Gehu Lake Research Articles

Monitoring water clarity of lakes in the Middle-Lower Yangtze Plain using Landsat observations (1984–2023)

Using the improved Quasi-Analytical Algorithm (QAA) and Landsat data, we documented the long-term changes in water clarity of the 17 largest lakes in the Middle-Lower Yangtze Plain from 1984 to 2023. A comprehensive dataset with over 4600 water clarity maps, reconstructed from 2511 Landsat series images, was compiled. The water clarity changes of these 17 lakes have a clear seasonal variation pattern, with the highest in summer and the lowest in winter. Over the past 40 years, water clarity of 59 % lakes shows a downward trend, with Junshan Lake showing the highest decrease rate of −0.0231 m/yr. 41 % lakes water clarity are showing an upward trend. From 1984 to 1990, the highest average ZSD (Secchi disk depth) values were recorded in Changhu Lake, Junshan Lake, Honghu Lake, Futou Lake, and Gehu Lake. These lakes, however, experienced the most significant declines compared to period from 2021 to 2023. Chaohu Lake, Taihu Lake, Caizi Lake, and Nanyi Lake, which had the lowest average ZSD during 1984–1990, showed the most substantial increases. Analyzing the monthly distribution of water level and ZSD data reveals that water clarity exhibits different seasonal variations in relation to water levels. The comprehensive dataset and analysis provide a crucial scientific basis for informed water resource management and policy-making in the region.

Reconstruction of Historical Metal Backgrounds in Lacustrine Environments of China Using an Anodonta woodiana "Specimen Bank".

Anodonta woodiana samples from Xidong Water Works and Mashan in Taihu Lake, Yiyang near Dongting Lake, and Taiping Harbor in Gehu Lake preserved in a "specimen bank" established for the "Freshwater Mussel Watch" monitoring program were used to determine the historical metal backgrounds from different waters in the present study. The elements Co, Ni, Mo, Cd, Al, Cr, Mn, Fe, Cu, Zn, As, Ba, and Pb were determined using A. woodiana from four lacustrine sites. The results showed that Al, Cr, Mn, Fe, Cu, Zn, As, Ba, and Pb were all detected, whereas Co, Ni, Mo, and Cd were below the detection limits of 0.0165, 0.0106, 0.0189 and 0.0182µg kg- 1, respectively. In particular, A. woodiana was noted to be an unusual Mn hyperaccumulator (ranged from 5124.09 to 13015.47µg g- 1). The results of discriminant analysis showed that the four water samples could be accurately separated. This difference has the potential to infer the background difference of heavy metal pollution in different lacustrine habitats.

Modeling the inhibition effect of recreating submerged plants habitat on sediment resuspension in Lake Gehu

Modeling the inhibition effect of recreating submerged plants habitat on sediment resuspension in Lake Gehu

Temporal dynamics of the Chlorophyll a-Total phosphorus relationship and algal production efficiency: Drivers and management implications

In recent decades, climate change has significantly affected water quality and algal blooms in lakes worldwide. Studying the temporal dynamics patterns of algal production efficiency and its drivers in individual lakes is useful for analyzing the evolutionary trajectory of Chla-TP changes, and identifying the main controlling factors of eutrophication to guide lake management. In this study, we used a dataset for the Lake Gehu (1986–2020) to analyze the drivers of the ETP variability on interannual and seasonal time scales and to quantify the relative impacts and contributions of nutrient and climatic factors on the ETP. The results showed a negative correlation of the Chla-TP relationship appeared in years with very high ETP. The effects of nutritional and climatic factors on the ETP at different time scales were quantified using a generalized additive model. The results showed that the total phosphorus (TP) concentration had a significant effect on the interannual ETP variation, explaining up to 28.9 %. At the intra-annual scale, climatic variables had a much greater effect on the ETP than the nutrient concentration, and the explanatory effect was ranked as temperature > wind speed > rainfall > total nitrogen (TN). Based on the characteristics of seasonal ETP variations, the TPa of Lake Gehu were 50 μg/L, 33 μg/L, 20 μg/L with ETP levels of 0.2, 0.3, 0.5, respectively. This research highlights the significance of nutrient and climatic factors in interannual and seasonal scale, respectively. In addition, ETP influenced by the coupling of nutrient and climate provides a criterion for establishing the seasonal nutrient threshold of lakes.

Model evaluation of total phosphorus prediction based on model accuracy and interpretability for the surface water in the river network of the Jiangnan Plain, China.

Due to climatic and hydrological changes and human activities, eutrophication and frequent outbreaks of cyanobacteria are prominent in the Jiangnan Plain basin of China. Therefore, building a suitable model to accurately predict the phosphorus concentration in surface water is of practical significance to prevent the above problems. This study built 10 models to predict the phosphorus element in the surface water of the river network in the Jiangnan Plain. The main water types in the basin include the Yangtze River, the Beijing-Hangzhou Canal, and the Gehu Lake. The 10 models in different datasets have been comprehensively evaluated by the prediction accuracy and interpretability of the model, and the calculation of the partial dependence diagram (PDP) and SHAP has proved that there is a transparent response relationship between phosphorus and different factors. The results show that the Yangtze River, Beijing-Hangzhou Canal, and Gehu Lake are suitable for random forest, linear regression, and random forest models, respectively, under the comprehensive evaluation of the prediction accuracy and interpretability of the model. Models with low prediction accuracy often show strong interpretability. In different water body types, turbidity, water temperature, and chlorophyll-a are the three factors that affect the model in predicting phosphorus.

Practice of ecological remediation and restoration in plain river network -- a Case Study of Gehu Lake in Changzhou, China

This study provides a design diagram which involves a series of pragmatic strategies for ecological remediation and restoration of plain river networks in the Yangtze River Delta. The design diagram is composed of two stages: the first concerns the reduction of pollutants, including those from non-point sources, point sources, and river sediments; the second, the restoration of the biological habitat, including the riparian zone and aquatic habitat. A case study of Gehu Lake was used as an example for the implementation of the suggested design diagram, and further suggestions were provided for the improvement of remediation work in plain river network areas. This research provides valuable insights into the methods of ecological restoration, and demonstrates the potential for multidisciplinary collaboration to help improve the environmental health of plain river networks.

Pollution Characteristics and Risk Assessment of Typical Antibiotics and Persistent Organic Pollutants in Reservoir Water Sources

The major task of Chinese water governance has gradually shifted away from water environment protection to water ecology remediation, and the governance of trace organic pollutants, including persistent organic pollutants and antibiotics, has attracted growing concern. The present study examined the seasonal distribution and sources of typical persistent organic pollutants and antibiotics in six representative water sources in the lower reaches of the Yangtze River, as well as their ecological risk to the environment. Six representative surface water and surface sediment samples were collected at different time intervals, i.e., December 2018, March 2019, and June 2019, and the concentrations of nineteen organochlorine pesticides (OCPs), seventeen polychlorinated biphenyls (PCBs), and eight polybrominated diphenyl ethers (PBDEs) were analyzed by GC-MS. The major findings are listed below: ① Endosulfan sulfate, Beta-endosulfan, and methoxychlor were the major persistent organic pollutants (POPs) detected in the sediments from Gaoyou Lake, Gonghu Lake, and Gehu Lake, with concentrations ranging from 9.0 to 10.6 ng/g. ② The target antibiotics in water sources were at relatively low levels. Occurrences of sulfonamide antibiotics in water and surface sediments were NF~37.4 ng·L−1 and NF~47.3 ng·g−1. Concentrations of quinolone antibiotics in the two media were NF~5.3 ng·L−1, 0.4~32.5 ng·g−1. ③ The combined toxicity of antibiotics (risk quotient, RQ) in Lake Gehu was 0.18, which was at a moderate risk level. There was no obvious ecological risk in most water sources affected by POPs. However, there were certain ecological risks in the water sources of Gaoyou Lake, Gonghu Lake, and Sanjiangying, induced by OCPs and PCBs. This study provides a scientific basis for the treatment of antibiotics and organic pollutants in reservoir water sources.

Investigating the effects of inflow river water quality on lake nutrient-concentration variations: a case study in Gehu Lake, China

Context Controlling the inputs of nutrients, one of the main sources of lake pollution from inflow rivers, is an important way to protect lakes. Aims To obtain a whole picture of spatiotemporal variation of water quality in Gehu lake and its main inflow rivers from 2011 to 2018, and to study relationship of water quality between lake and inflow rivers. Methods We analysed the relationship by using correlation analysis and BATHTUB model and discussed the goal of collaborative control by setting up different scenarios. Key results The concentrations of total nitrogen (ρ(TN)) and total phosphorus (ρ(TP)) are the main water pollutants in Gehu Lake and it continues to maintain the middle-eutropher state. ρ(TN) and ρ(TP) in the lake have a significant negative correlation with the quantity of water inflow and a significant positive correlation with ρ(TN) and ρ(TP) in inflow rivers. Conclusions It showed that when ρ(TN) and ρ(TP) in inflow rivers decreased by 25%, ρ(TN) and ρ(TP) in Gehu Lake decreased by 21.01 and 22.64%. Furthermore, when ρ(TN) and ρ(TP) in inflow rivers decreased by 50%, they correspondingly decreased by 40 and 36.91% in the lake. Implications Our findings provide effective control of water quality in Gehu Lake and give a guide for environmental governance and water-quality improvement measures.

Genetic Diversity Evaluation and Conservation of Topmouth Culter (Culter alburnus) Germplasm in Five River Basins in China.

To study the genetic diversity of Culter alburnus (C. alburnus) populations, we analyzed the genetic diversity of five C. alburnus populations from Songhua Lake (SH), Huaihe River (HH), Changjiang River (CJ), Taihu Lake (TH), and Gehu Lake (GH) based on mitochondrial COI gene sequences. The results showed that the average contents of bases T, C, A, and G in the 526 bp COI gene sequence were 25.3%, 18.1%, 28.1%, and 28.6%, respectively, which showed AT bias. A total of 115 polymorphic sites were detected in the five populations, and 11 haplotypes (Hap) were defined. The nucleotide diversity (Pi) of the five populations ranged from 0.00053 to 0.01834, and the haplotype diversity (Hd) ranged from 0.280 to 0.746, with the highest genetic diversity in the TH population, followed by the SH population, with lower genetic diversity in the HH, CJ and GH populations. The analysis of the fixation index (Fst) and the genetic distance between populations showed that there was significant genetic differentiation between the SH population and the other populations, and the genetic distances between all of them were far; the genetic diversity within populations was higher than that between populations. Neutral tests, mismatch distributions, and Bayesian skyline plot (BSP) analyses showed that the C. alburnus populations have not experienced population expansion and are relatively stable in historical dynamics.

Changes in Fish Assemblage Structure after Pen Culture Removal in Gehu Lake, China

The removal of the net enclosure has been used as a lake management strategy in various regions of China as ecological development is given more attention. Nevertheless, little is known about the substantive impact of this measure on fish communities in inland lakes. To this end, the fish community composition and structural features after the removal of the net enclosure in Gehu Lake were explored and evaluated in this study from 2021 to 2022 and compared to the investigation before the net enclosure removal from 2017 to 2018. Belonging to 7 orders, 10 families, and 46 species, a total of 17,151 fish were collected, with pelagic, sedentary, and omnivorous species dominating. In comparison, the number of species increased by 10 after removal, and fish alpha diversity increased. The Index of Relative Importance (IRI) revealed that the composition of dominating species remained constant, including Coilia nasus, Hypophthalmichthys molitrix, and Hypophthalmichthys nobilis; Parabramis pekinensis, Megalobrama amblycephal, and Culter mongolicus were upgraded from common species to general species. Culter alburnus, Hemiculter bleekeri, and Pseudobrama simoni were downgraded from general species to common species. Elopichthys bambusa had become a common species (IRI = 109.35), which was not discovered before removal. According to the hierarchical clustering (HC) and non-metric multidimensional sequencing (NMDS), the fish community of the northern reserve was highly aggregated. As the Abundance Biomass Comparison (ABC) curve and biodiversity index indicated, the fish community structure of the whole lake was in a state of moderate anthropogenic disturbance with reduced stability, while that of the northern reserve was in a state of light anthropogenic disturbance with greater stability. The number of fish species increased in this survey compared to the period before removal, species and dominant species composition altered dramatically, and total lake stability declined. This study demonstrates that the fish diversity in Gehu Lake increased after the removal of the net enclosure. Meanwhile, the stability of the fish community structure was decreased temporarily. Lake restoration is a long-term process, and the underlying impact of the removal of the net enclosure still requires continuous monitoring and further studies.

Horizontal and vertical distribution of microplastics in Gehu Lake, China

Abstract Microplastics (MPs) widely exist in the aquatic environment. In this study, the horizontal and vertical distribution of MPs in different depths of Gehu Lake was analyzed. The study found that MPs were detected in water bodies at different depths. The Gehu Lake Basin's MP abundance throughout the entire lake region ranged from 1.40 to 5.53 n/L. Microplastic abundance in surface water (3.13 ± 0.32 n/L) was highest, and the average abundance of MPs in the middle water (2.28 ± 0.24 n/L) and bottom water (1.03 ± 0.14 n/L) was appreciably reduced (p < 0.05). The microplastics observed in water samples were analyzed, and it was found that the particle size of most of the obtained microplastic particles was between 100 and 500 microns, the main shape was fibrous MP, and the MP content of transparent color was highest, and the four most common MPs was polyethylene (PE), polystyrene, polyester (PES), and polypropylene (PP). In this article, we emphasize the importance of comprehending the specific distribution characteristics of MPs in Gehu Lake. It provides a data foundation for future monitoring of MPs present in Gehu Lake, provides scientific and technological support for the assessment and prevention of microplastic pollution in this area, and offers some assistance for future lake water quality regulation.

The Effects of Water Depth on the Growth of Two Emergent Plants in an In-Situ Experiment

With the degradation of the global lake ecosystem, aquatic plants are more and more widely used in lake ecological restoration. The effects of water depths on the growth and photosynthetic fluorescence characteristics of two emergent plants (Typha orientalis and Zizania caduciflora) were studied in eutrophic Lake Gehu by in-situ experiments. The results showed that water depth had no significant effect on germination of emergent plants. The water depth changed the morphological characteristics of emergent plants. Plant height, tiller number, leaf length, leaf width, the number of leaf, and the root-shoot ratio decreased with increasing water depth, whereas the number of dead leaves increased with increasing water depth. The biomass of emergent plants was highest when water depth was 40 cm. Water depth had a significant effect on the photosynthetic fluorescence of the emergent plant. Fv/Fm tended to decrease first and then increase with increasing water depth. When the water depth was 20 cm, the ETRmax of emergent plants was significantly higher than that of plants at the other water depths. These results show the suitable water depth range for T. orientalis and Z. caduciflora is 20–60 cm. A deeper water depth for a long time is not conducive to the growth of emergent plants.

Comparison of fish communities using environmental DNA metabarcoding and capture methods in a freshwater lake: A new set of universal PCR primers

Freshwater biodiversity is under pressure from the detrimental effects of climate change, habitat degradation, biological invasion, and overfishing. Environmental DNA (eDNA) obtained directly from environmental samples can be used to evaluate the distribution of aquatic species. We developed a new set of universal PCR primers (16 S 200) for eDNA metabarcoding from mitochondrial DNA sequences. Using the new 16 S 200 primers, we detected the presence of 27 fish species distributed across four families in Lake Gehu, in southeastern China. eDNA metabarcoding and live capture methods identified 16 species in common; however, the two methods identified nine and 12 unique species, respectively. Data from eDNA metabarcoding were more consistent with results from gill net capture methods than from ground cage capture. The present study supports the effectiveness of eDNA for rapidly assessing the species composition of fish communities.This is the first attempt to designed new sets of primers for eDNA-based metabarcoding analysis of freshwater fish in China. Despite pitfalls and limitations, eDNA metabarcoding is a promising approach for assessing fish communities in freshwater lakes. Current applications of eDNA are widespread, but the new technology requires further refinement.The eDNA metabarcoding is an efficient and cost-effective method that can be used in conjunction with traditional survey methods for analyzing fish communities.

Temporal-Spatial Pattern of Dissolved Organic Carbon and Its Influencing Factors in a Typical Subtropical Lake, Lake Gehu, China

Temporal-Spatial Pattern of Dissolved Organic Carbon and Its Influencing Factors in a Typical Subtropical Lake, Lake Gehu, China

A pollution risk assessment and source analysis of heavy metals in sediments: A case study of Lake Gehu, China

• Conduct a pollution risk assessment of heavy metals in the sediments of Gehu Lake during the high water period and normal water period in Jiangsu Province, and analyze the possible sources. • The average concentrations of Hg, Pb, Cu, Zn, Co, As, Cd, Cr, Mn, and Ni all exceed the corresponding background value, and the coefficient of variation is greater than 20%. • The heavy metal pollution risk assessment results show that the pollution of Cd in the sediments of Gehu Lake is the most serious, especially in the normal water period. • The PMF analysis results show that the printing and dyeing textile industry and the metal manufacturing industry contribute more to the heavy metals in the sediments of Gehu Lake. The electroplating industry takes the second place, and the agriculture and chemical industries account for a relatively small proportion. This study concerned the sampling and detection of 10 heavy metals, including Hg, Pb, Cu, Zn, Co, As, Cd, Cr, Mn, and Ni, in the sediment of Lake Gehu in Jiangsu Province. A geographic information system (GIS) was used to show the spatial distribution of the heavy metals in the sediments of the lake. Then, the geological accumulation index, enrichment coefficient and potential ecological risk index was used to assess the potential risks brought by the accumulation of these heavy metals. Correlation analysis was used to qualitatively analyze the sources of the heavy metals and determine the correlation between them. The positive definite matrix factorization model (PMF) was also used to quantitatively analyze the source of the heavy metals. The study concluded that the concentration of heavy metals in the southwest of Lake Gehu is relatively low. According to the calculation results of the geological accumulation index and the enrichment coefficient, the sediments of Lake Gehu are most seriously polluted by Cd, especially during the period of normal water levels. The potential ecological risk index shows that the central part of Lake Gehu poses the highest risk of pollution from heavy metals, and nearly reaches the High Risk category. There is a positive correlation between the heavy metals Hg, Cu, Co, and a significant positive correlation between Pb, Zn, As, Cr, Mn, and Ni. These two groups of heavy metals are also highly homologous. Local industries including printing and dyeing textiles, electroplating, chemical making, agriculture, and metal manufacturing are all causes of heavy metal pollution. From all of these, factories that dye and print textiles, and metal manufacturing plants are the main causes of pollution. .

Eutrophication evolution trajectory influenced by human activities and climate in the shallow Lake Gehu, China

Lake eutrophication has become a global environmental pollution problem. Analysis of the eutrophication recovery trajectory of lakes can help to accurately implement regulations and reduce the cost of management. The degradation and recovery trajectories of Lake Gehu were firstly analyzed based on 34-years monitoring data of water quality. A dynamic correlation analysis of the relationship between chlorophyll-a (Chla) and the total phosphorus (TP) (total nitrogen [TN]) at an annual scale was conducted using the filtering trajectory method (FTM). The result showed that the recovery trajectory of Lake Gehu was nonlinear, and showed a short lag time in Chla decrease. The regime shift from a clear-water state to a turbid-water state occurred in Lake Gehu when the TP threshold was 120 μg/L. Combined the filtering trajectory diagram with a principal component analysis, the results revealed that the adverse climate change did not completely offset the positive effect of nutrient load reduction, which required further attention and had significance for eutrophication control. According to the dynamic changes in the algae production efficiency of total phosphorus (ETP), the result showed that the sensitivity of lake eutrophication increased and the TP carrying concentration reduced by 40%-60%. The water quality goal for controlling algae was determined as TP = 40 μg/L (Chla = 10 μg/L), which was 20% stricter than the national standard (TP = 50 μg/L). In conclusion, aquatic vegetation restoration and biological manipulation can be effective alternatives for controlling eutrophication in addition to nutrient load reduction. The eutrophication control target and adaptive strategies were determined according to the recovery trajectory of Lake Gehu in this study. The ETP has reference significance for the management of shallow lakes.

Trends and Causes of Raw Water Quality Indicators in the Five Most Famous Lakes of Jiangsu Province, China.

Due to pollutants from industrial and agricultural activities, the lakes in China are faced with ecological and environmental problems. The five most famous lakes of Jiangsu Province, Taihu Lake, Gehu Lake, Gaobaoshaobo Lake, Hongze Lake, and Luoma Lake, have long-term fixed monitoring points for water body-related indicators. Over a five-year period, the monitoring showed that Gehu Lake had the highest average total nitrogen (TN) and total phosphorus (TP) concentrations among all lakes which were close to the Grade V critical value of the China’s Environmental Quality Standards for Surface Water (CEQSW). The NH3-N concentrations in all lakes were Grade IV according to the China’s Water Quality Standard for Drinking Water Sources (CWQSDWS) and Grade II according to the CEQSW. In addition, although TP concentrations in Taihu Lake did not exceed Grade V in the CEQSW, TP removal was the main factor controlling eutrophication. It was also found that the petroleum concentrations in all lakes were lower than the Grade I according to the CEQSW. Despite this relatively low petroleum pollution, the concentration of petroleum was negatively correlated with the phytoplankton densities in all lakes. This indicated that phytoplankton density was very sensitive to petroleum concentration. For heavy metals, the concentrations of Pb, Cu, As, and Cd in all lakes were significantly lower than Grade I (CEQSW) from 2013 to 2017. However, the accumulated heavy metals in sediments will remain an important pollution source affecting water quality and aquatic products in the future. The comprehensive pollution index analysis showed that the five lakes were often moderately polluted, indicating that the protection of lake resources in China should not be relaxed for a long time in the future.

Groundwater recharge pathway according to the environmental isotope: the case of Changwu area, Yangtze River Delta Region of China

Abstract Groundwater recharge is an important factor affecting water circulation. As groundwater has slow seepage, directly observing the seepage velocity and recharge path of groundwater in the aquifer is difficult. Environmental isotope technology has become an important means to clarify the mechanism of groundwater movement and the mechanism by which groundwater recharges from the micro and macro perspectives. The Changwu area of Jiangsu Province was taken as an example to identify the recharge sources of groundwater and the recharge paths of groundwater and surface water by using the measured data of isotopes D, 18O, 34S, and T. The results indicated that the shallow aquifer and the I confined aquifer in the Changwu area are mainly recharged by precipitation and surface lake water. The II confined aquifer along the Yangtze River is recharged by modern precipitation. Moreover, the II confined aquifer in the Henglin area was recharged by the ancient Yangtze River before 4,000 years ago, and no recharge relationship exists now. the recharge condition of the II confined aquifer around the northwest of Gehu Lake is in the climate environment of 8,000 years ago and was caused by the surface depression lake water at that time. Additionally, the concealed limestone aquifer is primarily supplied by the II confined aquifer, while the concealed sandstone aquifer supplies the II confined aquifer. Hence, to find out the recharge conditions of groundwater aquifers based on the environmental isotope is conducive to scientific and reasonable evaluation of groundwater resources and to ensure the sustainable development and utilization of groundwater resources.

The Water Quality Improvement through Two Pollutant Load Allocation Methods in Gehu Lake, China

AbstractDue to many industrial and domestic pollution sources gathered around Gehu Lake and the lack of effective reduction measures, the ammonia nitrogen and total phosphorus in a large area of th...

Study on the proportion and flow path of Yangtze River water diversion into Taihu Lake

Abstract The purpose of this study is to quantify the proportion and flow path of the water diversion from Yangtze River (YRD) into Taihu Lake. Based on the analysis of rainfall and data of Taihu basin in the recent 30 years, a 1-D hydrodynamic model of the main inflow river network area of Taihu basin was constructed, coupled the convection-diffusion model with conservative material, the characteristics of YRD and the water inflow into Taihu Lake (WITL) in three typical years were calculated. The results show that the YRD has shown a significant upward trend in the past 30 years, accounting for 26.4, 35.6 and 42% of the total WITL in three typical years of wet, normal and dry conditions respectively. From the perspective of space, Taige River is the largest river in the western part of the lake that is affected by the river diversion (35%–72%), and Wuxi River is the smallest (1–3%). In addition, the primary flow path of YRD to Taihu Lake was through the Wuyi River and Lake Gehu from the water diversion station west of the Zao River.