Abstract:Due to limitation of short time series of hydrological observations, it is hard to know the centennial timescale chance of extreme floods. The present study simulated catchment runoff and discharge of the 1889 flood year in Lake Taihu, on basis of historical flood records and by means of the catchment hydrology model. Three experiments were performed in the simulations:firstly control-run simulations for 1988-2002 to calibrate and validate the modeling, secondly simulations of daily processes for the 1889 flood year driven by observed climate records during the end of 19th century; thirdly simulations of 15 year-Monte Carlo Bootstrap resampling for the special flood year to decrease the 1-year sample uncertainty. Results showed that the 1889 flood peaks occurred during the end of 1889 June and the greater than 99th percentile of monthly runoff reached 8.6 mm/d (the 95%CI errors between -2.94 and 3.26 mm/d). The discharge peak to Lake Taihu also occurred in the same month, and the greater than 99th percentile of daily discharge reached 1286.9 m³/s (the 95%CI errors between-128.3 and 165.7 m³/s). Following the Log-Normal distribution that has been tested in the control run simulations, return period of the 1889 flood year is 149 years. After simulations for the error intervals by the Bootstrap confidence interval method, the return period during 70-175 years is much confident. The study will provide scientific basis of hydrological dynamics for extending the time series of the 20th century hydrology and knowing the centennial timescale chance of extreme floods.

Abstract:Based on the synchronous water quality and quantity monitoring of the rivers surrounding Lake Taihu in Zhejiang Province during hydrological year of 2010-2011, we have made a thorough analysis over the temporal and spatial variations of water quantity, quality and pollutant fluxes of the rivers connected to the Lake Taihu with the jurisdiction of Zhejiang Province. In the whole hydrological year, total inflowing water was 22.890×10⁸ m³, and total outflowing water was 31.576×10⁸ m³, water quality of the rivers was regular and steady, indexes of main pollutants were categorized into National Grade Ⅱ-Ⅲ. The estimation of pollutant fluxes has shown that the CODMn, ammonia nitrogen, total phosphorus and total nitrogen outfluxes were more than influxes. The decline of pollutants influxes is mainly due to the increases of countercurrent flow of rivers flowing into the Lake Taihu.

Abstract:The objectivity and accuracy of the analysis results of pollutant load into the Lake Taihu are controlled by the calculation precision. The paper takes Lake Taihu as an example, analyses not only pollutant load of rivers into Lake Taihu in 2010, but also the temporal and spatial distributions and variation of the pollutant load. The daily monitoring data of water yield and water quality under the existing monitoring network are used to calculate pollutant load into the Lake Taihu in a daily accumulation period, which is assumed the highest calculation precision for existing analysis and calculation of pollutant load of rivers into the Lake Taihu. With different monitoring schemes and different calculation methods, the study analysed pollutant load of rivers into the Lake Taihu and the calculation precision achieved. It is found that pollutant load of rivers into the lake analysed and calculated nowadays accounts for 80 percents of which monitored everyday simultaneously. Technical support is provided by analysing the calculation precision of pollutant load of rivers into the Lake Taihu to make scientific monitoring schemes and to improve the computation precision of the pollutant load of rivers into the Lake Taihu.

Abstract:In order to study the shrinkage of the Lake Hulun, monthly water balance model was used to analyze the characteristics and causes of water changes. Based on available continuous lake level monitoring data from 1963 to 1980, there are exchange between groundwater of surrounding areas and lake water according to the principle of water balance and other auxiliary calculations. The exchange has a certain regularity, which is the accumulated snow of the period from November to March when snows begin to melt and then infiltrate the soil with the increase of temperature. This part of water recharges the lake in the form of subsurface flow in spring, which causes the lake water level increases slightly. The lake will recharge the surrounding prairie through strong evaporation after July. On the basis of above observations, the unknown items, i. e. the exchange and overland flow, were taken into balance equation as a constant to simulate water level. There is high goodness of fit between simulated values and related research results. Finally, the influence of precipitation, runoff and evaporation under different climate scenarios on lake water level were used to determine the cause of the drastic decrease of the lake level. The results show that decline of the lake water level after 2000 is mainly due to the sharp drop of river runoff.

Abstract:Using the hydrology monitoring data in Lake Poyang area during 1952-2011, the characteristics and variations of lowwater level in Lake Poyang in recent 60 years were analyzed. Possible mechanisms for the variations of low-water level changes in Lake Poyang were discussed, i. e. influences from precipitation within the basin, inflows from the five rivers within the catchment, and from the middle and lower reaches of Yangtze River, and lake basin topography. The results showed that the low-water level status was aggravating in the last 11 years, especially in the last 5 years, since the inflows from the five rivers were decreased due to less precipitation in Lake Poyang Basin. Secondly, the control of low-water level in Lake Poyang by inflows from the middle and lower reaches of Yangtze River was strengthened during the past 10 years, especially the effects were enhanced after the operation of the Three-Gorge Dam.

Abstract:Based on the monthly runoff data during 1950-2007 at Wujiadu Hydrologic Station in the Huaihe River Basin, the drought-flood abrupt alternation phenomena(including drought to flood and flood to drought) based on runoff was analyzed during the main rainy season(MJJA) by using long-and short-cycle runoff drought-flood abrupt alternation index(RDFAI). The results are as follows:1) the frequency of long-cycle runoff drought-flood abrupt alternations was higher in the period before 1986, and then decreased after the late 1980s; 2) Inter-annual changes of the short-cycle runoff drought-flood abrupt alternation phenomena between the adjacent months varied from each other, with the change between June and July being the most obvious one, and the long-term changes are similar to that of the long-cycle runoff drought-flood abrupt alternation phenomena; 3) Both the occurrence of long-and short-cycle runoff drought-flood abrupt alternation phenomena showed decreasing trends during the past 57 years, however, the total drought and total flood phenomena were on the rise; 4) During the 2000s, both the long-cycle and short-cycle runoff drought to flood abrupt alternation in June and July increased, and this might be one of the major reasons for the runoff increase during the rainy season at the same period.

Abstract:In order to investigate the impact of microorganism in constructed wetland on purification efficiencies for slightly polluted river water in Three Gorges Reservoir Region, four horizontal subsurface flow wetlands planted with Arundo domax, Acorus calamus, Ipomoea aquatica and without plants (blank) were built in situ next to the Lushan River. The distribution of microbial basic flora and function flora in the wetlands were monitored, purification efficiencies of the constructed wetland systems were studied, and the correlation between microorganism and removal rates of pollutants were analyzed. The results showed that the experimental wetlands were adaptive to variation of inflow quality and quantity, and the removal efficiency of pollutants could be improved by planting hydrophytes. Microbial population in the planted wetlands was more than that in the blank wetland. There was positive correlation between microorganism quantity and temperature in all four wetlands, and quantity of ammonifying bacteria, nitrifying bacteria and denitrifying bacteria decreased significantly with the decline of temperature. There was conspicuous positive correlation between fungus population and removal of ammonia in summer, as well as bacteria population and removal of CODMn. It is similar positive correlation between denitrifying bacteria population and removal of total nitrogen in winter.

Abstract:Aiming at the wind-driven current in Lake Taihu, a calculation method of combining joint frequency of wind directions, wind speeds and pollution zone control was used to study the capacity of water environment for Lake Taihu. A 2-D unstable-state model of water quantity and quality in Lake Taihu was established. By using hydrological data, the fields of flow and concentrations were numerically simulated, and the simulations were inter-compared. The pollution zone control method which is used to calculate the water environmental capacity was advanced by considering the affect of the speed and direction of wind. Control principia are single pollution control areas between 1 km² and 3 km², and the total length of pollution zone less than 10% of land line. The CODCr capacity of Lake Taihu is 132727 t/a, and TN is 7700 t/a.

Abstract:Based on an eco-model, we analyzed the monthly monitoring data of Lake Taihu from April 2009 to November 2010, and found that the growth rates of Lake Taihu cyanobacteria showed significant both temporal and spatial differences. The growth rates of cyanobacteria were low from January to April, and from October to December, while high level from June to September. But the growth rates in May showed annual difference. Furthermore, the growth rates in western lakeshore were higher than those in the central lake. The growth of cyanobacteria from surface water to one-meter depth was active. Growth of cyanobacteria was mainly controlled by water temperature, illumination and phosphorus concentration. These three limiting factors showed significant seasonal variation and interchanged with the others. In the surface water, temperature and phosphorus were the main limiting factors, while temperature, phosphorus and illumination at the depth of half a meter, and illumination below one-meter depth. The result showed that phosphorus concentration in summer and fall was the major limit on nutrient phosphorus, and also limit on nitrogen in some areas.

Abstract:To investigate clonal growth and foraging behavior of a submerged macrophyte Vallisneria natans, biomass, ramet number, bud number, total stolon length, shoot height and maximum root length responses of V. natans ramets were investigated experimentally at five water depths (1.0, 2.5, 4.0, 5.5 and 7.0 m). The study showed biomass, ramet number, bud number, total stolon length and maximum root length all decreased significantly with increasing water depths. The shoot height exhibited a unimodal pattern along with increasing water depths, with the maximum value at the water depth of 2.5 m. The plant biomass significantly affected all the growth traits except for the bud number. Furthermore, ramet number and total stolon length were significantly affected by the interactive effect between water depth and plant biomass, suggesting that the effects of water depth on ramet number and total stolon length were depended on plant development.

Abstract:Phytoplankton lysis rate in three different eutrophic regions of Lake Taihu was measured by the activities of particle and dissolved esterase, as well as the decay rate of the latter, from August 2009 to October 2010. The present results showed that the particulate, dissolved esterase activity, half life time of dissolved esterase, and cell lysis rates ranged from 0.58-35.15 nmol FDA/(L·h), 0.55-7.59 nmol FDA/(L·h), 7-75 h, and 0.02-0.77 d^-1, respectively. No significant differences were found in the cell lysis rates among the three sampling sites. The significant linear relationship between Chl.a concentration and particulate esterase activities suggests that it is feasible to assess phytoplankton cell lysis rate in Lake Taihu by the esterase assay. Furthermore, Chl.a concentration showed the same pattern with water temperature, a significant difference was observed in Chl.a concentration between Meiliang Bay and lake centre. The strong, negative correlation between Chl.a concentration and lysis rate in Gonghu Bay suggests that phytoplankton biomass was affected by the lysis rate in Lake Taihu.

Abstract:Through a self-designed experimental device according to hydrodynamic conditions of backwater area of branch of Three Gorges Reservoir, the experiment was carried out to study the effects of reynolds number and turbulent flow on the vertical distributions of algae and its suspension and gathered behavior in different water depths. In the condition that water temperature is 20℃, illumination is 5000 lx and there are enough nutrient concentrations in water, the experiment results showed that Cyanophyta cells are mainly in the depth ranging from 0.2 m to 0.8 m when average flow velocity is within 0-0.005 m/s and reynolds number is within 0-1750 while Bacillariophyta cells are mainly in the depth ranging from 0.2 m to 0.8 m when average flow velocity is within 0.1-0.5 m/s and reynolds number is within 35000-175000. Compared to Cyanophyta and Bacillariophyta, a considerable part of Chlorophyta cells could suspend in the depth ranging from 0.2 m to 0.8 m when flow velocity is within 0-0.05 m/s and reynolds number is within 0-17500.

Abstract:Although diatom has been widely used in biological or ecological monitoring of rivers, there is little information on diatom communities in most of Chinese rivers. In this study, we reported periphytic diatoms on artificial substrata(tile) in the Huizhou section of the Dongjiang River. We analyzed seasonal variations of the species composition and the relationship between the relative abundance and seasonal environmental factors at five sampling stations in 2010. A total of 153 periphytic diatom species, belonging to 40 genera, were identified. Dominant genera included Achnanthidium, Gomphonema, Melosira, Navicula, Nitzschia and Synedra. Gomphonema parvulum and Nitzschia palea were the common species in all the sampling sites with relative abundance > 1%. However, the relative abundance of the two species varied largely in seasons. Chl. a concentrations of the periphytic algae were positively correlated with the temperature. Redundancy analysis showed that water temperature, DO, NH₄⁺-N, PO₄^3--P, conductivity and pH were the major factors influencing the community structure of periphytic diatoms. Furthermore, hydrographic condition was crucial to some mobile species such as Nitzschia palea, whose relative abundance was low in summer mainly due to flushing in flood season.

Abstract:To determine the impacts of cutting on the growth and photosynthetic fluorescence characteristics of Potamogeton crispus, apexes of the plant were cut with different cutting intensities(0, 15, 30, 45, 60, 75, 90 and 105 cm) in a pool depth of 1.5 m. Results show that:Cutting significantly affected the growth and recovery of the shoot of P. crispus. The plant height of the control group(0 cm) was maximum and had formed canopy on the surface of water. The group of 15 cm restored on the twentieth day of the experiment. The recovery rates of the groups from 30 cm to 105 cm were 69.67%, 17.78%, 8.83%, 5.33%, 2.28% and 1.90%, respectively; Cutting significantly reduced the biomass of P. crispus. Comparing with the control group, the increment of fresh weight of the cutting groups decreased by 23.71%, 54.90%, 81.19%, 85.82%, 90.72%, 94.07% and 95.10%, respectively. The final biomass of the cutting groups from 15 cm to 105 cm declined to 59.36%, 43.16%, 27.69%, 18.73%, 14.66%, 8.14% and 4.07% of the control group, respectively; Cutting has significantly reduced the quantity of the brood bud and the size of each individual and the fresh weight of P. crispus; Cutting with medium and low intensity did not have obvious impact on the leaves of Fv/Fm of P. crispus, but Fv/Fm of high intensity cutting groups(especially 105 cm) has significant impact. The maximal relative electron transport rate(ETR_max) of the leaves rapid light curves had no significant difference. The groups with medium and low intensity increased slightly while the ETR_max of high intensity cutting groups declined. The experimental results show that cutting had obvious effect on controlling biomass of P. crispus and numbers of brood buds, but medium and low cutting intensity was less obvious.

Abstract:Monthly whole-lake samplings (9 selected sites) were conducted from March 2010 to February 2011 to study the temporal and spatial distributions of phytoplankton and various forms of inorganic nitrogen and their relationships in Lake Taihu. Nitrate and ammonium were the major forms of inorganic nitrogen in the lake, which accounted for 76% and 22%, respectively. Concentrations of ammonium and nitrite in the northwest coastal belt and Zhushan Bay in the northern lake were usually significantly higher than other sampling sites. Seasonal variations of total soluble inorganic nitrogen (TIN) were very similar, in various sampling sites, which had generally a highest concentration in the spring, declined during summer-fall seasons, and then recovered in the winter. The summer TIN variations declined in the northern lake and was larger than these in the southern lake, which made the ratio of TIN:TSP in the northern lake much lower than that in the southern lake. Spring Microcystis spp. recruitment in the southern lake was more than that in the northern, but summer-fall blooms of Microcystis spp. mainly occurred in the northern lake, and the sites where Microcystis spp. greatly bloomed (e. g. Meiliang Bay) were usually accompanied with low levels of nitrite concentration and TIN:TSP ratio. The ratio of Chl.a:phytoplankton was significantly negative-correlated with phytoplankton number and positivecorrelated with the ratio of TIN:TSP, which indicated that the average content of Chl.a per phytoplankton cell declined with algae bloom and the ratio of TIN:TSP declines. The cause of this phenomenon needs further investigation. Temporal and spatial distributions of bacillariophyta, chlorophyta, euglenophyta and cryptophyta were similar to each other, but differed from that of Microcystis spp..

Abstract:In situ growth rates of the typical dominant algae species in Pengxi River were investigated using two kinds of in situ incubation devices (incubation cage and incubation bucket) for field incubation experiment in Lake Gaoyang of Pengxi River. Adequate nutrients, superior solar-thermal and relatively stable hydrodynamic conditions are the main characteristic of the habitat during the study. The selected environment was suitable for the algal growth and the period chosen was sensitive for the occurrence of algal blooms. During this period, in situ growth rates of Cyllotella and Cryptomonas representing phytoplankton with CR and CRS growth strategies, respectively, were both gradually declined, and those of Anabaena and Eudorina which both represent the CS growth strategies increased firstly and then declined. The in situ growth rate of Microcystis which represents the S growth strategy was negative in early days, however, the general trend of growth rate was increased. The maximum specific growth rate of each species in the incubation cage and incubation bucket were Cyllotella hubeiana 0.31, 0.21 d^-1, Microcystis aeruginosa 0.09, 0.03 d^-1, Eudorina elegans 0.16, 0.42 d^-1, Anabaena flos-aquae 0.30, 0.26 d^-1, Cryptomonas ovata 0.49, 0.95 d^-1, respectively. In this study, changes in the algae growth rates of the different growth strategies to a certain extent reflected the different growth trend. In addition, comprehensive analysis of the results of the performance test and in situ incubation experiment suggested that both of the two devices were able to meet the testing requirements of in situ growth rate of algae in natural water. There were potential impacts of the incubation devices on the in situ growth of phytoplankton.

Abstract:Cell number, cell size, chlorophyll-a (Chl.a) concentration, absorption and specific absorption coefficients of Microcystis aeruginosa and Scenedesmus obliqnus were determined in the different culture times at three different irradiation intensities. Oneway analysis of variance showed that irradiation intensity had great significant effects on cell number, Chl.a concentration and phytoplankton absorption coefficients at 440 nm a_ph (440), 675 nm a_ph (675) in the entire experimental period. The largest values of these parameters were recorded in the light condition with 50 μmol/(m²·s). Phytoplankton needs optimal growth irradiation intensity because over-low or high light density could have negative effects on the growth rate of phytoplankton. Correlation analysis showed that there were significant positive correlations between a_ph (440), a_ph (675) and Chl.a concentration under three different irradiation intensities for M. aeruginosa and S. obliqnus. Power correlation could be best used to describe the correlations between a_ph (440), a_ph (675) and Chl.a concentration, while the linear correlation could be used to explain the relationships between a_ph (440), a_ph (675) and cell number. Meanwhile the specific absorption coefficients of M. aeruginosa and S. obliqnus fluctuated within small range in different irradiation intensities at different experimental periods, and increased with increasing irradiation intensity. A significant negative relationship was found between M. aeruginosa specific absorption coefficients at 440 nm, 675 nm and Chl.a concentration. However, the specific absorption coefficients of S. obliqnus had no relationship with Chl.a concentration mainly due to the composition and proportion of pigments and package effects. The average specific absorption coefficient integrated over the range of PAR (400-700 nm) of M. aeruginosa and S. obliqnus at three irradiation intensities of 5, 50, 100 μmol/(m²·s) are 0.0144, 0.0134, 0.0160 and 0.0086, 0.0088, 0.0105 m²/(mg Chl.a), respectively. The specific absorption coefficients of M. aeruginosa were significantly higher than those of S. obliqnus mainly due to the algae cell size of M. aeruginosa, 3.14 ± 0.43 μm, twice smaller than that of S. obliqnus, 7.24 ± 0.79 μm.

Abstract:Coilia ectenes taihuensis Yen et Lin(C. ectenes) is the dominant fish species in Lake Taihu, and the catch has been increasing with the eutrophication of Lake Taihu. In this study, in order to investigate the seasonal diets variations of C. ectenes in Gonghu Bay of Lake Taihu, we sampled the fish by gill net and analyzed bimonthly the gut contents of C. ectenes from April to December, 2009. Meanwhile, selectivity for different food items was also analyzed for the purpose to study the food preference of the fish. The results showed that the food composition of C. ectenes varied from month to month. Zooplankton, fish larvae, shrimp and insects were found in the stomach contents of the fish, but zooplankton was the dominant food. Among the zooplankton species, Copepod was the main food in April with close mean percentages diet composition of Copepodite, Sinocalanus dorrii Brehm and Cyclops spp. In June, August and October, C. ectenes fed mainly on cladoceran with Moina spp. as the dominated mean percentage diet composition in June and Bosmina spp. in August and October, respectively. Small zooplankton composed the main percentage diet composition, such as Bosmina spp. and Moina spp., in all sampling months. However, C. ectenes negatively selected Bosmina spp. for their food, but positively selected Moina spp. and other large-sized zooplankton species. But when Daphnia spp. and Leptodora kindti Focke were present in the sampling months, C. ectenes showed high selectivity for them. From this investigation, we can conclude that C. ectenes feed mainly on planktonic crustaceans, and showed high selectivity for large-sized zooplankton. Moreover, fish larvae, shrimp and insects may be their potential food for the fish when its total length is longer than 130 mm. Different food items varied largely in fish food composition among different seasons. Studying on the diet composition of C. ectenes can help us understand the seasonal effects of C. ectenes on zooplankton community structures better, and provide evidences and foundations for making rational plans of fisheries and lake management.

Abstract:The annual dynamics of phytoplankton community structure in Lake Caizi has been investigated in 2010. The results indicated that:(1) A total of 285 phytoplankton species from 110 genera of 8 phylum were identified. Phytoplankton species composition in different months showed significant difference. The maximal number of phytoplankton species (173) occurred in March while the minimum (105) in January. The dominant class of phytoplankton changed seasonally. Cyanophyta peaked all the year round; diatoms had an apparent dominance in January, May, September and November; Xanthophyta also played an important role in January, March and May; Chlorophyta dominated in November, Cryptophyta dominated in May while Chrysophyta dominated in January. The cell density and biomass of phytoplankton were higher in summer and autumn than that in winter and spring. The cell density of phytoplankton between different months had significant difference. The maximal density, with the value (66.13 ± 8.58)×10⁵ cells/L occurred in July while the minimal value of (12.78 ± 0.61)×10⁵ cells/L appeared in January. Whereas, the maximal biomass of phytoplankton(2.80 ± 0.17 mg/L) occurred in September and the minimal(0.72 ± 0.03 mg/L) appeared in May, and the biomass in different months was also significant different. (2) Temporal variations of three indices (including Margalef index, Shannon-Wiener index and Pielou evenness index) were obvious. All the indices were higher in winter and spring than those in summer and autumn. The maximal value occurred in March while the minimal one appeared in July. (3) The phytoplankton community structure was influenced by different factors in different months. As a result, the groups of sampling station changed seasonally according to cluster analysis. (4) The obvious variation of phytoplankton community structure was present in 2010 compared with that in 2007. The number of species decreased from 340 in 2007 to 285 in 2010, however, the cell density increased obviously from (5.91 ± 0.90)×10⁵ cells/L in 2007 to (33.81 ± 10.10)×10⁵ cells/L in 2010. At the same time, both the numbers of oligotrophic algae and perphytic algae decreased to the same extent and eutrophic, filamentous and planktonic algae increased.

Abstract:A great number of palaeoclimatic proxies and modern instrumental data have indicated that the climate of Yunnan- Guizhou Plateau has undergone a significant warming during the past hundred years. In this study to reveal the impact of the region climate change on lake ecosystems, physical and chemical proxies in sediment core from the Lake Lugu were examined, including Loss-on-ignition at 550℃(LOI_550℃), the concentrations of pigments, chlorophyll derivatives (CD), total carotenoids (TC), Oscillaxanthin (Osc), Myxanthophyll (Myx), biogenic silicon and C/N values. The correlations of those proxies with climate data of both temperature and precipitation from nearby Lijiang station during 1951-2010 AD were analyzed. The results showed that four pigment contents and two ratios CD/TC and Osc/Myx were sensitive to regional temperature changes. The CD, TC, Osc, Myx, LOI_550℃ and biogenic silica content showed significantly positive correlations with average annual temperature in the last 60 years, while CD, TC, Osc, Myx and C/N had significantly positive correlations with the 5 years moving average precipitations. The result indicated that warming was possibly one of the main factors driving the increasing of primary productivity of the lake, while the effect of precipitation shows a secondary factor in the comparison. Since 1990, all the four pigments and LOI_550℃ increased significantly while C/N ratios decreased, which indicated that the lake primary productivity were enhanced and its contribution to the total organic matter in sediments increased as well. The increasing of Osc and Myx contents and Osc/Myx ratio in the lake sediments reflected the increase of productivity of Cyanophyceae and the proportion of Oscillatoria in Cyanophyceae. The results indicated that the regional climate change over the last 20 years not only led to the increase of lake primary productivity, but also the change of composition of phytoplankton community, in Lake Lugu.

Abstract:Lake Hongfeng is a man-made deep lake. Phosphorus of sediment samples that were collected from representative six water areas were analyzed. Water temperature and dissolved oxygen were investigated four times in the field by multi-parameter water quality observation analyzer YSI. The results showed that total phosphorus in sediment was generally high. The average value of total phosphorus in surface sediment was more than 1500 mg/kg, significantly higher than that in the bottom sediments. NaOHSRP and rest-P were the main forms of phosphorus in sediment. NH₄Cl-P, BD-P and HCl-P contents decreased with depth, and rest-P contents were stabile in vertical. Human activities (e. g. chemical waste water and artificial fish) greatly increased NaOHSRP contents in sediment. Temperature of bottom water was between 14.5-23.5℃, and the maximum temperature differences was 9.9℃ in different seasons. The bottom water was seasonal anoxic or anaerobic, which may result in changes of sediment phosphorus forms. Risk of endogenous phosphorus release increased due to anoxic condition of sediment-water interface in deep lake.

Abstract:So far, more than 100 species of genus Anabaena have been recorded in the world, and about 50 taxa were described in China. During our recent field investigations for water-bloom forming cyanobacteria in China, several filamentous cyanobacterial species were examined in the samples. In this study, we demonstrated that two Anabaena species as Anabaena viguieri Denis et Frémy 1923 and Anabaena smithii (Komárek) Watanabe 1992, had never been reported in China, and they are newly described and discussed in the present study.