Variation of cyanobacteria with different environmental conditions in Nansi Lake, China

Nansi Lake is located on the east line of the South-to-North Water Diversion Project in China. A comprehensive study was carried out to investigate the spatial and temporal distribution of cyanobacteria in the lake from June 2008 to May 2011 based on monthly sample monitoring from five stations. The effect of environmental factors on cyanobacterial abundance was also evaluated. The cyanobacterial community contained 15 genera and 23 species. The cyanobacterial abundance of each monitoring station ranged from 0 to 1.53× 10⁷ cells/L with an average of 1.45×10⁶ cells/L, which accounted for 11.66% of the total phytoplankton abundance. The dominant species of cyanobacteria were Pseudanabaena (32.94%) and Merismopedia (19.85%), not the bloom-forming algae such as Microcystis and Anabaena. In addition, the cyanobacterial community structure and water quality variables changed substantially over the survey period. Redundancy analysis (RDA) suggested that temperature and phosphorus were important environmental factors that affected cyanobacteria. Temperature was the most important factor affecting cyanobacterial abundance. The effect of phosphorus on cyanobacterial abundance was more notable in warm periods than in periods with low temperature.     

Spatial and temporal distribution of cyanobacteria in Batticaloa Lagoon

The necessity to understand the relationship between cyanobacterial species abundance and water quality variations in coastal lagoons is crucial to develop strategies to prevent further cyanobacterial proliferation. This paper evaluates the relationship between water quality variations on the distribution of cyanobacteria during a 12-month period in Batticaloa Lagoon (Sri Lanka) using Redundancy analysis and Pearson correlations. Drastic variations in pH, temperature, salinity, dissolved oxygen (DO) and total phosphorus (TP) levels were reported, but not turbidity and NO₃⁻. This brackish waterbody is hypereutrophic (TP levels > 0.1 mg/L). The cyanobacterial community contained 13 genera and 22 species. NO₃⁻, TP and turbidity levels positively influenced cyanobacterial abundance during all seasons indicating that nutrient (largely phosphorus) and sediment entry control is highly crucial along with periodic monitoring of cyanobacterial growth.     

风场对太湖梅梁湾水华及营养盐空间分布的影响

为了解风场对湖泊表层蓝藻水华及营养盐空间分布的影响,以太湖梅梁湾为例,在蓝藻水华期间开展表层粒子漂流实验,研究风场对水体表层物质的推移规律,并开展全水域水体表、中、底层密集布点采样,测定水体藻类叶绿素a、氮、磷、高锰酸盐指数、溶解性有机碳、溶解氧等水质指标,探讨风场驱动下大型浅水湖泊蓝藻水华及营养盐时空分布特征.结果表明,在平均风速1. 9 m·s~(-1)和2. 3 m·s~(-1)的情况下,表层粒子的平均漂移速度分别为3. 0 cm·s~(-1)和5. 0 cm·s~(-1);风场对表层水体蓝藻水华的空间分布具有决定性影响,能够引起蓝藻水华在空间上较高的异质性;蓝藻水华物质的空间变化对水体颗粒态氮、磷、有机质和溶解氧等水质指标产生较大影响,表、中、底层颗粒态氮和磷、高锰酸盐指数与叶绿素a浓度的空间分布一致,而溶解态氮、磷浓度及溶解性有机碳的分布与叶绿素a浓度分布不尽相同;蓝藻水华物质在风场作用下的再分配对水体溶解氧产生复杂的影响,底层溶解氧平均值低于表层与中层,可能对沉积物营养盐释放产生影响;依据高密度布点调查估算,仅表层20 cm,梅梁湾水域的蓝藻干物质赋存量约396 t,远大于蓝藻打捞工程的清除量.研究表明,鉴于水华期间风场作用下对蓝藻水华漂移的巨大影响,在湖泊水质调查采样方法及数据分析时应充分考虑蓝藻水华漂移的影响因素;防控湖泛灾害的蓝藻打捞作业对湖体蓝藻水华赋存量的清除能力有限,只能对岸边带湖泛的预防产生影响.     

Environmental factors influencing cyanobacteria community structure in Dongping Lake, China

The present study was conducted to provide a detailed understanding of the variation in cyanobacterial communities of Dongping Lake, which is the final water volume adjusting and storing lake in the east route of the South-to-North Water Diversion Project in China. The spatial and temporal distribution of cyanobacteria was assessed from May 2010 to October 2012 based on monthly samples collected from three stations. Over the 30-month survey, 15 genera and 25 species of cyanobacteria were identified, with cyanobacterial abundance at each monitoring station ranging from undetected to 3.04×107 cells/L, average of 4.27×106 cells/L. The dominant cyanobacterial species were Pseudanabaena limnetica and Aphanizomenon issatschenkoi and not the usual bloom-forming genera such as Microcystis and Anabaena. Cyanobacterial community structure and water quality variables exhibited substantial changes over the period of survey. Redundancy analysis, Pearson correlations, and regression analysis were applied to analyze the relationships among the variables. The results suggested that temperature and chemical oxygen demand were key drivers of the cyanobacterial community composition in Dongping Lake. In addition, the concentration of inorganic nitrogen in the lake had a profound efect on the cyanobacterial abundance as a non-limiting factor in warm periods.     

Use of Fe/Al drinking water treatment residuals as amendments for enhancing the retention capacity of glyphosate in agricultural soils

Fe/Al drinking water treatment residuals (WTRs), ubiquitous and non-hazardous by-products of drinking water purification, are cost-effective adsorbents for glyphosate. Given that repeated glyphosate applications could significantly decrease glyphosate retention by soils and that the adsorbed glyphosate is potentially mobile, high sorption capacity and stability of glyphosate in agricultural soils are needed to prevent pollution of water by glyphosate. Therefore, we investigated the feasibility of reusing Fe/Al WTR as a soil amendment to enhance the retention capacity of glyphosate in two agricultural soils. The results of batch experiments showed that the Fe/Al WTR amendment significantly enhanced the glyphosate sorption capacity of both soils (p < 0.001). Up to 30% of the previously adsorbed glyphosate desorbed from the non-amended soils, and the Fe/Al WTR amendment effectively decreased the proportion of glyphosate desorbed. Fractionation analyses further demonstrated that glyphosate adsorbed to non-amended soils was primarily retained in the readily labile fraction (NaHCO₃-glyphosate). The WTR amendment significantly increased the relative proportion of the moderately labile fraction (HCl-glyphosate) and concomitantly reduced that of the NaHCO₃-glyphosate, hence reducing the potential for the release of soil-adsorbed glyphosate into the aqueous phase. Furthermore, Fe/Al WTR amendment minimized the inhibitory effect of increasing solution pH on glyphosate sorption by soils and mitigated the effects of increasing solution ionic strength. The present results indicate that Fe/Al WTR is suitable for use as a soil amendment to prevent glyphosate pollution of aquatic ecosystems by enhancing the glyphosate retention capacity in soils.     

模拟自然水体中藻-溞-草间的相互作用研究

为了解氮磷浓度对生物操纵效果及同时恢复水生植被的影响,以小球藻、大型溞和金鱼藻分别作为浮游植物、浮游动物和大型沉水植物的代表,模拟自然条件研究了不同氮磷浓度对三者生长和相互作用的影响.结果表明:金鱼藻和小球藻共培养时,在氮浓度介于2.92～12.60mg·L-1、磷浓度介于0.06 ～0.85 mg·L-1,金鱼藻增长不明显,甚至出现负增长;而小球藻的增长率则远高于金鱼藻.小球藻和大型溞共培养时,氮、磷浓度分别为1.26～ 10.53 mg·L-1和0.04～1.16 mg·L-1时均占据优势,对小球藻的抑制效果显著,抑藻及氮磷去除效果明显好于金鱼藻和小球藻共培养,而且磷的去除效果优于氮.三者共培养时,在氮浓度介于3.15 ～23.92 mg·L-1、磷浓度介于0.07 ～0.64 mg·L-1时,大型溞与金鱼藻的增长率都较高,而小球藻则维持在较低的增长水平,水质改善效果较好;当氮、磷浓度分别升至25.95 mg·L-1和1.18 mg·L-1时,大型潘和金鱼藻的增长率均下降,水质变差.大型溞和金鱼藻的联合控藻效果好于其单一的控制效果,该效果明显受到氮磷浓度的影响.     

Isolation, identification and characterization of an algicidal bacterium from Lake Taihu and preliminary studies on its algicidal compounds

In an effort to identify a bio-agent capable of controlling cyanobacterial blooms, we isolated a bacterial strain, A27, which exhibited strong algicidal activity against the dominant bloom-forming species of Microcystis aeruginosa in Lake Taihu. Based on 16S rRNA gene sequence analysis, this strain belongs to the genus Exiguobacterium. This is the first report of an algicidal bacterial strain belonging to the genus Exiguobacterium. Strain A27 exhibited algicidal activity against a broad range of cyanobacteria, but elicited little or no algicidal activity against the two green algal strains tested. The algicidal activity of strain A27 was shown to be dependent on the density of the bacteria and to have a threshold density of 1.5× 10⁶ CFU/mL. Our data also showed that the algicidal activity of strain A27 depended on different growth stages of Microcystis aeruginosa (exponential ≈ lag phase > early stationary) rather than that of the bacterium itself. Our results also suggested the algicidal activity of strain A27 occurred via the production of extracellular algicidal compounds. Investigation of the algicidal compounds revealed that there were at least two different algicidal compounds produced by strain A27. These results indicated that strain A27 has great potential for use in the control of outbreaks of cyanobacterial blooms in Lake Taihu.     

Electrochemical inactivation of cyanobacteria and microcystin degradation using a boron-doped diamond anode——A potential tool for cyanobacterial bloom control

Cyanobacterial blooms are global phenomena that can occur in calm and nutrient-rich(eutrophic) fresh and marine waters. Human exposure to cyanobacteria and their biologically active products is possible during water sports and various water activities, or by ingestion of contaminated water. Although the vast majority of harmful cyanobacterial products are confined to the interior of the cells, these are eventually released into the surrounding water following natural or artificially induced cell death. Electrochemical oxidation has been used here to damage cyanobacteria to halt their proliferation, and for microcystin degradation under in-vitro conditions. Partially spent Jaworski growth medium with no addition of supporting electrolytes was used. Electrochemical treatment resulted in the cyanobacterial loss of cell-buoyancy regulation, cell proliferation arrest, and eventual cell death. Microcystin degradation was studied separately in two basic modes of treatment: batch-wise flow, and constant flow, for electrolytic-cell exposure. Batch-wise exposure simulates treatment under environmental conditions, while constant flow is more appropriate for the study of boron-doped diamond electrode efficacy under laboratory conditions. The effectiveness of microcystin degradation was established using high-performance liquid chromatography–photodiode array detector analysis, while the biological activities of the products were estimated using a colorimetric protein phosphatase-1 inhibition assay. The results indicate potential for the application of electro-oxidation methods for the control of bloom events by taking advantage of specific intrinsic ecological characteristics of bloom-forming cyanobacteria. The applicability of the use of boron-doped diamond electrodes in remediation of water exposed to cyanobacteria bloom events is discussed.     

营养盐水平对念珠藻胞外有机物产生的影响

以我国湖泊典型固氮蓝藻发状念珠藻(Nostoc flagelliforme)为研究对象,考察了氮、磷营养盐对发状念珠藻生长特性及其胞外有机物产生的影响.采用藻细胞浓度计数法表征发状念珠藻生长特性;分别采用溶解性有机碳(DOC)、三维荧光光谱(EEM)和紫外-可见光谱法,从总量和主要物质方面分析了发状念珠藻胞外有机物的产生规律.结果表明,在不同氮、磷营养水平下,发状念珠藻的4个关键生长时期基本相同,氮是控制发状念珠藻生长的关键营养控制要素;氮营养元素浓度的增高,有利于发状念珠藻产生胞外有机物,其产生量逐渐增大,而磷营养元素浓度的增高对胞外有机物产生量贡献较小,氮营养盐是发状念珠藻产生胞外有机物的关键限制因子;通过EEM谱图分析,发状念珠藻胞外有机物主要以类氨基酸类物质和类富里酸物质为主.以磷为控制营养盐时,类富里酸是主要的胞外有机物之一,以氮为控制营养盐时,类富里酸产生量极低;作为主要的胞外有机物,蛋白质和碳水化合物的产生规律显著不同,其中蛋白质含量显著高于碳水化合物含量.