Lake Qiandaohu Research Articles

Retrieval of absorption coefficients for a drinking water source using a green–red band quasianalytical algorithm

This study proposed a green–red band quasianalytical algorithm, QAA-GRI, and evaluates its performance using an in situ dataset from Lake Qiandaohu, a drinking water source, in China. First, by shifting the reference wavelength from 555 to 510 nm, a green–red index (GRI) can be calculated from remote sensing reflectance at 510, 560, and 620 nm, and the index was then used to retrieve the total absorption coefficients at the reference band, a ( 510 ) . Second, a semianalytical model based on a ( 510 ) and the GRI was deduced to establish the QAA-GRI, replacing the empirical model in quasianalytical algorithm version 5 (QAA-v5). The QAA-GRI was applied to retrieve absorption coefficients from an in situ dataset of Lake Qiandaohu, and the QAA-GRI’s performance was compared with that of QAA-v5 and another red–green QAA-based approach (QAA-RGR). The results demonstrate that, for this dataset, the QAA-GRI exhibited better performance (R2 = 0.81, mean absolute percentage error, MAPE = 15.7 % ), which indicated a clear improvement in the accuracy of absorption coefficient retrieval, compared with QAA-v5 (R2 = 0.56, MAPE = 21.2 % ) and QAA-RGR (R2 = 0.67, MAPE = 22.6 % ). In addition, to illustrate the QAA-GRI’s assumptions and its applicability, the QAA-GRI was also applied to an in situ dataset from Taihu Lake, a highly turbid and eutrophic water source. As predicted, when applied to Taihu Lake, the QAA-GRI did not perform as well as it did when applied to Lake Qiandaohu because of the former’s extremely high turbidity, which can cause greater uncertainty with regard to backscattering coefficients. This study suggests that the QAA-GRI is better suited to the retrieval of absorption coefficients from drinking water resources. Our algorithm will also have potential applications to satellite data from the Medium Resolution Imaging Spectrometer or Ocean and Land Color Instrument.

Variations in Spectral Absorption Properties of Phytoplankton, Non-algal Particles and Chromophoric Dissolved Organic Matter in Lake Qiandaohu

Light absorption by phytoplankton, non-algal particles (NAP) and chromophoric dissolved organic matter (CDOM) was investigated at 90 sites of a clear, deep artificial lake (Lake Qiandaohu) to study natural variability of absorption coefficients. Our study shows that CDOM absorption is a major contributor to the total absorption signal in Lake Qiandaohu during all seasons, except autumn when it has an equivalent contribution as total particle absorption. The exponential slope of CDOM absorption varies within a narrow range around a mean value of 0.0164 nm−1 ( s d = 0.00176 nm−1). Our study finds some evidence for thIS autochthonous production of CDOM in winter and spring. Absorption by phytoplankton, and therefore its contribution to total absorption, is generally greatest in spring, suggesting that phytoplankton growth in Lake Qiandaohu occurs predominantly in the spring. Phytoplankton absorption in freshwater lakes generally has a direct relationship with chlorophyll-a concentration, similar to the one established for open ocean waters. The NAP absorption, whose relative contribution to total absorption is highest in summer, has a spectral shape that can be well fitted by an exponential function with an average slope of 0.0065 nm−1 ( s d = 0.00076 nm−1). There is significant spatial variability present in the summer of Lake Qiandaohu, especially in the northwestern and southwestern extremes where the optical properties of the water column are strongly affected by the presence of allochthonous matter. Variations in the properties of the particle absorption spectra with depths provides evidence that the water column was vertically inhomogeneous and can be monitored with an optical measurement program. Moreover, the optical inhomogeneity in winter is less obvious. Our study will support the parameterization of the Bio-optical model for Lake Qiandaohu from in situ or remotely sensing aquatic color signals.

Dissolved oxygen stratification and response to thermal structure and long-term climate change in a large and deep subtropical reservoir (Lake Qiandaohu, China)

From January 2010 to March 2014, detailed depth profiles of water temperature, dissolved oxygen (DO), and chromophoric dissolved organic matter (CDOM) were collected at three sites in Lake Qiandaohu, a large, deep subtropical reservoir in China. Additionally, we assessed the changes in DO stratification over the past 61 years (1953–2013) based on our empirical models and long-term air temperature and transparency data. The DO concentration never fell below 2 mg/L, the critical value for anoxia, and the DO depth profiles were closely linked to the water temperature depth profiles. In the stable stratification period in summer and autumn, the significant increase in CDOM in the metalimnion explained the decrease in DO due to the oxygen consumed by CDOM. Well-developed oxygen stratification was detected at the three sites in spring, summer and autumn and was associated with thermal stratification. Oxycline depth was significantly negatively correlated with daily air temperature and thermocline thickness but significantly positively correlated with thermocline depth during the stratification weakness period (July–February). However, there were no significant correlations among these parameters during the stratification formation period (March–June). The increase of 1.67 °C in yearly average daily air temperature between 1980 and 2013 and the decrease of 0.78 m in Secchi disk depth caused a decrease of 1.65 m and 2.78 m in oxycline depth, respectively, facilitating oxygen stratification and decreasing water quality. Therefore, climate warming has had a substantial effect on water quality through changing the DO regime in Lake Qiandaohu.

Thermal structure and response to long‐term climatic changes in Lake Qiandaohu, a deep subtropical reservoir in China

Using the vertical temperature profiles of Lake Qiandaohu from January 2010 to April 2013, we evaluated the monthly and seasonal variations of water temperature and thermocline parameters, and developed empirical models among thermocline depth (TD), thickness (TT), and strength (TS). We also developed empirical models between TD, TT, TS, and surface‐water temperature (0–2 m) (T0–2 m), and transparency (Secchi disk depth, SDD). Additionally, we assessed the changes in TD, TT, and TS over the past 62 yr, based on our empirical models, air temperature data from 1951 to 2012, and SDD data from 1987 to 2012. Lake Qiandaohu is warm monomictic, with a long period of thermal stratification from April until January, and only a short period of mixing in the winter or spring (February or March). There were significant correlations between SDD and TD (positive), and between SDD and TT (negative). There was a significant negative correlation between T0–2 m and TD during the stratification weakness period (July—February), and a significant positive correlation between T0–2 m and TT for all data, including the stratification formation and weakness periods. Air temperature near the lake rose 1.2°C between 1951 and 2012, corresponding to a 0.8°C increase in T0–2 m, and a 0.78 m decrease in SDD between 1987 and 2012. The increase in air temperature and the decrease in SDD caused a decrease in TD and an increase in TT, facilitating the thermal stratification and stability of the lake; therefore, climate warming has had a significant effect on the thermal regime of Lake Qiandaohu.

控(微囊)藻鲢、鳙排泄物光能与生长活性

PDF HTML阅读 XML下载 导出引用 引用提醒 控(微囊)藻鲢、鳙排泄物光能与生长活性 DOI: 10.5846/stxb201211151602 作者: 作者单位: 中国科学院南京地理与湖泊研究所湖泊与环境国家重点实验室;中国科学院大学,中国科学院南京地理与湖泊研究所湖泊与环境国家重点实验室,中国科学院南京地理与湖泊研究所湖泊与环境国家重点实验室,中科院南京地理与湖泊研究所,中科院南京地理与湖泊研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家“十二五”农村领域科技计划课题（2012BAD25B06/07）；国家自然科学基金项目（31270506）；环保部环保公益项目科研专项（2010467014） Growth and photosynthetic activity of Microcystis colonies after gut passage through silver carp and bighead carp Author: Affiliation: Key laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology,Chinese Academy of Sciences;College of Forestry,Henan Agricultural University,,Key laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:利用叶绿素荧光技术，通过原位培养滤食性鱼类鲢（Hypophthalmichthys molitrix）、鳙（Aristichthys nobilis）摄食微囊藻（Microcysis）后的排泄物，研究鲢、鳙滤食对藻类光能及生长活性的影响。结果表明，微囊藻经鲢、鳙滤食后，排泄当天，其叶绿素荧光参数PSⅡ最大光能转化效率（Fv/Fm）、PSⅡ潜在光合活性（Fv/Fo）、PSⅡ实际光能转化效率（Yield）和光合电子传递速率（ETR）显著低于对照组（P < 0.05），而光化学猝灭（qP）和非光化学猝灭（NPQ）显著高于对照组（P < 0.05）。随后，微囊藻的光合活性逐渐恢复，鲢、鳙组的Fv/Fm、Fv/Fo、Yield和qP分别在第3天和第5天开始呈上升趋势，至实验结束时显著高于对照组，其中鲢组高于鳙组。而NPQ呈下降趋势，第13 d极显著低于对照组（P < 0.01）。原位培养期间，鲢、鳙组藻细胞密度和叶绿素a（Chl a）浓度呈增长趋势，且鲢组明显高于鳙组；鳙组藻类游离胞外多糖含量增长幅度高于鲢组。实验结束时，鲢、鳙组浮游藻类总生物量分别为对照组7.78、6.55倍，绿藻（Chlorophyta）和硅藻（Bacillariophyta）相对生物量增加，但微囊藻贡献率达93%以上。相关性分析显示，鲢组藻细胞密度、Chl a浓度和胞外多糖含量与Fv/Fm、Fv/Fo、Yield、ETR、qP均极显著正相关（P < 0.01），而与NPQ呈极显著负相关（P < 0.01）。鳙组藻细胞密度、Chl a浓度和胞外多糖含量仅与ETR呈极显著正相关（P < 0.01），与NPQ呈极显著负相关（P < 0.01）。可见，鲢、鳙单次滤食未对微囊藻造成生理上的致命损伤，藻类由于超补偿生长，其光合及生长活性在短期恢复并显著增强，有潜在加速水体富营养化可能，鲢、鳙增殖放流以控制蓝藻水华的措施值得商榷。 Abstract:Proliferation of cyanobacteria is a global problem in eutrophic freshwater ecosystems. Silver carp (Hypophthalmichthys molitrix) and bighead carp (Aristichthys nobilis) have been considered effective in suppressing cyanobacterial blooms in eutrophic lakes. Long-term observations in Lake Donghu and Lake Qiandaohu documented that silver carp and bighead carp can efficiently suppress Microcystis blooms. However, the introduction of silver carp and bighead carp into blooming waters not always brings about the expected result, namely a decrease in phytoplankton biomass. Some ponds stocked with planktivorous carp have been reported to show an increase in phytoplankton biomass. One of the reasons may come from that the photosynthetic activity of Cyanobacteria after gut passage remains unaffected or even increases. In order to test the effect of silver carp and bighead carp's digest on Microcystis, chlorophyll fluorescence technique was employed. Chlorophyll fluorescence technique provides a swift, accurate, and nondestructive way for assessing the efficiency of photochemical conversion and it has become an increasingly powerful tool widely used in the study of photosynthesis. In our study, the growth and photosynthetic activity of Cyanobacteria after passage through the intestines of silver carp and bighead carp were compared with those taken directly from Lake Taihu during a 13-day in situ dialysis culture. The hypothesis for experiment reported in the study was that cyanobacteria in excretions might retain photosynthetic activity after gut passage. The aim of this work was to prove viability of the digested phytoplankton using multi-fluorescence parameters in comparison to the untreated water bloom from the same source population.Chlorophyll fluorescence parameters (including maximal optical quantum efficiency of PSⅡ(Fv/Fm), Potential activity of PSⅡ(Fv/Fo), effective optical quantu yield of PSⅡ(Yield), PSⅡ-driven electron transport rate (ETR), photochemical quenching (qP) and nonphotochemical quenching (NPQ)) were determined by PAM fluorimeter (Dual-PAM-100), and phytoplankton community structure and biomass were determined at the same time. The results indicated that Fv/Fm, Fv/Fo, Yield and ETR reduced significantly after passage through silver carp and bighead carp (P < 0.05), whereas qP and NPQ significantly increased (P < 0.05). After the first three to five days of reduced activity after excretion by silver carp and bighead carp, the metabolic activity of cyanobacteria recovered and rose significantly higher(P < 0.01) than the levels in the control population. The Fv/Fm, Fv/Fo, Yield and qP values were significantly higher in silver carp and bighead carp groups than in the control at the end of culture (P < 0.01), while NPQ was significantly lower on the 13rd day (P < 0.01). The phytoplankton cell density and chlorophyll a content of silver carp group were growing faster than that of bighead carp group. The extrtracellular exopolysaccharide (EPS) of bighead carp group was higher than that of silver carp group during culture. At the end of the experiment, the total biomass of phytoplankton showed a 6-to 8-fold increase of growth in the two fish groups compared to the control. The relative biomass of green algae (Chlorophyta) and diatom (Bacillariophyta) increased a little, and their biomass was low when compared to cyanobacteria (93% of the total phytoplankton biomass). Moreover, EPS production was also stimulated after the passage through silver carp and bighead carp. The correlation analysis showed that the phytoplankton cell density, chlorophyll a and EPS concentrations in silver carp group showed significantly positive correlation with Fv/Fm, Fv/Fo, Yield, ETR and qP (P < 0.01), but significantly negative with NPQ (P < 0.01). In bighead carp group, the phytoplankton cell density, chlorophyll a and EPS concentrations were only significantly positive (P < 0.01) with ETR and significantly negative (P < 0.01) with NPQ. It was obviously that silver carp and bighead carp digestion do not cause fatal injury to Microcystis. And the Microcystis might exhibit over-compensatory growth resulting from fish digestion during cultivation. The increase in photosynthesis and growth of living cells after passage through the gut of silver carp and bighead carp may be one of the factors affecting the formation and maintenance of water blooms. Therefore, the use of silver carp and bighead carp as biological manipulation tool for cyanobacterial blooms control in lakes need more discussion. 参考文献 相似文献 引证文献

A Review of Nontraditional Biomanipulation

The aim of this review is to identify problems, find general patterns, and extract recommendations for successful management using nontraditional biomanipulation to improve water quality. There are many obstacles that prevent traditional biomanipulation from achieving expectations: expending largely to remove planktivorous fish, reduction of external and internal phosphorus, and macrophyte re-establishment. Grazing pressure from large zooplankton is decoupled in hypereutrophic waters where cyanobacterial blooms flourish. The original idea of biomanipulation (increased zooplankton grazing rate as a tool for controlling nuisance algae) is not the only means of controlling nuisance algae via biotic manipulations. Stocking phytoplanktivorous fish may be considered to be a nontraditional method; however, it can be an effective management tool to control nuisance algal blooms in tropical lakes that are highly productive and unmanageable to reduce nutrient concentrations to low levels.Although small enclosures increase spatial overlap between predators and prey, leading to overestimates of the impact of predation, microcosm and whole-lake experiments have revealed similar community responses to major factors that regulate lake communities, such as nutrients and planktivorous fish. Both enclosure experiments and large-scale observations revealed that the initial phytoplankton community composition greatly impacted the success of biomanipulation. Long-term observations in Lake Donghu and Lake Qiandaohu have documented that silver carp (Hypophthalmichthys molitrix) and bighead carp (H. nobilis) (two filter-feeding planktivorous species commonly used in management) can suppress Microcystis blooms efficiently. The introduction of silver and bighead carp could be an effective management technique in eutrophic systems that lack macrozooplankton. We confirmed that nontraditional biomanipulation is only appropriate if the primary aim is to reduce nuisance blooms of large algal species, which cannot be controlled effectively by large herbivorous zooplankton. Alternatively, this type of biomanipulation did not work efficiently in less eutrophic systems where nanophytoplankton dominated.

The food web structure and ecosystem properties of a filter-feeding carps dominated deep reservoir ecosystem

An Ecopath model was constructed to describe the ecosystem of Lake Qiandaohu, a stock-enhanced large deep Chinese reservoir with silver carp ( Hypophthalmichthys molitrix) and bighead carp ( Aristichthys nobilis) dominated in its pelagic community. The food web structure and ecosystem property of the reservoir were analyzed and evaluated. The results showed that there were seven trophic levels (TLs) in the system, with the trophic flows primarily occurring through the first four TLs. The food web structure of this ecosystem was characterized with a bulged intermediate trophic level, which was contrary to the wasp-waist food web structure occurred in most natural aquatic ecosystems. The corresponding trophic flow pattern showing by transfer efficiencies (TEs) between TLs indicated that the trophic flows primarily went through from TL I to II with a high TE (of over 50%) and through a flow loop or short cut between detritus and TL II but greatly reduced from TL II to III with a lowest TE of 2.5% due to the bulged biomass at TL II. The trophic flow loop greatly increased the throughput recycled, which, together with high connectance index (CI), system omnivory index (SOI), Finn's cycled index (FCI) and Finn's mean path length (FML), might be beneficial to the maintaining of ecosystem stability. Finally, ecosystem property indices showed that this reservoir had a high value of P p/ R and P p/ B, indicating this ecosystem of short history was immature, but highly productive. This silver carp and bighead carp dominated deep reservoir ecosystem had both the characteristics of high productivity of an immature ecosystem and the feature of high stability of a mature ecosystem.

A study on the diversity of a zooplankton community in Lake Qiandaohu, Zhejiang

A study on the diversity of a zooplankton community in Lake Qiandaohu, Zhejiang