Lake Chaohu Research Articles

Order Construction: The Art Characteristics and Cultural Roots of Folk Lantern in Chaohu Area

Lantern is a popular folk activity in the area around Chaohu Lake, which has many kinds, wide distribution and great influence. From the overall macro perspective and the horizontal comparative research method, this paper explores the relationship and laws between the explicit personality characteristics and the connotative common nature of the lantern color around Chaohu Lake, and constructs the order characteristics running through the visual art, activity procedure and cultural origin of the lantern color. Based on the rural space, the ring nest lantern indirectly constructs the social space order across the border in the traditional festivals with their own characteristics. It virtually realizes the order and standardization of the local and rural real life, and objectively reflects the remarkable characteristics and excellent quality of the regional culture around Chaohu Lake, which is conducive to the protection of the folk intangible cultural heritage around Chaohu Lake Inheritance has positive significance.

Annual dynamic remote sensing monitoring of phycocyanin concentration in Lake Chaohu based on Sentinel-3 OLCI images

藻蓝素（PC）是水体蓝藻的指示性色素，其浓度反映了蓝藻生物量，利用卫星遥感监测藻蓝素浓度年内动态对蓝藻水华的有效防控有着重要意义.根据不同季节的巢湖藻蓝素浓度实测数据与同期Sentinel-3 OLCI影像，构建机器学习回归反演模型，应用于巢湖2019年OLCI影像集上，对巢湖藻蓝素浓度的空间分布、年内变化进行遥感监测.研究表明：在MUMM和C2RCC水体大气校正方法中，C2RCC的大气校正结果更接近实测光谱反射率；在机器学习回归算法中，基于梯度提升回归的藻蓝素浓度反演模型精度最高，其R²、RMSE和rRMSE分别达到0.84、49.76 μg/L和34.1%.水体藻蓝素浓度在1—4月及12月较低，在5—11月浓度较高且波动频繁，日均气温是水体藻蓝素浓度年内变化的主要原因，而藻蓝素短期剧烈波动主要是受到日降水量和日照时数的影响；在夏、秋季节，西湖区藻蓝素浓度明显高于中、东湖区，主要与入湖河流中氮磷等物质的高输入有关.Sentinel-3 OLCI影像为湖库水体藻蓝素浓度动态监测提供了重要数据源，梯度提升回归算法在富营养化水体藻蓝素浓度反演中具有较大的应用潜力.;Phycocyanin (PC) is an indicator pigment of cyanobacteria in water, and its concentration reflects the biomass of cyanobacteria. Monitoring the annual dynamics of PC concentration by satellite remote sensing is of great significance for the effective prevention and control of cyanobacteria bloom. Based on the measured data of phycocyanin concentration in Lake Chaohu in different seasons and the Sentinel-3 OLCI images of the same period, a machine learning regression retrieval model was constructed and applied to the 2019 OLCI image set of Lake Chaohu to monitor the spatial distribution and annual variation of PC concentration. The results show that among MUMM and C2RCC atmospheric correction methods, the atmospheric correction result of C2RCC is closer to the measured spectral reflectance. Among the machine learning regression algorithms, the retrieval model of PC concentration based on gradient boosting regression has the highest accuracy, its R², RMSE and rRMSE reach 0.84, 49.76 μg/L and 34.1%, respectively. The concentration of PC was low from January to April and December, but high from May to November and fluctuated frequently. The average daily temperature was the main reason for the annual variation of PC concentration, and the short-term fluctuation of PC was mainly affected by the daily precipitation and sunshine duration. In summer and autumn, the PC concentration in the West Lake area was significantly higher than that in the middle and east lake area, which was mainly related to the high input of nitrogen and phosphorus into the lake. Sentinel-3 OLCI images provide important data sources for the dynamic monitoring of PC concentration in lake and reservoir waters, and the gradient boosting regression algorithm has great application potential in the retrieval of PC concentration in eutrophication waters.

Real-time monitoring of cyanobacterial blooms dynamics around Lake Chaohu based on video surveillance images

蓝藻的防控与治理是湖泊水环境、水生态管理的重要内容，实时获取蓝藻的空间分布信息对于降低蓝藻灾害风险具有重要意义.针对地面调查费时费力、卫星遥感监测粒度较粗且时效性不强等问题，本文提出了一种基于视频监控网络的湖泊蓝藻实时监测技术.基于环巢湖视频监控网络的33个功能摄像机，研究如何从视频图像中实时、准确提取蓝藻的分布信息.为克服不同摄像头的观测角度不一致、光照强度和背景条件不一致等诸多挑战，在视频图像蓝藻表征分析的基础上，通过多尺度深度网络进行图像粗粒度分类，区分蓝藻与浑浊、阴影水体；基于随机森林进行蓝藻精细化识别，克服蓝藻的强异质性.最后以渔政站沿岸水域的日均蓝藻覆盖率和月均蓝藻覆盖率为统计单位，开展了巢湖沿岸蓝藻的动态监测.研究成果可为科学制定蓝藻治理方案提供技术支撑.;The prevention and management of cyanobacterial blooms is an important part of lake environment and water ecological management. Real-time acquisition of spatial distribution of cyanobacterial blooms is of great significance for timely salvage and disaster reduction. Aiming at the problems of time-consuming and laborious ground surveys, satellite remote sensing monitoring with a low spatial and temporal resolution, a new method for real-time monitoring of cyanobacterial blooms in lakes using video surveillance network (VSN) was proposed. Based on the 33 cameras of VSN around Lake Chaohu, the study focuses on the real-time and accurate extraction of cyanobacteria distribution information from video images. First, in order to overcome the challenges of different observation angles from different cameras, light intensities and background conditions, the representation of cyanobacterial blooms in video images was analyzed. Then, a multi-scale depth network was used for coarse-grained image classification to distinguish cyanobacteria from turbid and shadowed water; Random forest method was used to finely recognize cyanobacterial blooms to overcome the strong heterogeneity of cyanobacteria. Finally, the distribution information of cyanobacterial blooms was acquired. Based on the average daily and monthly cyanobacteria coverage of the coastal waters of the fishery administration station, monitoring of cyanobacterial blooms dynamics along the Lake Chaohu coast was completed, which can provide technical support for the management of cyanobacterial blooms.

Recognition and evaluation of city-lake symbiosis under the background of high-quality development: A case study of Hefei and Chaohu Lake in Yangtze River Delta

Recognition and evaluation of city-lake symbiosis under the background of high-quality development: A case study of Hefei and Chaohu Lake in Yangtze River Delta

Fast-changing wind waves and their environmental effects in Lake Chaohu

Fast-changing wind waves and their environmental effects in Lake Chaohu

Monitoring Fractional Floating Algae Cover Over Eutrophic Lakes Using Multisensor Satellite Images: MODIS, VIIRS, GOCI, and OLCI

Coarse-resolution sensors have been used operationally to monitor floating algal blooms with near daily revisit in coastal and inland waters. Most of the current methods in estimating fractional floating algae cover (FAC) were based on the linear pixel un-mixing assumption. In this study, a new FAC model following logistic curve was developed and applied to multisensor satellite data in two large shallow eutrophic lakes, Lake Taihu and Lake Chaohu, in China. The results indicated that after resampling to 250 m, match-up pairs of MODIS (Moderate Resolution Imaging Spectroradiometer), VIIRS (The Visible and Infrared Imager/Radiometer Suite), GOCI (Geostationary Ocean Color Imager) and OLCI (Ocean and Land Color Instrument) possessed consistent Rayleigh corrected reflectance ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R_rc</i> ) and FAI (floating algae index) or AFAI (alternative floating algae index). The FAC model was developed based on the simulated AFAI data of GOCI using point spread function (PSF) and bloom percent derived from OLI (Operational Land Imager), and then was applied to MODIS, VIIRS, and OLCI. Compared with the linear pixel un-mixing method, the FAC model reflects the asymptotic reflectance saturation in the NIR (near infrared) band with the accumulation of blooms. Besides, the equivalent bloom area (EBA) of GOCI was validated using OLI matched pairs with UPD 37.6% (N=39, R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> =0.96). The spatial-temporal dataset of FAC (2002-2020) shows that Lake Taihu and Lake Chaohu experienced severe algal blooms after 2010, partly resulting from the higher frequency of multisensor data. This study provides a method in building a lasting and comparable FAC dataset using multisensors.

Comparison of Acid Volatile Sulfide, Metals Speciation and Diffusive Gradients in Thin-Film Measurement as an Indicator of Sediment Toxicity Assessment in Lake Chaohu, China

Comparison of Acid Volatile Sulfide, Metals Speciation and Diffusive Gradients in Thin-Film Measurement as an Indicator of Sediment Toxicity Assessment in Lake Chaohu, China

Theoretical basis and Chinese practice for environmental protection of lakes with better water quality

目前，我国湖泊富营养化及蓝藻水华问题十分突出，国家高度重视湖泊的生态环境保护.自“九五”以来，国家就投入太湖、巢湖、滇池“老三湖”等重污染湖泊的治理，但成本巨大，且历经近30年才初见成效.按照湖泊污染程度，湖泊治理与保护可分为“污染治理型”“防治结合型”“生态保育型”3大类.“老三湖”的治理是典型的“先污染、后治理”的模式，水质较好湖泊主要属于生态保育型湖泊，因此，“老三湖”治理模式不适用于水质较好湖泊的保护.本文系统总结了我国水质较好湖泊优先保护理念的形成和水质较好湖泊专项实施的历程.根据水质较好湖泊的特点，及其生态系统退化与修复的一般过程，提出了水质较好湖泊保护的基本思路.从热力学角度，阐明了氮磷营养盐输入湖泊生态系统中是熵增过程，也是湖泊生态系统退化的根本原因，湖泊氮磷污染负荷源头控制是关键.湖泊流域生态安全格局是确保湖泊生态系统健康的基础，从景观生态学角度，阐明了优化湖泊流域水土资源利用、优化发展模式是减轻湖泊环境压力的重要途径.在浅水湖泊生态系统，以沉水植物占优势的“清水态”和以浮游植物占优势的“浊水态”转换过程不是沿着同一条途径，存在上临界阈值和下临界阈值，水生态修复过程表现出一种迟滞的现象.从湖泊水生态系统稳态转换理论角度，阐明了湖泊生态修复工程应在湖泊生态系统发生退化转变之前实施，才能获得较高的环境效益.通过国家财政专项对81个水质较好湖泊的支持，既能促进湖泊流域经济社会发展，又能确保湖泊水环境质量变好，湖泊水生态系统逐步改善.建议加强不同类型湖泊保护模式的总结，深入对水质较好湖泊生态系统演替理论和保护技术研究，支撑国家系统开展水质较好湖泊保护.;At present, the problems of lake eutrophication and cyanobacterial blooms in China are still very prominent and the state attaches great importance to the ecological environment protection of lakes. Since the Ninth Five-Year Plan, the government has started to control the old three lakes of Lake Taihu, Lake Chaohu and Lake Dianchi, but it has spent huge treatment costs. After nearly 30 years of governance, the trend of further deterioration of water quality in the old three lakes was initially curbed. According to the degree of lake pollution, lake control and protection can be divided into three types:pollution control type, combined prevention and control type and ecological conservation type. The governance of the old three lakes was a typical pollution first, treatment later model, and the lakes with better water quality mainly belong to ecological conservation type, so the treatment model for old three lakes is not suitable for the protection of lakes with better water quality. This paper systematically summarizes the formation of the concept of priority protection of lakes with better water quality in China and the implementation history of special lakes with better water quality. According to the characteristics of the lake with better water quality and the general process of ecosystem degradation and restoration, the basic idea for the protection of the lakes with better water quality was put forward. From a thermodynamic perspective, the entropy increase process of nitrogen and phosphorus nutrient input into the lake ecosystem was analyzed, revealing the root cause of the degradation of the lake ecosystem and the importance of source control of nitrogen and phosphorus pollution load into lakes. The ecological security pattern of lake basin is the basis for ensuring the health of lake basin ecosystem. From the perspective of landscape ecology, this paper clarifies that optimizing the use of soil and water resources in lake basin and optimizing the development pattern are important ways to reduce the environmental pressure on the lake. The transition process of the clear water state dominated by submerged plants and the turbid water state dominated by phytoplankton in shallow lake ecosystems is not along the same pathway. There are upper and lower critical thresholds, and the aquatic ecological restoration process shows a hysteresis phenomenon. From the theory of steady-state transformation of lake water ecosystem, we clarified that the lake ecological restoration project should be implemented before the degradation transformation of lake ecosystem to obtain higher protection benefits. The support of 81 lakes with better water quality through the special national finance can not only promote the economic and social development of the lake basin, but also ensure the improvement of the quality of the lake water environment and improvement of lake water ecosystem. We recommended to strengthen the summary of different types of lake protection models, conduct in-depth research on the theory of ecosystem succession and protection technology of lakes with better water quality, and support the state to carry out the protection of lakes with better water quality systematically.

Effects of cyanobacterial growth and decline on the &lt;i&gt;phoD&lt;/i&gt;-harboring bacterial community structure in sediments of Lake Chaohu

phoD基因编码的碱性磷酸酶驱动沉积物有机磷矿化并释放生物可利用磷，促进了富营养化湖泊蓝藻的生长与暴发，但对富营养化湖泊蓝藻生消周期phoD基因细菌群落动态变化的认识依然有限.本文研究了中国典型富营养化湖泊巢湖蓝藻生消过程沉积物碱性磷酸酶活性（APA）、phoD基因细菌多样性和群落结构的动态变化及其与环境的关系.结果显示：巢湖沉积物APA活性在蓝藻生长与暴发阶段显著升高，且与水温、pH、溶解氧（DO）等环境因子显著相关.蓝藻生消各阶段沉积物phoD基因细菌群落的优势菌属均由Pseudonocardia和Friedmanniella构成；与蓝藻潜伏期和衰亡期相比，生长初期与暴发期大多数样点沉积物Pseudonocardia的丰度显著降低而Friedmanniella显著升高.携带phoD基因的菌属丰度呈显著的时空变化，其中菌属丰度的空间异质性较高.蓝藻生长初期与暴发期的phoD基因细菌群落的Ace指数与Shannon多样性指数显著大于潜伏期与衰亡期.研究表明，携带phoD基因细菌群落结构的变化主要受APA、DO、叶绿素a、水温、总磷以及无机磷的驱动；春季蓝藻的生长消耗大量上覆水溶解性无机磷，激发了沉积物APA活性并诱发Friedmanniella生长从而缓解水体磷限制.;The alkaline phosphatase encoded by phoD gene drives the mineralization of organic phosphorus in sediments and thus the release of bioavailable phosphorus, and promotes the growth and blooms of cyanobacteria in eutrophic lakes. The dynamic variations of phoD-harboring bacterial community during the annual cyanobacterial growth and decline in eutrophic lakes, however, remain unclear. In this study, we analyzed the alkaline phosphatase activity (APA), phoD-harboring bacterial community diversity and structure and their associations with the physicochemical factors in a typical eutrophic lake (Lake Chaohu) in China during the entire cyanobacterial growth and decline. The results showed that the APA in sediments increased significantly during the initial growth and outbreaks of cyanobacteria. Pseudonocardia and Friedmanniella are the predominant phoD-harboring genera in sediments during the entire cyanobacterial growth and decline. In contrast to the abundance of Pseudonocardia and Friedmanniella in the incubation and decline stages of cyanobacteria, Pseudonocardia decreased significantly while Friedmanniella increased significantly in the early growth and outbreak stages. The abundance of phoD gene bacteria varies spatiotemporally, especially for its high spatial heterogeneity. The Ace and Shannon diversity index of phoD-harboring bacterial community during the early and outbreak stages of cyanobacteria were much higher than those in the incubation and decline stages. The changes of phoD-harboring bacterial community were mainly driven by APA, dissolved oxygen, chlorophyll-a, water temperature, total phosphorus and inorganic phosphorus. The rapid decline of dissolved inorganic phosphorus in overlying waters due to the increasing cyanobacterial photosynthesis in the early growth of cyanobacteria induces the APA, promotes the growth of Friedmanniella and alleviates the phosphorus restriction.

Elemental Metals in Agricultural Soils along Two Tributaries of Chaohu Lake: Implication on Soil Erosion Caused Enrichment in Sediments

Elemental Metals in Agricultural Soils along Two Tributaries of Chaohu Lake: Implication on Soil Erosion Caused Enrichment in Sediments

Impacts of the Yangtze River Water Transfer Project on water quality of Lake Chaohu in different typical years

“引江济巢”作为引江济淮的起始段工程，承担着改善巢湖水质的重要任务，调水路线的选取对水质改善效果有关键影响.本文基于MIKE21模型构建了巢湖水动力水质模型，分别模拟了丰水年、平水年和枯水年情景下巢湖流场和总氮、总磷浓度时空分布特征，以及不同调水路线在各典型年对巢湖水质的影响.结果显示巢湖流场和水质分布有明显的空间差异性，受入湖负荷和流量影响，巢湖在丰水年水质较差，整体来说东湖区水质优于西湖区.相比其他年份，丰水年调水对湖区水质的改善作用最明显；不同调水路线中，自白石天河入流相较兆河入流对巢湖，尤其是西湖区水质改善明显.;As the starting part of the Yangtze River Water Transfer Project, it plays an important role in improving the water quality of Lake Chaohu. The selection of the water diversion route has a key impact on the water quality improvements. Based on the two-dimensional model MIKE21, we simulated the hydrodynamic and water quality distribution of Lake Chaohu in wet, normal and dry years, as well as the influence of different water diversion routes on the water quality of Lake Chaohu in different years. The results showed that there were obvious spatial heterogeneity in the flow field and water quality of Lake Chaohu. The water quality of Lake Chaohu was poor in wet year and was better in the eastern area than that in the western area. Compared with other years, the water diversion in wet years has the most obvious effect on improving the water quality in the lake area. In different water diversion routes, the inflow from Baishitian River has significantly improved the water quality of Lake Chaohu, especially the west lake area, compared with the inflow of Zhaohe River.

Seasonal Patterns of P-Cycling-Related Microbes and Internal Phosphorus Release in the Eutrophic Lake Chaohu, China

Seasonal Patterns of P-Cycling-Related Microbes and Internal Phosphorus Release in the Eutrophic Lake Chaohu, China

A new data assimilation method coupled with real-time detection of sensitive parameters: An example of phytoplankton modeling in lakes

数据同化是提升复杂机理过程模型精度的关键技术之一，而湖泊藻类模型的敏感参数具有随时间动态变化的特征，导致数据同化过程中无法精准更新某一时段的敏感参数，影响数据同化的模型精度提升效果.针对上述问题，本研究耦合了参数敏感性分析与集合卡尔曼滤波，研发了一种能够实时识别模型敏感参数的新型数据同化算法；为验证研发算法的效率，依托巢湖的高频水质自动监测数据，测试算法对藻类动态模型的精度提升效果.测试结果表明：研发算法能够精准跟踪模型敏感参数的动态变化，并根据监测数据实时更新模型敏感参数，实现了水质高频自动监测数据与藻类动态模型的深度融合，藻类生物量模拟精度提升了55%，即纳什系数（NSE）从0.49提升到0.76，模拟精度提升效果也显著优于传统数据同化算法（NSE=0.63）.研发算法可应用于其它水生态环境模型的数据同化，为水生态环境相关要素的精准模拟预测提供关键技术支撑.;Data assimilation is a critical method to improve the performance of complex process-based models. However, the sensitive parameters for lake models are generally changing over time. Therefore, it is challenging to accurately update the sensitive parameters for a specific period, which affects the performance of data assimilation. To address the problem, this study developed a new data assimilation method by coupling the methods of parameter sensitivity analysis and the Ensemble Kalman Filter. The new method aimed to identify the model's sensitive parameters in real time. To evaluate its performance, we collected the high-frequency water quality automatic monitoring data of Lake Chaohu, and investigated the performance improvement of a phytoplankton dynamic model using a new data assimilation method. Our investigation results showed that the developed method was able to identify the sensitive parameters of the model in each simulation period, and updated them based on the measured data to achieve better performance. The simulation accuracy of phytoplankton biomass increased by 55%, i.e., the Nash-Sutcliffe Efficiency (NSE) increased from 0.49 to 0.76. This performance is better than that of the traditional data assimilation method (NSE=0.63). The method can be applied to the data assimilation of other ecological and environmental models, technically supporting an accurate prediction of environmental and ecological factors.

Predicting algal blooms in different zones of Lake Chaohu based on satellite-derived algal biomass and meteorological factors

Predicting algal blooms in different zones of Lake Chaohu based on satellite-derived algal biomass and meteorological factors

Bioaccumulation and trophic transfer of organic ultraviolet absorbents in the food web of a freshwater lake: Implications for risk estimation

Organic ultraviolet absorbents (UVAs) are increasingly reported in environmental matrices and organisms. However, available information on the bioaccumulation of UVAs in freshwater species is insufficient and their trophodynamics in lake food webs remain unknown. We measured the concentrations of twelve UVAs in the wild species from Lake Chaohu. Except for UV-320 not detected, the other UVAs were prevalent in the study species and their total concentrations were in the range of 5.44–131 ng/g dry weight, which were comparable to the concentrations reported in other waters. Compound and species-specific accumulations of UVAs in the organisms were observed. In the lake, the log-transformed concentrations of 4-methyl benzylidene camphor, octyl p-dimethylaminobenzoate, UV-326, and UV-327 related significantly to the trophic levels of species separately. The calculated trophic magnification factors (TMFs) of the four UVAs were 3.79, implying trophic magnification, and 0.18, 0.40 and 0.58, suggesting trophic dilution, respectively. These suggested that the magnification potential and the associated risks of individual UVAs in freshwater lake differed. To our knowledge, this is the first report of these TMFs in lake food webs. However, more investigation is needed to characterize their trophodynamic behaviors in lakes because food web characteristics likely affect trophic transfer of these chemicals.

A method to extract cyanobacteria blooms from satellite imagery with no requirements for any prior atmospheric correction or cloud-masking

Lake Chaohu has been suffering from harmful cyanobacteria blooms, while the clouds pixels in satellite images are usually mistaken as cyanobacteria blooms by some traditional indicators, leading to the need for cloud masking in advance. In addition, atmospheric correction is another challenge due to lack of a general atmospheric correction method and the difficulties in evaluating its accuracy without in situ investigations. Fortunately, tasseled cap transformation (TCT) allows to extract vegetation properties directly from satellite imagery digital numbers (DN), which provides a perspective for extracting cyanobacteria blooms independent from atmospheric correction. This study focuses on how to use TCT to establish an indicator, which allows to extract cyanobacteria blooms directly from image DN values without conducting any atmospheric correction or cloud-masking. Training and test sets containing over 200,000 pixels are constructed from 18 Sentinel-2A/B MSI images acquired in different seasons in recent three years. Four components are derived from TCT and they could form up to 81 linear combinations. Experimental results performed on the training set show that the candidate, which combines the last three components with the coefficients of 1,-1 and 0, assigns cyanobacteria blooms pixels in a completely separated value range from water, cloud, cloud shadow and cloud edge pixels. The candidate is defined as ICW3C index. Its threshold value range of (175 330) is given and the pixels with ICW3C values greater than its threshold could be classified as cyanobacteria blooms. Comparisons between ICW3C and the floating algae index (FAI) on the test set show that ICW3C misclassifies 0.02% of cloud pixels and 1.55% of yellow cloud edge pixels as cyanobacteria blooms, however, 19.18% clouds, 13.74% yellow cloud edges and 19.34% blue-green cloud edges are incorrectly identified as cyanobacteria blooms by FAI. Comparisons between ICW3C and FAI performed on image regions over time show that, in clear-sky regions with cyanobacteria blooms, FAI extracts 5.81% more pixels, which mainly lay in the edge of cyanobacteria blooms. In cloud-covered image regions without cyanobacteria blooms, FAI misclassifies over 608 times as many cloud and cloud edge pixels as ICW3C. Sensitivity test results suggest that the change of ICW3C threshold within its value range (175 330) will not lead to serious increase in misclassification, and ICW3C performs stable to variations of viewing geometry. Extension tests indicate that ICW3C is applicable for several other sensors. Further researches are still needed to test whether ICW3C is suitable for other inland lakes or seas.

Restoration of aquatic macrophytes with the seed bank is difficult in lakes with reservoir-like water-level fluctuations: A case study of Chaohu Lake in China

Aquatic vegetation in lakes along the middle and lower reaches of the Yangtze River has been seriously degraded by human disturbances such as river–lake disconnection and water eutrophication. Chaohu Lake is a typical lake with reservoir-like water-level fluctuations (WLFs). Since a sluice was built in 1962, the coverage of aquatic vegetation in Chaohu Lake has been very low (0.77%). In this study, field investigations of the aquatic vegetation and seed bank of Chaohu Lake were conducted, and aboveground vegetation diversity was found to be low. Forty-eight species were recorded, of which submerged, floating-leaved, and emergent macrophytes were 1, 5, and 10, respectively. Currently, artificially planted Phragmites australis and Salix communities have become the main community types. A total of 18 aquatic macrophytes were identified in the seed bank, of which the number of submerged, floating-leaved, and emergent macrophytes and hygrophytes were 2, 2, 3, and 11, respectively; the seed density was 2.05, 2.05, 16.93, and 9.30 ind./m2, respectively. The seed density of aquatic macrophytes was much lower in Chaohu Lake than in the lakes with quasi-natural WLFs, and the seeds were mainly distributed in the estuary area. Only two emergent macrophyte species (Typha) germinated in the open water area. Spearman correlation analysis showed that the distance to bank was the main environmental factor that affected aquatic macrophyte diversity and seed density in the seed bank. It is not feasible to promote the natural reconstruction and restoration of aquatic macrophytes in Chaohu Lake by decreasing the water level or increasing water transparency, but the area near the estuary can be identified as a priority restoration area (PRA) for aquatic macrophytes. Artificial transformation of the micro-topography can be used to guide some hydrochorous seeds in the tributaries to the PRA and restore aquatic vegetation in the local area.

Method development and validation for simultaneous quantification of microcystin congeners in water

BackgroundMicrocystins (MCs) are secondary metabolites of cyanobacteria that are hepatotoxic to humans through the ingestion of cyanobacteria-contaminated water and accidental inhalation from lake activities. MCs with diverse congeners in water can be precisely quantified using online solid-phase extraction-ultra performance liquid chromatography coupled with tandem mass spectrometry (online-SPE UPLC–MS/MS). A method was developed and validated to simultaneously quantify eight different MCs (microcystin-RR, -LR, -YR, -WR, -LA, -LF, -LY, and -LW) in water using online-SPE UPLC–MS/MS.ResultsThe method achieved the highest efficiency and sensitivity by selecting acetonitrile with 0.1% formic acid and water with 0.1% formic acid as the best mobile phase conditions. The linearity, accuracy, and precision were validated using matrix-mixed water with a leucine enkephalin internal standard. The limit of detection (LOD) was calculated using the signal-to-noise ratio of three passes of the daily water-surface inspection for MCs. This method showed both high sensitivity and high resolution for the separation of eight MC congeners with LODs ranging from 0.020 to 0.371 ng L–1 and limits of quantitation ranging from 0.066 to 1.24 ng L–1. The detection time was reduced to 11 min. Except for MC-RR (58.8% recovery at high concentration) and MC-WR (45.1% and 40.9% recoveries at medium and high concentrations, respectively), the recoveries of the other MCs ranged from 70 to 135%, and the relative standard deviation was less than 10%.ConclusionEight different MCs in 12 water samples collected from Chaohu Lake, China, were analyzed. The sum of all MC congeners was calculated to range from 101 to 585 ng L–1 (less than the World Health Organization’s safe drinking water limit of 1 μg L–1 for MC-LR).

Antibiotic resistome in a large urban-lake drinking water source in middle China: Dissemination mechanisms and risk assessment

The increasing pollution of urban drinking water sources by antibiotic resistance genes (ARGs) threatens human health worldwide. However, the distribution and influencing factors of ARGs, especially how to reveal the risks of ARGs in this environment remains unclear. Hence, Chaohu Lake was selected as an example to investigate the characteristics of ARGs and explore the interactions among physicochemical factors, microorganisms, and ARGs by metagenomic approach. In this work, 75 ARG subtypes with an average of 30.4 × /Gb (ranging from 15.2 ×/Gb to 57.9 ×/Gb) were identified, and multidrug and bacA were most frequent in Chaohu Lake. Non-random co-occurrence patterns and potential host bacteria of ARGs were revealed through co-occurrence networks. Microbial community and mobile genetic elements (MGEs) were the major direct factors in ARG profiles. The dissemination of ARGs was mainly driven by plasmids. Considering the interactions among MGEs, human bacterial pathogens, and ARGs, antibiotic resistome risk index (ARRI) was proposed to manifest the risks of ARGs. Overall, our work systemically investigated the composition and associated factors of ARGs and built ARRI to estimate the potential risks of ARGs in a typical urban drinking water source, providing an intuitive indicator for managing similar lakes.

Phosphorus internal loading and sediment diagenesis in a large eutrophic lake (Lake Chaohu, China)

Sediment phosphorus (P) release and retention are important in controlling whole-system P dynamics and budget in eutrophic lakes. Here we combine short- (seasonal) and long-term (years to decades) studies to quantify the internal P loading and P release potential in the sediments of Lake Chaohu and explore their controlling mechanisms. In the west region of the lake, short-term P diffusive fluxes ranged from 0.2 mg/m2·d−1 to 6.69 mg/m2·d−1 (averaged 2.76 mg/m2·d−1) and long-term net P release ranged from 2.25 mg/m2·d−1 to 8.94 mg/m2·d−1 (averaged 5.34 mg/m2·d−1); in the east region, short-term P diffusive fluxes varied from 0.73 mg/m2·d−1 to 1.76 mg/m2·d−1 (averaged 1.05 mg/m2·d−1) and long-term P release ranged from 0.13 mg/m2·d−1 to 4.15 mg/m2·d−1 (averaged 1.3 mg/m2·d−1). Both short- and long-term P releases were in the same order of magnitudes as the external P inputs (3.56 mg/m2·d−1). Comparison of the long-term and short-term sediment P release indicates that while the high summer P release in the east might only represent a snapshot value, the sediments in the west contribute to large P release for years or even decades, impeding water quality recovery under lake management. Mobilization of surface sediment legacy P accounted for 81% of short-term P release. The long-term release was dominated by remobilization of iron bond P (BD-P) (average 52.1%) at all sites, while Aluminium-bound P (NaOH-rP) exhibited partly reactive and potentially mobile, releasing P to the water column in most sites in the west. Our study demonstrates the importance of sediments as P sources in lake Chaohu. The combination of short- and long-term P release studies can help understand the roles of sediments in regulating the water quality and eutrophication.