Ultrastructural Evidence for a Novel Accumulation of Ca in a Microbial Mat from a Slight Acidic Hot Spring

<正>Microbial mats are ecosystems that can control or induce the precipitation of calcium(Ca) carbonate on Earth through geological time.In the present study,we report on a novel accumulation of Ca,together with iron(Fe),in a microbial mat collected from a slight acidic hot spring(pH=5.9) in south China.Combining an array of approaches,including environmental scanning electron microscopy,X-ray microanalysis,transmission electron microscopy,and selected area electron diffraction,we provide ultrastructral evidence for amorphous acicular aggregates containing Ca and Fe associated with cyanobacteria precipitating in the microbial mats.Cyanobacterial photosynthesis and exopolymeric organic matrixes are considered to be responsible for the precipitation of Ca.These amorphous acicular aggregates might imply the early stage of calcification occurring in microbial mats.Ca and Fe coprecipitation indicates another potential important way of inorganic element precipitation in hot spring microbial mats.Our results provide insight into the possible mechanism of cyanobacterial calcification and microfossil preservation in slight acidic hot spring environments.     

Production of polysaccharide slime by microbial mats in the hypersaline environment of a Western Australian solar saltfield

Of the many microorganisms present in the hypersline environment of the saltfield studied, the cyanobacteriumSynechococcus was found to be the major producer of polysaccharide slime. When dissolved in the brine, this slime caused elevated brine viscosities which impaired the quality of the salt crystallised from such brine.Synechococcus was present in benthic microbial mats throughout the 6 concentrating ponds of the saltfield, but it dominated in the ponds where brine density was above 1.10 g cm^–3, corresponding to the saturation density of gypsum (CaSO₄·2H₂O). At such density,Synechococcus was always associated with copious amounts of slime. At lower density, the nature of the substratum over which the mat was growing affected the slime content and productivity of the mat, presumably relatively to its ability to supply nutrients to the mat. Under laboratory conditions, the addition of gypsum stimulated the growth ofSynechococcus in the presence of excess phosphate (>15 mg L^–1 PO₄-P). Slime production however was not stimulated by high salinity, addition of (CaSO₄·2H₂O), NaSO₄ or nitrate deficiency. Only as cultures entered a stationary phase of growth did slime production increase. It was concluded that a nutrient limitation was probably responsible for the activation of extracellular polysaccharide production, possibly as a means of disposing of excess photosynthetically fixed carbon.     

Long chain glycolipids with pentose head groups as biomarkers for marine endosymbiotic heterocystous cyanobacteria

Marine endosymbiotic heterocystous cyanobacteria make unique heterocyst glycolipids (HGs) containing pentose (C₅) moieties. Functionally similar HGs with hexose (C₆) moieties found in free-living cyanobacteria occur in the sedimentary record, but C₅ HGs have not been documented in the natural environment. Here we developed a high performance liquid chromatography multiple reaction monitoring (MRM) mass spectrometry (HPLC–MS²) method specific for trace analysis of long chain C₅ HGs and applied it to cultures of Rhizosolenia clevei Ostenfeld and its symbiont Richelia intracellularis which were found to contain C₅ HGs and no C₆ HGs. The method was then applied to suspended particulate matter (SPM) and surface sediment from the Amazon plume region known to harbor marine diatoms carrying heterocystous cyanobacteria as endosymbionts. C₅ HGs were detected in both marine SPM and surface sediments, but not in SPM or surface sediment from freshwater settings in the Amazon basin. Rather, the latter contained C₆ HGs, established biomarkers for free-living heterocystous cyanobacteria. Our results indicate that the C₅ HGs may be potential biomarkers for marine endosymbiotic heterocystous cyanobacteria.     

太湖越冬蓝藻空间分布的初步研究

为确定2007-2008年冬季蓝藻在太湖各个湖区的分布及其变化规律,在冬季逐月对太湖主要湖区14个位点采集底泥和水样,应用荧光分析法测定样品中藻蓝素含量,以确定冬季太湖各个湖区的藻蓝素分布状况,比较冬季太湖各个湖区水体和底泥中蓝藻的分布差异.实验结果说明与夏季情况不同,相对于西南太湖水域,2007-2008年冬季北太湖水体和底泥中的蓝藻含量均较低,而西南湖区部分区域12月仍出现了蓝藻的聚集,底泥表面的藻蓝素含量也较高,说明调查期间,冬季越冬蓝藻主要分布于西太湖和南太湖.     

Bacterial and cyanobacterial diversities determined by T-RFLP analyses in the Jiaozhou Bay

1Introduction Bacteriaareactivelyinvolvedinthedecomposi tionanddegradationoforganicmatterandxenobiotic compound,biogeochemicaltransformationsandnu trientrecyclingoflife essentialelements.Owingto freshwaterrunoff,wastewaterdischargeandaquacul turalpractice…     

秋季聚积蓝藻打捞对蓝藻生长及水质影响的原位实验

在巢湖西北半湖近岸设置3组小型围隔模拟秋季湖岸带蓝藻聚积,并用单片鳃式过滤器原位打捞蓝藻,研究秋季打捞对蓝藻生长的影响及其对营养盐、藻源性有机物的控制效应.初始围隔水体叶绿素a浓度为309.5±3.7μg/L,总氮和总磷浓度分别为3.32±0.14和0.30±0.04 mg/L.蓝藻衰亡分解释放的藻源性有机物为水体溶解性有机物的主要来源,荧光有机物以类蛋白物质为主.经过打捞,浮游植物生物量削减了41.7%,解除了蓝藻生长"密度制约",24 h细胞分裂频率及原位生长速率均增大,说明打捞在短期内增强蓝藻细胞生长活力,减缓藻源性有机物的释放.与秋季蓝藻衰亡趋势一致,实验周期内围隔中叶绿素a浓度逐渐降低,秋季打捞不会造成蓝藻水华再次暴发.打捞通过削减蓝藻生物量,使水体初级生产力、氮、磷、高锰酸盐指数得到显著控制;而且打捞还可以控制藻源性有机物的释放,使藻源性大分子有机物更易降解为小分子有机物.因此,在秋季对湖岸带聚积蓝藻进行物理打捞,不仅可以控制蓝藻生物量,还可以有效控制营养盐和有机物的释放,降低生态风险.     

2005-2017年北部太湖水体叶绿素a和营养盐变化及影响因素

利用国家生态观测网络太湖湖泊生态系统研究站对北部太湖14个监测点2005-2017年的营养盐和叶绿素a浓度逐月监测数据,分析了北部太湖2005年以来水体营养盐和叶绿素a变化特征,探讨了叶绿素变化的影响因素.结果表明,2015年以来,北部太湖水体叶绿素a浓度呈现显著增高特征,特别是5-7月的蓝藻水华灾害关键期,水体叶绿素a浓度增幅更加明显;营养盐方面,氮、磷对治理的响应完全不同：水体总氮、溶解性总氮、氨氮的降幅很明显,甚至在春末夏初的蓝藻生长旺盛期出现了供给不足的征兆;但水体总磷降幅却不明显,加之蓝藻水华的磷"泵吸作用",近3 a来水体总磷浓度反而有升高趋势,溶解性总磷浓度也无明显下降趋势.不同湖区的营养盐变化也不相同：西北湖区溶解性总氮、溶解性总磷浓度显著高于梅梁湾、贡湖湾和湖心区,而且后3个湖区的水质呈现均一化趋势.统计分析表明,北部太湖水体叶绿素a浓度与颗粒氮、颗粒磷、总磷、高锰酸盐指数均呈显著正相关,与溶解态氮呈负相关;5-7月水华关键期北部太湖水体叶绿素a浓度与上半年（1-6月）逐日水温积温、总降雨量、年平均水位均呈显著正相关关系.从研究结果可以看出,近年来北部太湖水体叶绿素a浓度的波动很大程度上受水文气象因子的影响;2007年以来太湖流域一系列生态修复工程的实施,虽然明显降低了湖泊氮浓度,但由于流域和湖体的氮磷本底较高,磷的缓冲能力大,致使水体营养盐水平仍未降到能显著抑制蓝藻生长的水平,年际之间的水文气象条件差异成为蓝藻水华暴发强度差异的主控因素.为此,仍需加大对太湖流域氮、磷负荷的削减,使湖体氮、磷浓度降低到能显著影响蓝藻生长的水平,才能摆脱水文气象条件对蓝藻水华情势的决定作用.     

准噶尔盆地古尔班通古特沙漠生物结皮蓝藻研究

通过对古尔班通古特沙漠中9个样地73份生物土壤结皮蓝藻的研究,分析该沙漠生物结皮中蓝藻的区系组成、生态分布特点和蓝藻在生物结皮中的作用机制。研究表明,该沙漠中有蓝藻门植物6科25属77种,其中以丝状种类占优势;蓝藻在不同地貌部位分布略有差异,在丘间低地种类最为丰富;不同种类的蓝藻对地貌部位的选择性不同,大部分对地貌部位具有选择性;蓝藻种类和数量在结皮层较多,在结皮下层明显减少。生物结皮的显微观察揭示了丝状蓝藻和胞外多糖形成错综复杂的网状结构,起着捆绑、黏结沙粒和固定沙粒的作用。     

Planktonic cyanobacteria in New Zealand inland waters: Distribution and population dynamics

One hundred and four taxa of planktonic cyanobacteria (blue‐green algae) have been recorded from New Zealand lakes: 32 belong to the Chroococcales, 72 to the Nostocales. None of the taxa is endemic to New Zealand; most (if not all) are cosmopolitan. On average, more taxa have been reported from North Island (7.8 ± 6.7, N = 69) than South Island lakes (3.3 ± 3.9, N = 59). This difference is attributable, in part, to the large proportion of glacial lakes in the South Island, which are commonly poor in plant nutrients and possess sparse phytoplankton populations. Many of the taxa show a strong preference for eutrophic conditions. Notable exceptions are Anabaena affinis and Gomphosphaeria lacustris, which occur in a large proportion of mesotrophic (48%) and oligotrophic lakes (43%), respectively. Taxa which are often abundant and frequently responsible for conspicuous water‐blooms are Microcystis aeruginosa, Anabaena circinalis, A. flos‐aquae and A. spiroides. The limited population data available indicate a high level of interannual variability in the timing, magnitude, and duration of cyanobacterial blooms in New Zealand lakes.