典型湖泊有机聚集体时空特征及驱动因子

有机聚集体(OA)是水体中物质循环和能量流通的重要枢纽,但在不同营养水平湖泊中的比较研究仍相当匮乏.于2019～2021年间,采集了不同季节贫营养抚仙湖、中营养天目湖、中度富营养太湖和重度富营养星云湖表层水样,利用扫描电镜、表面荧光显微镜和流式细胞仪等研究了4个典型湖泊中OA及其附着细菌的时空变化特征.结果表明：(1)抚仙湖、天目湖、太湖和星云湖中,OA丰度的年均值分别为1.4×10⁴、 7.0×10⁴、 27.7×10⁴和16.0×10⁴ind·mL^-1; OA附着细菌丰度的年均值分别为0.3×10⁶、 1.9×10⁶、 4.9×10⁶和6.2×10⁶ cells·mL^-1;附着细菌占总细菌的比值分别为30%、 31%、 50%和38%.(2)夏季OA丰度显著高于秋冬季;但夏季附着细菌占总细菌的比值为26%,显著低于其它3个季节.(3)湖泊营养状态是影响OA及其附着细...     

Selection of water source for water transfer based on algal growth potential to prevent algal blooms

Water transfer is becoming a popular method for solving the problems of water quality deterioration and water level drawdown in lakes. However, the principle of choosing water sources for water transfer projects has mainly been based on the effects on water quality, which neglects the influence in the variation of phytoplankton community and the risk of algal blooms. In this study, algal growth potential (AGP) test was applied to predict changes in the phytoplankton community caused by water transfer projects. The feasibility of proposed water transfer sources (Baqing River and Jinsha River) was assessed through the changes in both water quality and phytoplankton community in Chenghai Lake, Southwest China. The results showed that the concentration of total nitrogen (TN) and total phosphorus (TP) in Chenghai Lake could be decreased to 0.52 mg/L and 0.02 mg/L respectively with the simulated water transfer source of Jinsha River. The algal cell density could be reduced by 60%, and the phytoplankton community would become relatively stable with the Jinsha River water transfer project, and the dominant species of Anabaena cylindrica evolved into Anabaenopsis arnoldii due to the species competition. However, the risk of algal blooms would be increased after the Baqing River water transfer project even with the improved water quality. Algae gained faster proliferation with the same dominant species in water transfer source. Therefore, water transfer projects should be assessed from not only the variation of water quality but also the risk of algal blooms.     

白鲢罗非鱼对微囊藻毒素急性、亚急性毒性响应

为了探究不同控藻鱼类对产毒微囊藻的适应机制,为生物操纵的鱼种选择提供依据,研究了白鲢和罗非鱼对微囊藻毒素（MC）的生物富集、降解,及两种鱼对毒素的抗性、解毒机制的差异性.结果发现：在喂食微囊藻实验中,白鲢、罗非鱼对MC日摄入量达到10mg/kg,2种鱼均对MC有较强抗性.微囊藻经鱼摄入后,MC总含量在白鲢、罗非鱼粪便中分别下降到71.5%、6.0%,罗非鱼对MC降解能力远高于白鲢.白鲢和罗非鱼的肝系数分别从（1.19±0.21）%、（2.24±0.19）%下降到（0.79±0.06）%、（1.72±0.07）%,均表现出显著差异性下降（P<0.05）.微囊藻毒素在白鲢、罗非鱼肌肉中积累量分别为（1.57±0.31）μg/kg、（10.81±6.52）μg/kg （鲜重）、肝脏中积累量分别为（4.28±1.64）mg/kg、（2.48±0.15）mg/kg （鲜重）.MC在白鲢、罗非鱼肌肉、肝脏中的积累量均存在显著差异性（P<0.05）.罗非鱼肌肉中毒素含量是白鲢的6.9倍.在微囊藻毒素LR （MC-LR）对白鲢和罗非鱼的急性毒性效应实验中,MC-LR对白鲢、罗非鱼的LD₅₀为270和790μg/kg,罗非鱼对毒素有更强耐受性.喂食毒藻和i.p.注射MC均导致白鲢和罗非鱼肝细胞内脂滴大量出现.2种鱼在MC-LR注射后,谷胱甘肽（GSH）含量均表现出6h内明显下降.6h后两种鱼GSH含量均逐步回升,二者差异显著（p<0.05）.实验结果表明,罗非鱼对MC降解能力远高于白鲢.白鲢主要摄食群体微囊藻的群体胶鞘和附着细菌,胞内微囊藻毒素释放量小,白鲢这种摄食机制导致它能以产毒微囊藻为食而受到较轻危害.罗非鱼体内消化酶对微囊藻和MC具较强的消化降解能力;GSH含量及相关酶活性水平高,对体内毒素清除效率高.从食用安全性角度出发,与罗非鱼相比,白鲢是更适合用于控制蓝藻水华的鱼种,可广泛应用于蓝藻水华控制中.     

蓝藻腐解对水中营养盐影响的模拟研究

为研究不同密度藻类腐解过程对水体营养盐再分配的影响,在太湖藻类聚集区采集沉积物柱状样进行室内加藻模拟实验,共设置B、C、D 3组加藻密度分别为2500、7500和15000 g·m-2的处理组,监测蓝藻腐解过程中上覆水体的溶解氧(DO)、氧化还原电位(Eh)、氨氮(NH_4~+-N)、总氮(TN)及总磷(TP)等理化指标的变化情况.结果表明,蓝藻腐解会使水体DO和Eh迅速下降,最终分别维持在0.1 mg·L~(-1)左右和-300~-400 mV之间,水体处于厌氧强还原状态;同时,厌氧强还原条件又加速了蓝藻死亡腐解过程,促进了藻体营养盐向上覆水的扩散,B、C、D组营养盐含量分别于实验第6、第10和第14 d达到峰值,TN平均增长速率分别为26.67、43.41和67.82 mg·L~(-1)·d~(-1),TP平均增长速率分别为3.30、5.53和8.35 mg·L~(-1)·d~(-1),NH_4~+-N浓度最大值分别为对照组的7、51、125倍,水体形成明显的氮磷污染负荷,且蓝藻衰亡导致的上覆水TN浓度升高持续时间较TP浓度升高持续时间要长.研究表明,蓝藻水华腐解过程中向上覆水体释放了大量的有机物和可溶性营养盐,降低了水体透明度,加剧了水体富营养化状况,诱发湖泛发生,也为蓝藻水华再次爆发提供了物质基础.     

不同营养水平下沉水植物的抑藻效应

控制水体的营养盐浓度,尤其是磷浓度,可以控制藻类水华的发生.然而,经济成本很高.相对藻类而言,沉水植物对水体营养盐升高敏感性更低,且沉水植物的存在可以改变藻类的群落结构和生长速率.为探讨沉水植物在营养盐与蓝藻水华控制关系中的作用,本研究探讨了有无水生植物存在下,不同营养盐浓度(磷浓度分别为0.025、0.05、0.1 mg·L~(-1),对应地表水Ⅲ～Ⅴ类)下蓝藻水华暴发(chlorophyll-a10μg·L~(-1))的频率、强度和持续时间.结果表明,初始藻浓度为5μg·L~(-1)和10μg·L~(-1)情况下,3种磷浓度下都会发生水华,磷浓度的升高会导致蓝藻水华暴发的强度和持续时间增加.然而,在加入水生植物金鱼藻后,初始藻浓度为5μg·L~(-1)的条件下,没有形成水华.初始藻浓度为10μg·L~(-1)的条件下,各处理组在实验初始时会形成短暂水华,之后,各处理组的叶绿素a浓度均低于10μg·L~(-1),显示蓝藻生长受到抑制.因此,沉水植物存在情况下,在营养盐较高的水体,蓝藻水华也不会发生.     

Macroalgal growth in nutrient-enriched estuaries: A biogeochemical and evolutionary perspective

Increased nutrient loading of a body of water leads to an increase in macroalgal growth. It is generally observed, however, that certain species thrive more than others, capitalising on the increased nutrient availability. These are usually small, fast-growing, ephemeral algae that often appear as nuisance blooms. This article discusses the correlation between nutrient increase and macroalgal bloom formation. From a historical perspective, the evolutionary history of nuisance macroalgae, and the habits available to them prior to anthropogenic influences on estuarine geochemistry are considered. The occurrence of macroalgal genera whose distribution is commonly related to estuaries with high nutrient loading is discussed, along with evidence suggesting that the ecophysiological traits of r-selected, ephemeral algae largely contribute to their ecological success and bloom-formation at nutrient-enriched sites.     

四斗朱水库蓝藻水华爆发成因分析及治理对策研究

作为饮用水源的小型水库四斗朱连续几年在早春即开始爆发严重束丝藻水华（属于蓝藻）。水质分析发现,四斗朱水库的水质参数如总氮（TN）、总磷（TP）、氨氮（NH4^＋-N）以及BOD和COD浓度并不高,但明显高于其上游的石门塘水库,这说明在四斗朱水库的集水区存在污染源。本文分析了在低营养盐浓度情况下四斗朱水库蓝藻水华爆发的原因,认为由于集水区内的农业、生活、水土淋失以及自然沉降等途径导致水库营养浓度升高。并由于未知营养、气温回升以及水库生态系统失衡等因素,导致蓝藻水华暴发。最后,提出了相应的综合治理对策。     

Seasonal variation of Microcystis in Lake Taihu and its relationships with environmental factors

In order to monitor the changes of Microcystis along with temporal and spatial variations, seasonal variation of Microcystis in Lake Taihu was investigated by 16S-23S rRNA internal transcribed spacer denaturing gradient gel electrophoresis (16S-23S rRNA-ITS DGGE) and microscopic evaluation. Samples were collected quarterly at four sites (River Mouth, Meiliang Bay, Cross Area, and Lake Center) from August 2006 to April 2007. Results showed that Microcystis dominated total phytoplankton abundance at the four sites in all seasons except winter. The average annual abundance of Microcystis was relatively high at River Mouth and Meiliang Bay, reaching 81.22×106 and 61.32×106 cells/L, respectively. For temporal variations, Shannon-Wiener diversity index (H') according to DGGE profile revealed the richness of Microcystis in summer (H'=1.375±0.034) and winter (H'=1.650±0.032) was lower than that in spring (H'=2.078±0.031) and autumn (H'=2.365±0.032) (P<0.05). While for spatial variations, the richness of Microcystis at River Mouth (H'=2.015±0.074) was higher than at other sites during four seasons (P<0.01). Very few differences of Microcystis diversity in the same season were observed among the other three sites (P>0.05). Canonical correspondence analysis (CCA) was performed to elucidate the relationships between Microcystis operational taxonomic units (OTUs) composition and the environmental factors. Results of CCA revealed that temperature was strongly positively correlated with the first axis (r=0.963), while TSS was negative correlated with the second axis (r=-0.716). Phylogenetic tree based on the sequencing results of target bands on DGGE gel indicated that samples collected in summer and winter constituted two separated clusters.     

Cyanobacteria-/cyanotoxin-contaminations and eutrophication status before Wuxi Drinking Water Crisis in Lake Taihu, China

After the appalling “Wuxi DrinkingWater Crisis”, increasing investigations concerning the contaminations of cyanobacterial blooms and their toxins in Lake Taihu have been performed and reported in the last two years. However, information regarding these issues before the crisis in 2007 remained insu cient. To provide some background data for further comparisons, the present study reported our investigations conducted in 2004, associated with the cyanotoxin contaminations as well as the eutrophication status in Lake Taihu. Results from the one-year-study near a drinking water resource for Wuxi City indicated that, unlike the status in recent two years, cyanobacteria and chlorophyta are the co-dominance species throughout the year. The highest toxin concentration (34.2 ng/mL) in water columns occurred in August. In bloom biomass, the peak value of intracellular toxin (0.59 g/mg DW) was determined in October, which was lag behind that in water column. In addition, MC-RR was the major toxin variant throughout the year. During the study period, nutrients levels of total nitrogen and phosphorus were also recorded monthly. Results from the present study will lead to a better understanding of the eutrophication status and the potential risks before “Wuxi Drinking Water Crisis”.     

环境因子对水华暴发的影响研究

水华是当水体藻类开始大量生长和繁殖并且聚集,最终达到一定浓度的现象。综述国内大型浅水湖泊及水库中影响水华暴发的环境因素的研究现状,分析水体营养条件以及适宜的气象、水文、生物条件等有利于藻类生长或聚集的环境影响因子,同时简介中国水华污染现状。对水华暴发研究领域的未来发展具有一定参考价值。