Yang Liuyan

Mechanism and control of lake eutrophication

A review about lake naturally eutrophicating, the internal loading of nutrients from lake sediment as well as the mechanism of algal blooms and the control practices was made, especially the eutrophication problem of shallow lakes since seventy percent of fresh water lakes in China are shallow lakes. It was found that shallow lakes are apt toward eutrophication than deep lakes. Without any influences of human activity, shallow lakes in the middle and lower reaches of Yangtze River are still easily eutrophicated, which may be owing to the effects of flood in this area. In shallow lakes, sediments are frequently disturbed by wind-wave and resuspended, which result in huge nutrients release to overlying water. This may be the major reason for higher internal loading of nutrients in shallow lakes than in deep lakes. Algal bloom is an extreme response of lake ecosystem to the eutrophication. Appearance of algal blooms is related to physical condition of lakes, such as underwater radiation (or transparency), temperature, and hydrodynamic conditions, or related to geochemical conditions of lakes, like concentrations of nutrients and ratio of nitrogen to phosphorus, as well as the physiological advantage of cyanobacteria such as vacuole for moving towards the radiant energy-rich zone and the mycosporine-like amino acids (MAAs) for resisting the harm of ultraviolet radiation. In shallow lakes, these advantages of cyanobacteria are favorable in the competition than in deep lakes. Also being the shallowness, it is more difficult to reduce nutrient loading and to control algae blooms in shallow lakes. For the control of eutrophication, people should follow the sequence from pollution sources control, ecological restoration to catchment management. To control the internal nutrient release, physical, chemical, biological techniques, and even bionic techniques could be selected. The idea of ecological restoration for a eutrophic lake is to shift the ecosystem from phytoplankton-dominant state to macrophyte-dominant state. To realize the shift of ecosystem state, environmental condition improvement is the fundamental work. Nowadays, we should do more work on environmental condition improvement than on planting of macrophytes since we are lack of the knowledge about the relationship between macrophyte and lake ecosystem. Emphasizing the macrophyte planting, therefore, has blindness at present. Because all lakes have different characteristics of environment and ecosystem, applicable lake harness techniques should be selected based on the distinct ecosystem types and environmental problems.

Effect of the growth of Microcystis aeruginosa on the pH value and the nitrogen transformation in the medium

Microcystis aeruginosa,dominance specie in the cyanobacterial bloom,was cultured under the different initial pH values in order to study the effect of the growth of M.aeruginosa on the pH value and the nitrogen transformation in the medium.The results showed that the pH value rose in the lag phase and exponential phase of M.aeruginosa,and the maximum pH values rose from 7.2,8.0 and 8.8 to 10.02,10.34 and 10.94 respectively,then decreased in the stationary phase and the decline phase of M. aeruginosa.While initial pH value was 8.8,it decreased to 8.66 at the end of the experiment.NO3-concentration decreased and NO_2~- concentration rose earlier then decreased later in the medium during the growth period of/14~ aeruginosa.Both the concentrations of NO_3~-and NO_2~-decreased next to zero in the 60th and the 67th days,respectively.Compared with the initial total nitrogen content,the final total nitrogen contents decreased 25.97%,27.52% and 28.16% under different initial pH values,respectively.The nitrogenous compound was transformed to N_2 through denitrification.Thus,there is distinct decrease of nitrogenous compound by denitrification in M.aeruginosa bloom.

Biogeochemicai cycling of nitrogen in lakes and the role of microorganisms in conversion of nitrogen compounds

It is generally considered that nitrogen is one of the major factors regulating the trophic status of lakes, and the biogeochemical cycling of nitrogen serves the most important function in lake systems.Lakes often receive large anthropogenic inputs of nitrogen that cause eutrophication,and the exchange of nitrogen-compounds between sediment and water has a profound effect in all kinds of lakes.Such increased nutrient loading promotes the growth of phytoplankton while rooted plants and benthic are suppressed due to reduced light availability,the transfer of the nitrogen through the food chains in algal lake and macrophytic lake is different accordingly.Meanwhile,in this re- view progresses made on the processes such as nitrification,denitrification,nitrogen fixation and anammox(anaero- bic ammonium oxidation)are emphasized.Methods and techniques applied in the research of biogeochemical cyc- ling of nitrogen are also summarized,and the development of molecular techniques has contributed enormously to the rapid recent progress in the field.Current insufficiencies are pointed out and future directions are recommended in the end.

蓝藻水华对羽摇蚊(Chironomus plumosus)幼虫N 2 O排放通量的影响

底栖动物是湖泊生态环境的重要组成部分，在泥水界面氮循环中扮演着重要的作用，是一个潜在的N2O排放源，但其在富营养化湖泊中N2O排放机制还不清楚.通过室内微宇宙实验，采用气相色谱和现代分子生物学相结合的技术，研究蓝藻存在时底栖动物摇蚊幼虫排放N2O特征及其内在生物学机制.结果显示底栖动物羽摇蚊幼虫（Chironomus plumosus）肠道是N2O排放的主要场所，约占活体释放通量的77%.蓝藻存在时羽摇蚊幼虫的N2O排放通量减少60%左右，肠道内细菌多样性明显下降，肠道中β-变形菌相对丰度增加21%，δ-变形菌相对丰度减少62%，从而改变肠道内细菌群落结构；同时肠道内nirS基因多样性显著增加，出现较多的nirS型反硝化菌的表型，硝酸盐的还原作用得到增强.研究结果有助于揭示富营养化湖泊底栖动物摇蚊幼虫的环境效应，丰富湖泊氮素生物地球化学循环的新过程.

生物质炭对苦草( Vallisneria spiralis )种子萌发与生长的影响

为了探究生物质炭作为生长基质对水生植物种子萌发和生长的影响，选用典型沉水植物苦草（Vallisneria spiralis）作为受试植物，测定不同氮、磷营养盐浓度和不同粒径的生物质炭作用下对苦草种子萌发率、幼苗形态与生物量，同时分析水体中硝态氮、亚硝态氮、氨氮和正磷酸盐磷浓度变化过程.结果表明：生物质炭存在使水体中亚硝态氮浓度低于检测限，使水体正磷酸盐磷浓度上升至1.28~2.43 mg/L，为最高添加磷浓度的3.2~6.1倍，从而改变了苦草生长环境.小粒径生物质炭（0.25~0.5 mm）组中水体最终氨氮浓度（0.05 mg/L）远远低于大粒径生物质炭（1~2 mm）组中水体最终氨氮浓度（0.39~0.85 mg/L），即生物质炭粒径大小会影响水体最终营养盐浓度和氮素赋存形态.与大粒径生物质炭组和石英砂对照相比，小粒径组苦草种子萌发率明显升高，可达80%以上，并促进苦草幼苗生长.因此，小粒径生物质炭能提高苦草种子萌发和幼苗生长，在大型水生植物恢复工程中具有一定的应用前景.

Free radical generation and stress effect on Scenedesmus obliquus exposed to phenanthrene

通过静态模拟实验,研究不同浓度（0.005、0.01、0.025、0.05和0.1 mg/L）菲暴露96 h后,对斜生栅藻的生长、自由基含量、抗氧化系统以及脂质过氧化产物（MDA）的影响.结果表明,0.01 mg/L菲开始对藻细胞生长产生显著抑制作用,在此浓度下电子自旋共振检测到的自由基信号（g=2.0033,幅宽10.15 mT）显著增强;在浓度设置范围内,超氧化物酶歧化酶、过氧化物酶、谷胱甘肽-S-转移酶活性均被显著诱导,显示出抗氧化系统的应激机制.谷胱甘肽和MDA含量均在0.025 mg/L时被显著诱导.这说明斜生栅藻对菲暴露比较敏感,0.01 mg/L即已显示胁迫效应,自由基的诱导是斜生栅藻产生损伤的重要原因,藻细胞的生长量是比较敏感的损伤指标.

Characteristics and source identification of the dissolved organic matter in the lakes of west Jiangsu by spectroscopy

The composition and origin of the dissolved organic matter(DOM) in some lakes of west Jiangsu was investigated using UV-Vis absorbance and fluorescence spectroscopy.The specific ultraviolet absorption(SUVA) at 254 nm and 280 nm indicated that the aromaticity and molecular weight of DOM ranked in the order of Lake Shaobo,Lake Tiangang,Lake Baima,Lake Shijiu,Lake Hongze,Lake Gucheng,Lake Luoma,Lake Gaoyou and Lake Baoying.The E2/E3 and E3/E4 values suggested that the DOM of Lake Shaobo and Lake Baima was structural complex with humic acid being the primary component,while other lakes DOM was less complex and constituted mostly by fulvic acid.The exponential slope parameter(S275-295nm) values results were consistent with the conclusion obtained from SUVA,E2/E3 and E3/E4.Fluorescence indexes and biological index of these lakes DOM were ranged of 1.13-1.30,0.47-0.67,respectively,suggesting DOM a strong terrestrial origin.Significant correlation was found between the fluorescence intensities per unit organic carbon at different peaks,which indicated that the humic-like and protein-like materials in these lakes have a similar source.Considered the characterization of these lakes and the economic development,it can be deduced that most of these DOM are produced by agriculture and its downstream industries and imported with inflow rivers.

Growth inhibition and recovery from low oxidation reduction potential to Microcystis aeruginosa

In this experiment,cysteine was used as an Oxidation Reduction Potential(ORP) adjustment to explore the responses of Microcystis aeruginosa(FACHB 469) under different ORPs stimulation.A recovery experiment was also designed with M.aeruginosa separated from the former experiment and cultured in fresh medium.Results showed a negative effect of low ORP stimulation on the growth of M.aeruginosa.Within the range of-50 to-100 mV,inhibition effect was intensified with the ORPs decline.The uptake rate of phosphorus decreased under low ORPs stress but had no relationship with stress strength.A proper low ORPs stimulation(e.g.-50 and-75 mV) could intensify the SOD enzyme activity of M.aeruginosa,while over low(e.g.-90 and-100 mV) had negative effects.M.aeruginosa could recover its growing ability after removing the lower ORPs stimulation.The uptake rate of phosphorus and the SOD enzyme activity returned to normal as well.Moreover,the enhancement of growth ability was observed by a low ORPs stimulation(e.g.-50 and-75 mV).Thus,the low ORPs stimulation had negative effect on the growth of M.aeruginosa,however the process can be reversible.In this experiment,cysteine was used as an Oxidation Reduction Potential(ORP) adjustment to explore the responses of Microcystis aeruginosa(FACHB 469) under different ORPs stimulation.A recovery experiment was also designed with M.aeruginosa separated from the former experiment and cultured in fresh medium.Results showed a negative effect of low ORP stimulation on the growth of M.aeruginosa.Within the range of-50 to-100 mV,inhibition effect was intensified with the ORPs decline.The uptake rate of phosphorus decreased under low ORPs stress but had no relationship with stress strength.A proper low ORPs stimulation(e.g.-50 and-75 mV) could intensify the SOD enzyme activity of M.aeruginosa,while over low(e.g.-90 and-100 mV) had negative effects.M.aeruginosa could recover its growing ability after removing the lower ORPs stimulation.The uptake rate of phosphorus and the SOD enzyme activity returned to normal as well.Moreover,the enhancement of growth ability was observed by a low ORPs stimulation(e.g.-50 and-75 mV).Thus,the low ORPs stimulation had negative effect on the growth of M.aeruginosa,however the process can be reversible.