典型红树林生态系统藻类多样性及其在生态过程中的作用

藻类是红树林生态系统重要的生物类群, 根据生态习性可分为浮游植物、底栖微藻和大型藻类三个生态类群, 它们在红树林生态系统生物多样性、初级生产、元素循环等方面起着重要作用。但在红树林生态系统中, 关注重点多集中在红树植物和动物, 对其中的藻类重视不够, 且多数研究集中在近20年以及亚洲的红树林区。事实上, 红树林生态系统藻类非常丰富, 其多样性研究有助于深入揭示红树林生态系统的结构与功能。本文介绍了红树林生态系统藻类的组成类群及其重要性, 重点对红树林区浮游植物、底栖硅藻和大型海藻的种类组成、地理分布及其与初级生产力、水质污染、元素循环、碳库形成等生态过程中的作用的研究动态和进展等进行了总结。根据已有研究, 红树林区浮游植物和底栖硅藻的种类数一般为几十到上百种, 其中硅藻在种类和数量上都占绝对优势, 它们是重要的初级生产者、饵料生物和水质污染指示生物; 红树林区底栖大型藻类主要由红藻、绿藻、褐藻、蓝藻组成, 绿藻的种类较多, 红藻在数量上占优势; 藻类是红树林湿地碳库的重要贡献者, 在红树林湿地生态系统碳汇和碳循环中起重要作用。红树林生态系统是个高度动态和异质的系统, 今后应加强红树林藻类多样性的长周期、大尺度变化及不同生境藻类的综合研究, 关注大陆径流和潮汐对藻类多样性和蓝碳的影响, 借助沉积物藻类记录, 探明红树林区藻类的长周期变化, 反演气候变化和人类活动对红树林生态系统的影响过程和机制。     

锥状施克里普藻孢囊的多种形态特征

休眠孢囊是某些甲藻生活史的重要阶段, 它被认为是甲藻赤潮爆发的种源。通过观察我国沿海海域采集的锥状施克里普藻(Scrippsiella trochoidea (Stein) Loebl ich)休眠孢囊的类型以及形态特征, 并将实验条件下形成的休眠孢囊与海区沉积物中休眠孢囊的形态特征进行比较, 结果表明, 锥状施克里普藻细胞在20°C、12小时光照/12小时黑暗、f/2培养基和f/2-N培养基中分别培养至第14天和第8天, 可以观察到休眠孢囊的产生。培养30天后, 培养液中有大量休眠孢囊, 将藻液避光保存90天后, 观察到培养基中有4种类型的休眠孢囊产生: (1)球形到椭球形(长25-39 μm), 钙质外壁, 稀疏或密被钙质附属物(长1-4 μm); (2)球形(直径为29-35 μm), 钙质外壁, 附属物非钙质(长0.5-1.5 μm); (3) 球形到椭球形(长29-35 μm), 钙质, 表面光滑, 无附属物; (4) 球形(直径24-35 μm ), 有机外壁, 无附属物。第1种类型的孢囊最为常见, 分别占到2种培养条件下所得全部孢囊的77.70%和95.18%。从沉积物中所得的孢囊多属于第1种类型。分析了实验条件下形成不同类型休眠孢囊的原因和比例, 同时探讨了海区沉积物中形成多种孢囊形态特征的原因, 为锥状施克里普藻孢囊的生态研究提供了依据。     

广东大亚湾甲藻孢囊及其与锥状斯氏藻赤潮的关系

1999年12月至2001年1月,在大亚湾澳头海域用沉积物捕捉器(Sediment trap)及TFO重力采泥器对甲藻孢囊进行每月一次的周年监测,并同时研究了浮游植物的季节变化.结果显示,晚秋孢囊形成率最高(3.48105 cysts/m2d),冬季形成率较低,年平均为1.28105 cysts/m2d.锥状斯氏藻(Scrippsiella trochoidea)是大亚湾沉积物孢囊中的绝对优势种,除个别季节外,其形成率一般占孢囊总形成率的50%以上.2000年8月至9月,该海域发生了一次较大规模的锥状斯氏藻赤潮,最高细胞密度达4.0104 cells/mL.赤潮中后期,锥状斯氏藻孢囊包括暂时性孢囊和休眠孢囊大量形成,孢囊的形成减少了水体中营养细胞数量,是赤潮消退原因之一.       

锥状施克里普藻孢囊的多种形态特征

休眠孢囊是某些甲藻生活史的重要阶段,它被认为是甲藻赤潮爆发的种源。通过观察我国沿海海域采集的锥状施克里普藻（Scrippsiella trochoidea（Stein）Loeblich）休眠孢囊的类型以及形态特征,并将实验条件下形成的休眠孢囊与海区沉积物中休眠孢囊的形态特征进行比较,结果表明,锥状施克里普藻细胞在20°C、12小时光照/12小时黑暗、f/2培养基和f/2-N培养基中分别培养至第14天和第8天,可以观察到休眠孢囊的产生。培养30天后,培养液中有大量休眠孢囊,将藻液避光保存90天后,观察到培养基中有4种类型的休眠孢囊产生：（1）球形到椭球形（长25-39μm）,钙质外壁,稀疏或密被钙质附属物（长1-4μm）;（2）球形（直径为29-35μm）,钙质外壁,附属物非钙质（长0.5-1.5μm）;（3）球形到椭球形（长29-35μm）,钙质,表面光滑,无附属物;（4）球形（直径24-35μm）,有机外壁,无附属物。第1种类型的孢囊最为常见,分别占到2种培养条件下所得全部孢囊的77.70%和95.18%。从沉积物中所得的孢囊多属于第1种类型。分析了实验条件下形成不同类型休眠孢囊的原因和比例,同时探讨了海区沉积物中形成多种孢囊形态特征的原因,为锥状施克里普藻孢囊的生态研究提供了依据。     

大亚湾春季卡盾藻种群动态及其赤潮成因分析

研究了2000年春季大亚湾古老卡盾藻/海洋卡盾藻(Chattonella antique/marina)种群动态及其与环境因子的关系。卡盾藻是一种沿岸分布的有害赤潮针孢藻,2000年春在大亚湾海域高密度高频率出现,最高细胞密度为129cells/mL。大亚湾合适的水温、盐度及丰富的营养盐含量为卡盾藻的生长提供了良好的环境条件,而较低的Si∶N及持续的阴雨天气抑制了小型硅藻的生长,使卡盾藻在浮游植物种群竞争中占据一定地位。孢囊萌发被认为是水体中卡盾藻营养细胞及其赤潮发生的种源,但孢囊需经过4个月以上、11℃以下低温处理后方可成熟和萌发,大亚湾冬季水温,不能满足卡盾藻孢囊休眠成熟的需要。作者推测,2000年春大亚湾高密度卡盾藻营养细胞的种源可能来源于由船舶压舱水所带来的成熟孢囊。       

浮游植物稳定碳同位素分馏机制及环境应用

浮游植物驱动水体碳循环,是解释全球碳生物地球化学过程的关键因素。相对于陆地植物,浮游植物碳在合成过程中的分馏机制较为复杂。为了系统了解藻类碳同位素分馏过程及其同位素在环境中的应用,本文调研了国内外的相关研究进展,并以蓝藻、绿藻和硅藻为代表,阐述了浮游植物碳浓缩及其同位素分馏的机制。此外,本文还总结了目前藻类碳同位素信号的变化范围及其影响因素,并探讨了藻类碳同位素在古海洋、水生食物网与水体碳循环研究中的应用。     

电旋转技术用于少根根霉孢囊孢子介电性的测定

利用电旋转技术研究了少根根霉（Rhizopus arrhizus）孢囊孢子的电旋转谱,在发现另外两个峰的同时,在场频500Hz附近又发现了1个明显的正旋转峰。同时还发现萌发孢囊孢子与休眠孢囊孢子的电旋转谱有明显的差别,其负旋转峰值明显地小于休眠孢囊孢子的负旋转峰值。借助经修改的椭圆细胞双壳模型（two-shell model) 模拟出了原生质膜和原生质的电常数,结果表明萌发孢子的原生质膜和原生质的电导率较休眠孢子的相应电导率有明显增大。说明电旋转技术能够反映活细胞的生理变化。     

大型浅水富营养化湖泊中蓝藻水华形成机理的思考

湖泊富营养化依然是我国目前以及今后相当长一段时期内的重大水环境问题。研究蓝藻水华的形成机制 ,对于科学预测湖泊中蓝藻水华的产生 ,并采取相应措施减少其带来的影响具有重要的生态和环境意义。为探索富营养化湖泊中蓝藻水华形成机理 ,综述了目前对我国大型浅水湖泊蓝藻水华成因研究现状和对水华形成机理的一般认识。分析了导致蓝藻水华形成的化学、物理和生物等主要环境因素 ,论述了蓝藻 ,尤其是微囊藻成为水华优势种的可能原因。认为对水华的形成需要全面认识 ,营养盐浓度的升高可能仅是蓝藻水华形成、且人们可以加以控制的因素之一 ;在探索水华成因时 ,不能仅仅局限于夏季蓝藻水华发生时环境特征的研究与观察 ,而应该提前关注蓝藻的越冬生理生态特征、春季复苏的生态诱导因子及其阈值以及在复苏后 ,蓝藻如何在生长过程中形成群体 ,并逐步成为湖泊水生生态系统中的优势种乃至形成水华的过程。并需要对蓝藻越冬的生存对策、蓝藻群体的形成的条件、蓝藻在春季复苏的触发条件及其生态阈值、以及蓝藻在与其它藻类种群竞争中取胜的生理生化特征有足够的认识。蓝藻水华的“暴发”是表观现象 ,其前提还是藻类一定的生物量 ,且是一个逐渐形成的过程。根据生态学的基本理论和野外对水华形成过程的原位观测     

全球CO2 水平升高对浮游植物生理和生态影响的研究进展

工业革命以来由于化石燃料的大量燃烧,大气CO₂水平不断增加,预计在21世纪末将增至现有水平的两倍,达到750 μL/L。作为全球初级生产力的重要贡献者,浮游植物应对CO₂水平升高的生理生态响应必然会对水生生态系统和碳、氮等元素的生物地球化学循环产生重要影响。全球CO₂水平的升高将显著改变水体的碳化学环境,淡水生态系统(湖泊和河流)由于容量小变化比海洋更为显著。水体碳化学环境的改变首先会影响浮游植物个体,在高CO₂水平下,浮游植物的细胞会有变小的趋势,并且细胞的光合作用强度也会有不同程度的增加,其中细胞较小或者不具有碳浓缩机制(CCM)的浮游植物增加较多,此外浮游植物细胞的化学元素计量值也将显著改变。随后浮游植物个体水平上的变化会进一步影响水生生态系统,例如水体初级生产力水平的提高,浮游植物、浮游动物群落结构组成以及水体微食物网结构的变化等。此外浮游植物对CO₂水平升高的生理生态响应程度还与水体的营养水平有关。总结了大气CO₂水平升高对浮游植物生理生态影响的研究方法,展望了未来可能的研究方向。     

候选门级辐射类群（candidate phyla radiation）细菌的生理生态与进化

候选门级辐射类群（candidate phyla radiation,CPR）细菌是一大支与绝大多数已知细菌系统发育地位、基因组大小、细胞形态和生理代谢特征具有显著差异的独特细菌类群。CPR细菌在地球上分布广泛,且群落多样性极高。然而,由于被发现较晚,人们对CPR细菌的认识还非常有限。针对CPR细菌发现历程、细胞形态、基因组学特征、生理代谢潜能、生态学功能、实验室纯培养以及遗传进化等方面进行系统地归纳与总结,以期为未来CPR细菌的生态生理和遗传进化等研究提供参考,进一步加深对地球微生物物种多样性和生命进化的认识。     

CYST FORMATION IN THE RED TIDE DINOFLAGELLATE ALEXANDRIUM TAMARENSE (DINOPHYCEAE): EFFECTS OF IRON STRESS1

The toxic red tide dinoflagellate Alexandrium tamarense (Lebour) Balech (synonymous with Protogonyaulax tamarensis (Lebour) Taylor) was subjected to iron stress in batch culture over a 24-day time course. Monitoring of life history stages indicated that iron stress induced formation of both temporary (= pellicular) and resting (= hypnozygotic) cysts. Our experimental induction of sexuality appeared to be associated with iron limitation rather than the total depletion of biologically available iron. Degenerative changes in organelle (i.e. chloroplast, mitochondrion and chromosome) ultrastructure were largely restricted to pellicular cysts, suggesting that these temporary cysts were more susceptible to short-term iron stress effects than were hypnozygotes. These results are consistent with the hypothesized ecological roles of cysts in maintaining viability over brief (pellicular cysts) and extended (hypnozygotes) exposure to adverse environmental conditions.     

Epidemiology of hydatid disease in Sardinia: a study of fertility of cysts in sheep

Hydatidosis, caused by Echinococcus granulosus, is a cyclozoonotic disease of economic significance in Sardinia. The life-cycle involves stray and sheep dogs as definitive hosts and sheep, pigs, goats and cattle as intermediate hosts. The most important intermediate host is sheep, due to home slaughtering with ready access of the viscera to dogs. This survey was undertaken in 1987 to ascertain the epidemiological significance of sheep in maintaining the life-cycle. A total of 700 (91.3%) of 767 sheep harboured hydatid cysts. The frequency distribution of the number of hydatid cysts was over-dispersed. Of 497 infected sheep, 7.6% had fertile cysts, 75.7% sterile cysts and 16.7% fertile + sterile cysts.     

Observations on the suitability and importance of the domestic intermediate hosts of Echinococcus granulosus in Uttah Pradesh, India

The present study investigated the suitability and importance of buffaloes, camels, sheep, goats and pigs in maintaining the life-cycle of Echinococcus granulosus in Aligarh, India. A total of 565 (36%) of 1556 buffaloes, 20 (2%) of 1208 goats, 5 (1%) of 559 pigs, 6 (6%) of 109 sheep and two of three camels were found to harbour hydatid cysts. The frequency distribution of the hydatid cysts in each intermediate host species was over-dispersed and in buffaloes cyst fertility increased with increasing cyst size. Of 2171, 95 and four buffalo, goat, and camel cysts examined 327 (15%), two (2%) and three cysts respectively were fertile. No pig or sheep cysts were found to contain protoscoleces. The unfenced buffalo abattoir and the large number of dogs allowed access to the abattoir coupled to the number of buffalo slaughtered in comparison to the other potential hosts, indicates that the buffalo is the most significant host for maintaining the life-cycle of the parasite in this area of India. Applicable control measures for the region are suggested.     

微生物在藻际环境中的物质循环作用

浮游植物作为海洋初级生产力的主要驱动者,其功能的发挥与共生微生物密不可分.藻类(甲藻、硅藻或蓝藻)的栖息环境中存在多样的共生细菌,各类细菌拥有不同的组成比例,但某些异养细菌在藻际环境中总是占据优势地位,如变形杆菌、黄杆菌及放线菌等.基于微生物在调节微食物网、促进物质循环和维持生态系统平衡中的重要意义,本文主要以赤潮事件的藻际环境为例,尝试梳理上述主导性“常驻微生物”在“藻-菌”共生体物质转化中的作用.特别是针对近些年来倍受关注的黄杆菌和玫瑰杆菌,着重例述了它们在物质代谢中的行为与生态策略,以更好地理解常驻物种在藻际生态位中的生态行为与协同进化.     

In vivo antioxidant role of astaxanthin under oxidative stress in the green alga Haematococcus pluvialis

Intracellular production of active oxygen in the green alga Haematococcus pluvialis was studied by measuring the capacity for in vivo conversion of 2′,7′-dichlorohydrofluorescein diacetate to the fluorescent dye dichlorofluorescein in different algal cell types (i.e., vegetative, immature cyst and mature cyst cells). The increase in formation of dichlorofluorescein by methyl viologen (superoxide anion radical generator) was linear for 2 h in immature cyst cells (low astaxanthin) in a methyl viologen-concentration-dependent manner, while no production was detected in mature (high astaxanthin) cysts. Compared to cyst cells, formation of dichlorofluorescein in vegetative cells (no astaxanthin) was markedly increased by methyl viologen. The formation of dichlorofluorescein in cyst cells was decreased with higher astaxanthin content under excessive oxidative stress. All of the active oxygen species tested (singlet oxygen, superoxide anion radical, hydrogen peroxide and peroxy radical) at 10⁻³ M increased the intracellular dichlorofluorescein formation in immature cysts, but did not increase the dichlorofluorescein content of mature cysts. Therefore, astaxanthin in cyst cells appeared to function as an antioxidant agent against oxidative stress. Received: 26 January 2000 / Received revision: 5 April 2000 / Accepted: 1 May 2000     

Factors controlling induction of reproduction in algae—review: the text

This review surveys on the influence of different environmental factors like light (intensity, quality, photoperiod), temperature, season, nutrients (inorganic, organic), biotic factors (algal extracellular products, bacterial association, animals grazing), osmotic stress, pH of the medium, wave motion and mechanical shock, pollution, and radiations (UV, X-rays, gamma radiation) on the induction (or inhibition) of algal reproduction like cell division in unicellular algae, and formation of zoospores, aplanospores, akinetes, cysts, antheridia, oogonia, zygospores, etc.     

Astaxanthin biosynthesis enhanced by reactive oxygen species in the green algaHaematococcus pluvialis

The unicellular green algaHaematococcus pluvialis has recently attracted great interest due to its large amounts of ketocarotenoid astaxanthin, 3,3′-dihydroxy-β,β-carotene-4,4′-dione, widely used commercially as a source of pigment for aquaculture. In the life cycle ofH. pluvialis, astaxanthin biosynthesis is associated with a remarkable morphological change from green motile vegetative cells into red immotile cyst cells as the resting stage. In recent years we have studied this morphological process from two aspects: defining conditions governing astaxanthin biosynthesis and questioning the possible function of astaxanthin in protecting algal cells against environmental stress. Astaxanthin accumulation in cysts was induced by a variety of environmental conditions of oxidative stress caused by reactive oxygen species, intense light, drought, high salinity, and high temperature. In the adaptation to stress, abscisic acid induced by reactive oxygen species, would function as a hormone in algal morphogenesis from vegetative to cyst cells. Furthermore, measurements of bothin vitro andin vivo antioxidative activities of astaxanthin clearly demonstrated that tolerance to excessive reactive oxygen species is greater in astaxanthin-rich cysts than in astaxanthin-poor cysts or astaxanthin-less vegetative genesis and carotenogenesis, and the accumulated astaxanthin in cysts can function as a protective agent against oxidative stress damage. In this study, the physiological roles of astaxanthin in stress response and cell protection are reviewed.     

128 Capturing the Light Fantastic: Oceanographic and Tidal Influences on Intertidal Algae

Seaweeds experience many challenges to their persistence in intertidal zone habitats. Their growth rates must exceed losses associated with a range of ecological and physiological factors including desiccation, herbivory and wave forces. Growth rates depend on an alga's ability to capture and process light to build carbon-based molecules. We examined local (tidal height) and large (oceanographic) scale influences on algal photosynthetic efficiency and light climate, respectively. At the local scale, we combined periodic measurements of physiological state using PAM fluorometry with traditional demographic monitoring of a Postelsia palmaeformis , population over a tidal height gradient. Parameter estimates derived from rapid fluorescence-irradiance curves were correlated with longer-term ecological performance measures including growth rate, morphology, survivorship and reproductive output. At larger scales, we made continuous in situ measurements of chlorophyll fluorescence and light attenuation in the intertidal zone at six sites during 2001 and 2002. Light attenuation to the benthos was sharply reduced at sites when chl-a fluorescence was high. Long-term, large-scale monitoring of intertidal zone chl-a and macroalgal abundances documents that striking differences among sites are persistent and associated with oceanographic factors. The light saturation parameter and maximum photosynthetic rate calculated for several common intertidal macrophytes, along with published values of the irradiance needed to saturate their growth rates, suggest that underwater light levels may limit intertidal algal growth where phytoplankton blooms are common and persistent. We conclude that physiological stress associated with tidal and oceanographic factors contribute to macroalgal distributions.     

Ecological Consequences of Sediment on High-Energy Coral Reefs

Sediments are widely accepted as a threat to coral reefs but our understanding of their ecological impacts is limited. Evidence has suggested that benthic sediments bound within the epilithic algal matrix (EAM) suppress reef fish herbivory, a key ecological process maintaining reef resilience. An experimental combination of caging and sediment addition treatments were used to investigate the effects of sediment pulses on herbivory and EAMs and to determine whether sediment addition could trigger a positive-feedback loop, leading to deep, sediment-rich turfs. A 1-week pulsed sediment addition resulted in rapid increases in algal turf length with effects comparable to those seen in herbivore exclusion cages. Contrary to the hypothesised positive-feedback mechanism, benthic sediment loads returned to natural levels within 3 weeks, however, the EAM turfs remained almost 60% longer for at least 3 months. While reduced herbivore density is widely understood to be a major threat to reefs, we show that acute disturbances to reef sediments elicit similar ecological responses in the EAM. With reefs increasingly threatened by both reductions in herbivore biomass and altered sediment fluxes, the development of longer turfs may become more common on coral reefs.     

藻际环境中胞外聚合物的研究进展

微藻向细胞周围释放营养物质而形成了独特的藻际微环境,吸引了大量细菌的定殖。藻际环境中藻菌关系错综复杂,其间充斥着多样的物质交换与信息交流。以胞外聚合物(extracellularpolymeric substances,EPS)为代表的有机质在其中起着纽带作用。微藻和细菌都可以产生EPS,其过程受多种因素的调节。EPS在藻际环境中具有重要的生态功能,包括参与生物被膜(biofilm)的形成,影响藻菌共生关系的建立以及调节藻际微生物群落组成等。此外,EPS中的一大类别透明胞外聚合物颗粒(transparent exopolymer particles,TEP)还介导了海洋溶解有机碳向颗粒有机碳的转化,参与了海洋碳循环过程。本文以EPS的产生、组成以及对碳转化的影响为重点,综述了其在藻际生态位(Niche)中的生态功能,以期为深入理解藻际环境中的有机质特征和藻菌共生关系提供理论依据。