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Abstract Background The drastic change in an ecosystem as a threshold phenomenon caused by abrupt changes in environmental conditions is a focus of current ecological research. However, the study of ecological thresholds has generally been limited to estimating the threshold values of single factors. Using eDNA metabarcoding technology, we collected zooplankton data from Baiyangdian Lake, the largest freshwater lake in the North China Plain, to explore the zooplankton community distribution characteristics and the relevant environmental factors. We used Threshold Indicator Taxa Analysis (TITAN) to determine the thresholds of key environmental factors and to identify the factors influencing biological diversity. Results By comparing previous studies, we found that the zooplankton community composition based on eDNA metabarcoding was similar to that based on morphological methods, and that the data could be used to estimate ecological thresholds and assess risk conditions. Temperature (T), electrical conductivity (EC), and turbidity were the major environmental factors affecting the zooplankton community structure. The composition and structure of zooplankton communities in rivers and lakes were significantly different due to the influence of specific environmental factors. The results of TITAN analysis showed that there were different indicator species for T and EC in rivers and lakes. The protection thresholds of zooplankton in rivers were T = 19.0 °C and EC = 795 μS/cm, whereas the protection thresholds of zooplankton in lakes were T = 14.3 °C and EC = 1920 μS/cm. The overall values for the Baiyangdian watershed were T = 15.5 °C and EC = 1073 μS/cm. Compared with the field monitoring results, approximately 50% of the water quality index values at the sampling points in the Baiyangdian watershed exceeded the negative response threshold, indicating that Baiyangdian Lake was disturbed. Conclusions The validity of eDNA technology in biodiversity analysis was confirmed by the zooplankton community data from Baiyangdian Lake. The ecological thresholds derived by combining eDNA technology with Threshold Indicator Taxa Analysis (TITAN) are beneficial to the biological conservation of the region.

Background: The drastic change in an ecosystem as a threshold phenomenon caused by abrupt changes in environmental conditions is a focus of current ecological research. However, the study of ecological thresholds has generally been limited to estimating the threshold values of single factors. Using eDNA metabarcoding technology, we collected zooplankton data from Baiyangdian Lake, the largest freshwater lake in the North China Plain, to explore the zooplankton community distribution characteristics and the relevant environmental factors. We used Threshold Indicator Taxa Analysis (TITAN) to determine the thresholds of key environmental factors and to identify the factors influencing biological diversity. Results: By comparing previous studies, we found that the zooplankton community composition based on eDNA metabarcoding was similar to that based on morphological methods, and that the data could be used to estimate ecological thresholds and assess risk conditions. Temperature (T), electrical conductivity (EC), and turbidity were the major environmental factors affecting the zooplankton community structure. The composition and structure of zooplankton communities in rivers and lakes were significantly different due to the influence of specific environmental factors. The results of TITAN analysis showed that there were different indicator species for T and EC in rivers and lakes. The protection thresholds of zooplankton in rivers were T = 19.0 °C and EC = 795 μS/cm, whereas the protection thresholds of zooplankton in lakes were T = 14.3 °C and EC = 1920 μS/cm. The overall values for the Baiyangdian watershed were T = 15.5 °C and EC = 1073 μS/cm. Compared with the field monitoring results, approximately 50% of the water quality index values at the sampling points in the Baiyangdian watershed exceeded the negative response threshold, indicating that Baiyangdian Lake was disturbed. Conclusions: The validity of eDNA technology in biodiversity analysis was confirmed by the zooplankton community data from Baiyangdian Lake. The ecological thresholds derived by combining eDNA technology with Threshold Indicator Taxa Analysis (TITAN) are beneficial to the biological conservation of the region. [ABSTRACT FROM AUTHOR]

Introduction: As the largest shallow freshwater lake in the North China Plain, Baiyangdian lake is essential for maintaining ecosystem functioning in this highly populated region. Sediments are considered to record the impacts of human activities. Methods: The abundance, diversity and metabolic pathways of microbial communities in sediments were studied by metagenomic approach to reveal patterns and mechanism of C, N, P and S cycling under the threat of lake eutrophication. Results: Many genera, with plural genes encoding key enzymes involved in genes, belonging to Proteobacteria and Actinobacteria which were the most main phylum in bacterial community of Baiyangdian sediment were involved in C, N, S, P cycling processes, such as Nocardioides (Actinobacteria), Thiobacillus, Nitrosomonas, Rhodoplanes and Sulfuricaulis (Proteobacteria). For instance, the abundance of Nocardioides were positively correlated to TN, EC, SOC and N/P ratio in pathways of phytase, regulation of phosphate starvation, dissimilatory sulfate reduction and oxidation, assimilatory sulfate reduction, assimilatory nitrate reduction and reductive tricarboxylic acid (rTCA) cycle. Many key genes in C, N, P, S cycling were closely related to the reductive citrate cycle. A complete while weaker sulfur cycle between SO42- and HS- might occur in Baiyangdian lake sediments compared to C fixation and N cycling. In addition, dissimilatory nitrate reduction to ammonia was determined to co-occur with denitrification. Methanogenesis was the main pathway of methane metabolism and the reductive citrate cycle was accounted for the highest proportion of C fixation processes. The abundance of pathways of assimilatory nitrate reduction, denitrification and dissimilatory nitrate reduction of nitrogen cycling in sediments with higher TN content was higher than those with lower TN content. Besides, Nocardioides with plural genes encoding key enzymes involved in nasAB and nirBD gene were involved in these pathways. Discussion: Nocardioides involved in the processes of assimilatory nitrate reduction, denitrification and dissimilatory nitrate reduction of nitrogen cycling may have important effects on nitrogen transformation. [ABSTRACT FROM AUTHOR]

Pollution in inflow rivers seriously endangers the water environment in downstream lakes. In this study, an inflow river system of the Baiyangdian-Fuhe river system (FRS) was investigated to display timely pollution patterns of eutrophication and heavy metals after the establishment of Xiongan New Area, aiming to reveal the weak parts in current pollution treatments and guide the further water quality management. The results showed that the pollution of eutrophication was worse than the heavy metals in FRS, with serious eutrophic parameters of ammonia nitrogen (NH4+-N) and chemical oxygen demand (COD). There were greatly spatiotemporal variations of the pollution in FRS. (1) Concentrations of NH4+-N and total phosphorus were all higher in summer and autumn, whereas, COD contents were higher in spring; the water quality index (WQI) of eutrophication linearly increased along FRS in summer and autumn, with pollution hotspots around the estuary area. (2) The pollution levels of plumbum exceeded cadmium (Cd) and chromium (Cr) but without strongly spatiotemporal changes; however, Cd and Cr in the town area and Cd in spring showed higher concentrations; the WQI of heavy metals showed single peak curves along FRS, with significantly higher values around the town area. Additionally, the four potential pollution sources: domestic sewage, traffic pollution, agricultural wastewater and polluted sediments were identified based on the pollution patterns and pollutant associations. These findings demonstrated current treatments failed to eliminate the pollution in some hotspots and periods, and the in-depth understanding of the pollution spatiotemporal patterns in this study, especially the pollution hotspots, serious periods and potential sources, are crucial to furtherly develop spatiotemporally flexible pollution treatment strategies. [ABSTRACT FROM AUTHOR]

Water diversion is crucial for maintaining sustainable development in populated lake areas. However, there has been no clear evaluation of how water diversion affects lake health in these areas, which are often limited by scarce in situ observations. To address this issue, we selected Baiyangdian, a fragmented freshwater shallow lake in Xiongan New Area, as our study area. We conducted a time series analysis of Baiyangdian’s water level and area changes, and identified the impact of water diversion on Baiyangdian. We used laser altimetry data (ICESat, ICESat-2), remotely-sensed lake extent, water diversion data, precipitation data, and in situ lake level data. Our results show that water diversion, rather than natural precipitation, has maintained healthy water levels in Baiyangdian in recent years. Baiyangdian’s water level has risen significantly and stabilized, moving from a drying-up level to a healthy level. The intensity of water diversion has increased from 0.91 million m ^3 in the 2000s to 7.17 million m ^3 in the 2020 s, with a corresponding water level rise from 4.93 m to 7.14 m, respectively. Moreover, a positive feedback loop between economic development, policy-making, and the lake’s ecological health can promote the sustainable development of both people and nature.

Novel 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA) and legacy PFASs, such as perfluorohexane sulfonate (PFHxS), have been used to replace perfluorooctane sulfonate (PFOS), a known persistent organic pollutant. Thus, it is critical to understand these PFOS alternatives regarding their sources and concentrations in the natural environment. In this study, 41 surface water samples as well as edible aquatic organisms were collected from Baiyangdian Lake, the largest freshwater lake in Hebei Province, China. Perfluorooctanoate acid (PFOA) and PFHxS were the predominant PFASs detected in the surface water, reaching concentrations of 8 397.23 ng/L and 1 478.03 ng/L, respectively, with PFHxS accounting for the greatest proportion (∼80.00%) in most water samples. PFHxS (mean: 87.53 ng/g) and PFOS (mean: 35.94 ng/g) were also the most prevalent compounds detected in aquatic organisms. Estimated daily intake (EDI) values of PFOS (16.56 ng/kg bw/d) and PFHxS (16.11 ng/kg bw/d) via aquatic food and drinking water were the highest among PFASs, indicating potential exposure risks to residents. In addition, fish product consumption was the important exposure pathway for residents to PFOA, PFHxS, PFOS, and 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA). This study reports on the highest PFHxS levels ever recorded in surface water, suggesting that further quantification of PFHxS in human serum and assessment of its health risks to local residents are warranted and critical. [ABSTRACT FROM AUTHOR]

Objective: To establish an ultra-performance liquid chromatography (UPLC) fingerprinting method for quality control of Phragmitis rhizoma from Baiyangdian. Materials and Methods: Ultrasonic extraction with 70% methanol was performed on 10 samples of P. rhizoma collected from 10 different villages in Baiyangdian. The sample solutions were analyzed by Waters UPLC equipped with the ACQUITY UPLC BEH C18 column and photodiode array (PDA) detector, and gradient eluted with acetonitrile/water as the mobile phase. The flow rate was set to 0.1 mL/min; the column temperature was set to 25°C; and the detection wavelength was set to 285 nm. Results: The chromatograms of the 10 samples showed 27 common peaks, of which one was identified as the ferulic acid standard. The similarity indexes were all above 0.82. Hierarchical cluster analysis showed that the constituents and their quantities differed according to the diameter of the original plant, which is related to its age. Conclusion: The UPLC fingerprinting method had the advantages of being fast, accurate, and highly efficient; this indicated that it can be used for quality control of P. rhizoma produced in Baiyangdian. Also, the relation between the quality and diameter/age of the plant needs to be further investigated. [ABSTRACT FROM AUTHOR]

Abstract: Water quality is sensitive to changes in landscape patterns in a watershed, particularly during urbanization. Using GIS tools, the landscape pattern index method was proposed to compare the landscape patterns of Baiyangdian Watershed in 2002 and 2007, determine the transformation rules of landscape essential factors, and analyze the correlation between the changes of landscape patterns and water quality in Baiyangdian Watershed. The study shows that 1) the degree of fragmentation of man-made landscape is decreasing and that of the natural landscape is increasing in the watershed during its urbanization; 2) Construction land and farmland are the dominant factors leading to river pollution in most cases, while a higher percentage of forest cover contributes to improved water quality. Furthermore, other physical and social factors were analyzed that may influence the relationship between water quality patterns of land use in the study area. [Copyright &y& Elsevier]

Abstract: Wetland ecosystem occupies an important position in the global carbon cycle with a strong ability of carbon storage and fixation. On the basis of field investigation and laboratory measurement, in the paper, the standing biomass and primary production of wetland Phragmites australis in Baiyangdian were study, and its ability of carbon storage and fixation in accordance with the principle of photosynthesis was measured, and then the potential ability of carbon storage from the perspective of efficiency for solar energy utilization was discussed. The results show that carbon storage of wetland Phragmites australis is large in Baiyangdian with 5.81kg • m-2, 7.14kg • m-2 and 8.72kg • m-2 respectively; carbon fixation is also very large with 2.54kg • m-2, 3.12kg • m-2 and 3.81kg • m-2 respectively. In addition, the underground biomass is larger than the aboveground biomass, and the ratio of the two is 2.38-3.30 with the average of 2.90. The underground carbon storage is nearly 3 times as much as the aboveground carbon storage. Wetland Phragmites australis in Baiyangdian has a strong ability of carbon fixation with 1.17kg • m-2 • a-1, 1.49kg • m-2 • a-1 and 1.76kg • m-2 • a-1 respectively, which is 1.7-3.4 times as much as the average ability of carbon fixation of the national terrestrial plants and 2.0- 4.0 times of that of the global plants. [Copyright &y& Elsevier]

Abstract: In order to study the seasonal variations in the structure and dynamics of phytoplankton community of the Lake Baiyangdian in China, quantitative samples were collected in each season during 2005. A total of 152 taxa were identified by microscope, phytoplankton had an abundance ranging from 131.25×104 ind. L-1 to 745.88×104 ind. L-1. The highest phytoplankton abundance were observed in spring and the lowest in autumn. Cyanophyta, Euglenophyta and Cryptophyta were the most important groups in terms of abundance and biomass. The preponderant and sub-preponderant species changed in accordance with the seasons. Canonical Correspondence Analysis (CCA) was used to investigate the relationship between environmental factors and phytoplankton community. The results indicated that nutrient gradient had a positive correlation with axis 1 in spring, summer and autumn. But in winter, the nutrient gradient had a positive correlation with axis 2. The varieties of environmental factors affected the structure of phytoplankton community in each season. CCA shows a slight, but significant method to understand the spatial distribution of phytoplankton community in lake systems. [ABSTRACT FROM AUTHOR]