Urban Lake Research Articles

Assessment of Critical Environmental Risk Zones Around Wetlands in Colombo, Sri Lanka, Using Satellite Remote Sensing and Multi-criteria Decision Tools

Colombo, Sri Lanka’s commercial capital, is recognized as one of the first 18 global sites that were awarded the Ramsar Wetland City accreditation, and is a prime example of the intersection between urbanization and wetland conservation. Thus, this study aims to conduct an environmental risk assessment that can provide insights into the changes in biophysical properties driven by urbanization over the 2000–2020 period. The study used Geographical Information Systems and a remote sensing approach to assess critical environmental risk zones around urban freshwater lakes in the Colombo district of Sri Lanka, including Thalangama, an environmental protection area experiencing sub-urbanization. Satellite data (2000–2020) were employed, and spectral indices, including NDVI, NDBI, NDWI, NDMI, RVI and LST, were calculated. Intersecting areas with multiple risk factors were determined, and distances from these zones to lakes were calculated to generate spatially explicit risk maps using inverse distance weighting. The building density has consistently increased from 2000 to 2020 in all three sites, with ‘very high’ density areas expanding notably. NDVI reveals a gradual increase in ‘very high’ categories until 2015. Plant-water stress analysis shows significant water stress in 2015, and water body areas have decreased after 2010 in all the sites. Multi-criteria assessment identifies critical environmental risk zones around urban lakes, indicating high vulnerability to environmental damage and degradation. Overall, the study emphasizes the importance of leveraging data and risk analysis to inform decision-making processes in environmental management. By doing so, policymakers can enhance the effectiveness of conservation measures and promote the long-term sustainability of natural resources.

How Can Restoration Improve the Environmental Conditions of a Meromictic Urban Lake?

This study was conducted on Klasztorne Małe Lake located in the city of Kartuzy. For about 100 years, the lake served as a receiver of domestic, industrial, and rain sewage. The lake was completely degraded. In addition, excessive sewage inflow caused the accumulation of dense pollution in the area of the lake’s deepest part, which caused the formation of a monimolimnion layer. The bradymictic KML became a meromictic lake. After cutting off the inflow of pollutants, the lake was restored by the P inactivation method using coagulants PIX 111 and PAX 18. Before the restoration process of this lake, concentrations of nutrients in the bottom water layers achieved very high values of TN (total N) 65 mg/L and TP (total P) 30 mg/L. An average concentration of chlorophyll was 65 µg/L and visibility did not exceed 1 m. The method used brought very good results. In the entire volume of water, over 90% reduction in TP and a several-fold decrease in the content of TN were noted. The withdrawal of mineral P from the water limited the production processes in the lake, which was reflected in the reduction in chlorophyll amounts (19 µg/L) and the increase in water visibility (2 m). In addition, oxygen conditions in the lake improved. The application of coagulants caused a decrease in the density of the monimolimnion water, which was indicated by a significant decrease in water conductivity. However, the restoration method did not improve the water dynamics.

An Urban Lake Drainage Catena: Influences of Terrain, Soils, and Precipitation

Urban lake drainage systems are heavily impacted by terrain, soil characteristics, and precipitation, which influence water infiltration and groundwater movement. This study focused on the drainage catena around Lake Nokomis in Minneapolis, Minnesota, where local residents have experienced wet basements and yards. The primary goal was to identify the factors contributing to these water-related problems, particularly soil permeability and how it responds to precipitation. By conducting soil borings, using pressure transducers, and measuring saturated hydraulic conductivity (Kfs), the study compared upland and lowland areas. Findings indicated that upland soils, primarily composed of sandy fill, had much higher infiltration rates, with Kfs values ranging from 72.4 cm/hr to 149 cm/hr. In contrast, lowland areas characterized by lacustrine and organic soils exhibited significantly lower Kfs values, ranging from 1 cm/hr to 14.8 cm/hr. Between 2022 and 2024, wet and dry seasons occurred, yet recorded more than 127.5 cm of rain and snow water equivalent, further contributing to groundwater rise and surface water presence in low-lying regions. The study concluded that increased precipitation, coupled with specific hydrogeologic conditions, was the main factor causing elevated groundwater levels and surface saturation in these areas. To address these challenges, Minnesota's water management authorities are encouraged to implement strategies that consider the increasing magnitude and intensity of precipitation events due to climate change. Incorporating hydrogeologic assessments into urban planning is recommended to better manage water infiltration, reduce flood risks, and strengthen the resilience of drainage systems to changing climate patterns.

Eutrophication and Dissolved Organic Matter Exacerbate the Diel Discrepancy of CO2 Emissions in China's Largest Urban Lake.

The large variability in the emissions of carbon dioxide (CO2) from urban lakes remains a challenge for partitioning these sources at meaningful spatial and temporal scales. Dissolved organic matter (DOM) governs the spatial and temporal variations in CO2, yet relationships of the CO2 concentration (cCO2) and emission flux (FCO2) with DOM in urban lakes have rarely been reported. In this study, we monitored levels of cCO2, FCO2, and the composition of DOM over a 24 h period at three sites during the dry and wet seasons in China's largest urban lake, Tangxun Lake. Our study found the ratio of day/night FCO2 (millimoles per square meter per day) decreased from the dry season (0.79; 7.68/9.68) to the wet season (0.25; 6.05/24.16), averaging 0.42 (6.77/15.97), implying that accounting for nighttime CO2 emissions can increase regional estimates by 70%. This study revealed that eutrophication affected diurnal CO2 emissions with greater algal growth enhancing daytime CO2 uptake and subsequently increasing nighttime CO2 emissions via DOM degradation (larger protein-like DOM fraction). We anticipate that the relative magnitude of FCO2 between day and night from lakes is likely to increase due to urbanization and climate change, underscoring the importance of treating urban lakes as a distinct group and integrating DOM dynamics into carbon cycling in future research.

Tissue distribution, biomagnification, human health risk, and risk mitigation of perfluoroalkyl acids (PFAAs) in the aquatic food web of an urban fringe lake: Insights from urban-rural and seasonal scales

Perfluoroalkyl acids (PFAAs), renowned for their exceptional physical and chemical properties, are ubiquitous in urban and rural environments. Despite their widespread usage, more knowledge is needed concerning their accumulation and transfer mechanisms within the aquatic food webs of urban fringe lakes, especially across rural-urban and seasonal scales. This study investigated the tissue distribution, bioaccumulation, biomagnification, associated human health risks, and potential risk mitigation strategies of 15 PFAAs within the food web of Luoma Lake, a prototypical urban fringe lake. All targeted PFAAs were detected in samples, with ∑PFAA concentrations ranging from 116.97 to 564.26 ng/g dw in muscles and 26.96–1850.95 ng/g dw in viscera. Spatial variations revealed significantly higher ∑PFAA concentrations in the muscles from the urban subregion (∑PFAA: 359.66 ± 76.48 ng/g dw) compared to the rural subregion (∑PFAA: 328.86 ± 87.51 ng/g dw). Seasonal fluctuations impacted PFAA concentrations in fish and crustacean muscles but exhibited negligible effects on bivalve muscles. Spatial variations only influenced PFAA concentrations in specific viscera (gill, liver, kidney), while seasonal changes had minimal effects on viscera. The organisms demonstrated varying bioaccumulation capacities, with crustaceans displaying the highest bioaccumulation potential, followed by crustaceans and fish. Both spatial and seasonal variations modulated the bioaccumulation patterns of PFAA in muscles, whereas bioaccumulation in viscera was only influenced by seasonal factors. Notably, PFAA biomagnification along the food web was exclusively governed by spatial distribution, remaining unaffected by seasonal changes. The human health risk assessment underscored the potential adverse health impacts of PFOS and PFOA, particularly on young children (aged 2 to <6 years). This study further proposed comprehensive recommendations for mitigating PFAA-induced health risks, encompassing source control, selective consumption, pre-cooking treatments, and strategic cooking method selection. This research provides crucial insights into the ecological behaviors and health implications of PFAA in urban fringe lakes.

Movement and Growth of Translocated Coastrange Sculpin and Prickly Sculpin in Two Urban Lake Washington Tributaries, Washington

Abstract Urbanization and other forms of land conversion have led to dramatic changes in freshwater ecosystems. We assessed the movement and growth of Coastrange Sculpin Cottus aleuticus and Prickly Sculpin C. asper, two species that are considered migratory based on their potamodromous and amphidromous life history strategies. We determined critical aspects of their ecology in two urban streams where they are rare or absent. Both species were collected near the stream mouth or in Lake Washington, implanted with passive integrated transponder (PIT) tags, and translocated to an upper stream reach where their downstream movements and growth were monitored. Detections at stationary antennas indicated most downstream movements occurred from January to April, as has been observed in other Pacific Northwest systems. About 80% of the translocated sculpins remained in the study reach for at least 2 months before moving downstream and 10% remained more than a year. Smaller Prickly Sculpin generally remained in the study reach longer than larger Prickly Sculpin; however, no size effect was observed for Coastrange Sculpin. Most downstream movements occurred during low and moderate streamflow levels during each season for both streams; however, downstream movements occurred at relatively higher flows compared to the cumulative distribution of observed flows during most seasons. Both species appeared to grow well in the study streams; although, Prickly Sculpin growth rates were approximately double that of Coastrange Sculpin. Coastrange Sculpin often inhabit riffles where increased fine sediments and embeddedness from urbanization may impact them more than Prickly Sculpin, which typically inhabit pools. The overall survival and growth of both species in the two highly urbanized streams was better than expected. This study suggests that the lack of sculpins in some urban streams may be a result of stream barriers to movement rather than poor habitat conditions.

Synergistic management of nitrogen contamination in overflow wastewater and algal proliferation in lake receiving wastewater based on electrochemical oxidation process

Urban lake eutrophication, largely driven by overflow wastewater, plays a pivotal role in precipitating algal proliferation due to heightened nitrogen levels in aquatic ecosystem. In addressing this question, this study investigated the chloride-mediated electrochemical oxidation system as a promising solution for controlling nitrogen contamination in overflow wastewater and inhibiting algal proliferation in wastewater-receiving urban lakes, and also evaluated the influence of essential operational parameters on the performance of system. The results indicated that, under the environmental conditions set by this experiment, the removal efficiency ranges of ammonia nitrogen and total nitrogen were 14.91 % - 100 % and 13.98 % - 99.62 %, respectively; meanwhile, the maximum algae inhibition rate could reach 100 % at a capacity ratio of 0.01. Response Surface Method analysis highlighted current density as the preeminent factor in nitrogen removal and algae inhibition, surpassing the influence of initial chloride ion and nitrogen concentrations within the system. Notably, an excessive current density could inadvertently lead to the nitrate nitrogen accumulation (up to 29 %), thereby diminishing the total nitrogen removal efficiency, particularly in low nitrogen-concentrated overflow wastewater scenarios. With respect to algae inhibition, a direct correlation was identified between higher residual total chlorine concentrations in the receiving lake and increased algae inhibition rates (R = 0.90, P < 0.05), and the residual total chlorine was found to exert pronounced inhibition on cyanobacteria compared to other algal forms. However, caution was advised regarding potential algal growth stimulation if the initial received total chlorine concentration in the urban lake receiving wastewater below 0.5 mg/L. These findings not only affirm the feasibility of this synergistic approach but also elucidate critical aspects for process optimization and control.

Petroleum hydrocarbons in arctic urban lake sediments (Murmansk, Russia)

The level of pollution of lake sediments located in the city of Murmansk (Russia) with petroleum hydrocarbons was studied. The most urban lakes can be classified as slightly polluted, representing the maximum acceptable risk for human health and ecosystems; Lake Yuzhnoe – as moderately polluted with a negative impact on the aquatic environment, and Lake Ledovoe located near the highway, gas station, and car service, – as dangerously polluted, posing a threat to human health and requiring remediation. The background content of organic compounds identified as petroleum hydrocarbons in the sediments of Murmansk lakes ranges from 76 to 307 mg TPH/kg. High background concentrations of hydrocarbons can be associated with a large amount of organic matter in the sediments of lakes. The standards for the content of hydrocarbons in sediments, developed for other regions, give an ambiguous assessment of their content in the sediments of lakes in Murmansk. It is not entirely correct to use the background content of hydrocarbons in the sediments of lakes in other regions, which differ in particle size distribution, content of organic matter, and chemical composition, to assess the degree of pollution. Additional research is needed to determine the content of hydrocarbons in the sediments of background lakes in the Murmansk region and to develop standards for the content of hydrocarbons in the bottom sediments of Arctic cities.

Efficacy of P-sorbent material combined with aquatic plants in controlling nutrient release from urban lake sediment: Field investigation

The release of stored nutrients from sediments is thought to substantially affect water quality in urban lakes. To explore the efficiency of different in-situ remediation methods on controlling high internal urban lake sediments, 120 days of field-enclosure experiments were conducted to investigate the efficacy of P-sorbent materials combined with aquatic plants in controlling nutrient release from urban-lake sediments. The lanthanum-modified clay (LMC) effectively reduced sediment P release flux and could temporarily lead to a small increase in N concentration in the overlying water. In contrast, Vallisneria spiralis (V. spiralis) has a relatively weak effect on controlling nutrient release and can even cause an increase in P concentration. The combined restoration technique of V. spiralis + LMC can overcome the drawbacks of a single method, reduce the nutrient content in overlying water, and inhibit the sediment internal release. Relative to the control, the V. spiralis + LMC treatment reduced mobile P content by 52.5% and increased Ca-P content by 34.5%. The added lanthanum contained material can quickly bind the readily released P in sediment and porewater, transforming it into intert P over time. Submerged macrophytes can absorb active P in water and sediments and transport oxygen to sediments promoting denitrification and N removal. The combined restoration technique synergistically combines the high P sorption affinity of LMC and the substrate improvement effect of V. spiralis, thus realizing the long-term control of endogenous release in urban lakes. This approach holds great promise for restoring urban lakes with high endogenous nutrient loading.

A One Health exploration of antimicrobial resistance in Escherichia coli originated from urban and rural lakes ecosystem.

Antimicrobial resistance (AMR) has become one of the most serious threats to One Health. Aquatic environments are an ideal non-clinical AMR reservoir and can act as a key battlefront for tackling the AMR. However, AMR data using the One Health approach remain scarce in aquatic environments worldwide. Here, we extensively assessed AMR in Escherichia coli isolated from urban and rural lake ecosystems using the One Health perspective. A total of 162 E. coli isolates obtained from lakes were tested against 25 antimicrobials using an in-vitro antimicrobial susceptibility testing method. A low (2%) to moderate (45%) drug resistance rate was found for all antimicrobials used in human/veterinary medicine or animal/plant agriculture. However, <80% E. coli isolates exhibited multidrug resistance (MDR) phenotype to highly important (amikacin, gentamicin, trimethoprim) or critically important (amoxicillin, ampicillin, colistin) drugs of both human and veterinary medicine. Of concern, >50% of E. coli isolates exhibited MDR to drugs used as last-resorts (chloramphenicol, colistin) or as frontline (nitrofurantoin, sulfamethoxazole, ampicillin, gentamicin) against E. coli infections. In conclusion, the presence of MDR E. coli strains in urban or rural lake ecosystems highlights their possible role as AMR reservoirs with potential One Health risks.

Chemical composition of sediment and macrozoobenthos of small urban lakes, the Republic of Karelia, Russia

Assessing the benthic communities in water bodies under increasing anthropogenic pressure seems to be an urgent task of scientific research aimed at short-term and long-term monitoring of water bodies. This study focuses on the chemical composition of modern sediment and the current state of macrozoobenthos of small lakes in the Republic of Karelia (Kitaiskoe and Plotichie) influenced by anthropogenic factors. It was discovered that the lakes of Medvezhyegorsk have a higher concentration of heavy metals (such as lead (Pb), cadmium (Cd), molybdenum (Mo), and antimony (Sb),) compared to the Earth’s crust and natural background levels. The current study established the significant impact of industry and transportation on the movement and build up of pollutants in these lakes. The qualitative and quantitative parameters analysed for the benthic communities in the littoral and profundal zones included the species diversity, the structure of dominant species, and their percentage in the samples. According to the level of macrozoobenthos development, both reservoirs (lakes) were classified as mesotrophic, and according to the values of the chironomid index “K” as moderately polluted. The Pantle–Buck method (saprobic index) showed that the lakes can be classified as polluted (water quality class 4). Macrozoobenthos groups most tolerant to environmental conditions, for example, Chironomidae larvae, prevailed in the studied urban lakes. The economic development of the lakes leads to ecosystem transformation and long-term eutrophication over time affecting the biotic indicators of surface water quality. The results obtained can serve as a basis for complex environmental monitoring of the urbanized territories in the taiga zone.

Relationships between extracellular microcystin LR and fecal bacterial indicators in a shallow urban lake: the Ypacarai Lake (Paraguay)

Relationships between extracellular microcystin LR and fecal bacterial indicators in a shallow urban lake: the Ypacarai Lake (Paraguay)

Effect of sponge city facilities on the exposure characteristics and ecological risks of antibiotics in urban inland lakes: A case study at Fuzhou, China.

Antibiotics are increasingly found in urban lakes, posing significant ecological risks to lake ecosystems. The impact of sponge city facilities on urban flood control is significant; however, their influence on the exposure characteristics and risks associated with antibiotics in urban inland lakes remains unclear. This study investigated the exposure characteristics and evaluated the ecological risks of 15 antibiotics across seven lakes of Fuzhou (as the target of sponge city) in different seasons, in comparison to non-sponge cities. The results revealed that 12 antibiotics were consistently detectable across all lakes, with concentrations ranging from non-detectable (ND) to 20.61ng/L, with sulfamethoxazole (SMX) emerging as the predominant contaminant. Most antibiotics exhibited higher concentrations in the dry season, attributed to environmental conditions, biological mechanisms, and their physicochemical properties. SMX, tetracycline (TTC), oxytetracycline (OTC), and ciprofloxacin (CIP) posed moderate to high ecological risks, with risk quotient (RQ) values of 0.46, 0.14, 0.17, and 0.61, respectively, while the remaining antibiotics presented lower ecological risks in both seasons. Notably, the RQ values for TTC, OTC, and CIP were elevated during the dry season, whereas SMX displayed a higher RQ value in the wet season, indicating an increased ecological risk during the dry months. In comparison to non-sponge cities, sponge cities exhibited significantly lower concentrations of nearly all antibiotics, particularly during the wet season (p ≤ 0.05). Moreover, over 85% of the antibiotics in non-sponge cities were classified as high risk, contrasted with only 55% in sponge cities, underscoring the heightened ecological risks associated with non-sponge urban designs. This study provides critical insights for controlling antibiotic pollution in the lakes of Fuzhou and serves as a valuable reference for maintaining aquatic ecosystem health through the implementation of sponge city infrastructure.

Eutrophication constrains driving forces of dissolved organic carbon biodegradation in metropolitan lake systems

Dissolved organic carbon (DOC) components can be highly variable in aquatic ecosystems, and play a pivotal role in the global carbon cycles. To comprehend potential effects of nutrient enrichment on portion of DOC biodegradability (%BDOC), we conducted an extensive investigation on 26 urban lakes in a major metropolitan area in subtropical China in a small gradient of trophic levels from mesotrophic to light and middle eutrophic. In addition to field measurements on lake ambient conditions and laboratory analysis of DOC characteristics, we conducted a 28-day temperature-controlled incubation experiment, in which %BDOC of lake waters was determined. In the mesotrophic waters, %BDOC ranged from 0.6 to 41.4 % (11.2 ± 8.9 %). The %BDOC levels spanned from 5.2 to 20.2 % (10.7 ± 4.0 %) in the light eutrophic waters, and the %BDOC ranged from 2.7 to 35.0 % (13.7 ± 8.4 %) in the middle eutrophic waters. We found a significant change in DOC chemical composition across the study lakes characterized by shifting of trophic levels. Although the experiment found significant changes in the factors that can influence %BDOC, a significant difference was not observed in %BDOC among the three trophic levels. The %BDOC was primarily influenced by the inherent DOC concentration and aromaticity, with eutrophication leading to the varied driving factors of %BDOC in lake systems. We show that most of the lake water DOC was stable. The findings indicate the intricate interplay between biological metabolism and nutrient availability governing %BDOC dynamics in urban lake ecosystems.

Urban Lake Health Assessment Based on the Synergistic Perspective of Water Environment and Social Service Functions.

Urban lakes serve as vital ecological and recreational anchors within built environments, essential for enhancing urban resilience. Evaluating lake health predominantly focuses on water quality, assessing indicators such as nutrient levels, toxicity, pH balance, and water clarity to monitor changes. This study proposes a comprehensive evaluation framework that systematically describes specific spatiotemporal manifestations and periodic exogenous regulation characteristics across five dimensions: physical structure, water quality, shoreline dynamics, external regulation, and social service. Furthermore, it introduces an urban lake health assessment model based on synergistic development to evaluate the integrated development and interaction between water environments and social services. This model is applied across urban lakes in various developmental stages in China. Key findings include: 1) Urban development often impacts lake health disparately, with varying degrees of synergy observed between water environments and social services across different urban lakes. However, shifts in urban ideologies and improvements in governance, along with protective policies and project implementations, have contributed to improving water quality to some extent. 2) Engineering interventions do not consistently correspond with improvements in water quality, and governance measures sometimes yield mixed outcomes, underscoring the necessity for systematic solutions to lake health. Restoring hydrological processes emerges as crucial for enhancing sustainability.

Chronological evaluation of polycyclic aromatic hydrocarbons in sediments of tangxun lake in central China and impacts of human activities.

This study sheds light on the contamination of polycyclic aromatic hydrocarbons (PAHs) in Tangxun Lake sediments, an urban lake reflecting environmental changes in Central China. By analyzing sediment cores from both the inner and outer areas of the lake, we determined the historical trends and sources of PAHs over the past century. The results reveal a significant increase in PAHs concentrations, particularly since the 1980s, coinciding with China's rapid urbanization and industrialization. Using diagnostic ratios and Absolute principal component score-multivariate linear regression (APCS-MLR) methods, we identified petroleum combustion, coal combustion, and biomass combustion as the primary sources of PAHs in the lake sediments. The spatial analysis indicates higher PAHs levels in the inner lake, likely due to its closer proximity to industrial activities. Moreover, by comparing PAH trends in Tangxun Lake with those in other urban, suburban, and remote lakes across China, based on data from 49 sedimentary cores, we highlight the impact of regional socio-economic dynamics on PAH deposition. These insights are crucial for developing effective pollution mitigation strategies and promoting sustainable development in rapidly urbanizing regions.

Application of Synchronous Evaluation-Diagnosis Model with Quantitative Stressor-Response Analysis (SED-QSR) to Urban Lake Ecological Status: A Proposed Multiple-Level System.

Ecological integrity assessment and degradation diagnosis are used globally to evaluate the health of water bodies and pinpoint critical stressors. However, current studies mainly focus on separate evaluation or diagnosis, leading to an inadequate exploration of the relationship between stressors and responses. Here, based on multiple data sets in an urban lake system, a synchronous evaluation-diagnosis model with quantitative stressor-response analysis was advanced, aiming to improve the accuracy of evaluation and diagnosis. The weights for key physicochemical stressors were quantitatively determined in the sequence of NDAVIadj > CODMn > TP > NH4+-N by the combination of generalized additive model and structural equation modeling, clarifying the most significant effects of aquatic vegetation on the degradation of fish assemblages. Then, sensitive biological metrics were screened by considering the distinct contributions of four key stressors to alleviate the possible deviation caused by common methods. Finally, ecological integrity was evaluated by summing the key physicochemical stressors and sensitive biological metrics according to the model-deduced weights instead of empirical weights. Our system's diagnosis and evaluation results achieved an accuracy of over 80% when predicting anthropogenic stress and biological status, which highlights the great potential of our multiple-level system for ecosystem management.

Female-biased sex ratios and delayed puberty in two fish species with different Ecologies in an Anthropogenically affected urban lake

In aquatic ecosystems, endocrine-disrupting compounds (EDCs) pose a growing concern for their potential adverse effects on fish reproduction and development. In lake Pyhäjärvi, located in the urban boreal region of Tampere, Finland, a significant number of sexually immature pikeperch (Sander lucioperca) individuals have been identified in size and age categories that are expected to be sexually mature. To explore if this phenomenon is attributed to estrogenic endocrine disruption, we conducted a comprehensive study comparing fish from lake Pyhäjärvi with those from a nearby reference lake, lake Näsijärvi. Roach (Rutilus rutilus), known for its susceptibility to EDCs, was also included for comparison. We examined various parameters in both pikeperch and roach, including size, condition factor, age, reproductive indicators, biometric indices and gonadal histology. We also assessed liver vitellogenin mRNA levels and genetic sex in roach, and measured estrogen levels in lake waters and wastewater treatment plant effluents. Results revealed that approximately one-third of fish in both species exhibited sexual immaturity in lake Pyhäjärvi, with a female-biased sex ratio. Surprisingly, we found no signs of estrogenic endocrine disruption, indicated by the absence of intersex fish in both species. Furthermore, vitellogenin levels in roach closely resembled those in the reference lake. Estrogens were undetectable in the lake waters, suggesting that factors other than estrogenic EDCs, including other potential endocrine disruptors such as PCBs or heavy metals, may be influencing delayed sexual maturity and skewed sex ratios. Further inquiry is needed to pinpoint these underlying causes. Our study provides essential baseline information on fish sexual development in lake Pyhäjärvi, emphasizing the need for ongoing monitoring and research to understand delayed sexual maturity and biased sex ratios. This is vital given the increasing concern about EDC impacts on aquatic ecosystems and the necessity for effective management strategies to protect these ecosystems' health and integrity.

Occurrence, source apportionment, and ecological risk of potentially toxic elements in an urban shallow lake sediment

ABSTRACT This study evaluated the occurrence, spatial distribution, source, and ecological risk of potentially toxic elements (PTEs) in the sediment of an urban shallow lake in a mid-sized city. The ecological risk indices, enrichment factor (EF) and geoaccumulation index (Igeo) indicated high enrichment and contamination with Cd and moderate enrichment with Ni and Hg, while the potential risk index (RI) showed a moderate ecological risk. The mean contributions of individual PTE species to the total risk were in the following order: Cd > Hg > Ni > As > Cu > Pb > Cr > Zn. The sediment quality guideline (SQG) indices revealed that biological effects might occur occasionally due to the Cd and Ni contamination and a low or relatively insignificant risk of adverse biological effects from other PTEs. There were moderate to strong positive inter-metal relationships that suggested their common sources. The primary source responsible for elevated PTE concentrations was the traffic-related discharge. The main contributors to ecological risks were Cd and Ni. These findings highlight the importance of paying attention to the ecological environment of urban shallow lakes, which are particularly sensitive to their surroundings.

Biodegradable microplastics aggravate greenhouse gas emissions from urban lake sediments more severely than conventional microplastics

Freshwater ecosystems, such as urban lake sediments, have been identified as important sources of greenhouse gases (GHGs) to the atmosphere, as well as persistent sinks for ubiquitous microplastics due to the high population density and frequent anthropogenic activity. The potential impacts of microplastics on GHG production, however, remain underexplored. In this study, four types of common biodegradable microplastics (BMPs) versus four conventional non-biodegradable microplastics (NBMPs) were artificially exposed to urban lake sediments to investigate the responses of nitrous oxide (N2O) and methane (CH4) production, and make a comparison regarding how the biodegradability of microplastics affected GHG emissions. Importantly, results suggested that BMPs aggravated N2O and CH4 production in urban lake sediments more severely than conventional NBMPs. The production rates of N2O and CH4 increased by 48.78–71.88 % and 30.87–69.12 %, respectively, in BMPs groups, while those increased by only 0–25.69 % and 6.46–10.46 % with NBMPs exposure. Moreover, BMPs insignificantly affected nitrification but facilitated denitrification, while NBMPs inhibited both processes. BMPs not only created more oxygen-limited microenvironment, greatly promoting N2O production via nitrifier denitrification pathway, but also provided dissolved organic carbon favoring heterotrophic denitrification, which was primarily supported by the enriched denitrifiers and functional genes. In contrast, NBMPs slightly upregulated nitrifier denitrification pathway to generate N2O, and showed a toxic inhibition on both nitrifiers and denitrifiers. In addition, both BMPs and NBMPs promoted hydrogen-dependent methanogenic pathway but suppressed acetate-dependent pathway. The greater enhancement of CH4 production with BMPs exposure was attributed to the additional organic carbon substrates derived from BMPs and the stimulated microbial methane metabolism activities.