Lake Chaohu Research Articles

Climate change impacts on polychlorinated biphenyls (PCBs) deposition in a shallow lake, China

The deposition of PCBs in lake sediments was affected by climate change and anthropogenic activities. To better understand the mechanism, GAMs models were performed to investigate the relationship between sedimentary PCBs and the two influential factors. The results showed the average contribution value of the sum of temperature and evaporation to PCBs (7.1%) was larger than that of the sum of aquatic TP and GDP (17.9%), indicating human activity is a major factor compared to climate change. The increasing total phosphorus and Gross Domestic Product in Lake Chaohu with the development of urbanization and industrialization promoted the deposition of PCBs in Lake Chaohu sediments before the consideration of environment management. The fitted relationship between sedimentary PCBs concentrations and Temperature was linear for Lake Chaohu, suggesting that increasing temperature enhanced the volatilization from primary and secondary sources and reduced the fugacity capacity of PCBs in water and sediments. The sedimentary PCBs concentrations increased with decreasing evaporation. In consequence, the interactive effect of climate change and anthropogenic activities must be addressed from a scientific perspective for future regulatory actions.

Sediment phosphorus fraction and release potential in the major inflow rivers of Chaohu Lake, Eastern China

Surface sediment samples from nine inflow rivers of Chaohu Lake in Eastern China were analyzed by the sequential extraction procedure and the zero equilibrium phosphorus concentration (EPC0) was determined to evaluate the behavior of phosphorous at the water–sediment interface. The results reveal that substantial amounts of P had accumulated in river sediments from agricultural runoff and domestic sewage. For most of the sample sites, the total P content was higher in sediments from urban rivers than in those from rural rivers. On average, the reactive inorganic P consisted of slightly more than 60% of the total P, with Fe-P being the dominant P form. Compared with rural sediments, the Al-P contents were significantly higher in urban sediments, while the Res-P contents were significantly lower. The differences can be attributed to the differential discharge of P from watersheds with contrasting land uses and to the dramatic changes in the ambient conditions of urban rivers. A higher soluble reactive phosphorus (SRP) value of the overlying water relative to the EPC0 value in the mouth of the urban rivers of Chaohu Lake indicates that bottom sediments still play a role in adsorbing phosphorus from the water column before it reaches Chaohu Lake.

Role of Differences in Surface Diurnal–Nocturnal Thermodynamics over Complex Terrain in a Squall Line Process

Squall lines frequently invade the Yangtze–Huaihe River region (YHR), where the complex terrain of rivers, lakes, and mountains plays an important role in the initiation and maintenance of convection. The surface heat flux not only varies with surface conditions, but also changes between day and night. Coupled with the terrain forcing, such diur-nal–nocturnal thermodynamic differences shift the low-level baroclinity, and thus further complicate the convective activities. To investigate the integrated impact of diurnal–nocturnal thermodynamic differences on the development of squall lines over complex terrain including disasters that might ensue, numerical modeling experiments on a squall line in July 2014 were performed by forcing a squall line to pass the YHR separately at daytime and nighttime. The results show that the low-level instability during the day is much larger than that during the night, and is determined predominantly by the shortwave heating of the surface. Specifically, the solar radiation enhances the temperature gradient between the warmland ahead of the squall line and the convectively generated cold pool in the region around Chaohu Lake and the Yangtze River. Such low-level baroclinity sets preconditions in the environment towards the occurrence of deep convection. The increased precipitation and the evaporation of rain in the daytime also enhance the cold pool and the associated downdraft, which further intensify the squall line. Meanwhile, the valley breeze is intensified during the day. Such scenarios promote convection that extends the squall line and the associated heavy precipitation and wind gusts southward. This research may have significant implications for enhancing the squall line prediction capability in the YHR and improving our understanding of the physical mechanisms of convective activities over complex terrain.

Application of Bayesian network including Microcystis morphospecies for microcystin risk assessment in three cyanobacterial bloom-plagued lakes, China

Microcystis spp., which occur as colonies of different sizes under natural conditions, have expanded in temperate and tropical freshwater ecosystems and caused seriously environmental and ecological problems. In the current study, a Bayesian network (BN) framework was developed to access the probability of microcystins (MCs) risk in large shallow eutrophic lakes in China, namely, Taihu Lake, Chaohu Lake, and Dianchi Lake. By means of a knowledge-supported way, physicochemical factors, Microcystis morphospecies, and MCs were integrated into different network structures. The sensitive analysis illustrated that Microcystis aeruginosa biomass was overall the best predictor of MCs risk, and its high biomass relied on the combined condition that water temperature exceeded 24 °C and total phosphorus was above 0.2 mg/L. Simulated scenarios suggested that the probability of hazardous MCs (≥1.0 μg/L) was higher under interactive effect of temperature increase and nutrients (nitrogen and phosphorus) imbalance than that of warming alone. Likewise, data-driven model development using a naïve Bayes classifier and equal frequency discretization resulted in a substantial technical performance (CCI = 0.83, K = 0.60), but the performance significantly decreased when model excluded species-specific biomasses from input variables (CCI = 0.76, K = 0.40). The BN framework provided a useful screening tool to evaluate cyanotoxin in three studied lakes in China, and it can also be used in other lakes suffering from cyanobacterial blooms dominated by Microcystis.

Optical Classification of the Remote Sensing Reflectance and Its Application in Deriving the Specific Phytoplankton Absorption in Optically Complex Lakes

Optical water types (OWTs) were identified from remote sensing reflectance (Rrs(λ)) values in a field-measured dataset of several large lakes in the lower reaches of the Yangtze and Huai River (LYHR) Basin. Four OWTs were determined from normalized remote sensing reflectance spectra (NRrs(λ)) using the k-means clustering approach, and were identified in the Sentinel 3A OLCI (Ocean Land Color Instrument) image data over lakes in the LYHR Basin. The results showed that 1) Each OWT is associated with different bio-optical properties, such as the concentration of chlorophyll-a (Chla), suspended particulate matter (SPM), proportion of suspended particulate inorganic matter (SPIM), and absorption coefficient of each component. One optical water type showed an obvious characteristic with a high contribution of mineral particles, while one type was mostly determined by a high content of phytoplankton. The other types belonged to the optically mixed water types. 2) Class-specific Chla inversion algorithms performed better for all water types, except type 4, compared to the overall dataset. In addition, class-specific inversion algorithms for estimating the Chla-specific absorption coefficient of phytoplankton at 443 nm (a*ph(443)) were developed based on the relationship between a*ph(443) and Chla of each OWT. The spatial variations in the class-specific model-derived a*ph(443) values were illustrated for 2 March 2017, and 24 October 2017. 3) The dominant water type and the Shannon index (H) were used to characterize the optical variability or similarity of the lakes in the LYHR Basin using cloud-free OLCI images in 2017. A high optical variation was located in the western and southern parts of Lake Taihu, the southern part of Lake Hongze, Lake Chaohu, and several small lakes near the Yangtze River, while the northern part of Lake Hongze had a low optical diversity. This work demonstrates the potential and necessity of optical classification in estimating bio-optical parameters using class-specific inversion algorithms and monitoring of the optical variations in optically complex and dynamic lake waters.

The Assessment of Landsat-8 OLI Atmospheric Correction Algorithms for Inland Waters

The OLI (Operational Land Imager) sensor on Landsat-8 has the potential to meet the requirements of remote sensing of water color. However, the optical properties of inland waters are more complex than those of oceanic waters, and inland atmospheric correction presents additional challenges. We examined the performance of atmospheric correction (AC) methods for remote sensing over three highly turbid or hypereutrophic inland waters in China: Lake Hongze, Lake Chaohu, and Lake Taihu. Four water-AC algorithms (SWIR (Short Wave Infrared), EXP (Exponential Extrapolation), DSF (Dark Spectrum Fitting), and MUMM (Management Unit Mathematics Models)) and three land-AC algorithms (FLAASH (Fast Line-of-sight Atmospheric Analysis of Spectral Hypercubes), 6SV (a version of Second Simulation of the Satellite Signal in the Solar Spectrum), and QUAC (Quick Atmospheric Correction)) were assessed using Landsat-8 OLI data and concurrent in situ data. The results showed that the EXP (and DSF) together with 6SV algorithms provided the best estimates of the remote sensing reflectance (Rrs) and band ratios in water-AC algorithms and land-AC algorithms, respectively. AC algorithms showed a discriminating accuracy for different water types (turbid waters, in-water algae waters, and floating bloom waters). For turbid waters, EXP gave the best Rrs in visible bands. For the in-water algae and floating bloom waters, however, all water-algorithms failed due to an inappropriate aerosol model and non-zero reflectance at 1609 nm. The results of the study show the improvements that can be achieved considering SWIR bands and using band ratios, and the need for further development of AC algorithms for complex aquatic and atmospheric conditions, typical of inland waters.

The occurrence, composition and partitioning of phthalate esters (PAEs) in the water-suspended particulate matter (SPM) system of Lake Chaohu, China

The occurrence, composition, and partitioning of six phthalate esters (PAEs) (dimethyl phthalate (DMP), diethyl phthalate (DEP), diisobutyl phthalate (DIBP), dibutyl phthalate (DBP), butyl benzyl phthalate (BBP) and di(2-ethylhexyl) phthalate (DEHP)) in the water-suspended particulate matter (SPM) system of Lake Chaohu were investigated in this study. Our results showed that PAEs were ubiquitous contaminants in Lake Chaohu. The concentration of the Σ6 PAEs in dissolved and particulate phases ranged from 0.370 to 13.2 μg·L−1 and from 14.4 to 7129 μg·L−1, respectively. The Σ6 PAEs in water and SPM phases exhibited different seasonal trends. PAEs with different degrees of hydrophobicity demonstrated different temporal distributions in the dissolved phase. In particulate phase, all PAEs exhibited the same temporal distribution. Regarding the occurrence of PAEs, significant spatial differences exist between lake and estuary. However, there were no specific differences in PAEs across lake zones and river types of Lake Chaohu. River input should be considered an important source of PAEs in Lake Chaohu. DIBP and DBP were the most abundant PAEs in Lake Chaohu, and DIBP should attract more attention in the future. The organic carbon normalized partitioning coefficient (logKoc) ranged from an average of 2.38 ± 0.86 L·g−1 for BBP to 3.98 ± 0.66 L·g−1 for DEHP, and approximately 2 to 3 unit variations of logKoc existed for the individual PAEs. It was difficult to ascertain whether the partitioning of PAEs was in, near or far from the equilibrium. No linear relationship was found between logKoc and the octanol-water partitioning coefficient (logKow) for PAEs. Koc might not be suitable for describing the partitioning of PAEs in the water-SPM system. The hydrophobicity of PAEs may have little impact on their partitioning in the complex environmental system, and the Kow model may be inappropriate to predict the partitioning of PAEs in natural large lakes.

Purification of Phycocyanin from Chaohu Algae by Various Salting out Methods

This research was carried out to extract and purify phycocyanin from blue algae in Chaohu Lake by utilizing salting out methods. Thus a two-step salting out was performed using Ammonium sulphate, Triammonium citrate, Sodium citrate and Sodium sulfate. The phycocyanin and the impurity solution collected at each phase were subjected to analysis by using UV-Vis spectrophotometer to identify the optimal dose of ammonium sulfate, triammonium citrate, sodium citrate and sodium sulfate. The optimal molar concentration for Ammonium sulphate, Triammonium citrate, Sodium citrate and Sodium sulfate in the first and second salting out process were 1.0 mol/L and 1.7mol/L for Ammonium sulphate (NH4)2SO4, 0.7, mol/L and 1.3 mol/L for Triammonium citrate C6H17N3O7, 0.5mol/L and 0.9 mol/L for Sodium citrate C6H5Na3O7, 1.0mol/L and 1.3 mol/L for Sodium sulfate Na2S04. After the two-step salting out processes, it was observed that higher molar concentrations can remove impurities in large quantities, and both purity and yield was greatly increased. The results indicate a purity of phycocyanin above 2.0 with a phycocyanin recovery relatively high. This was carried out to affirm and estimate if the result from the salt use will vary from a previous experiment carried out on the same river by the authors with three (3) different kinds of salt K3C6H5O7H2O, C6H5O7(NH4)3 and (NH4)2SO4 as compared to the four (4) salt compound used in this experiment.

Nitrification Rates and Pollution Characteristics of Sediments with Different Geomorphic Features in the Shiwuli Stream, Chaohu Lake Basin

Sediment and overlying water samples were collected seasonally from five different geomorphic structures (i.e., pools, riffles, gravel bars, point bars, and runs) from two urban reaches of the Shiwulihe River in the Chaohu Lake Basin dominated by high ammonia concentration between July 2017 and March 2018. Both the sediment potential and areal nitrification rates were measured and their seasonal and geomorphological variability were evaluated. The specific differences between every two geomorphic structures were determined using the Mann-Whitney U test and the relationship between the overlying water environment or benthic sediments and sediment nitrification was explored based on regression analysis. The results show that:① The studied reaches are seriously polluted by nitrogen and phosphorus and most of the oxidation-reduction potential (ORP) values in the overlying water were are below 0 mV, suggesting strong reducing conditions of the water column. ② The potential nitrification rates (PNRs) across the five geomorphic structures range from 0.002 to 0.079 μmol·(g·h)-1, with a mean value of 0.023 μmol·(g·h)-1. The ranking order of PNRs is pools > point bars > riffles > gravel bars > runs, with a seasonal change pattern of summer > spring > autumn > winter. ③ The areal nitrification rates (ANRs) across the five geomorphic structures range between 0.140 and 13.543 μmol·(m2·h)-1, with an average of 3.658 μmol·(m2·h)-1. In general, the highest mean value was observed in riffles, followed by runs, and gravel bars and point bars; the smallest value was observed in pools. In addition, ANRs appear to have seasonal change patterns similar to that of the PNRs. ④ According to the difference analysis, there are significant differences between pools or riffles and other features of the PNRs. Extremely significant ANR differences were observed between more than half of the geomorphic structures. ⑤ Regression analysis shows a stronger correlation between sediment nitrification and the overlying water environment, compared with the surface sediment properties.

Watershed scale patterns in steroid hormones composition and content characters at a typical eutrophic lake in southeastern China.

Natural steroid hormones in the aquatic environment have attracted increasing attention because of their strong endocrine disrupting potency. Seven steroid hormones (estrone, 17α-estradiol, 17β-estradiol, estriol, testosterone, androstenedione, and progesterone) were analyzed from surface water and sediment sampled from Chaohu Lake, its upstream rivers (the Hangbu River, Nanfei River, Shiwuli River, and Pai River), drainage from the adjacent farmland, and treated and untreated municipal sewage. Concentrations of the seven target steroid hormones ranged from below the detection limit (ND) to 69.5ngL-1 in the water of Chaohu Lake and the upstream rivers. Three steroids-estrone, estriol, and 17α-estradiol-were found in relatively high residual concentrations in the water, with maximum concentrations of 69.5ngL-1, 51.5ngL-1, and 23.3ngL-1, respectively. All of the target steroid hormones except estriol were detected in the sediment in concentrations of ND-16344ngkg-1. The dominant steroid hormone in the sediment of Chaohu Lake and the upstream rivers was 17α-estradiol. In the Shiwuli River and the Pai River, the dominant steroid hormones (estrone and estriol) were the same as those in the untreated municipal sewage. This confirmed the deduction that untreated municipal sewage was the major source of steroid hormone residues in these two rivers. The main steroid hormone in the water of the Hangbu River and Chaohu Lake was 17α-estradiol, the same as that in the farmland drainage. In addition, 17α-estradiol was verified as the major factor in the contribution of farmland drainage to the pollution in these rivers. The water in the Nanfei River had high concentrations of estriol and 17α-estradiol. This indicates that both untreated municipal sewage and farmland drainage were the major sources. The discharge of steroid hormones from the four rivers to Chaohu Lake was approximately 75.1kgyear-1, with the highest contributor being 17α-estradiol (24kgyear-1). Therefore, based on the results of this study, the farmland drainage should be controlled to reduce the steroid hormone pollution in Chaohu Lake.

Comparison of phosphorus sorption characteristics in the soils of riparian buffer strips with different land use patterns and distances from the shoreline around Lake Chaohu

Purpose The construction of riparian buffer strips has become increasingly important due to the effective phosphorus (P) retention of the strips, thus preventing eutrophication in freshwater ecosystems. The key mechanism is P sorption in soils. To provide some suggestions for increasing the sorption ability of P, the relationships between P sorption behavior and both land use patterns and distance from the shoreline were determined. Materials and methods In April, July, and October 2013, field investigations were carried out along the shoreline of Lake Chaohu. Eleven sections, including 36 sampling sites at different distances from the shoreline, were chosen, and these sections contained different types of riparian buffer strips, such as grassland, farmland, forest, wetland, and forest/grassland. The P species, sorption parameters, and dominant vegetation species were analyzed. Results and discussion The total P (TP) and P sorption maximum (Q(max)) showed no recognizable seasonal variation and were closely correlated with the distance from the shoreline. The further the distance from the shoreline, the higher the TP and Q(max) values, suggesting that soil traits could determine the P sorption extent. However, the Olsen-P content and equilibrium P concentration (EPC0) fluctuated greatly, with the peak occurring in spring and the minimum occurring in summer in the majority of the sampling sites. In addition, positive relationships existed between the TP content and the Q(max) value as well as the Olsen-P content and the EPC0 value. Canonical correlation analysis (CCA) further showed that the Olsen-P content and EPC0 values were closely related to the dominant vegetation species, indicating that land use patterns played a decisive role in regulating the P sorption strength and the level of available P. Conclusions To effectively adsorb P (increase Q(max)) and prevent P leaching (reduce the EPC0), we recommend changing the land use patterns (more constructed wetlands and forests with grass) in riparian buffers.

Temporal trends of polybrominated diphenyl ethers in the sediment cores from different areas in China

This paper presented the historical data on the temporal trends of polybrominated diphenyl ethers (PBDEs) in the sediment cores collected from the Huaihe River, Yellow River and Chaohu Lake, China. Among the 40 targeted PBDE congeners, only 10, 6, and 9 of them were detected respectively in the samples from the Huaihe River, Yellow River and Chaohu Lake. On average, the total PBDEs concentrations in sediments were highest in Chaohu Lake followed by the Huaihe River and the Yellow River. As compared to other PBDE congeners, BDE-209 had higher concentrations and detection rates. The similar down core variation between PBDEs and total organic carbon (TOC) suggests that TOC is an important factor influencing PBDEs distribution in the sediments. The total PBDEs concentrations showed an increasing trend from bottom to upper sediments before a decreasing trend in the topmost sediments. The rapid urbanization and industrialization of these regions in recent decades may cause the historically increasing concentrations of sedimentary PBDEs, especially BDE-209. The decreasing PBDEs concentrations in topmost sediments was probably related to the strict environmental policies at present.

The complete mitogenome and phylogenetic analysis of Coilia brachygnathus (Clupeiformes: Engraulidae) from Chaohu Lake

Coilia brachygnathus is the only one freshwater fish of the genus Coilia in China. In this study, we determined the complete mitochondrial genome of Coilia brachygnathus from Chaohu Lake. It is 16,896 bp in length and consists of 13 protein-coding genes, 2 rRNA genes, 22 transfer RNA genes as well as a control region (CR). Over base composition of the mitogenome is A(31.2%), C(27.0%), T(26.3%), and G(15.5%), respectively. Phylogenetic analysis confirmed the evolutionary relatedness of C. brachygnathus to other fishes of genus Coilia and also revealed the phylogenetic relationship of this genus within Engraulidae at molecular levels.

Impact of organic matter and meteorological factors on the long-term trend, seasonality, and gas/particle partitioning behavior of atmospheric PBDEs

We extended our knowledge of the impact of organic matter (OM) and meteorological factors on the long-term trend, seasonality and gas/particle partitioning behavior of polybrominated diphenyl ethers (PBDEs). In Lake Chaohu, PBDEs had an increasing trend, with a doubling time of 13.4 years at the urban site, and a decreasing trend, with a halving time of 6.1 years at the rural site. At the urban site, the negative association of OM with most congeners indicated that the graphene-like carbonaceous components might carry or release PBDEs, and the negative association of long-term rain fall and wind speed with most congeners was suggested to dilute or increase the transport speed of PBDEs in the atmosphere. At the rural site, the negative association with PM10 and positive association with OM indicated that the PBDEs-buried OM was mainly from non-local sources. Restricted to the temperature seasonality, the frequency of PBDE congeners decreased with seasonality from 64% and 43% to 50% and 43% at the urban and rural sites, respectively. The slope of the simplified Pankow adsorption model in samples with larger absolute OM content (>10 μgC m−3) was steeper than that with lower absolute OM content (<5 μgC m−3), indicating that OM facilitated the gas-particle partitioning equilibrium. Interestingly, the theoretic partitioning coefficients were much lower than the measured ones for less brominated BDEs, whereas the highly brominated BDEs did the opposite. The theoretic partitioning coefficient should be further modified by considering the molecular weight distribution of the OM and the corresponding activity coefficients of the target compound in a specific type of OM phase.

The Contributions of Climate Changes and Human Activities to Long-Term Variations in Lake Sediments Based on Results from Generalized Additive Models

Climate changes and human activities can influence lake sediments, which may lead to disruptions in aquatic environments. A better understanding of these effects is crucial for the future management of lakes and reservoirs. The impacts of climate change and human activity factors, such as air temperature, land use patterns, population size, and gross domestic product (GDP), on lake sediments in China were considered in this study. A generalized additive model (GAM) was applied to quantitatively assess the relationships among climate change, human activities, and sediment variables, namely, total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP), in Lake Chaohu and Lake Chenghai. Both lakes are located in climate-sensitive areas, where the annual average temperature has risen by more than 1 °C over the past three decades. The impacts of climate changes and human activities on TOC, TN, and TP were quantitatively interpreted with the results of the GAMs. The results indicated that the contributions of air temperature to the variations in the sediment variables were significant but smaller than the contributions of human activities (e.g., percent of urban and paddy land, population size, and GDP) in both lakes. The fits of all GAMs were better than the fits of the stepwise linear regression comparisons. These findings demonstrate that GAMs are an effective tool for estimating the impacts of climate change and human activities on TOC, TN, and TP in lake sediments, suggesting that policy makers must further consider climate change when making management plans for water quality.

Temporal and spatial variation of carbon dioxide concentration and its exchange fluxes in Lake Chaohu

为揭示巢湖水体二氧化碳浓度（cCO₂）时空变化特征及其影响因素，2017年2、4、8和11月分别采集巢湖表层水样，测定水样的理化、生物学参数以及cCO₂，并以此计算其水-气界面交换通量.结果表明：巢湖表层水体cCO₂的变化范围为13.31~55.47 μmol/L，年平均值为26.27 μmol/L，在空间上呈现出西高东低的分布趋势；在季节上表现为暖季（夏季）低、冷季（春、秋和冬季）高的规律.巢湖表层水体cCO₂与溶解性有机碳浓度呈显著正相关，与叶绿素a浓度呈显著负相关，说明有机质分解和光合作用在巢湖CO₂生物化学循环过程中占重要作用；同时，南淝河等入湖河流污染严重，输入大量有机和无机碳，对西巢湖水体CO₂贡献较大.总体上，巢湖CO₂排放量相对较低，巢湖部分区域在冷季（2、11月）表现为CO₂的汇.本研究对于明晰富营养化湖泊CO₂排放特征以及准确估算全球内陆湖泊碳通量等都具有参考价值.;In order to understand the temporal and spatial variation of carbon dioxide concentration (cCO₂)and its influencing factors in the surface water of Lake Chaohu, the physicochemical parameters, biological parameters, and cCO₂ of surface (15-30 cm)water samples collected in February, April, August and November in 2017 from Lake Chaohu, representing different seasons, were measured. The surface water-air flux of CO₂ was then calculated based on gradient method as well. The results showed that the cCO₂ ranged from 13.31-55.47 μmol/L. The average annual cCO₂ was 26.27 μmol/L. The cCO₂ was higher in the west lake sub-lake zone than that in the central and east sub-lake zones. The surface water of Lake Chaohu had a lower cCO₂ in the warm season (summer) than in cool and cold seasons (spring, autumn and winter). cCO₂ was positively correlated with dissolved organic carbon (DOC)concentration and negatively correlated with chlorophyll-a concentration, suggesting that photosynthesis and decomposition of organic matter plays an important role in the biochemical cycle of CO₂. Due to the serious pollution of inflowing rivers surrounding Lake Chaohu, DOC input from the watershed supplied substrates for CO₂ production. Lake Chaohu was a relatively small source for atmosphere CO₂ compared to others studies. Lake Chaohu shifted from a CO₂ source to a sink in cold seasons.

Bacterial community composition in aquatic and sediment samples with spatiotemporal dynamics in large, shallow, eutrophic Lake Chaohu, China

Lake Chaohu is a representative lake in China that suffers from severe eutrophication and algal blooms. In this study, the composition of bacterial communities in the water and sediment from one of the inlets and outlets of Lake Chaohu in response to spatiotemporal changes was analyzed by Illumina MiSeq sequencing of the V4 region of the 16S rRNA gene. Substantially distinct bacterial community composition was observed between the water column and sediments in both the Zhaohe (the inlet, C1) and Yuxihe Rivers (the outlet, C2). The phyla of the water samples were Cyanobacteria, Proteobacteria, Actinobacteria and Bacteroidetes, whereas the sediment samples were dominated by Proteobacteria, Acidobacteria, Chloroflexi and Nitrospirae. The sediment exhibited higher diversity and richness than did the water column at the two sites, with the sediment samples from the Yuxihe River showing higher richness and lower diversity than those from the Zhaohe River. The pattern of spatiotemporal changes indicated the seasonal factor, rather than the region, to be the primary cause of the observed variation in the bacterial structure in Lake Chaohu. In water samples from the two study areas, unclassified genera of Cyanobacteria dominated in winter, with members of unclassified FamilyI and unclassified Cyanobacterium. Moreover, redundancy analysis indicated that water temperature (T), total phosphorus (TP), organic carbon (OC) and total nitrogen (TN) were all determined to be related to bacterial community structure. And T and TP were the main factors influencing the water bacterial structure and that OC and TN were the main indicators determining the sediment bacterial structure. The results of this study may be useful for indicating the tendency of bacteria to respond to environmental changes in Lake Chaohu.

多源卫星遥感数据监测巢湖蓝藻水华爆发研究

Dynamically, accurately monitoring of cyanobacteria blooms in the inland lakes can provide a basis for evaluating the control effects of polluted water bodies, moreover optimize and adjust prevention policies for water conservancy and environmental protection departments. In this paper, Chaohu Lake was chosen as there search object, the satellite imagery data with different spatial resolution such as the Landsat TM/OLI, HJ-1B CCD/IRS and NPP-VⅡRS, were used to extract the Chaohu water body by the Normalized Difference Water Index(NDWI). And then the areas of cyanobacterial blooms in the Chaohu Lake were calculated using the Normalized Difference Vegetation Index(NDVI) and the Floating Algae Index (FAI). Further, the extracted cyanobacterial areas using the different methods were compared and analyzed, and the monitoring effects and applicability were evaluated by the spatial and temporal characteristics for Landsat, HJ-1B and VⅡRS imagery data. Additionally, the effects of different meteorological factors on the cyanobacterial blooms were also analyzed. The research results displayed that comparing with the NDVI index, the FAI index calculated from the Landsat, HJ-1B and VⅡRS imagery data can reduce the effect of thin cloud on the extraction of cyanobacterial blooms, and improve the recognition ability of cyanobacterial blooms and extents. Secondly, the temperature and sunshine duration of meteorological factors aggravate the severity of cyanobacterial blooms, and the rainfall plays a certain role in inhibiting the outbreak of cyanobacterial blooms. In summary, this study introduced the VⅡRS imagery data to study the cyanobacterial blooms in Chaohu Lake, and used the FAI index to reduce the influence of thin cloud on the extraction precision of cyanobacterial blooms. These results show that multi-source satellite imagery data can provide the important method support for the development of dynamically monitoring system on cyanobacterial blooms. This is useful to promote the satellite remote sensing technology to improve the river system and lake system in Anhui Province.

Spatiotemporal characteristics of microcystin variants composition and associations with environmental parameters in Lake Chaohu, China

Spatiotemporal characteristics of microcystin variants composition and associations with environmental parameters in Lake Chaohu, China

多种集成方法在巢湖流域面雨量预报中的效果检验

多种集成方法在巢湖流域面雨量预报中的效果检验