硅藻硅酸转运子（silicon transporters, SITs）研究进展

硅藻是海洋浮游植物主要类群和海洋生态系统的重要初级生产者，其硅质壁的存在使其成为了海洋生物硅的最大贡献者，而且成为海洋碳汇的主要来源。因此，硅质壁形成机制的阐明至关重要。硅酸转运是硅藻硅质壁形成中的关键，阐明其转运机制对建立硅藻代谢途径模型和进一步理解硅藻在海洋生态系统及生物地球化学循环中的作用具有重大意义。硅酸转运子(silicon transporters, SITs)是硅藻中参与硅吸收或转运的一类膜蛋白，因其重要性及多样性成为讨论及研究的焦点。本文综述了硅藻中SITs的分子特征、分子机制、功能多样性及进化关系，为SITs转运机制的研究提供了理论基础。     

海洋硅藻硅质细胞壁结构的形成机理研究概述

硅藻具有形态各异、结构复杂、精美绝伦的硅质细胞壁,是海洋中进行生物硅化最主要的生物体。硅质细胞壁的形成同样是一个错综复杂的过程,它涉及硅藻细胞将硅酸从胞外转运到胞内;硅酸在细胞内的转移;在硅沉积囊泡(SDV)中的浓缩沉积;最后合成具种类特异性的细胞壁。重点介绍硅酸转运基因(SITs)的分子特征与作用机制;与生物硅化相关的三种蛋白即硅体蛋白(frus-tulins)、亲硅蛋白(silaffins)和侧壁蛋白(pleuralins)的结构与功能;硅质结构如何在硅沉积囊泡内最终形成的模式。     

Fronts and surface zonal geostrophic current along 115°E in the southern Indian Ocean

硅藻具有形态各异、结构复杂、精美绝伦的硅质细胞壁,是海洋中进行生物硅化最主要的生物体。硅质细胞壁的形成同样是一个错综复杂的过程,它涉及硅藻细胞将硅酸从胞外转运到胞内;硅酸在细胞内的转移;在硅沉积囊泡(SDV)中的浓缩沉积;最后合成具种类特异性的细胞壁。重点介绍硅酸转运基因(SITs)的分子特征与作用机制;与生物硅化相关的三种蛋白即硅体蛋白(frustulins)、亲硅蛋白(silaffins)和侧壁蛋白(pleuralins)的结构与功能;硅质结构如何在硅沉积囊泡内最终形成的模式。     

悬浮颗粒物中生物硅测定方法的改进与应用

硅是河流和海洋中非常重要的营养盐,硅藻、放射虫、硅质海绵、硅鞭毛虫的生长和骨骼形成都离不开硅[1].硅在河流和沿岸海域生态系统中扮演着非常重要的角色,在浮游植物大量繁殖季节,由于硅藻的大量繁殖,使活性硅酸盐含量急剧下降,甚至使硅藻的生长繁殖受到限制.在其他环境条件适宜的情况下,充足的硅又将成为发生硅藻赤潮的物质基础[2].生物硅是用化学方法测定的无定形硅的含量[3],称为生物蛋白石或简称蛋白石,是地球化学、古海洋学研究中非常重要的参数[4].根据世界部分河流生物硅和溶解硅的平均值计算,河流输送入海的硅中有16%的是生物硅,因此河流输送的生物硅的量是全球海洋硅收支中不可忽略的部分[5].     

硅藻硅质化蛋白——亲硅蛋白(silaffins)

硅藻是一类在全世界水环境中都有发现的单细胞真核藻类,其特有的硅质壁使其成为海洋生物硅的最大贡献者,它们在全球碳/硅元素的生物地球化学循环中扮演至关重要的角色。亲硅蛋白(silaffins)是一种分离于硅藻硅质壁,并与其硅质化密切相关的蛋白。亲硅蛋白可以在体外硅酸溶液中沉淀二氧化硅(SiO_2),这种活性来自其特有的蛋白序列和翻译后修饰调节。基于对亲硅蛋白结构的理解,多种与其相似的仿生多肽被应用到人工SiO_2的合成中。本文综述了硅藻亲硅蛋白的分离鉴定、功能以及其在生物技术和生物医药方面的应用,为亲硅蛋白基础研究和应用潜力提供基础。     

海水中可溶性无机硅

海水中可溶性无机硅(以下简称硅),是海洋浮游植物所必须的营养盐之一,尤其是对硅藻类浮游植物、放射虫和硅质海绵,硅更是构成机体不可缺少的组分。在海洋浮游植物中硅藻占很大部分,硅藻繁殖时摄取硅使海水中硅的含量下降。浮游植物死亡下沉分解又释放出硅,使海水中硅的含量再生。另外放射虫也能排泄出二氧化硅,硅质死亡迅速释放二氧化硅进入海水中。总之硅的含量对于海洋生物产量具有直接和间     

基于海洋硅藻三维结构的微纳米材料研究进展

海洋硅藻种类繁多,具有因种而异的形状奇特的刚性细胞壁,称作硅质壳。硅质壳主要由无定形的二氧化硅构成,在纳米至微米尺度的三维结构(如孔、脊或管状结构)上表现出高度的规律性和精确的重现性。仿效硅藻,在温和的条件下制造超精细微纳米材料,成为众多从事生物、化学、材料研究工作者追逐的焦点。本文从硅藻硅质壳的形成机理及体外仿生、影响硅藻硅质壳结构的外在因素、硅藻硅质壳的化学修饰与应用3个方面的研究进展进行了综述。     

第五节 海水中可溶性无机硅

海水巾可溶性无机硅(以下简称硅)，是海洋浮游植物所必须的营养盐之一，尤其是对硅藻类浮游植物、放射虫和硅质海绵，硅更是构成机体不可缺少的组分。在海洋浮游植物中硅藻占很大部分，硅藻繁殖时摄取硅使海水中硅的含量下降。浮游植物死亡下沉分解又释放出硅，使海水中硅的含量再生。另外放射虫也能排泄出二氧化硅，硅质死亡迅速释放二氧化硅进入海水中。总之硅的含量对于海洋生物产量具有直接和间接影响，由此可知生物活动使海水中硅的含量随季节呈现周期性变化。     

海洋纹层硅藻席古海洋学与生物地球化学研究进展

海洋大型硅藻的勃发及其在海底的纹层硅藻席沉积代表大规模的有机碳和生物硅输出通量,该生物堆积事件或过程对海洋酸化和全球变暖产生负反馈,因而在气候变化中的地位不容小觑。本文在融入作者研究成果的基础上总结了国内外关于海洋纹层硅藻席的研究现状,认为大型硅藻勃发不能直接和上涌活动相关联,在热带海区一般与成层化相关,在亚热带海区总体上与锋面作用相关。大型硅藻勃发时,表层水不一定贫养,也可以是富养的,也不总是需要借助浮力下沉到营养跃层吸收营养物,可直接吸收海洋表层中的营养物(如风尘溶解来源的硅酸)。大型硅藻通过高的初级生产力吸收大气中的CO_2,尔后在海洋深部降解形成的CO_2在海洋成层化条件下以巨大"呼吸CO_2库"得以封存,代表促使冰期大气pCO_2降低的一种重要机制。海洋纹层硅藻席的保存环境由多种因素制约,可以是氧化的也可以是亚氧化的,因而对用纹层沉积物来指示缺氧底层水条件应持谨慎态度。另外,提出了解释大型硅藻勃发和硅藻席形成机制的新模式"风尘触发硅藻席沉积",极大地促进了硅藻席沉积成因谜团的解决。最后,指出了目前海洋纹层硅藻席研究中存在的问题并阐述了未来可以开展的研究方向。     

沉积物中生物硅分析方法评述

硅是水生态系统中构成生物群落的重要元素。硅藻、放射虫、硅质海绵和硅鞭毛虫生长和骨骼形成都离不开硅。ＤｅＭａｓｔｅｒ１９８１年研究指出海洋硅主要来源于河流(４．２±０．８×１０１４ｇ／ａ，ＳｉＯ２)和热液喷发 (１．９±１．０×１０１４ｇ／ａ，ＳｉＯ２)。另外冰川风化、低温海底玄武岩风化和沉积物的成岩作用亦是其来源之一。而Ｃｏｎｌｅｙ等１９９３年报道富营养化往往引起水体中溶解硅的浓度逐渐降低。生物硅（Ｂｉｏｇｅｎｉｃｓｉｌｉｃａ）指化学方法测定的无定形硅的含量 ,亦称为生物蛋白石或简称蛋白石。生源无定形…     

3种海洋硅藻不同培养阶段挥发性成分的比较分析

本文应用顶空固相微萃取气相色谱-质谱联用技术,对威氏海链藻Thalassiosira weissflogii、小新月菱形藻Nitzschia closterium、角毛藻Chaetoceros calcitrons 3种硅藻的挥发性成分进行分析。结果表明,在3种硅藻的培养过程中,其挥发性成分除了壬醛及醇类呈现先增后降的趋势外,大多数不饱和醛类的含量在不断增加,烷烯烃类物质在不断减少,而乙酸乙酯、2-甲基-2-丙酸甲酯这类酯类化合物在角毛藻衰败期会显著富集。通过对代表性饵料硅藻的挥发性成分进行研究,可为海水养殖过程中微藻投喂种类、投喂时机的选择提供理论依据,并为海洋硅藻的进一步开发奠定基础。     

Biological controls on dissolution of diatom frustules during their descent to the deep ocean: Lessons learned from controlled laboratory experiments

The majority of opal produced by diatoms dissolves during their sedimentation to the seafloor, but spatial and temporal variability of dissolution rates are large. Controlled laboratory experiments using live phytoplankton or phyto-detritus may help identify the different processes, including those that are biologically mediated or physico-chemically driven, that impact the dissolution of frustules and the aforementioned variability. Results of eight bSiO₂ dissolution experiments, seven of which were conducted at low temperatures (<6 °C) are presented within the context of earlier similar studies, and different phases of dissolution dynamics characterized. TEP concentration, aggregation and the physiological status of the diatoms determined the period during which diatoms may maintain the protective membrane that surrounds their frustule and effectively reduces or completely inhibits (lag period) dissolution for some time. Once diatoms loose the capability to maintain their protective membrane, bacterial activity compromises it. Physico-chemical dissolution, which depends on frustule structure and abiotic environmental conditions, begins once the protective membrane is damaged. The ability of diatoms to maintain their membrane, the bacterial composition and activity governing its degradation, and the physico-chemical dissolution dynamics of exposed frustules are all impacted by temperature. In our experiments instantaneous dissolution rates were not dependant on bSiO₂ concentration at low temperatures, although such a relationship was observed under otherwise identical conditions at 15 °C, implying that biotic factors rather than physico-chemical processes initially dominated dissolution at polar temperatures. Since inhibition of bSiO₂ dissolution at low temperatures was inhibited to a greater extent than organic matter degradation, we postulate that it was not reduced bacterial activity but the enhanced ability of diatoms to maintain their membrane and thus withstand microbial attack that caused the low initial dissolution rates at <6 °C. In situ, interactions between the different biotic and abiotic processes impacting dissolution combined with differences in sinking velocity of diatom aggregates and grazing effects could easily explain high spatial and temporal variability in the accumulation of diatoms on the seafloor. Simple calculations based on our experimental results suggest that Fragilariopsis kerguelensis, for example, would be appreciably more likely to reach the seafloor than Chaetoceros debilis if both grow at low growth rates, e.g. under growth limiting conditions. However, dissolution behavior of Chaetoceros debilis during sedimentation may differ under conditions where this species forms large blooms.     

海洋沉积硅藻研究进展

综述了国外近40 a海洋沉积硅藻表层组合及其在地层划分与对比、古地理环境重建、海平面升降和岸线变迁等方面的应用,以及硅藻休眠孢子化石的分类学、地层学和分子系统发育学研究的最新进展.对中国海洋沉积硅藻的研究进展作了概述,基本查明了渤海、黄海、东海、南海4大海区表层硅藻属种组成及表层硅藻组合面貌;利用硅藻组合进行了地层划分与对比、古海洋环境演变过程的研究;并将各种数理统计方法结合到硅藻分析中,使中国海洋沉积硅藻研究逐渐由定性或半定量向定量研究发展.但在利用硅藻进行古环境定量重建等方面,与国外的研究还存在一定差距.今后应加强建立现代硅藻-环境变量数据库、表层沉积生物硅的溶解、硅藻休眠孢子化石的分类学和地层学等方面的研究.     

往复潮流作用下推移质粒径趋势形成模拟初探

粒径趋势分析是一种用于判断海洋环境中沉积物净输运方向的方法，但是至今粒径趋势形成的物理机制尚不够清楚，因而影响了粒径趋势分析适用条件的确定。针对这个问题，本文通过建立一维、推移质、往复流（近岸潮流）条件下的数值模型，采用正演方法模拟粒度参数在输运方向上的分布．以评价沉积动力过程的影响，初步探讨粒径趋势形成的物理机制。数值模型实验的初步结果显示，水动力条件的空间差异导致的沉积物粒度参数的空间分布符合粒径趋势分析的假设，粒径趋势分析中定义的两种粒径趋势可由沉积物输运强度的空间梯度而形成，并且在沉积物净输运方向上出现的频率最高。     

Competition within the marine microalgae over the polar dark period in the Greenland Sea of high Arctic

Abstract-With the onset of winter, polar marine microalgae would have faced total darkness for aperiod of up to 6 months. A natural autumn community of Arctic sea ice microalgae was collected fordark survival experiments from the Greenland Sea during the ARKTIS-XI/2 Expedition of RV Po-larstern in October 1995. After a dark period of 161 days, species dominance in the algal assemblagehave changed from initially pennate diatoms to small phytoflagellates (<20μm). Over the entire darkperiod, the mean algal growth rate was-0.01 d~(-1). Nearly all diatom species had negative growthrates, while phytoflagellate abundance increased. Resting spore formation during the dark period was ob-served in less than 4.5% of all cells and only for dinoflagellates and the diatom Chaetoceros spp. We as-sume that facultative heterotrophy and energy storage are the main processes enabling survival during thedark Arctic winter. After an increase in light intensity, microalgal cells reacted with fast growth withindays. Phytoffa     

Growth,feeding and ecological roles of the mixotrophic and heterotrophic dinoflagellates in marine planktonic food webs

Planktonic mixotrophic and heterotrophic dinoflagellates are ubiquitous protists and often abundant in marine environments. Recently many phototrophic dinoflagellate species have been revealed to be mixotrophic organisms and also it is suggested that most dinoflagellates may be mixotrophic or heterotrophic protists. The mixotrophic and heterotrophic dinoflagellates are able to feed on diverse prey items including bacteria, picoeukaryotes, nanoflagellates, diatoms, other dinoflagellates, heterotrophic protists, and metazoans due to their diverse feeding mechanisms. In turn they are ingested by many kinds of predators. Thus, the roles of the dinoflagellates in marine planktonic food webs are very diverse. The present paper reviewed the kind of prey which mixotrophic and heterotrophic dinoflagellates are able to feed on, feeding mechanisms, growth and ingestion rates of dinoflagellates, grazing impact by dinoflagellate predators on natural prey populations, predators on dinoflagellates, and red tides dominated by dinoflagellates. Based on this information, we suggested a new marine planktonic food web focusing on mixotrophic and heterotrophic dinoflagellates and provided an insight on the roles of dinoflagellates in the food web.     

氧含量及附着面积对海洋底栖硅藻生长和胞外多聚物的影响

胞外多聚物(extracellular polymeric substance, EPS)是海洋底栖硅藻在水下表面附着时分泌的物质,环境因素对胞外多聚物的组成和分泌行为有直接影响,本文重点探讨了氧含量和附着面积对胞外多聚物的影响。采用热溶剂浸提法提取硅藻胞外多聚物,利用苯酚-硫酸法定量其中的多糖成分,利用考马斯亮蓝G-250法定量蛋白质成分,通过血球计数板法和紫外分光光度法计算细胞数量。结果表明,在氧含量高、可附着面积大的条件下,硅藻的生长繁殖速率快,且单个细胞的胞外多聚物分泌量大。氧含量对胞外多聚物主要成分中的水溶性多糖含量影响大,而对其余成分含量影响小。可附着面积对硅藻附着和生长的影响比氧含量影响小。     

Molecular insights into the circadian clock in marine diatoms

The circadian clock is a fundamental endogenous mechanism of adaptation that coordinates the physiology and behavior of most organisms with diel variations in the external environment to maintain temporal homeostasis. Diatoms are the major primary producers in the ocean. However, little is known about the circadian clock in marine diatoms compared with other organisms. Here, we investigated circadian clock genes, their expression patterns, and responses to environmental stimuli such as light, nitrogen and phosphorus in two marine diatoms, Skeletonema costatum and Phaeodactylum tricornutum, using a combination of qRT-PCR and bioinformatic analysis. We identified 17 and 18 circadian clock genes in P. tricornutum and S. costatum, respectively. Despite significant evolutionary differences, these genes were similar to those of the higher plant Arabidopsis. We also established a molecular model for the marine diatom circadian clock comprising an input pathway, core oscillator, output pathway, and valve effector. Notably, the expression patterns of core clock genes (circadian clock associated 1 (CCA1), late elongated hypocotyl (LHY) and timing of cab 1 (TOC1)) in both species differed from those of terrestrial plants. Furthermore, the expression of these genes was influenced by variations in ambient light, nitrogen and phosphorus availability. Although marine diatoms and higher plants share common circadian clock components, their clock genes have diverged throughout evolution, likely as a result of adapting to contrasting environments.