Limnological Review

17 pages, 3688 KiB

Open AccessArticle

Reaeration Coefficient Empirical Equation Selection for Water Quality Modeling in Surface Waterbodies: An Integrated Numerical-Modeling-Based Technique with Field Case Study

by Balsam J. M. Al-Saadi and Hussein A. M. Al-Zubaidi

Limnol. Rev. 2025, 25(2), 15; https://doi.org/10.3390/limnolrev25020015 - 25 Apr 2025

Abstract

Empirical equations were developed by many investigators to determine the reaeration coefficients (Ka) required for predicting dissolved oxygen concentrations (DO) in surface waters, especially rivers, lakes, and reservoirs. However, these equations yield a wide range of Ka values. In this paper, an integrated [...] Read more.

Empirical equations were developed by many investigators to determine the reaeration coefficients (Ka) required for predicting dissolved oxygen concentrations (DO) in surface waters, especially rivers, lakes, and reservoirs. However, these equations yield a wide range of Ka values. In this paper, an integrated numerical-modeling-based technique was developed to check the validity of the equations before using them in water quality modeling for rivers, lakes, and reservoirs. Depending on direct field measurements at the Hilla River headwater (Saddat Al-Hindiyah Reservoir, Iraq), the temporal oxygen mass transport at the water surface was estimated numerically by solving the one-dimensional advection diffusion equation and then using each Ka empirical equation separately in the numerical model obtained the best specific-waterbody equation. The DO modeling results showed that using a reservoir reaeration coefficient of 0.1 day⁻¹ at 20 °C predicts the best DO simulation with low MAEs of 0.4987 and 0.7880 mg/L during the study years 2021 and 2022, respectively, compared to the field data. However, using the Ka empirical equations simulates the DO with wide-ranging statistical errors even though the temporal Ka values have a similar trend during the year. It was noticed that the empirical equations produced maximum Ka values of (0.0080–0.0967 day⁻¹) and minimum Ka values of (0.00052–0.0267 day⁻¹) in 2021 and maximum Ka values of (0.0079 to 0.0951 day⁻¹) and minimum Ka values of (0.00012 and 0.0231 day⁻¹) in 2022. The present equation selection technique revealed that Broecker et al.’s equation followed by Smith’s equation, developed in 1978, are the best selection for water quality modeling at the Hilla River headwater (MAEs: 0.1347 and 0.1686 mg/L in 2021, respectively; and MAEs: 0.1400 and 0.1744 mg/L in 2022, respectively). Hence, it is necessary to find good agreement for the equation-based prediction of DO, DO source–sink, and Ka values compared to the validated model before making selection. Full article

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22 pages, 3150 KiB

Open AccessArticle

Influence of Experimental Eutrophication on Macrozoobenthos in Tufa-Depositing System of Plitvice Lakes National Park, Croatia

by Maja Vurnek and Renata Matoničkin Kepčija

Limnol. Rev. 2025, 25(2), 14; https://doi.org/10.3390/limnolrev25020014 - 17 Apr 2025

Abstract

The process of tufa deposition created the Plitvice Lakes, a unique freshwater cascade system of 16 lakes separated by tufa barriers. This complex karst hydrosystem reacts very sensitively to even small changes, and eutrophication can directly and indirectly affect tufa formation. With the [...] Read more.

The process of tufa deposition created the Plitvice Lakes, a unique freshwater cascade system of 16 lakes separated by tufa barriers. This complex karst hydrosystem reacts very sensitively to even small changes, and eutrophication can directly and indirectly affect tufa formation. With the purpose of determining the influence of nitrogen (N) and phosphorus (P) on periphyton’s chlorophyll a concentration, tufa deposition, and macrozoobenthos, we used nutrient-diffusing substrates. The in situ experiment combined the effects of seasons, stronger/weaker tufa deposition, and the presence/absence of macrophytes. The season was the dominant factor influencing hydrology, physicochemical factors, tufa deposition, and the effects of eutrophication. Phosphorus was the limiting factor for periphyton developing on artificial substrates, as evidenced by the highest chlorophyll a level on P and N+P substrates. Lower tufa deposition supported a higher chlorophyll a level, while macrophytes reduced the chlorophyll a concentration and tufa deposition, possibly through effects on the flow and via root respiration. The effects of nutrients on tufa deposition were not recorded. P and N+P treatment increased macrozoobenthos abundance only in some seasons. Trophic groups of macrozoobenthos responded to the addition of P and N+P in the form of higher proportions of gazers and detritivores; however, the response of macrozoobenthos was generally weaker than that of autotrophs. Full article

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14 pages, 2012 KiB

Open AccessArticle

Impact of Sugarcane Cultivation on Benthic Macroinvertebrate Communities in Tropical Streams

by Marcus Vinícius França, Erika Mayumi Shimabukuro, Welber Senteio Smith, Mariana Morilla and Ricardo Hideo Taniwaki

Limnol. Rev. 2025, 25(2), 13; https://doi.org/10.3390/limnolrev25020013 - 16 Apr 2025

Abstract

Tropical streams host diverse benthic macroinvertebrates, essential for ecological processes and bioindicators of ecosystem health. However, land use changes, such as sugarcane cultivation, negatively impact stream structure and function. This study examined these effects by comparing streams in sugarcane-dominated areas with those in [...] Read more.

Tropical streams host diverse benthic macroinvertebrates, essential for ecological processes and bioindicators of ecosystem health. However, land use changes, such as sugarcane cultivation, negatively impact stream structure and function. This study examined these effects by comparing streams in sugarcane-dominated areas with those in native vegetation. Streams with native vegetation showed 2226 individuals across 107 taxa, 39 families, and 52 genera, with Chironomidae (Chironominae, Tanypodinae), Leptoceridae, Leptophlebiidae, and Calamoceratidae being the most abundant. In contrast, sugarcane streams showed 692 individuals from 47 taxa, 24 families, and 19 genera, with Chironomidae (Chironominae, Tanypodinae), Dryopidae, and Simuliidae dominating. The first hypothesis suggested that sugarcane plantations reduce taxonomic and functional diversity. The results partially confirmed this, showing lower abundance and richness in sugarcane streams, though functionality remained unchanged. The second hypothesis proposed greater seasonal taxonomic variation in sugarcane streams due to hydrological differences. Results supported this, revealing stronger seasonal shifts, particularly during the rainy season. These findings highlight the significant impact of sugarcane cultivation on aquatic ecosystems. Continuous monitoring of macroinvertebrates in agricultural landscapes is crucial for assessing environmental impacts and guiding conservation strategies. Full article

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13 pages, 2194 KiB

Open AccessArticle

Elemental Associations with Groundwater Nitrate in Northeastern Region of Saudi Arabia: Implications for Sustainable Water Management

by Al Mamun

Limnol. Rev. 2025, 25(2), 12; https://doi.org/10.3390/limnolrev25020012 - 1 Apr 2025

Abstract

Nitrate pollution in drinking water is a major environmental and health issue. High levels of nitrates in water sources present serious risks to both the environment and public health, highlighting the need for immediate research and management efforts to reduce pollution sources and [...] Read more.

Nitrate pollution in drinking water is a major environmental and health issue. High levels of nitrates in water sources present serious risks to both the environment and public health, highlighting the need for immediate research and management efforts to reduce pollution sources and safeguard water resources for sustainable growth. This study investigates the elemental associations with nitrate concentrations in groundwater across the northeastern region of Saudi Arabia, employing diverse analytical techniques to assess water quality and develop sustainable management strategies. Spatial variations in nitrate levels were observed in both deep and shallow wells using GIS-based interpolation, revealing distinct patterns influenced by geological, hydrological, and anthropogenic factors. A strong linear correlation with a high coefficient of determination (R² of 0.99) between electrical conductivity and dilution factor suggests the potential interchangeability of ion-selective electrode methods and conductivity meters for EC determination. The study identified a positive correlation between nitrate concentration and electrical conductivity in groundwater samples (R² of 0.70), indicating that conductivity measurements could potentially serve as a proxy for estimating nitrate levels. However, a very weak negative correlation between nitrate and pH suggests other factors may have a more significant impact on groundwater pH. The research also highlights the strong positive correlation between nitrate and nitrate-nitrogen concentrations, reflecting their close chemical association in water. These findings contribute to the understanding of nitrate dynamics in groundwater and emphasize the importance of comprehensive water quality assessments. Future research should focus on elucidating factors influencing nitrate distribution in groundwater systems and developing more robust predictive models based on readily measurable water quality parameters. Full article

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18 pages, 4254 KiB

Open AccessArticle

Species-Specific Responses of Baikal Amphipods to Artificial Lighting of Varying Intensity and Spectral Composition

by Dmitry Karnaukhov, Yana Ermolaeva, Maria Maslennikova, Bogdan Osadchy, Sofya Biritskaya, Arina Lavnikova, Natalia Kulbachnaya, Anastasia Solodkova, Artem Guliguev, Ivan Kodatenko, Diana Rechile, Kristina Ruban, Darya Kondratieva, Alexandr Bashkirtsev, Alyona Slepchenko, Anna Solomka, Sophia Nazarova and Eugene Silow

Limnol. Rev. 2025, 25(2), 11; https://doi.org/10.3390/limnolrev25020011 - 1 Apr 2025

Abstract

Light pollution can have a variety of effects on aquatic organisms. Despite the fact that amphipods are one of the model organisms for studying the effects of light among macroinvertebrates, data on the reaction of Baikal amphipods to artificial lighting are limited and [...] Read more.

Light pollution can have a variety of effects on aquatic organisms. Despite the fact that amphipods are one of the model organisms for studying the effects of light among macroinvertebrates, data on the reaction of Baikal amphipods to artificial lighting are limited and contradictory. In this study, we examine the response of Baikal littoral and sublittoral amphipod species to artificial lighting of varying intensity and spectral composition. In the experiments, amphipods were exposed to warm and white light at three different intensity ranges (5–15, 20–35, and 80–100 lx), as well as blue and red light. As a result, it was found that the reaction of Baikal amphipods to different lighting conditions was species-specific and dependent on the spectral composition of the light more so than the intensity of the light. In particular, white LED light generally repulsed E. cyaneus, but tended to attract A. godlevskii. P. cancelloides, and G. fasciatus, suggesting that white LED light may have a greater negative impact on wildlife than warm LED light. Generally, artificial light influences the behavior of Baikal amphipods, and an increase in light pollution on Lake Baikal may lead to changes in the littoral community in certain areas of the lake subject to pollution. Full article

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16 pages, 4604 KiB

Open AccessArticle

Historical Phosphorus Kinetics and Ambient Orthophosphate Concentrations in the St. Lawrence Great Lakes Erie, Huron, Michigan, St. Clair, and Superior by a Modified Inverse Isotope Dilution Method

by John T. Lehman

Limnol. Rev. 2025, 25(2), 10; https://doi.org/10.3390/limnolrev25020010 - 21 Mar 2025

Abstract

Historical measurements of phosphate turnover and uptake confirm that bacterioplankton dominate phosphate dynamics at ambient steady state conditions in all but the most eutrophic samples, but phytoplankton exhibits increased control at phosphate additions as low as +10 nM. The results are consistent with [...] Read more.

Historical measurements of phosphate turnover and uptake confirm that bacterioplankton dominate phosphate dynamics at ambient steady state conditions in all but the most eutrophic samples, but phytoplankton exhibits increased control at phosphate additions as low as +10 nM. The results are consistent with the theory that uptake mechanisms of bacterioplankton become saturated as soon as phosphate concentrations are elevated above ambient levels. Uptake dynamics were consistent with multiphasic kinetics by bacterioplankton versus phytoplankton. Temperature dependence of phosphate turnover was demonstrated for Lake Superior but not for other Great Lakes in which temperatures were largely homogeneous. Ambient concentrations of orthophosphate were estimated by an inverse isotope dilution method that indicated concentrations ranged from roughly 1 to 7 nM across all the lakes surveyed. Full article

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16 pages, 2440 KiB

Open AccessArticle

Maximum Potential Age of Pondcypress Hydrologic Indicators Using Diameter at Breast Height

by Cortney R. Cameron and Thomas J. Venning

Limnol. Rev. 2025, 25(1), 9; https://doi.org/10.3390/limnolrev25010009 - 20 Mar 2025

Abstract

In the absence of long-term hydrologic records, field-measured hydrologic indicators are useful for inferring past wetland hydrologic conditions, which can support research, regulation, and restoration. Inflection points on the buttresses of pondcypress trees (Taxodium ascendens) are frequently used in west-central Florida [...] Read more.

In the absence of long-term hydrologic records, field-measured hydrologic indicators are useful for inferring past wetland hydrologic conditions, which can support research, regulation, and restoration. Inflection points on the buttresses of pondcypress trees (Taxodium ascendens) are frequently used in west-central Florida to estimate cypress wetland high water levels, known as normal pool. However, little is known about how this indicator develops. A method to estimate tree age using diameter at breast height was developed for Florida pondcypress, which can be used by forested wetland managers to constrain the maximum potential age of hydrologic indicators in groups of cypress trees. This model was applied to a waterbody with a complex history of hydrologic alterations. The waterbody had two distinct populations of buttress inflection elevations, corresponding to historic versus current water level regimes. This represents one of the first documented instances in the literature where a waterbody showed multiple buttress inflection populations in the absence of soil subsidence. This work underscores the need to consider the development timelines when interpreting the hydrologic meaning of indicator elevations. Full article

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16 pages, 1489 KiB

Open AccessArticle

Longitudinal Distribution of Benthic Macroinvertebrates Related to River Ecological Quality

by Māra Kostanda, Gunta Spriņģe, Dāvis Ozoliņš, Agnija Skuja and Oskars Purmalis

Limnol. Rev. 2025, 25(1), 8; https://doi.org/10.3390/limnolrev25010008 - 14 Mar 2025

Abstract

Macroinvertebrates of the Venta River have been studied since the beginning of the 20th century. However, complex studies along the Venta River from the Latvian–Lithuanian border to its mouth into the Baltic Sea have been irregular and fragmentary. The aim of this study [...] Read more.

Macroinvertebrates of the Venta River have been studied since the beginning of the 20th century. However, complex studies along the Venta River from the Latvian–Lithuanian border to its mouth into the Baltic Sea have been irregular and fragmentary. The aim of this study was to assess the ecological status of the Venta River and to analyze the abundance and fauna composition of macroinvertebrates along the entire length of the river in the territory of Latvia. This is the first study of its kind for the Venta River examining the specialization of macroinvertebrates in sediment substrates and their functional feeding groups. Within the framework of the study, the composition and functional importance of macroinvertebrates was assessed in 10 sampling sites together with the ecological quality of the river using several indices. The results show that the Venta River is dominated by benthic invertebrate collectors/gatherers, active filterers, grazers, and scrapers that have adapted to the particular type of sediments formed by silt, macrophytes, rocks, and pebbles. Different indices were calculated in order to assess the ecological quality of the Venta River. According to the saprobity index, the water quality corresponds to β-mesosaprobity, while ecological quality is mostly average; however, according to the multimetric indices, the quality of the Venta River varies from poor to high depending on the sampling station. Full article

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15 pages, 5073 KiB

Open AccessArticle

Influence of Optically Active Substances on Light Attenuation in a Tropical Eutrophic Urban Reservoir

by Renata C. H. Amancio, Stella P. Pacheco, Karen A. F. Moura, Bianca L. Valle, Julia T. C. Alves, Fernanda F. Melo, Vitor J. G. Silva, Lívia S. Botelho, Raquel T. Rocha, Daiana R. Pelegrine, Thiago M. Salgueiro, Carlos M. O. Tadeu, Vitor G. Elian, Giulia A. Ducca, Arielli G. Zavaski, Renata L. Moreira, Winnícius M. S. Sá, Estevão E. O. Eller, Renato B. de Oliveira-Junior, Ivan M. Monteiro, Lorena T. Oporto, Diego G. F. Pujoni and José F. Bezerra-Neto Show full author list Hide full author list

Limnol. Rev. 2025, 25(1), 7; https://doi.org/10.3390/limnolrev25010007 - 12 Mar 2025

Cited by 1

Abstract

This study investigated the impact of optically active substances on light attenuation in a tropical eutrophic urban reservoir under different seasonal conditions. Diffuse attenuation coefficients for photosynthetically active radiation (Kd_PAR) and ultraviolet radiation (Kd_UVA and Kd_UVB) [...] Read more.

This study investigated the impact of optically active substances on light attenuation in a tropical eutrophic urban reservoir under different seasonal conditions. Diffuse attenuation coefficients for photosynthetically active radiation (Kd_PAR) and ultraviolet radiation (Kd_UVA and Kd_UVB) were measured at three representative sites and correlated with water quality parameters (chlorophyll-a, total suspended solids [TSS], dissolved organic carbon, and colored dissolved organic matter [CDOM]). The results revealed significant spatial and seasonal differences, with the highest attenuation observed during the rainy season. The Ilha site exhibited the greatest coefficients (Kd_PAR = 6.0 m⁻¹, Kd_UVA = 17.9 m⁻¹, Kd_UVB = 19.0 m⁻¹), while lower values were recorded at Barragem (Kd_PAR = 2.4 m⁻¹, Kd_UVA = 9.1 m⁻¹, Kd_UVB = 12.0 m⁻¹) and Igrejinha (Kd_PAR = 3.1 m⁻¹, Kd_UVA = 10.8 m⁻¹, Kd_UVB = 11.9 m⁻¹). Statistical analyses showed strong correlations between TSS and Kd_PAR (r = 0.66) and between CDOM and both Kd_UVA (r = 0.66) and Kd_UVB (r = 0.59), with regression models confirming TSS and CDOM as key predictors of light attenuation. These findings underscore the pivotal role of particulate and dissolved organic matter in underwater light dynamics, emphasizing the need to reduce their input during periods of heavy rainfall. Full article

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19 pages, 5256 KiB

Open AccessArticle

Comparison of Machine Learning Models for Real-Time Flow Forecasting in the Semi-Arid Bouregreg Basin

by Fatima Zehrae Elhallaoui Oueldkaddour, Fatima Wariaghli, Hassane Brirhet, Ahmed Yahyaoui and Hassane Jaziri

Limnol. Rev. 2025, 25(1), 6; https://doi.org/10.3390/limnolrev25010006 - 5 Mar 2025

Abstract

Morocco is geographically located between two distinct climatic zones: temperate in the north and tropical in the south. This situation is the reason for the temporal and spatial variability of the Moroccan climate. In recent years, the increasing scarcity of water resources, exacerbated [...] Read more.

Morocco is geographically located between two distinct climatic zones: temperate in the north and tropical in the south. This situation is the reason for the temporal and spatial variability of the Moroccan climate. In recent years, the increasing scarcity of water resources, exacerbated by climate change, has underscored the critical role of dams as essential water reservoirs. These dams serve multiple purposes, including flood management, hydropower generation, irrigation, and drinking water supply. Accurate estimation of reservoir flow rates is vital for effective water resource management, particularly in the context of climate variability. The prediction of monthly runoff time series is a key component of water resources planning and development projects. In this study, we employ Machine Learning (ML) techniques—specifically, Random Forest (RF), Support Vector Regression (SVR), and XGBoost—to predict monthly river flows in the Bouregreg basin, using data collected from the Sidi Mohamed Ben Abdellah (SMBA) Dam between 2010 and 2020. The primary objective of this paper is to comparatively evaluate the applicability of these three ML models for flow forecasting in the Bouregreg River. The models’ performance was assessed using three key criteria: the correlation coefficient (R²), Akaike Information Criterion (AIC), and Bayesian Information Criterion (BIC). The results demonstrate that the SVR model outperformed the RF and XGBoost models, achieving high accuracy in flow prediction. These findings are highly encouraging and highlight the potential of machine learning approaches for hydrological forecasting in semi-arid regions. Notably, the models used in this study are less data-intensive compared to traditional methods, addressing a significant challenge in hydrological modeling. This research opens new avenues for the application of ML techniques in water resource management and suggests that these methods could be generalized to other basins in Morocco, promoting efficient, effective, and integrated water resource management strategies. Full article

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24 pages, 2186 KiB

Open AccessArticle

Characteristics of the Zooplankton Community Structure in Shengjin Lake and Its Response to the Restored Aquatic Vegetation

by Dagne Tafa Dibar, Kun Zhang and Zhongze Zhou

Limnol. Rev. 2025, 25(1), 5; https://doi.org/10.3390/limnolrev25010005 - 25 Feb 2025

Abstract

Macrophytes taxa composition determines microinvertebrates utilized as environmental indicators in freshwater ecosystems. This study was conducted in Shengjin Lake. In this lake, local communities have been practicing using sine fishing nets for fishing and this has a disrupting effect on macrophyte vegetation, even [...] Read more.

Macrophytes taxa composition determines microinvertebrates utilized as environmental indicators in freshwater ecosystems. This study was conducted in Shengjin Lake. In this lake, local communities have been practicing using sine fishing nets for fishing and this has a disrupting effect on macrophyte vegetation, even though it was the major for the disappearance of submerged vegetation before it was banned. As a result of this sine fishing net ban by the local authorities, the vegetation that had disappeared began to recover. Thus, this study investigated the role of architecturally differentiated macrophytes restoration effect on zooplankton communities’ diversity, abundance, and species composition; open water was used as a control. For this, the data were collected from different habitats via site 1 (open water) site 2, (free-floating), site 3 (emergent and submerged), site 4 (submerged), and site 5 (emergent) macrophytes. In the present study, the results demonstrated that the relative mean density of Rotifer was measured high which ranged from (219 ± 141–678 ± 401 ind L⁻¹), mainly dominated by Keratella cochlearis and Lecane cornuta species. Following Rotifera, Cladocera population density was reported high and ranged within (36 ± 6.2–262.5 ± 49.4 ind L⁻¹). The Cladocera group was dominated by Daphnia spp., Moina micura, Ceriodaphnia reticulata, and Chydorus latus species. Compared to Rotifer and Cladocera, Copepod community were recoded least with relative mean density ranged within (11.52 ± 2.22–85.5 ± 27 ind L⁻¹) and dominated by Microcyclops javanus, Thermodiaptomus galebi, and Sinocalanus doerrii species. From environmental variables and the zooplankton density relationship analyzed, the redundancy analysis (RDA) results indicated that Water Temperature, Chlorophyll a, Dissolved Oxygen, Total Phosphorus, and Ammonium Nitrogen were found the most influential variables on zooplankton communities. Stepwise regression correlation showed that Copepod and Cladocera were found more dependent on environmental factors. For instance, Nitrate Nitrogen was negatively correlated with Cladocera, Copepod, and total zooplankton biomass but positively with Cladocera diversity. Water Temperature showed a positive relationship with Rotifer diversity; however, both Chlorophyll a and Electrical Conductivity were correlated positively with Cladocera biomass. Species diversity by the Shannon–Wiener index (H) illustrated a dynamic trend among the monitored sites which ranged between (0.65–4.25). From the three groups of zooplankton communities in contrast to Cladocera and Copepod, Rotifer species obtained more diversity across the studied sites. The Cladocera diversity (H′) index indicated a similar tendency in all sites. However, more Copepod diversity (H′) was observed in site 4. In conclusion, this study results can provide valuable insights into the health and dynamics of the aquatic ecosystem to understand factors deriving ecological imbalance and develop an integrated approach for effective strategies for management and conservation. Full article

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20 pages, 2950 KiB

Open AccessArticle

Nutrient Load Fluctuations in the Bottom Water of Estuarine Lakes Under the El Niño Phenomenon: Possible Connections and Coping Strategies—Based on the Preliminary Studies of Lake Nakaumi

by Xizhe Wang and Kengo Kurata

Limnol. Rev. 2025, 25(1), 4; https://doi.org/10.3390/limnolrev25010004 - 21 Feb 2025

Abstract

Estuarine lakes possess significant ecological value. Their complex hydrological environments give rise to diverse habitats, providing a home to numerous life forms. However, with the intensification of the impacts of global climate change, the estuarine lake ecosystem is facing severe challenges. Through trend [...] Read more.

Estuarine lakes possess significant ecological value. Their complex hydrological environments give rise to diverse habitats, providing a home to numerous life forms. However, with the intensification of the impacts of global climate change, the estuarine lake ecosystem is facing severe challenges. Through trend analysis and differential analysis, this paper elaborates on the changes in nitrogen and phosphorus nutrients in the bottom water of Lake Nakaumi from 2013 to 2017. It analyzes the differences between the El Niño period and the non-El Niño period, speculates on the possible connections between the changes in nutrient load and the El Niño phenomenon, and uses the traditional water quality assessment method of the WQI to more intuitively demonstrate the fluctuations in nutrient load. Based on the analysis of the case of Lake Nakaumi, possible environmental management suggestions are put forward. Additionally, the paper compares and discusses the differences in the changes of lakes at adjacent latitudes during similar periods. As for the bottom water of Lake Nakaumi, there may be the following connections between the changes in its nutrient load and the El Niño phenomenon: (1) DPO₄-P was most sensitive to the peak intensity of the El Niño phenomenon. (2) Compared with NO₃-N, the changes in NO₂-N and DPO₄-P were more sensitive to the start of the El Niño cycle. (3) The El Niño phenomenon had differential impacts on various forms of nitrogen and phosphorus in Lake Nakaumi. The focus of this paper is to explore the connection between the El Niño phenomenon and the changes in the nutrient load of the bottom water of estuarine lakes and to find a method beneficial to environmental management. However, due to the limitations of the currently available data, there are still many deficiencies that need to be further addressed. It is hoped that this paper can attract the attention of relevant researchers to this issue. Full article

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15 pages, 1262 KiB

Open AccessArticle

A Study on the Optimal Planning of Forest Ecosystems on Hainan Island in the Context of the Integrated Development of Lakes, Wetlands and Forests

by Ying Zhang, Keren Zhang and Zixuan Zhang

Limnol. Rev. 2025, 25(1), 3; https://doi.org/10.3390/limnolrev25010003 - 10 Feb 2025

Abstract

Hainan Island has rich water resources and unique lake ecosystems. Organically connecting lakes and wetlands with forest ecosystems should be considered in order to strengthen biodiversity protection, form a continuous green corridor to promote species migration and gene exchange, and enhance the stability [...] Read more.

Hainan Island has rich water resources and unique lake ecosystems. Organically connecting lakes and wetlands with forest ecosystems should be considered in order to strengthen biodiversity protection, form a continuous green corridor to promote species migration and gene exchange, and enhance the stability and resilience of the overall ecological system and maximize its benefits. The method of linear programming was used in this study to analyze the forest ecosystem on Hainan Island in China in order to provide a scientific basis for the integration, protection and management of lakes, wetlands and forests. This study points out that the ratio of the area of timber forest, protection forest, special-purpose forest and bamboo forest should be adjusted from the current 68:22.9:7.1:1.8 to 24:72.8:2.5:0.6. The average shadow price of the reasonable use of different forest lands on Hainan Island is 2512.46 CNY/ha and the optimal value of special-purpose forest is 4376.04 CNY/ha, rather than the current 6888.50 CNY/ha. This study also shows that the timber forest, special-purpose forest and bamboo forest on Hainan Island are short-term products, while protection forest, wood-fuel forest, economic forest, open forest land, shrub land, young afforested land and non-forest land are long-term products, for which it is not easy to obtain benefits in the short-term. A combination of long- and short-term forest ecological planning should be considered to maintain the various long-term benefits. This study finally proposes that Hainan Island should reduce its proportion of timber forest area; increase its proportion of protection forest area; focus on the integrated development of lakes, wetlands and forests and biodiversity conservation goals; and pay close attention to the adjustment of forest type structure in order to meet the needs of ecological province construction and sustainable development. Full article

(This article belongs to the Special Issue Trends in the Trophic State of Freshwater Ecosystems)

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13 pages, 6041 KiB

Open AccessReview

Recent Progress in Diatom Research in the Yangtze River Basin

by Hui Liu, Xiangqun Wu and Xu Chen

Limnol. Rev. 2025, 25(1), 2; https://doi.org/10.3390/limnolrev25010002 - 10 Feb 2025

Abstract

Diatoms have been widely used for aquatic environment assessment. However, the progress of diatom research is uneven in different regions of the world. This study gathered both Chinese and English articles on diatom research in the Yangtze River Basin in order to explore [...] Read more.

Diatoms have been widely used for aquatic environment assessment. However, the progress of diatom research is uneven in different regions of the world. This study gathered both Chinese and English articles on diatom research in the Yangtze River Basin in order to explore recent progress in this field. Using the Web of Science, China National Knowledge Infrastructure (CNKI), and Wanfang databases, we gathered 419 articles (1995–2024) on diatom research in the Yangtze River Basin. There is a substantial increase in the number of articles since 2000. Since the mid-1990s, a total of 63 new diatom species have been identified in this region. Based on limnological investigations of lakes in the Yangtze River Basin, diatom-based conductivity and total phosphorus (TP) transfer functions have been developed for quantitative reconstruction of past conductivity and TP in the water column. The results revealed a recent shift in thematic focus from eutrophication to biodiversity dynamics, the ecosystem regime shift, and ecohydrological change. Although diatom research in the Yangtze River Basin has achieved fruitful outputs, further studies are urgently needed to explore diatom biodiversity and the ecological status of aquatic ecosystems in this rapidly-developing region. The results can improve our understanding of diatom research progress and hence provide important clues for further studies. Full article

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11 pages, 1123 KiB

Open AccessArticle

Risk of Chemical Pollution in Olifants River Basin, South Africa: Human Health Implications

by Abraham Addo-Bediako

Limnol. Rev. 2025, 25(1), 1; https://doi.org/10.3390/limnolrev25010001 - 7 Jan 2025

Cited by 1

Abstract

Chemical pollution in freshwater ecosystems poses a significant environmental threat, often hindering access to safe drinking water for human populations. The Olifants River Basin in South Africa is particularly vulnerable due to escalating mining and agricultural activities, and domestic waste discharged into the [...] Read more.

Chemical pollution in freshwater ecosystems poses a significant environmental threat, often hindering access to safe drinking water for human populations. The Olifants River Basin in South Africa is particularly vulnerable due to escalating mining and agricultural activities, and domestic waste discharged into the rivers. In this study, the risk posed to humans by exposure to potentially toxic elements (PTEs) in water from two rivers, the Blyde and Steelpoort, was assessed. Water samples were collected from upstream, midstream, and downstream locations of these rivers, and the concentrations of eight PTEs (Arsenic, Cadmium, Chromium, Iron, Manganese, Nickel, Lead, and Zinc) were determined using inductively coupled plasma-optical emission spectrophotometry. Furthermore, two pathways of exposure, direct ingestion and dermal absorption, were used to evaluate their potential impacts on human health. The findings indicate that direct ingestion poses a greater risk to human health compared to dermal absorption. While PTEs may pose little non-carcinogenic risk for adults, higher risk was observed in children. This is an indication that children are at higher risk using water from the rivers, sometimes without any form of treatment. When carcinogenic risks (CRs) were computed for both adults and children for As, Cr, Ni, and Pb levels, the CR values were above the threshold limit, except for Pb, indicating a potential carcinogenic risk. This study underscores the need for regular monitoring of chemical pollution, and the implementation of effective mitigation strategies to safeguard both river ecosystems and human health, including proper treatment of water for domestic and agricultural purposes. Full article

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19 pages, 8094 KiB

Open AccessArticle

Improving the Quality of the Water Flowing over a Stepped Spillway in Open Canals by Increasing Its Degree of Aeration

by Mohamed A. Ashour, Mohamed Khairy Ali and Tawab E. Aly

Limnol. Rev. 2024, 24(4), 653-671; https://doi.org/10.3390/limnolrev24040038 - 12 Dec 2024

Abstract

As spillways are hydraulic structures constructed for the safe release of floodwater from the upstream (US) side of a dam to the downstream side, or from the end of canals and drains to a lower stream, the upstream water flow of such structures [...] Read more.

As spillways are hydraulic structures constructed for the safe release of floodwater from the upstream (US) side of a dam to the downstream side, or from the end of canals and drains to a lower stream, the upstream water flow of such structures gains significant amounts of potential energy. As this water flows over a spillway or escapes, the gained potential energy is converted into kinetic energy, resulting in the water gaining an increasing velocity, thereby enhancing the flow’s destructive potential. This can have a harmful impact on the hydraulic performance and the structural stability of the spillway itself. To avoid such harmful effects, engineers and designers of such structures usually provide the spillways and water escapes with some tools for dissipating that kinetic energy and decreasing the flowing water’s velocity. The present study aims to enhance the performance efficiency of such dissipating tools, as well as to improve the quality of the flowing water by leveraging the significant turbulence generated by the existing energy dissipators on the back of the spillway body. The aeration process enabled by this turbulence increases the dissolved oxygen contents, thereby enhancing the water quality, which is one of the main objectives of this work. On the back surface of the spillway, various dissipater shapes with different geometrical configurations, dimensions, and combinations were tested, in order to determine the most suitable engineering treatments for maximizing the dissolved oxygen content and improving the water quality for various uses, as the study’s main goal. By testing 21 different model configurations with the available laboratory discharges, the study successfully identified the most effective shape and properties of the desired dissipator, which increased the dissolved oxygen content by an average of 21.70% and dissipated water energy by about 69%. Full article

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16 pages, 5541 KiB

Open AccessArticle

Resilience or Collapse? Reconstructing the Water Quality Time Series of a Tropical River Impacted by a Mine Tailings Dam Failure

by Anelise Rodrigues Machado Garcia, Diego Guimarães Florencio Pujoni and José Fernandes Bezerra-Neto

Limnol. Rev. 2024, 24(4), 637-652; https://doi.org/10.3390/limnolrev24040037 - 6 Dec 2024

Abstract

The 2015 Fundão tailings dam collapse in Mariana, Brazil, was a major environmental catastrophe. Assessing its long-term effects on water quality is critical for environmental restoration and policy development. In this study, we reconstructed a 15-year time series of five water quality parameters [...] Read more.

The 2015 Fundão tailings dam collapse in Mariana, Brazil, was a major environmental catastrophe. Assessing its long-term effects on water quality is critical for environmental restoration and policy development. In this study, we reconstructed a 15-year time series of five water quality parameters to assess whether the collapse caused permanent changes. Using public data from the Minas Gerais Water Institute (IGAM), we fitted generalized additive models for location, scale, and shape to model long-term trends in turbidity, total solids, conductivity, pH, and dissolved oxygen. Predictor variables included daily precipitation and smooth functions for time and longitudinal distance along the river. As expected, turbidity and total solids increased sharply after the collapse; however, the mean values returned to pre-collapse levels within four years. Conductivity, which was already elevated pre-collapse, remained high following the passage of the tailings plume. Although we observed a tendency toward pre-collapse values, the long-term conductivity mean did not fully stabilize to previous levels. No clear patterns were observed for pH or dissolved oxygen. This study highlights the acute impact of the dam collapse on five water quality parameters in the Doce River and illustrates the river’s subsequent stabilization process, although other important and chronic impacts are still persistent. Long-term studies such as this provide valuable insights into the dynamics of fluvial systems. Full article

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21 pages, 963 KiB

Open AccessReview

The Influence of Abiotic Factors on the Distribution of Macrophytes in Small Water Bodies in Temperate Ecosystems

by Isabel Navarro Law, Isabelle Durance, Rachel Benstead, Michael E. Fryer and Colin D. Brown

Limnol. Rev. 2024, 24(4), 616-636; https://doi.org/10.3390/limnolrev24040036 - 6 Dec 2024

Abstract

Currently, reviews focusing on the distribution of macrophytes focus primarily on large water bodies, regardless of the fact that small water bodies (SWBs), such as ponds, ditches and streams, often support higher levels of gamma macrophyte richness. This review investigates the direction and [...] Read more.

Currently, reviews focusing on the distribution of macrophytes focus primarily on large water bodies, regardless of the fact that small water bodies (SWBs), such as ponds, ditches and streams, often support higher levels of gamma macrophyte richness. This review investigates the direction and strength of the relationship between 13 abiotic factors and macrophyte distribution in SWBs. Results demonstrate that there are distinct differences between the effects of abiotic factors on bryophytes and those on vascular macrophytes of different morphological forms. Whilst shading and velocity have a significant (p < 0.05) negative relationship with vascular macrophyte richness and a positive relationship with bryophyte richness, the reverse is true for the size of a water body, depth and concentration of nitrogen. Vascular macrophyte richness has a significant (p < 0.05) negative relationship with distance to a stream source, isolation, the proportion of surrounding land that is woodland, total phosphorus concentrations and pH. The strength of the influence of substrate size and water body size differs between vascular macrophyte morphologies. Key knowledge gaps include bryophyte distribution and the effect of hydroperiod and surrounding land use on macrophyte communities. In order to conserve all macrophyte morphologies and taxa, it is important to protect SWBs with a diverse set of conditions. Full article

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23 pages, 6039 KiB

Open AccessArticle

Hydrobiological and Geochemical Responses to Trout Cage Aquaculture in Lake Ecosystem

by Artem Lapenkov, Alina Guzeva, Ksenia Zaripova, Dina Dudakova and Artem Trifonov

Limnol. Rev. 2024, 24(4), 593-615; https://doi.org/10.3390/limnolrev24040035 - 3 Dec 2024

Cited by 1

Abstract

This study investigates the seasonal dynamics and interrelationships between geochemical and hydrobiological parameters in lake ecosystems impacted by fish cage farming in Lake Ladoga, Russia. Environmental conditions at three trout farms were assessed, focusing on water and sediment quality as well as benthic [...] Read more.

This study investigates the seasonal dynamics and interrelationships between geochemical and hydrobiological parameters in lake ecosystems impacted by fish cage farming in Lake Ladoga, Russia. Environmental conditions at three trout farms were assessed, focusing on water and sediment quality as well as benthic and zooplankton communities. For each farm, two categories of sampling sites were designated: cage sites and reference sites located 100–600 m away from the cages. Fieldwork was carried out across four seasons in 2023: February, June, August, and November. The findings indicate that intensive fish feeding results in significant organic waste accumulation beneath trout cages, altering the composition and abundance of planktonic and benthic organisms. The organic matter content in sediments beneath the cages during periods of intensive feeding was found to increase 2–5 times compared to the reference sites. In winter, accumulated organic matter in the sediments underwent mineralization, bringing hydrobiological indicators closer to the reference values. The geochemical and hydrobiological parameters analyzed in this study serve as valuable indicators for developing ecological monitoring approaches in freshwater cage aquaculture. Full article

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