of combining measures in restoring eutrophic lakes.