Microplastics can enter freshwater lakes through many sources. They can act as carriers to adsorb bacteria, virus, or pollutants (e.g., heavy metal and toxic organic compounds) that threaten human ...health through food chain. Microplastics can exist in surface water and sediments in freshwater lakes after they enter the lakes through discharge points. Wastewater discharge is the main cause of lake eutrophication and is the main emission source of microplastics. The correlation between lake trophic state and microplastic abundance has been rarely reported. This study investigated the microplastic contamination in surface water and sediments of 18 lakes along the middle and lower reaches of the Yangtze River Basin in the period of August–September 2018. The correlation between lake trophic state and microplastic abundance in surface water and sediments was investigated and discussed. The microplastic abundance in surface water was approximately two orders of magnitude lower than that in sediments in all 18 lakes. Hong Lake had the highest microplastic abundance in surface water sample, and Nantaizi Lake had the highest microplastic abundance in sediment sample. The dominant microplastic shape was fiber of 93.81% in surface water sample and 94.77% in sediment sample. Blue-colored microplastics were dominant in nearly all lakes in surface water sample (around 40%–60%) and sediment sample (around 60%–80%), followed by purple- and green-colored ones. The microplastics size <1 mm was dominant in surface water sample (around 40%–60%) and sediment sample (around 50%–80%). The dominant material was polypropylene in surface water sample (around 60%–80%) and sediment sample (around 40%–60%).
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•Microplastics occurrence in 18 different trophic level Lakes along the middle and lower reaches of Yangtze River Basin were investigated.•Correlation of lake trophic state and microplastics abundance was discussed.•Microplastics shape, size, material and color in each lakes were investigated.
Water quality management in shallow impounded lakes is challenging due to nutrient's enrichment and algal blooms. Lake Hongze is a reservoir for the South-to-North Water Diversion Project's Eastern ...Route and an essential water source for Jiangsu Province, China, and its water quality closely relates to the local aquatic ecosystem and affects the water supply security of the surrounding areas. The spatial and seasonal patterns of total nitrogen, total phosphorus (TP), and chlorophyll-a (Chl-a) in the lake were investigated and the effects of floods on these patterns were assessed. Hydrological data and trophic state parameters were analyzed using 7 years of monitoring data from 16 water sampling sites throughout the lake. The statistical analysis revealed the seasonal variation characteristics affected by floods and the differences in material transport continuity between inflow and outflow boundaries. Eutrophication assessment using the trophic level index and Chl-a concentrations also indicated eutrophication was concentrated at the southeast side of the lake. Spatial interpolation of Chl-a using the ordinary kriging method clarified that existence and movement of the localized eutrophication area in Lake Hongze. The mass balance calculations of TP indicated that a substantial amount of phosphorus entered the lake during the flood season, however, most severe algal blooms occurring after the flood season. The onset of algal blooms exhibits a significant time lag in response to phosphorus input, primarily due to the influence of hydrodynamic processes within the lake during the flood season.
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•Connected reservoirs differed in Carlson’s Trophic Status Index during a drought.•AICc models were used to determine the strongest influence on chlorophyll-a values.•Mesotrophic ...models consisted of an additive influence of conductivity and rainfall.•Inorganic and organic nitrogen had an additive influence in eutrophic models.•The eutrophic model was correlated with high biovolumes of nuisance cyanobacteria.
Problems associated with eutrophication are increasing in freshwater reservoirs worldwide due to many factors, the majority of which are attributed directly to human development. Eutrophic bodies of water are much more susceptible to algal blooms, including potentially harmful species, as well as associated taste-and-odor compounds and toxic secondary metabolites. To assess the likelihood of eutrophication and harmful blooms, two reservoirs in the Highland Lakes of central Texas, which are located within the same drainage basin and climate zone, were observed for the duration of an extended drought period lasting from 2010 to 2015. This brief investigation examined a suite of physiochemical characteristics to determine which environmental factors had the most significant impacts on the eutrophication of a reservoir coupled with the abundance of microalgae. Standard water quality parameters that have been hypothesized to influence eutrophication were measured and compared with chlorophyll-a fluorescence as a proxy for phytoplankton abundance. Samples were taken every other month and each reservoir responded differently to the drought – Lake Lyndon B. Johnson (LBJ) became eutrophic while Lake Travis remained mesotrophic, according to Carlson’s Trophic State Index. Linear models using corrected Akaike Information Criterion analyses indicated that the primary indicators for microalgae in Lake LBJ were organic and inorganic nitrogen, but the indicators for Lake Travis were rainfall, chloride, sulfate, and conductivity. Preserved phytoplankton samples were analyzed from both reservoirs across seasons in 2013 and 2014 to supplement the models. Cyanobacteria were a significant factor in both lakes – samples indicated that the diazotroph and harmful genus, Aphanizomenon, was the most abundant cyanobacterium in Lake LBJ, while Limnothrix was dominant in Lake Travis. Although diazotrophic, it was hypothesized that Aphanizomenon used free nitrogen when available rather than fixing atmospheric nitrogen, thus allowing for rapid establishment and leaving less free nitrogen for plankton downstream. This study indicated that an increase in inorganic and organic nitrogen following a period of drought could amplify the potential for harmful blooms of Aphanizomenon in the upper Highland Lakes of central Texas.
•Lake depth integrates socio-ecological systems.•Lake depth relates potential susceptibility to anthropogenic stressors.•Shallow lakes are more susceptible to human forcing and eutrophication.•The ...eutrophication of shallow lakes may be not an occasional occurrence.
Understanding and managing the susceptibility of lakes to anthropogenic eutrophication has been a primary goal of limnological research for decades. To achieve United Nations’ Sustainable Development Goals, scientists have attempted to understand why shallow lakes appear to be prone to eutrophication and resistant to restoration. A rich data base of 1151 lakes (each ≥ 0.5 km2) located within the Europe and the United States of America offers a rare opportunity to explore potential answers. Analysis of sites showed that lake depth integrated socio-ecological systems and reflected potential susceptibility to anthropogenic stressors, as well as lake productivity. In this study, lakes distributed in agricultural plain and densely populated lowland areas were generally shallow and subjected to intense human activities with high external nutrient inputs. In contrast, deep lakes frequently occurred in upland regions, dominated by natural landscapes with little anthropogenic nutrient input. Lake depth appeared to not only reflect external nutrient load to the lake, but also acted as an amplifier that increased shallow lake susceptibility to anthropogenic disturbance. Our findings suggest that shallow lakes are more susceptible to human forcing and their eutrophication may be not an occasional occurrence, and that societal expectations, policy goals, and management plans should reflect this observation.
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Reservoir nearshore areas are influenced by both terrestrial and aquatic ecosystems, making them sensitive regions to water quality changes. The analysis of basin landscape hydrological features ...provides limited insight into the spatial heterogeneity of eutrophication in these areas. The complex characteristics of shoreline morphology and their impact on eutrophication are often overlooked. To comprehensively analyze the complex relationships between shoreline morphology and landscape hydrological features, with eutrophication, this study uses Danjiangkou Reservoir as a case study. Utilizing Landsat 8 OLI remote sensing data from 2013 to 2022, combined with a semi-analytical approach, the spatial distribution of the Trophic State Index (TSI) during flood discharge periods (FDPs) and water storage periods (WSPs) was obtained. Using Extreme Gradient Boosting (XGBoost) and SHapley Additive exPlanations (SHAP), explained the relationships between landscape composition, landscape configuration, hydrological topography, shoreline morphology, and TSI, identified key factors at different spatial scales and validated their reliability. The results showed that: (1) There is significant spatial heterogeneity in the TSI distribution of Danjiangkou Reservoir. The eutrophication levels are significant in the shoreline and bay areas, with a tendency to extend inward only during the WSPs. (2) The importance of landscape composition, landscape configuration, hydrological topography, and shoreline morphology to TSI variations during the FDPs are 25.12 %, 29.6 %, 23.09 %, and 22.19 % respectively. Besides shoreline distance, the Landscape Shape Index (LSI) and Hypsometric Integral (HI) are the two most significant environmental variables overall during the FDPs. Forest and grassland areas become the most influential factors during the WSPs. The influence of landscape patterns and hydrological topography on TSI varies at different spatial scales. At the 200 m riparian buffer zone, the increase in cropland and impervious areas significantly elevates eutrophication levels. (3) Morphology complexity, shows a noticeable threshold effect on TSI, with complex shoreline morphology increasing the risk of eutrophication.
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•Semi-analytical remote sensing methods analyze TSI spatial-temporal changes.•SHAP method identified key factors influencing TSI.•Complex shoreline morphology shows a threshold effect on eutrophication risk.•Increasing cropland distance and riparian forests mitigate eutrophication.
In a comprehensive study of microplastic contamination in southern Germany, 1167 individual fish of 22 different species were sampled from 11 rivers and 6 lakes across the state. The microplastic ...burden of investigated fish was analyzed on the basis of habitat type, location, and a number of abiotic and biotic factors. A particle size distribution analysis of the detected microplastics was carried out. The results showed a relatively low plastic prevalence of 18.8%, with significant differences between rivers (20.6%) and lakes (16.5%). The number of ingested plastic particles ranged between 1 and 4 particles per fish. The majority of abiotic and biotic factors seem to play little or no role in the ingestion of microplastics, suggesting that in most cases uptake is passive or accidental. It is notable that piscivorous fish appeared significantly less burdened, suggesting a low transfer rate and no accumulation in the food web. However, size distribution analysis identified a power law growth fit in particle numbers at the smallest end of the distribution. This carries a worrying implication, that >95% of particles are likely to be smaller than 40 μm and thereby beyond the detection range of this and most other microplastic surveys conducted so far. When the frequency development of small particles is taken into account, the likely microplastic prevalence in the present study increases to 100%, with an average intensity of around 23 predominantly small particles per fish. A striking 70% of those particles would be smaller than 5 μm and therefore eligible for translocation into tissues, with critical implications for fish health and consumer exposure. This raises a question as to whether current estimates of microplastic burden in fishes generally might be overlooking a majority of potential contamination within the critical smaller particle size classes.
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•A comprehensive study to examine microplastic burden in fishes was carried out•Ingested microplastics were detected in around one fifth of examined fishes•Piscivorous fish were significantly less burdened, indicating a excretory effect•Models indicate a hyperbolic increase of particle number with decreasing size•95% of particles are <40 μm and thus not detectable by current methods.
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•The dynamic of Lake TSI can be evaluated by Landsat 8 OLI derived FUI.•Sunshine is the main influencing factor for Lake Dianchi.•Temperature and wind are most relevant factor for ...Lake Donghu and Chaohu.•Pollution account for 10.5%–60.7% for eutrophication dynamics.
Lakes eutrophication have been a complex and serious problem for China’s Yangtze River Basin. A series of algorithms based on different remote sensing dataset have been proposed to simulate the lakes trophic state. However, these algorithms are often targeted at a particular lake and cannot be applied to a watershed management. In this study, a Forel-Ule index (FUI) method based on Landsat 8 OLI image is proposed to simulate trophic state index (TSI) in three typical urban lakes (Dianchi, Donghu, and Chaohu) from 2013 to 2018. The results show that the Landsat 8 derived FUI can well represent the lake TSI with an accuracy of R2 = 0.6464 for the in situ experimental TSI dataset (N = 115) and R2 = 0.8065 for the lake average TSI dataset (N = 315). In the study period 2013–2018, the order of the simulated TSI is Dianchi > Chaohu > Donghu. Seasonal dynamics show differences where the percentage of eutrophic area in summer is significantly lower than the other seasons for Lake Dianchi and Chaohu. However, the percentage of eutrophic area for Lake Donghu is highest in summer and lowest in winter. To further detect the driving factors of eutrophication in study lakes, the Pearson correlation and multiple linear regression analyses were conducted. The results show that sunshine and temperature are, respectively, the most and the second most significant factors for Lake Dianchi with explanations of 14.8% and 22.0%; temperature and pollution are the main influencing factors for Lake Donghu (39.2% and 10.9% explanation, respectively) and Chaohu (57.2% and 60.7% explanations, respectively). In addition, the wind is another negatively significant factor for Lake Chaohu with an explanation of 31.3%. Our results serve as an example for other lakes in the Yangtze River Basin and support the formulation of effective strategies to reduce seasonal eutrophication.
•DOM changes along trophic gradient lakes were characterized by optical properties and FT-ICR MS.•More S-containing and polycyclic aromatic materials were observed in eutrophic lakes.•More aliphatic ...compounds were detected in eutrophic lakes.•Eutrophication modifies the structure of DOM into more complex materials.•CDOM could serve as a potential predictor of lake eutrophication.
Dissolved organic matter (DOM) is an abundant and mobile part of the aquatic environment and plays important roles in aquatic biogeochemical cycles and the global carbon cycle. Recently, eutrophication has become an important environmental issue in global lakes, but how eutrophication drives changes in the molecular composition of DOM along trophic gradients remains poorly understood. We thus characterized 67 DOM isolates from 11 lakes along a trophic gradient in China by using a combined approach including absorption spectroscopy, excitation-emission matrix fluorescence and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Our results indicated that dissolved organic carbon and absorption coefficients at 350 nm increased with increasing trophic status index. The ultraviolet absorbance at 254 nm and fluorescence intensity of all fluorescent components were higher in eutrophic lakes than in oligotrophic lakes. DOM in high trophic state lakes tended to be dominated by higher molecular weight, unsaturation degree, greater abundance of S-containing compounds, and condensed or polycyclic aromatic compounds than oligotrophic lakes. Additionally, autochthonous DOM characterized by more aliphatic compounds increased with the increasing trophic state. We concluded that nutrient input along with allochthonous DOM favors the lake eutrophication and subsequently increases the release and accumulation of autochthonous DOM. Consequently, eutrophication modifies the structure of the organic matter into more complex materials with increased input of allochthonous DOM and increased release of autochthonous DOM, which could accelerate global carbon cycle processes. Our results here have potential to contribute significantly to future studies of DOM dynamics in eutrophic lakes.
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Zooplankton indicators based on rotifers (TSI
ROT
) and an indicator based on Secchi disk visibility (TSI
SD
) were used to assess trophic state changes in artificial, slow-flowing, and stagnant ...canal waters. The study was conducted in the summers of 2019, 2021, and 2022 in the Bydgoszcz Canal and the Noteć Canal (Poland). Water samples were taken from five sites once in the month of July and once in August. In terms of the species number and density, rotifers dominated among zooplankton (at almost all sites), which reflected the high trophic state. Our results showed statistically significant correlations between TSI
ROT
and TSI
SD
as well as between the individual indicators TSI
ROT1
(Rotifer numbers), TSI
ROT2
(Rotifer biomass), TSI
ROT3
(bacterivorous numbers of rotifers), TSI
ROT6
(rotifers indicating high trophic state), and TSI
SD
. According to our study, the presented indices most likely determine the trends between TSI
ROT
cumulative and TSI
SD
in the studied canals. Similarly to previous studies performed on lakes and small reservoirs, zooplankton constituted a useful indicator of trophic state. It seems that, for stagnant and slowly flowing waters of canals such as the Bydgoszcz Canal and the Noteć Canal, the method of zooplankton trophic status indicators based on rotifers may be applied.
Understanding the relationship between suspended particulate matter (SPM), sediment organic C, N stable isotopes, and lake trophic state index (TSI) is essential for managing lake pollution and ...eutrophication. According to the δ13C, δ15N, and C/N we found that the organic C in SPM and sediment of Caohai Lake primarily originated from macrophytes, while N was sourced from chemical fertilizers, phytoplankton, and aquatic plants. Total nitrogen, total phosphorus, NO3−-N, oxidation reduction potential, and Chl.a were identified as key factors influencing the sources and variations of SPM and sediment organic C and N stable isotopes in Caohai Lake, with a significant linear correlation observed between C, N stable isotopes, and TSI in sediments. To mitigate eutrophication in Caohai Lake, it is recommended that farmers apply fertilizers judiciously to minimize nutrient loss and that aquatic plants be regularly harvested to reduce N release from plant residues.
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•Stable isotopes identify sources of C and N in lakes and provide recommendations for eutrophication management.•Consistency of organic C sources in lake suspended particulate matter and sediments•The multiple source pathways of organic N indicate the presence of multiple N pollution pathways in the lake.•There was a significant linear correlation between TSI and sediment C and N stable isotopes.•Reducing exogenous emissions and endogenous releases to control eutrophication in lakes
