Exopolysaccharide production by four cyanobacterial isolates and preliminary identification of these isolates

Four marine cyanobacterial isolates, named 104, 109, 113 and 115, from marine water off China＇s coast can release a large amount of exopolysaccharide （EPS） to medium. The effects of different components in medium on EPS production by the four isolates were investigated. Under the optimal condition, the EPS released by isolates 104,109, 113 and 115 reached 7.48 g L^-1, 8.33 g L^-1, 18.26 g L^-1, and 6.78 g L^-1 within 14 d,respectively. Based on the conventional identification methods for cyanobacteria,these isolates were assigned to genus Cyanothece.     

红藻石和蓝藻石概念及分类归属的综述和修订

在分析和总结前人对红藻石和蓝藻石研究成果基础上,结合岩石薄片显微镜下观察实例,发现在以往碳酸盐岩颗粒分类中没有红藻石和蓝藻石的合适位置。鉴于红藻石重要的成因意义和造礁作用,有必要明确红藻石的概念和归属。珊瑚藻本身极易钙化,经生物矿化作用最终保存下来的珊瑚藻屑一直放在生物碎屑中,而红藻石是由非固着的珊瑚藻构成的钙质独立结核,因此也可以被划分到生物碎屑中。蓝藻石作为蓝细菌钙化作用的产物,同时鉴于蓝藻石的广泛存在,把钙化蓝细菌形成的核形石命名为蓝藻石,这一重要概念从提出到现在一直被使用。然而蓝绿藻概念已变更为蓝细菌,蓝藻石的形成与藻类无关,显然将其称作蓝菌石更加确切。因此,应将红藻石和蓝藻石分别归为生物碎屑和核形石当中,并用新的术语蓝菌石替代蓝藻石。其意义在于使红藻石和蓝藻石的概念及归属更为规范,并为碳酸盐岩颗粒的深入研究提供有益线索。     

上震旦统灯影组中非叠层石生态系兰细菌白云岩

上震旦统灯影组 2段和 3段是四川盆地主要天然气储层之一。在浅色白云岩地层中富含炭化的黑色非叠层石生态系兰细菌白云岩。它既可发育于沉积期和胶结作用期 ,也可发育于表生成岩作用期。沉积期发育的非叠层石生态系兰细菌白云岩呈纹层状产出或围绕颗粒的四周生长。这类兰细菌白云岩的单层厚度从 1mm到 >10 cm不等 ,其总厚度约占灯影组 2段和 3段的 1/ 10左右 ,有时也呈不连续的黑色小点发育于白色叠层石生态系兰细菌白云岩的叠层石、层纹石中。胶结作用期 ,二或三个世代亮晶胶结物交替发育“充填”孔隙。表生成岩作用期 ,黑色的兰细菌主要呈多世代的线状纹层与白色纤维状白云石组成多世代的间互纹层充填在岩溶溶洞、溶沟以及扩溶的裂隙中。非叠层石生态系兰细菌主要形态有球形、椭球形和棒形 ,偶有蘑菇形及其它形状。群体呈现为串珠状、草丛状、分叉树枝状和类似于火山喷发状等等。群体的古生态表现为向上生长、围绕颗粒向四周发散生长、粘结颗粒 ,或向原生粒间孔隙、次生溶洞、溶沟中心向心生长。对现代兰细菌的降解实验佐证所讨论的非叠层石生态系兰细菌是灯影组中烃源岩之一。     

全球变暖对淡水湖泊浮游植物影响研究进展

全球变暖对湖泊生态系统的影响已经成为近年来湖沼学领域的研究热点.本文首先列举了目前研究全球变暖对淡水湖泊浮游植物影响的常用方法:监测数据分析、时空转换、遥感信息提取、控制实验、模型预测和古湖沼学技术等.研究结果表明气候变暖导致的气温升高、湖泊热力分层提前破坏以及无冰期提前等因素可导致春季物候提前;在全球变暖大背景下浮游植物群落结构正朝着蓝藻占优的方向发展,但是不同地区以及不同物种对全球变暖的响应不一致.在营养盐充足的湖泊中,由于全球变暖延长了浮游植物生长季节等,从而能提高浮游植物初级生产力;但在贫营养湖泊中,浮游植物初级生产力与变暖趋势甚至可能呈负相关.由于生态系统往往是多因子的共同作用,这也使得全球变暖对浮游植物群落的影响效应复杂化,区分各因子的净影响份额是目前研究的一个难点;全球变暖引起的风场改变会促进浅水湖泊中营养盐从底泥的释放,同时也会增加水体中悬浮物的浓度而影响水下光场,因此开展气候变化对再悬浮及浮游植物群落结构的影响可能是将来研究的一个切入点.     

广东省高州水库春季蓝藻水华成因初步探讨

高州水库为广东省茂名市重要的饮用水源地,2009年和2010年春季相继出现蓝藻水华,给居民饮水带来安全隐患.对高州水库2009年和2010年春季水华情况进行分析,结果表明:两年浮游藻类细胞密度最高分别达4.08×107 cel1s/L和1.47 x 108cells/L,其中蓝藻所占比例分别为98.2%和98.7%,优...     

The effect of light on the release of organic compounds by the cyanobacteriumOscillatoria rubescens

The effect of light intensity on the release of dissolved organic carbon during photosynthesis on NaH¹⁴CO₃ was investigated using the phytoplanktonic CyanobacteriumOscillatoria rubescens. The released products were fractionated by molecular size and chemical identifications attempted using combined thin-layer electrophoresis and chromatography, and high pressure liquid chromatography.Within the range of irradiances tested (from 6 to 60 µmole m^–2 sec^–1), though the upper one inhibited photosynthesis ofO. rubescens, light had little effect on the quantity and composition of the excreted products. The released carbon was always lower than 3% of the incorporated carbon, and mainly composed (62 to 86%) by small molecular weight compounds. The prevailing identified compounds were amino acids which represented more than 20% of the excreted carbon. Among organic acids, glycolic acid accounted for less than 2% of the recovered radioactivity. Glucose was the only identified sugar.Abbreviations EOC excreted organic carbon - DOC dissolved organic carbon - PER percent extracellular release - LMW low molecular weight - HMW high molecular weight - AA amino acids - µmoles m^–2 sec^–1 = µEinsteins m^–2 sec^–1     

Phosphorus metabolism in anthropogenically transformed lagoon ecosystems: The Comacchio lagoons (Ferrara, Italy)

Inorganic phosphorus dynamics were investigated with the use of ³²P in the hypertrophic Comacchio lagoons (NE Adriatic) during an extremely dense, quasi-permanent bloom of picocyanobacteria. Concentrations of dissolved inorganic phosphate (DIP) in waters of the blooming lagoons were usually near the detection limit (0.01 μmoles·dm⁻³). DIP uptake rates by microplankton at near-ambient concentrations (0.01 to 0.1 μmoles·dm⁻³) were in the range of 9.6 to 16.1 nmoles P·dm⁻³·min⁻¹, and turnover times were 1.5 to 3 min. The turnover time was >40 h in the eutrophic coastal waters of the adjacent Adriatic Sea. The uptake rate of DIP depended on its initial concentration. In water samples artificially enriched with DIP, the uptake rate rose to its maximum of 0.10 to 0.13 μmoles P·dm⁻³·min⁻¹ (or 6 to 7 μmoles·dm⁻³·h⁻¹) when the initial concentration of DIP was elevated to 10 to 20 μmoles·dm⁻³. The potential capacity of microplankton in the water samples to consume and retain DIP was estimated at 25 μmoles·dm⁻³. Specific features are discussed of phosphorus metabolism in the anthropogenically transformed lagoon ecosystem with an anomalous food web with few animals.     

Abundance and Photosynthetic Characteristics of Trichodesmium spp. Along the Atlantic Barrier Reef at Carrie Bow Cay, Belize

Abstract. Trichodesmium abundance and photosynthetic rates were determined across a transect of the Atlantic Barrier Reef at Carrie Bow Cay, Belize in May 1993 and May-June 1994. A fore reef station receiving oceanic water had a Trichodesmium abundance characteristic of the open Caribbean Sea (≤ 10² colonies m^-3 and 10⁴-^-10⁵ trichomes m^-3). Several species were present; however, in all cases a sharp decrease in abundance occurred across the reef to the coastal lagoon. At this latter site, virtually no Trichodesmium was present, although a substantial bloom of the diatom Proboscia alata occurred in 1994.
Maximum photosynthetic rates and the initial light-limited slope a were significantly lower in offshore stations than in reef top populations. The increased photosynthetic rates and light-harvesting ability in reef-top populations, as well as the lack of significant photoinhibition, indicated that the Trichodesmium abundance decrease was probably not due to a decline in photosynthetic capacity. Grazing and physical removal rather than a physiological decline were likely mechanisms operating to reduce Trichodesmium abundance in these regions. These data suggest that the Belizean barrier reef is a sink for Trichodesmium transported in from offshore regions.     

Salinity-Temperature Relations and Morphotypes of a Mixed Population of Coccoid Cyanobacteria from a Hot, Hypersaline Pond in Israel

Abstract. A mixed population of unicellular and colonial cyanobacteria was transferred into culture from a hypersaline helio-thermal pond in the vicinity of the Dead Sea. The entire complex of strains, incubated in Dead Sea water of varying salinity and temperature, showed a pronounced shift of the maximal growth from a salinity of 72 g l^-1 at 30 ^oC up to 142 g 1^-1 at 50 ^oC. Over the above range of salinities and temperatures, these cyanobacteria were capable of about four divisions per day, providing that any increase in salinity was coupled with the suitable increase in temperature. The above peculiar adaptation can explain the prominent success of this group of microorganisms in the extreme and unstable ecological conditions of hypersaline habitats. Amounts of slime accumulating in the cultures were proportional to the incubation temperature.     

The Effect of Salinity and Temperature Gradients on the Distribution of Littoral Microalgae in Experimental Solar Ponds, Dead Sea Area, Israel

Abstract. Several species of cyanobacteria, diatoms and one euglenid alga populated the littoral zone of hypersaline solar ponds investigated over a period of three years. The composition of the microalgae community changed with salinity and temperature. In the shallow marginal zone the diatoms predominated in winter and spring, at salinities of 30–72 g-1^-1 and at temperatures not exceeding 30o°C, whereas in summer, cyanobacteria were the most abundant. In the deeper zone, at higher salinities and temperatures, cyanobacteria predominated throughout the year. The depth limit of algal growth was 60-80cm, where salinity and temperature exceeded 211 g-1^-1 and 48°C.
The most euryhaline and eurythermal among cyanobacteria were Aphanolhece halophytica F remy and Phormidium hypolimneticum C ampbell , among diatoms Nitzschia sp. aff. N. rostellata H ustedt , Amphora coffeaeformis (A gardh ) K utzing , and Navicula massadaea E hrlich .