光照、温度和营养盐对滇池微囊藻生长的影响

研究了光照、温度与营养盐对滇地铜绿微囊藻（Ｍｉｃｒｏｃｙｓｔｉｓａｅｒｕｇｉｎｏｓａ）生长的影响。实验表明，在５００～５０００ｌｘ光强范围内，随光强增加，比增殖速率加大；在２２～３５℃区间内，比增殖速率随温度的升高而增加，且温度的影响大于光照；氮磷比（Ｎ／Ｐ）值在５～１０范围内，比增殖速率变化较大，Ｎ／Ｐ值为１４．５时，比增殖速率达最大值。滇池湖水的氮磷比值为１４．４左右，与实验值相接近。根据实验结果及限制因子的定义，总体上讲，滇池中磷是藻类生长的主要限制因子，控制滇池富营养化应以控制磷为主。     

细菌产绿脓菌素对东海原甲藻生长的影响

以东海原甲藻(Prorocentrumdonghaiense)为实验材料,研究了铜绿假单胞菌(Pseudomonasaeruginosa)产绿脓菌素对藻细胞生长的影响。结果表明,当其浓度达到5.0mg.L-1时,对东海原甲藻的生长表现出明显的抑制效果,并且抑制效果随浓度的增加而增强。对裸甲藻而言,当其浓度增加至15.0mg.L-1时,裸甲藻的生长才开始受到较明显的抑制。8.0和15.0mg.L-1的绿脓菌素在实验初期对湛江叉鞭金藻的生长表现出了一定的抑制作用,但这种抑制作用不能持久。对绿藻而言,即使浓度增加至15.0mg.L-1,绿藻的生长受其影响也很弱。本文首次探讨了细菌产绿脓菌素对东海原甲藻的抑制作用,结果表明该类物质可以选择性的抑制东海原甲藻的生长。     

铜绿微囊藻、四尾栅藻和小环藻竞争实验培养基的选择

改变培养基的氮源形态和碳源浓度,研究铜绿微囊藻、小环藻和四尾栅藻的单藻增长行为,筛选适宜的培养基作为混藻竞争实验的共培养基。研究表明,铜绿微囊藻和四尾栅藻在氨氮培养基中的最大生物量K和最大比增长速率r均不及以硝态氮为氮源的培养基;添加高浓度HCO3-(NaHCO3 1.410 mmol/L)能够提高铜绿微囊藻和四尾栅藻藻细胞对氨氮的吸收能力;较低碳源浓度(NaCO3 0.0943 mmol/L)的培养基中,四尾栅藻的初始比增长速率及生物量远高于铜绿微囊藻,但其最大比增长速率r低于铜绿微囊藻,在实验的第10天左右铜绿微囊藻的生物量超过四尾栅藻;小环藻不能在较高浓度碳源(NaHCO3 1.504 mmol/L)下存活;铜绿微囊藻、四尾栅藻与小环藻均可在以氨氮(HA)或硝态氮(HN)为氮源的培养基中单独培养并达到实验所需生物量,因此,HN和HA可以作为实验室内这三种藻共培养适宜的培养基,为今后研究藻类种间资源竞争机制提供实验依据。     

不同质量浓度的磷对铜绿微囊藻生长及细胞内磷的影响

通过室内模拟的方法研究了在磷质量浓度不同的水体条件下,在铜绿微囊藻水华形成过程中微囊藻的增殖特征及细胞内磷、可溶性磷的变化特征.在模拟的太湖水体中,随着外源磷的增加,藻生长最终限制因素由磷限制(ρ(TP)≤0.045 mg/L)发展到光限制(ρ(TP)≥0.445 mg/L),而ρ(TP)=0.445 mg/L是微囊藻最适生长浓度;同时,微囊藻细胞内磷含量(QP)、水体可溶性磷(DTP)也随藻类生长而发生变化,在水体ρ(TP)＜0.445mg/L时,细胞内磷对微囊藻增殖有促进作用,而在ρ(TP)＞0.445 mg/L的水体中,磷对微囊藻增殖有抑制作用.     

暗光缺氧条件下微囊藻的存活及胞内物质释放

蓝藻水华爆发期间,沉降至底泥-水界面的蓝藻会面临暗光缺氧胁迫.为研究沉降蓝藻的存活及释放物,模拟暗光缺氧条件,利用不同生长期的微囊藻进行了一系列的实验.结果表明,微囊藻可以在暗光缺氧条件下存活至少6d,释放的溶解性有机碳达到1.86mg C/mg Chl a.不同生长期对微囊藻的存活和释放物产生影响,其中培养55d的微囊藻存活时间最长,培养28d的微囊藻溶解性有机碳的释放量最高.本研究证实暗光缺氧条件下,微囊藻能够存活一段时间并释放有机碳,且存活时间和有机碳释放量与微囊藻生长期相关.     

藻类光竞争模型构建及水体紊动对竞争的影响

光是藻类进行光合作用的重要能量来源,决定藻类的初始生产力,当多种浮游藻类共同生存时,会一起竞争光强.光竞争能力强的浮游藻类浓度增加,光竞争能力较弱的则减少,从而完成水体中浮游藻类优势藻的替代.本文通过在以往建立的单藻模型的基础上,耦合入竞争模型,构建两种（多种）浮游藻类光竞争模型,尝试通过数值模拟,研究不同水体紊动中竞争藻属分别取得竞争优势的机理.模拟结果表明：稳态水体中,竞争藻属的自身垂向迁移决定藻浓度的垂向分布,具有浮力调节能力的微囊藻属占据上层水体优势地位,并取得竞争优势;动态水体中,竞争藻属垂向分布均较为均匀,生长速率决定藻的竞争优势,小球藻属生长速率快,最终易取得竞争优势.此外,考虑浮游藻属的动态自遮蔽,会加速稳态水体中微囊藻属取得竞争优势,并限制动态水体中小球藻属的无限制生长,使得模拟结果更加符合实际情况.     

Effects of cyanobacteria producing microcystins on seed germination and seedling growth of several agricultural plants

The effects of cyanobacteria aqueous extracts containing Microcystin-LR (MC-LR) on the seed germination and growth of Pisum sativum, Lens esculenta, Zea mays and Triticum durum were investigated. Experiments were carried out on a range of doses of the extract (equivalent to 0, 1.6, 2.9, 5.8, 8.7 and 11.6 μ g MC-LR/mL). The results confirm that these plants were sensitive to cell-free extracts of a toxic Microcystis and that germination inhibition was dose dependent. One-way analysis of variance (ANOVA) showed that P. sativum is the most sensitive tested species with a 97% germination rate reduction and L. esculenta was the most resistant. At the 8th day, the exposure to the microcystins (MC) resulted in a significant decrease of plant epicotyls length, roots length and a net inhibition of lateral root formation. It is concluded that MC could affect also terrestrial plants seedling germination and growth. Therefore, the use of water for irrigation contaminated by MC could exert negative biochemical effects on seed and plant metabolism which might influence the agricultural crops.     

凤眼莲对铜绿微囊藻生长及藻毒素与营养盐释放的影响

针对目前我国凤眼莲治理富营养化水体技术的规模化应用现状,考虑到大面积控养的凤眼莲与暴发的水华蓝藻(尤其是产毒铜绿微囊藻)会在湖湾区短期内密集共存的情况,开展了凤眼莲对产毒铜绿微囊藻生长、生理特性、藻毒素生产与释放影响的研究,另外,也考察了短期共存下藻类营养盐释放与凤眼莲对藻毒素积累的情况.半连续共培养实验结果表明,凤眼莲能够有效抑制铜绿微囊藻的生长,促进藻细胞的衰亡.虽然凤眼莲未对铜绿微囊藻光合系统Ⅱ的电子传递产生影响,但减少了其光合系统中的藻蓝蛋白(PC)含量和藻蓝蛋白/别藻蓝蛋白(PC/APC)水平,10%和20%水体交换率处理的PC/APC水平第8 d时分别降至相应空白对照的54.93%±7.07%和55.81%±1.97%.凤眼莲对铜绿微囊藻形成了一定的氧化伤害,最终促进其抗氧化系统中超氧化物歧化酶比活显著下降,丙二醛含量显著提高,10%和20%水体交换率处理的丙二醛含量第8d时分别升至相应空白对照的2.95倍±0.074倍和2.22倍±0.086倍.凤眼莲通过促进蓝藻的衰亡和分解,加速了营养盐的释放.12 d内,可溶性总氮浓度回升到初始水平,而水体可溶性总磷的释放速度比氮营养盐更快.另一方面,凤眼莲并没有促进铜绿微囊藻毒素的生产,也没有使水体藻毒素含量显著提高.相反,和自然衰减不同,短期内显著促进了水体藻毒素的降解,第12 d时10%和20%水体交换率处理的水体藻毒素分别下降至12.07μg·L-1±0.63μg·L-1和11.36μg·L-1±0.04μg·L-1.而凤眼莲整株的藻毒素短期积累量(FW)仅为5.95 ng·g-1±0.76 ng·g-1.增加水体交换率能够在一定程度上减缓凤眼莲对铜绿微囊藻的伤害,减缓营养盐的释放速度,但对水体藻毒素消减的影响不显著.     

Growth and phosphate uptake kinetics of Microcystis aeruginosa under various environmental conditions

Growth and uptake of exogenous phosphate by Microcystis aeruginosa in batch culture under different temperature, photoperiod, and turbulence were studied by the method of phosphate isotope tracer. Relatively high temperature, long photoperiod and strong turbulence increased the cell density of M. aeruginosa in these batch cultures. The initial rapid uptake of phosphate by M. aeruginosa was independent of the temperature, photoperiod, and turbulence. Similarly, maximum exogenous phosphate uptake was not related to these environmental factors. However, elevated temperature and turbulence shortened the time, required to obtain maximum P accumulation. The growth of M. aeruginosa could alleviate the phosphorous leakage. Total amounts of exogenous phosphate uptake to M. aeruginosa and the phosphorus leakage of M. aeruginosa were significantly influenced by the growth state of M. aeruginosa closely correlated with the environmental factors. The maximum volume of exogenous phosphate uptake to M. aeruginosa was 46% of added exogenous phosphate in water with 16 hours of photoperiod. Thus, total amounts of exogenous phosphate uptake to M. aeruginosa were more strongly affected by the photoperiod length than temperature and turbulence.     

Experimental study on Cr(Ⅵ) reduction by Pseudomonas aeruginosa

Investigation on Cr(Ⅵ) reduction was conducted using Pseudomonas aeruginosa. The study demonstrated that the Cr(Ⅵ) can be effectively reduced to Cr(Ⅲ) by Pseudomonas aeruginosa. The effects of the factors affecting Cr(Ⅵ) reduction rate including carbon source type, pH, initial Cr(Ⅵ) concentration and amount of cells inoculum were thoroughly studied. Malate was found to yield maximum biotransformation, followed by succinate and glucose, with the reduction rate of 60.86%, 43.76% and 28.86% respectively. The optimum pH for Cr(Ⅵ) reduction was 7.0, with reduction efficiency of 61.71% being achieved. With the increase of initial Cr(Ⅵ) concentration, the rate of Cr(Ⅵ) reduction decreased. The reduction was inhibited strongly when the initial Cr(Ⅵ) concentration increased to 157 mg/L. As the amount of cells inoculum increased, the rate of Cr(Ⅵ) reduction also increased. The mechanism of Cr(Ⅵ) reduction and final products were also analysed. The results suggested that the soluble enzymes appear to be responsible for Cr(Ⅵ) reduction by Pseudomonas aeruginosa, and the reduced Cr(Ⅲ) was not precipitated in the form of Cr(OH)3.