Limnological Review

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Long-Term Eutrophication in Mesotrophic–Eutrophic Lake Kawaguchi, Japan, Based on Observations of the Horizontal Distribution of Profundal Chironomid Larvae and Oligochaetes

by Kimio Hirabayashi and Masaaki Takeda

Limnol. Rev. 2025, 25(4), 53; https://doi.org/10.3390/limnolrev25040053 (registering DOI) - 1 Nov 2025

Abstract

Many researchers have used the species composition, relative abundance and distribution pattern of profundal benthic macroinvertebrate communities in particular, especially chironomid fauna, as indicators of the trophic state and pollution of lakes. In addition, compared with previous benthic macroinvertebrate data, it is expected [...] Read more.

Many researchers have used the species composition, relative abundance and distribution pattern of profundal benthic macroinvertebrate communities in particular, especially chironomid fauna, as indicators of the trophic state and pollution of lakes. In addition, compared with previous benthic macroinvertebrate data, it is expected that the process of eutrophication/oligotrophication of lakes can also be traced. Benthic macroinvertebrate distribution was studied in Lake Kawaguchi, Japan (maximum depth 16.1 m; mean depth 9.3 m), on 7 March 2025. The benthic animals identified were aquatic oligochaetes, chironomid larvae, shellfish and others. Differences among environmental factors and zoobenthos densities and rank correlation were analyzed using a non-parametric test. The mean density of oligochaetes, which was the dominant group, was 2457 ± 1247 individuals/m², followed by chironomid larvae at 816 ± 391 individuals/m². The larvae of Propsilocerus akamusi were the most abundant species at 669 ± 358 individuals/m², followed by Chironomus plumosus at 109 ± 114 individuals/m². Other chironomids (38 ± 75 individuals/m²) were also captured. Benthic communities were collected at all sites, but each taxa had its own characteristics. Oligochaetes and C. plumosus were widely distributed throughout the lake, whereas the distribution of P. akamusi was skewed toward the western part of the lake. In comparison with previous studies, P. akamusi larvae were now found to be the most abundant chironomid species in this lake, accounting for an increased percentage of the chironomid community, while C. plumosus larvae had decreased in recent years. In addition, the higher levels of organic matter in the upper sediment layer of the lake suggest ongoing eutrophication. Previous studies classified Lake Kawaguchi as mesotrophic–eutrophic, but reconsideration of this classification is warranted given the above findings. We suggest that this lake be ranked as a eutrophic lake (chlorophyll-a concentration; ca. 0.05 mg/L) based on a long-term investigation of the changes in chironomid fauna. Full article

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

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16 pages, 1365 KB

Open AccessArticle

Perceptions of Four Rural Communities Regarding the Largest Hydropower Project in Ecuador: The Case of Coca Codo Sinclair

by Sebastian Naranjo-Silva, Diego Javier Punina-Guerrero and Edwin Angel Jacome-Dominguez

Limnol. Rev. 2025, 25(4), 52; https://doi.org/10.3390/limnolrev25040052 (registering DOI) - 1 Nov 2025

Abstract

The global transition towards renewable energy production has increased the demand for new and more flexible hydropower operations. Although hydropower is generally considered environmentally friendly, it can cause environmental and social impacts. As the biggest and most representative hydropower project in Ecuador, the [...] Read more.

The global transition towards renewable energy production has increased the demand for new and more flexible hydropower operations. Although hydropower is generally considered environmentally friendly, it can cause environmental and social impacts. As the biggest and most representative hydropower project in Ecuador, the Coca Codo Sinclair hydropower project (CCSHP) provides a relevant case of water use competition between local communities and the country’s development. In this study, perspectives of four communities near the CCSHP were analyzed through a survey with 183 responses collected in 52 days through door-to-door household visits in two upstream and two downstream towns. The analysis highlights that limited community participation in project design and insufficient communication strategies have undermined public acceptance, despite government promotion of its national benefits. Survey results reveal that 79% of respondents expressed negative perceptions, primarily about environmental change, displacement, and lack of compensation, while only 15% expressed positive views. It is important to note that the communities had no role in selecting the project location, and their involvement was limited, particularly regarding transportation, environmental changes, and the loss of local species. These findings suggest that project managers should strengthen dialogue with local communities and design participatory mechanisms that can improve trust and long-term project acceptance. Full article

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27 pages, 6753 KB

Open AccessArticle

Holistic Ecosystem Assessment of the Mangalia–Limanu Coastal Lake (Black Sea, Romania)

by Ana Bianca Pavel, Catalina Gavrila, Irina Catianis, Gabriel Iordache, Florina Radulescu, Adrian Teaca and Laura Dutu

Limnol. Rev. 2025, 25(4), 51; https://doi.org/10.3390/limnolrev25040051 - 23 Oct 2025

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Abstract

The Mangalia–Limanu coastal lake system, located in southeastern Romania along the Black Sea, represents a transitional aquatic environment shaped by the interplay between freshwater and marine influences. This study provides an integrated assessment of its physicochemical water parameters, sedimentological and geochemical properties, and [...] Read more.

The Mangalia–Limanu coastal lake system, located in southeastern Romania along the Black Sea, represents a transitional aquatic environment shaped by the interplay between freshwater and marine influences. This study provides an integrated assessment of its physicochemical water parameters, sedimentological and geochemical properties, and benthic macroinvertebrate communities, aiming to evaluate its current ecological status and environmental dynamics. Field measurements using a multiparameter sonde revealed a predominantly freshwater to oligohaline system with moderate spatial heterogeneity. DO levels frequently reached supersaturation (>180%), coupled with high pH (~9.1), indicating intense daytime photosynthetic activity. Conductivity, TDS, and salinity increased longitudinally toward the port water area, while nitrate concentrations showed stronger signals upstream. Sediments were dominated by organic matter (18–88%), with lower carbonate (3–53%) and siliciclastic (8–49%) contents. Organic-rich deposits prevailed in the western-central sector, where reduced hydrodynamics and submerged vegetation favor autochthonous organic accumulation, whereas the eastern sector, exposed to marine action, showed more siliciclastic-rich substrates. Geochemical analyses revealed localized exceedances of Cr, Ni, Cu, Zn, and Pb regulatory thresholds (Order 161/2006), suggesting potential contamination hotspots. Benthic communities included 26 taxa, dominated by polychaetas, gammarids, and gastropods, with moderate diversity (H′ < 2). The results highlight a system under moderate anthropogenic pressure but retaining transitional lagoon characteristics, emphasizing the need for continued ecological monitoring and integrated management measures. Full article

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15 pages, 816 KB

Open AccessReview

Management of Water Resources in South Africa: A Systematic Review

by Landry S. Omalanga and Ednah K. Onyari

Limnol. Rev. 2025, 25(4), 50; https://doi.org/10.3390/limnolrev25040050 - 16 Oct 2025

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Abstract

Water is a vital resource for human survival, economic development, and environmental sustainability. It is essential to agriculture, energy production, public health, and biodiversity preservation. Efficient water management is even more important in areas that are prone to scarcity. This paper presents a [...] Read more.

Water is a vital resource for human survival, economic development, and environmental sustainability. It is essential to agriculture, energy production, public health, and biodiversity preservation. Efficient water management is even more important in areas that are prone to scarcity. This paper presents a systematic review of the management of water resources in South Africa, a country characterized by significant water scarcity challenges compounded by its socio-economic and ecological needs. South Africa’s limited freshwater resources are under extreme stress due to its semi-arid climate, unequal rainfall distribution, expanding population, and industrial needs. The nation’s water security has also been made more difficult by historical injustices, climatic fluctuations, and decaying infrastructure. Through a systematic review of 60 scholarly articles published between 2011 and 2025 in the Web of Science database, this study discusses the historical context of water management in South Africa, including the legacy of apartheid-era policies and their impact on access to water. It also examines current management practices, governance structures involving national and local authorities, the role of key institutions such as the Department of Water and Sanitation (DWS), climate change impact on water availability, population growth and urbanization, inequality and access, and challenges in South Africa’s water resources management (WRM). In particular, this review highlights the integration of scientific water quality and biostability assessment into the Integrated Water Resources Management (IWRM) framework in order to produce actionable insights that enhance resilience, sustainability, and equity in WRM. Furthermore, it explores future strategies for sustainable WRM, emphasizing the importance of IWRM, community participation, technological innovation, and climate change adaptation. Through this comprehensive analysis, the paper aims to contribute to a deeper understanding of the complexities and opportunities in ensuring water security for all South Africans. Full article

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10 pages, 868 KB

Open AccessArticle

Studies of Volatile Organic Compounds Emission from Bottom Sediments of Mid–Forest Eutrophic Lake with the Use of Proton Transfer Reaction Mass Spectrometry

by Józef Antonowicz and Tomasz Wróblewski

Limnol. Rev. 2025, 25(4), 49; https://doi.org/10.3390/limnolrev25040049 - 14 Oct 2025

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Abstract

In 2023, studies were conducted on volatile organic compounds (VOCs) emitted from the bottom sediments of the mid-forest eutrophic lake. Lake Łętowskie is located in northern Poland and covers an area of 402 hectares. It is part of the “Łętowskie Lake and the [...] Read more.

In 2023, studies were conducted on volatile organic compounds (VOCs) emitted from the bottom sediments of the mid-forest eutrophic lake. Lake Łętowskie is located in northern Poland and covers an area of 402 hectares. It is part of the “Łętowskie Lake and the vicinity of Kępice” Protected Landscape Area. Bottom sediment samples were collected from five sites located on the lake. The study sites differed in shoreline development: forest, agricultural land, and the central part of the lake. The emissions from the bottom sediment to the atmosphere of 20 volatile organic compounds were measured in the samples using a proton transfer reaction mass spectrometer (PTR-MS). This analytical technique enables the detection and determination of concentrations of volatile organic compounds characterized by proton affinity greater than that of water. The VOC data obtained showed different characteristics for study sites bordering forests and agricultural areas, which was supported by statistical analysis. The VOC data obtained from Lake Łętowskie were compared with results from neighboring lakes, demonstrating similarities to those observed in a lake with a forest catchment area. Full article

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

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15 pages, 3711 KB

Open AccessArticle

Consequences of the Construction of a Small Dam on the Water Quality of an Urban Stream in Southeastern Brazil

by Lucas Galli do Rosário, Ricardo Hideo Taniwaki and Luis César Schiesari

Limnol. Rev. 2025, 25(4), 48; https://doi.org/10.3390/limnolrev25040048 - 5 Oct 2025

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Abstract

The growth of the human population, combined with climate change, has made the provisioning of water resources to human populations one of the greatest challenges of recent decades. One commonly adopted solution has been the construction of small dams and reservoirs close to [...] Read more.

The growth of the human population, combined with climate change, has made the provisioning of water resources to human populations one of the greatest challenges of recent decades. One commonly adopted solution has been the construction of small dams and reservoirs close to urban settlements. However, concerns have arisen that, despite their small size, small dams may have environmental impacts similar to those known for large dams. The severe water crisis observed between 2014 and 2015 led to the multiplication of small dams in southeastern Brazil, such as the one built on the Fetá stream at the Capivari River basin in the municipality of Louveira. This study aimed to contribute to the assessment of the impacts of small dam construction on water quality by monitoring basic parameters and nutrients during the filling and stabilization period of the Fetá reservoir. As expected, the interruption of water flow and the increase in water residence time led to increases in temperature, pH, electrical conductivity, dissolved oxygen and concentrations of dissolved carbon and nitrogen, as well as a reduction in turbidity. Consistent with the shallow depth of the water column, neither thermal nor chemical stratification was observed. Nevertheless, the water quality of surface and bottom layers was markedly different. Over time, water volume and water quality tended to stabilize. This research clearly demonstrates that small dams and reservoirs cause qualitatively similar environmental impacts to those of large-scale dams and reservoirs worldwide. Full article

(This article belongs to the Special Issue Functional Ecology of Urban Streams)

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17 pages, 3336 KB

Open AccessArticle

Surface Water Treatment with Carica papaya-Based Coagulants: A Natural and Sustainable Solution

by Guillermo Díaz-Martínez, Ricardo Navarro-Amador, José Luis Sánchez-Salas and Deborah Xanat Flores-Cervantes

Limnol. Rev. 2025, 25(4), 47; https://doi.org/10.3390/limnolrev25040047 - 4 Oct 2025

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Abstract

Access to clean water remains a global challenge, particularly in areas where populations rely on surface water. These water sources must be treated. Coagulation with chemicals causes environmental problems and adverse effects on human health. Natural coagulants obtained from papaya (Carica papaya [...] Read more.

Access to clean water remains a global challenge, particularly in areas where populations rely on surface water. These water sources must be treated. Coagulation with chemicals causes environmental problems and adverse effects on human health. Natural coagulants obtained from papaya (Carica papaya) waste are presented as an alternative that is safe for human health, non-polluting, and biodegradable. The effectiveness of these natural coagulants is compared to that of aluminum sulfate using jar tests and synthetic and natural surface water, with statistical tools to model treatment processes. All coagulants have competitive results, reaching turbidity remotion levels above 90%. However, in equivalent tested ranges, natural coagulants require lower dosages and perform better with high initial water turbidity due to their polymeric bridging mechanisms and adsorption processes through the action of their functional groups, as detected by FTIR analysis. Additional testing with contaminated water from the Valsequillo dam confirms the use of these coagulants to treat water, with papaya seed coagulant yielding the best results and requiring lower doses, making it a competitive alternative. It can be concluded that papaya-based coagulants obtained from waste can be used as an eco-friendly alternative to aluminum sulfate in physicochemical treatments to purify surface water for human consumption. Full article

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13 pages, 3029 KB

Open AccessArticle

Microplastics in Sediments of the Littoral Zone and Beach of Lake Baikal

by Anastasia Solodkova, Sofya Biritskaya, Artem Guliguev, Diana Rechile, Yana Ermolaeva, Arina Lavnikova, Dmitry Golubets, Alyona Slepchenko, Ivan Kodatenko, Alexander Bashkircev, Natalia Kulbachnaya, Darya Kondratieva, Anna Solomka, Dmitry Karnaukhov and Eugene Silow

Limnol. Rev. 2025, 25(4), 46; https://doi.org/10.3390/limnolrev25040046 - 24 Sep 2025

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Abstract

Most studies on microplastic pollution in aquatic ecosystems have focused on the quantitative and qualitative assessment of particles in surface waters. However, the highest concentrations and accumulation of microplastic particles are observed in bottom sediments. The aim of this study was to determine [...] Read more.

Most studies on microplastic pollution in aquatic ecosystems have focused on the quantitative and qualitative assessment of particles in surface waters. However, the highest concentrations and accumulation of microplastic particles are observed in bottom sediments. The aim of this study was to determine the concentrations of microplastic particles of different morphology in sediments in the beach and littoral zones of Lake Baikal. This study is the first in relation to Lake Baikal to focus specifically on the analysis of microplastic particles in bottom sediments. The results of the study showed that the registered values of concentration of microplastic particles do not exceed the average values for lakes around the world. The predominant type of particles in both the littoral zone and the beach is microplastic fibers. An exception is observed only for one of the locations. This exception is related to the permanent mooring of vessels in this place. Analysis of the types of artificial polymers showed that the microplastic fibers were represented by polyester, and the fragments were represented by alkyd resin (66%), polyvinyl alcohol (32%) and polyvinyl chloride (2%). Shown for the first time in this study, the presence of large numbers of microplastic particles with rare types of artificial polymers suggests that these particles may be under-reported in other studies. The underestimation of particles may be due either to the selection of sampling locations located far from heavily contaminated areas, or to the fragility of these polymers. Although the harm of these types of polymers has not yet been confirmed, the large number of these particles in local areas of lakes should be taken into account. This is due to the large number of organisms, which is usually characteristic of littoral areas, including Lake Baikal, with its diversity of fauna and flora. Full article

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Limnol. Rev., Volume 25, Issue 4 (December 2025) – 8 articles

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