广泛分布于海洋生态系统中的壳状珊瑚藻——冈村石叶藻的形态解剖学和分子生物学描述

冈村石叶藻（Lithophyllum okamurae）是一种重要的壳状珊瑚藻,在海洋生态系统中具有提供初级生产力、产生碳酸盐沉积物以及为海洋生物提供栖息环境等功能。本文于三亚的热带海岸采集L. okamurae,首次基于形态解剖学特征和分子生物学方法对其进行了详细的描述。研究表明,L. okamurae的藻体为二组织性的拟薄壁组织结构,被分成三部分,包括：由1-3层呈扁平状正方形或长方形表皮细胞组成的表层,由一层正方形或长方形细胞组成的基层,以及由多层正方形或狭长形细胞组成的围层。在围层中可观察到栅状细胞,相邻藻丝细胞间通过次生纹孔相连,未见细胞融合。本文观察到L. okamurae的四种单孔生殖窠,即果孢子囊生殖窠、精子囊生殖窠、二分孢子囊生殖窠以及四分孢子囊生殖窠。其中,精子囊生殖窠通常浅埋于藻体中并微凸于藻体表面,果孢子囊生殖窠和无性生殖窠呈突出的圆锥形。基于18S rDNA、COI、rbcL和psbA基因序列的系统发育研究表明,L. okamurae和L. atlanticum在同一个进化枝上,亲缘关系最近。本文基于形态解剖学特征和分子生物学数据详细地对L. okamurae进行了描述,为海洋生态系统中藻类资源的利用和保护工作提供理论基础。     

极地冰藻极端海冰生境适应机制及其受气候变化的影响

冰藻是南北极海冰生物群落中最主要的组成部分,通过固定和输出碳、吸收养分、生产释放氧气和有机化合物,推动高纬度生态系统的生物地球化学循环,在南北极海洋生态系统中发挥着重要作用.从宏观到微观综述了近年来在海冰栖息环境特征、冰藻种类组成和群落结构、冰藻对极端环境的适应机制以及气候变化对海冰环境和冰藻的影响等方面的研究进展,并...     

风场对藻类在太湖中迁移影响的动力学研究

在Ｗｅｂｓｔｅｒ等人工作的基础上,以三维湖流为背景,考虑了波浪及藻类自身浮力的影响,建立了一个太湖梅梁湾三维藻类迁多模型,以研究在不同几场作用下藻类在湖泊中的迁移过程。模拟结果表明,不同风场对于藻类在湖泊中的水平及垂直分布影响很大,并且存在着一临界风速,其范围在２－３ｍ／ｓ之间,当几速小于临床风速时,水面可以拟看作水动力学光滑,没有波浪产生,在水表面藻类顺着风向迅速的向迎风岸的边漂移,形成藻类大量     

三峡水库支流小江富营养化模型构建及在水量调度控藻中的应用

三峡水库蓄水以来,支流小江呈富营养化加重的趋势,且多次暴发春季水华.水库蓄水以后支流流速变缓,水体滞留时间增加,是引发支流水华的主要因素之一.基于MIKE软件,建立小江调节坝下游至河口的二维水动力-富营养化模型,考虑碳、氮、磷3种元素在浮游植物有机体、死亡腐屑和无机盐中的循环转化,模拟小江河段的春季水华过程.分析小江生态调节坝的水量调节抑藻作用,即人为制造"洪水脉冲",增加短时间内的水流流速,对下游流场进行扰动以控制水华.计算结果表明,增大泄水量对调节坝下游的小江河段的春季藻华总体上具有一定的抑制作用.小江上游河段调度作用效果明显,下游高阳至入汇口河段调节作用较小,上游调节坝水力调度可以作为三峡水库支流水华应急治理措施之一.营养盐控制应该是控制支流水华的根本措施.     

硝态氮对库区水体藻类和细菌群落的影响

水体富营养化极易引起湖泊水库如藻类水华等水生态系统环境问题。氮素作为初级生产力的限制性生源要素之一,认识其在水华形成过程中潜在作用至关重要。本研究选取胶东半岛低碳高氮水库水体进行模拟实验,通过添加不同剂量硝态氮,探究高硝态氮输入对库区水体藻类和细菌群落结构的影响。结果表明:(1)当硝态氮作为唯一氮源,随着培养时间延长,硝态氮浓度显著下降,亚硝态氮和氨氮浓度逐渐升高,表明微藻和细菌共同作用可能将硝态氮转化为亚硝态氮和氨氮;(2)当硝态氮浓度为6 mg/L时,藻类叶绿素a浓度达到最高值,随着硝态氮浓度升高,叶绿素a浓度则会降低;(3)添加硝态氮后,蓝藻门成为优势藻类,绿藻门次之;变形菌门相对丰度显著升高。研究结果为低碳高氮类水体暴发蓝绿藻水华及有效防控提供理论依据和技术支撑。     

太湖底泥表层越冬藻类群落动态的荧光分析法初步研究

为探索春季湖泊底泥表层不同藻类群落的复苏规律,本实验采集了太湖梅梁湾地区的底泥,应用荧光分析法测定藻蓝素,同时测定湖泊底泥中的叶绿素a和叶绿素b,确定春季梅梁湾底泥中不同藻类类群的色素含量变化,说明荧光分析法可以应用于底泥色素分析中,初步探讨了蓝藻群落和非蓝藻群落在春季温度上升期间恢复生长过程的差异。     

AN EVALUATION OF FRACTAL DIMENSIONS TO QUANTIFY CHANGES IN THE MORPHOLOGY OF FLUVIAL SUSPENDED SEDIMENT PARTICLES DURING BASEFLOW CONDITIONS

The morphology of suspended sediment particles reflects the origin of the suspended load and any modifying processes that may have occurred during transport and storage in the aquatic system. The objective of this study was to evaluate the use of four fractal dimensions to quantify visually observed changes in the morphology of fluvial suspended sediment particles during baseflow conditions. Samples were collected during summer low flow in a small stream on the Canadian Prairies. Particle morphology data were obtained with a transmitted light microscope, a CCD camera and an image analysis system. The morphology of the particle population was characterized using four fractal dimensions (D, D_K, D₁ and D₂). D was derived from the area–perimeter relationship and showed an increase from 1·26±0·02 on 30 June, to 1·34±0·02 on 4 July, to 1·42±0·01 on 7 July. Visually, the increase in D represented the formation of large particles with intricate shapes and increased perimeters. D_K was determined from the area–rank relationship and varied from 1·86±0·01 on 30 June, to 1·90±0·00 on 4 July, to 1·74±0·00 on 7 July. The decrease in D_K between 4 July and 7 July would indicate a greater concentration of the particle area over a small number of large particles. Although the decrease in D_K is consistent with observed changes in the particle size distributions, D_K should be used with the considerable caution because D_K varied more than one standard error between replicates. D₁ and D₂ were determined from the length–perimeter and length–area relationships, respectively. D₁ proved to be of little value for quantifying changes in particle morphology as it showed little change with time, despite considerable visual changes. D₂ however, was useful, despite some variation between replicates. Over the sampling period, D₂ for the composite data sets showed a steady decrease from 1·74±0·02 on 30 June, to 1·68±0·02 on 4 July, to 1·60±0·01 on 7 July. This change in D₂ indicates that, through time, the larger particles became longer and thinner relative to the smaller ones. This study shows that temporal changes in D, D_K and D₂ were consistent with, and allow quantification of, observed changes in particle morphology. D₁ did not reflect observed morphological changes, and is therefore of little value for this type of study. The changes in particle morphology coincided with an increase in primary production in the form of algae. © 1997 John Wiley & Sons, Ltd.     

A note on sand ripples developing in sandstone rock seepages of the Weald,UK

Ephemeral sand ripples are described from steep rock surfaces in the UK. They are unconsolidated or stabilized by algae and bryophytes. The sand is transported by flowing water to produce a semi-regular pattern of sinuous ripples averaging 6–8 mm apart and with a relief not exceeding 4 mm. The ripples may be initiated by the formation of a self-perpetuating capillary wave template. Sand grains accumulate on the template to form the fully developed ripples. Ultimately, gravitational forces or flooding lead to their destruction. Travertine rimstones may be initiated in the same manner. Copyright © 1999 John Wiley & Sons, Ltd.     

藻类捕光天线系统:结构与功能的统一

藻类是光合自养的水生孢子植物,为了适应水下弱光的特殊生境,藻类捕光天线历经亿万年的进化,形成了特殊的结构与功能.从发现藻类捕光天线的存在到至今的70多年间,其结构解析技术的发展共经历了4个阶段:首先是利用生化及普通光谱技术研究结构组成(1950-1980年);其次是利用X-ray晶体学技术研究局部精细结构(1980年至...     

Paleoecology of Late Carboniferous Phylloid Algae in Southern Guizhou, SW China

Phylloid algae arc important rcef-builders in the late Carboniferous. This paper focuses on the paleoecology of phylloid algae in the Late Carboniferous on well-exposed reefs in Ziyun County, Guizhou Province. Phylloid algae growing closely packed arc attached via holdfast or similar structure to substrate. They were growing in environments such as shallow water, photic zone and below the wave base with medium energy currents. They have a variety of morphological forms, such as single cup-shaped, cabbage-shaped and clustering cup-shaped. The thalli arc of certain tenacity and intensity. In the areas dominated by phylloid algae, other marine orgam＇sms arc relatively scarce. Obviously, phylloid algae arc stronger competitors for living space than other co-occurring organisms.