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.       

大亚湾近代沉积物中甲藻孢囊的垂直分布

用TFO采泥器于 2 0 0 1年 8月采集了大亚湾大鹏澳海域 6个采样点 8— 18cm柱状沉积物样品 ,分层研究了甲藻孢囊在该海域表层沉积物中的垂直分布。在 35个沉积物样品中共分析鉴定出甲藻孢囊 4 8种 ,其中自养型 2 0种 ,异养型 2 8种 ,优势种类为锥状斯氏藻。每个样品中所分析鉴定的孢囊种类数为 12— 2 9种 ,孢囊的香农—威弗种类多样性指数 (Shannon WeaverDiversityIndex,H′)为 0 6 1— 4 13,并且在 2— 4cm层次处 ,随深度的增加 ,两者均有一个明显上升趋势。除鱼类养殖区的上表层较高外 ,孢囊丰度大多为 10 0 0— 2 0 0 0cysts/gDWt,最高为 2 38× 10 4cysts/gDWt。亚历山大藻孢囊分布广泛且密度较高 ,最高丰度为 5 0 3cysts/gDWt,同时表层沉积物中高密度的亚历山大藻孢囊为该藻赤潮的发生提供了丰富的种源 ,而且也是该海域贝类体内冬季PSP毒素积累及高含量的重要原因。     

中国渤海海域甲藻孢囊的种类多样性和生态地理分布

在渤海湾24个站位采集0–10 cm表层沉积物144份样品, 进行甲藻孢囊的种类多样性和生态地理分布研究, 并分析渤海海域水体的富营养化趋势。在渤海海域共采集鉴定出6类32种甲藻孢囊, 包括原多甲藻类孢囊11种、裸甲藻类孢囊6种、膝沟藻类孢囊7种、钙质类孢囊5种、翼藻类孢囊2种及Tuberculodinioid类孢囊1种。其中, 自养型甲藻孢囊17种, 优势种为锥状斯氏藻(Scrippsiella trochoidea)孢囊, 丰富的孢囊库为锥状斯氏藻赤潮提供种源, 可作为该海域发生锥状斯氏藻赤潮的参考依据; 异养型甲藻孢囊15种, 优势种为无纹多沟藻(Polykrikos schwartzii)和锥形原多甲藻(Protoperidinium conicum)孢囊; 发现1种产麻痹性贝类毒素的孢囊--塔玛亚历山大藻(Alexandrium tamarense)孢囊, 但是仅在S6、S8和S14三个站位发现, 且孢囊数量较少。渤海甲藻孢囊组成与世界其它海域相似, 异养型甲藻孢囊种类丰富, 提示渤海海域富营养化程度较高。每个站位沉积物样品分为3层(每层约3 cm), 春夏两季表层、中层和底层之间孢囊组成差异不大, 平均种类数为5.58–7.29, 孢囊的平均密度范围在58.82–103.57 cysts·g^–1 DW之间; 孢囊种类丰富的站点, 孢囊密度也较高, 如S9、S14站位。对渤海海区表层沉积物中甲藻孢囊的生物多样性进行了统计分析, 发现表、中、底3层甲藻孢囊的平均种类多样性指数在春季(5月)分别为1.69、1.61和1.52; 略低于夏季(8月)的1.83、1.89和1.60。     

黑暗、温度对锥状斯氏藻暂时性孢囊形成、存活与萌发的影响

锥状斯氏藻(Scrippsiella trochoidea)是一种世界性的赤潮甲藻,暂时性孢囊是甲藻为了抵御瞬时不良环境条件而形成的不动细胞,暂时性孢囊在锥状斯氏藻生活史及其赤潮发生过程中充当着重要的角色。本文研究了黑暗和温度(8、20和25℃)对锥状斯氏藻暂时性孢囊形成、存活与萌发的影响。结果表明:暂时性孢囊在黑暗处理的第1天就开始形成,在第3～5天孢囊形成率达到最高,且常温下孢囊形成高峰延迟,8、20和25℃下孢囊的最终累积形成率分别为15.9%、20.1%和9.9%;同时,暂时性孢囊不耐保存,在形成后第1天即出现死亡,第8～16天后全部死亡;暂时性孢囊在低温下存活时间较长,8、20和25℃下半存活时间分别为5.9、2.9和2.7 d;暂时性孢囊不存在强制性休眠期,全部处理组的暂时性孢囊均在培养后的24 h内开始萌发,3～6 d内达到最大累积萌发率,为43.3%～65.6%,低温下形成的孢囊萌发率较高;锥状斯氏藻极易形成暂时性孢囊,当环境条件合适时能迅速萌发,说明暂时性孢囊在锥状斯氏藻种群动态以及赤潮形成和消亡过程中具有重要作用。     

深圳湾表层沉积物中甲藻孢囊的垂直分布

采集了深圳湾3个采样点约20cm的表层沉积物样品,研究了甲藻孢囊的垂直分布。共分析鉴定出孢囊类型37种,其中5种为我国沿海未报道的新记录类型,原多甲藻类孢囊是该海域种类最丰富的孢囊类型。除上表层沉积物外,深圳湾甲藻孢囊密度较低,孢囊密度大多在500cysts／gDWt以下,总孢囊密度变化范围为83～4036cysts／gDWt之间。锥状斯氏藻是深圳湾甲藻孢囊的优势种类,上表层沉积物中该孢囊密度的急剧上升证实了2000年附近海域所发生的该藻赤潮。而裸甲藻类孢囊含量明显比南海其他海域高。孢囊的香农-威弗种类多样性指数为1．50～3．96之间,并且在非养殖区、离岸海域及较深层次沉积物中较高,而孢囊密度则呈相反的变化趋势。种类多样性的下降及孢囊密度的上升在一定程度上说明深圳湾污染的变化趋势,富营养化程度非养殖区大于养殖区,近岸海域大于离岸海域,并且近年来污染逐渐加剧。     

氮磷限制对锥状斯氏藻孢囊形成的作用

在实验室研究了锥状斯氏藻(Scrippsiellatrochoidea)在N、P单因子营养限制(N:500μg.L-1,P:74～0.74μg.L-1和P:74μg.L-1,N:500～5μg.L-1)条件下的生长和孢囊形成。结果显示N、P限制不利于锥状斯氏藻的快速生长,其中低P对细胞生长的限制作用更显著。其孢囊形成率在15～99%之间,中度N限制能促进孢囊的形成,形成率几乎可达100%。孢囊一般在对数生长期结束、细胞数量达到最大值时开始形成。但由于接种后营养盐浓度的急剧降低,营养极度限制组孢囊可在接种后第1d就开始形成。结果显示稳定生长期孢囊的大量形成大大降低了锥状斯氏藻营养细胞数量,能在一定程度上促进其赤潮的消亡。     

热带亚热带植物学报 第15卷第1-6期总目录

第1期香根草属与狼尾草属植物对土壤线虫营养类群的影响邵元虎,夏汉平,周丽霞,林永标,赵灿灿,傅声雷(1)大亚湾海域锥状斯氏藻孢囊形成与萌发的季节变化王朝晖,齐雨藻,辜小莲(9)中国主栽香蕉品种和INIBAP引进品种的SSR分析研究宁淑萍,许林兵,魏平,葛学军(16)姜花(Hedychium coro     

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。       

甲藻孢囊在长江口海域表层沉积物中的分布

为了了解长江口海域赤潮爆发潜势,于2002年4月至5月用采泥器采集了位于122°～123．5°E、29°～32°N之间12个站位的表层沉积物,分析沉积物中甲藻孢囊的分布．共分析鉴定出孢囊类型29种,其中自养型11种,异养型18种．每个站位的孢囊种类在10～21之间,孢囊密度为11．7～587孢囊·g-1干泥之间．远岸海域孢囊种类较为丰富,密度也较高．在调查区域内,孢囊密度及种类自西向东、自北向南逐渐增加．亚历山大藻孢囊分布广泛,最高密度为40．4孢囊·g-1干泥,其他赤潮种类的孢囊如链状裸甲藻、多边舌甲藻、锥状斯氏藻、科夫多沟藻和无纹多沟藻等都在长江口海域有分布．     

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。     

Relationship between vegetative cells and cyst production during Alexandrium minutum bloom in Arenys de Mar harbour (NW Mediterranean)

A recurrent Alexandrium minutum bloom in the Arenys de Mar harbour(Catalan coast, North Western Mediterranean) was monitored inorder to establish the relationship between vegetative cellsand cyst production. The bloom lasted from January 21 to February24, 2002 and reached cell concentrations of up to 47 x 10⁶ cellL^–1. Two aspects related to the resting cysts depositionwere studied: (i) production of resting cysts during the bloomperiod (by means of sediment traps) and (ii) distribution ofresting cysts in the sediment after the bloom (May 2002). Cystformation in Arenys clearly started in a period with high vegetativecell densities in the water column. Once production was initiatedencystment fluxes remained constant for two weeks, and coveringthe periods of maintenance and decline of the bloom. High cystfluxes (up to 6000 cysts cm^–2 day^–1) were quantifiedas a result of the high vegetative cell concentration. Moreover,encystment occurring in less than 1% of the total populationindicates that most of the cells are not involved in restingcysts formation. A comparison of the resting cyst flux valuesobtained from the sediment traps and the resting cyst concentrationsin surface sediment (628–3270 cysts cm^–3) threemonths later, revealed that the number of cysts in the sedimentdecreased during that time. The studies of excystment showeda high germination percentage (91%) and germling viability (100%).These data, together with the resting cyst distribution in thesediment, are important in assessing the role of resting cystsin the bloom dynamics of A. minutum in confined waters.     

Distribution, dynamics and in situ seeding potential of Scrippsiella hangoei (Dinophyceae) cyst populations from the Baltic Sea

The distribution and seasonal dynamics of cyst populations ofthe spring bloom dinoflagellate Scrippsiella hangoei were studiedin surface sediments on the southwest coast of Finland, BalticSea. In situ germination was assessed by monitoring the fractionof empty cysts and chlorophyll a fluorescence in cyst populationsat different coastal sites throughout the annual cycle. Scrippsiellahangoei resting cysts were widely distributed in the study areaand occurred in exceptionally large numbers (magnitudes of 10⁴–10⁶cysts cm^–3) at all sampling locations between the innermostparts of the coastal archipelago and the open Gulf of Finland.The decreases in cyst number in winter and the increases occurringin late spring reflected the dynamics of germination and encystmentof the species. Chlorophyll fluorescence appeared in mid-winterin ~40% of cysts from well-aerated basins and 6–15% ofcysts from temporarily anoxic sediments. A generally low increasein the proportion of empty cysts indicated that only a partof the potentially germinable cysts actually germinates. Giventhe high cyst concentrations in the sediments, the potentialfor germination is considerable, despite the environmentallyand physiologically determined losses. In contrast, the sizeof the vegetative inoculum is very low, indicating that thesurvival of germlings is problematic under harsh winter conditions.This is an unusual life cycle strategy; however, the early releaseof cells into the water column provides a high probability forsuccessful bloom initiation under the unpredictable meteorologicalconditions in winter and early spring, which often lead to thesudden onset of favourable growth conditions.     

Encystment of Peridinium gatunense: occurrence, favourable environmental conditions and its role in the dinoflagellate life cycle in a subtropical lake

1. The abundance of cysts of the bloom‐forming dinoflagellate Peridinium gatunense in the sediments of Lake Kinneret and the effects of environmental conditions on encystment were studied in relation to bloom dynamics. Peak cyst formation coincided with the highest growth rate of the population, prior to bloom peak. 2. Peridinium cysts were counted in water and sediment corer samples from 2000 to 2003 and in archived sediment trap samples collected during 1993–94. The cyst data were examined in relation to ambient temperature and nutrient records, and revealed no direct correlation. 3. In laboratory encystment experiments with Peridinium cells collected from the lake, 0.2–3% of the vegetative cells encysted. Temperature, light and cell density had no significant effect on the percentage of encystment. 4. Cysts were always present in the lake sediments but their abundance in ‘non Peridinium’ years was much lower than after a massive bloom. Vegetative cells were always present in the water column after the collapse of the annual dinoflagellate bloom, potentially serving as the inoculum for the next bloom. We propose that the hardy cysts serve as an emergency ‘gene bank’ to initiate population build up following catastrophic die outs.     

Dinoflagellate resting cysts as factors in phytoplankton ecology of the North Sea

The occurrence and distribution of dinoflagellate resting cysts were investigated at 11 locations in the south-eastern part of the North Sea. Twenty-six known cyst species and 7 unknown cyst types, which may act as seed population for planktonic dinoflagellate blooms, have been recorded for the first time in the area. The most common cysts in recent sediments were those ofScrippsiella trochoidea, Zygabikodinium lenticulatum, Peridinium dalei, Scrippsiella lachrymosa, Protoceratium reticulatum, Protoperidinium denticulatum, andP. conicum. At all stations,S. trochoidea dominated the cyst assemblages with a maximal abundance of 1303 living cysts/cm³ in the uppermost half centimetre. Cysts of the potentially toxic dinoflagellatesAlexandrium cf.excavatum andA. cf.tamarense were scarce. In the upper 2-cm layer of sediment, dinoflagellate cysts were found in concentrations of 1.8 up to 682 living cysts/cm³. Empty cysts constituted 22–56% of total cyst abundance. The comparative distribution of the cysts showed a general increase in abundance from inshore sites to the offshore area, whereby sandy stations exhibited the lowest cyst abundance and diversity. The wide distribution of living and empty cysts ofScrippsiella lachrymosa suggests that its motile form, which has not been officially recorded in the area until now, is a common plankton organism in German coastal waters. The relatively high abundance of cysts in recent sediments demonstrates the potential importance of benthic resting stages for the initiation of dinoflagellate blooms in the study area.     

Cyst formation: an important mechanism for the termination of Scrippsiella trochoidea (Dinophyceae) bloom

A sediment trap study was conducted at Daya Bay, South ChinaSea, to investigate the relationships between encystment andpopulation dynamics of Scrippsiella trochoidea from December1999 to January 2001. A dense bloom of S. trochoidea occurredduring the study period from August to September 2000, withthe maximum cell number of 3.18 x 10⁴ cells mL^–1.Two morphotypes of cysts, one with a thick calcareous wall (calcifiedcyst) and another without the obvious calcareous cover (non-calcifiedcyst), were observed during this investigation. The morphologicaland excystment characteristics of these two cyst types werestudied as well. Mass encystments of S. trochoidea, with themaximum of 3.05 x 10⁵ cysts m^–2 d^–1for calcified cyst, and 1.54 x 10⁷ cysts m^–2 d^–1for non-calcified cyst, coincided with the maximum abundanceof the vegetative cells. Encystment caused the transfer of atotal of 2.24–4.49 x 10⁸ cells m^–2 vegetativecells from the water column to the sea bottom during the bloomand resulted in a considerable loss of the bloom population.High assemblages of cysts of S. trochoidea were detected inthe surface sediments as well. This rich ‘seed bed’in the surface sediments caused by the high efficiency of encystmentafter blooms acting as a benthic reservoir for future vegetativepopulation, together with the short dormant period (15–26days) and high germination rate (50–90%), may explainthe repeated occurrence of S. trochoidea blooms in Daya Bay.     

Dinoflagellate cysts from surface sediments of Saldanha Bay, South Africa: an indication of the potential risk of harmful algal blooms

The distribution and abundance of dinoflagellate cysts from recent coastal sediments in Saldanha Bay, was investigated, and compared to the cyst assemblages of the adjacent coastal upwelling system as reflected in the sediments off Lambert's Bay on the southern Namaqua shelf. Twenty-two cyst types were identified from three sample sites off Lambert's Bay with recorded abundances between 1726 and 1863 cysts ml⁻¹ wet sediment. At least 21 distinctive cyst types were identified from 32 sample sites within Saldanha Bay. Cyst abundance in Saldanha Bay was relatively low, averaging 116 cysts ml⁻¹ wet sediment. The region off Lambert's Bay is especially susceptible to the formation of harmful algal blooms attributed to high biomass dinoflagellate blooms. Owing to these blooms and the retentive circulation characteristics of this area, cyst formation and deposition is high. Blooms can be advected into Saldanha Bay, but their development and duration in the Bay is restricted by the system of exchange that operates between the Bay and the coastal upwelling system, in that there is a net export of surface waters from the Bay. Consequently, fewer cysts are formed and deposited within the Bay thereby reducing the likelihood of in situ bloom development initiated from the excystment of cysts.     

Germination fluctuation of toxic Alexandrium fundyense and A. pacificum cysts and the relationship with bloom occurrences in Kesennuma Bay,Japan

While cyst germination may be an important factor for the initiation of harmful/toxic blooms, assessments of the fluctuation in phytoplankton cyst germination, from bottom sediments to water columns, are rare in situ due to lack of technology that can detect germinated cells in natural bottom sediments. This study introduces a simple mesocosm method, modeled after previous in situ methods, to measure the germination of plankton resting stage cells. Using this method, seasonal changes in germination fluxes of toxic dinoflagellates resting cysts, specifically Alexandrium fundyense (A. tamarense species complex Group I) and A. pacificum (A. tamarense species complex Group IV), were investigated at a fixed station in Kesennuma Bay, northeast Japan, from April 2014 to April 2015. This investigation was conducted in addition to the typical samplings of seawater and bottom sediments to detect the dinoflagellates vegetative cells and resting cysts. Bloom occurrences of A. fundyense were observed June 2014 and February 2015 with maximum cell densities reaching 3.6 × 10⁶ cells m⁻² and 1.4 × 10⁷ cells m⁻², respectively. The maximum germination fluxes of A. fundyense cysts occurred in April 2014 and December 2014 and were 9.3 × 10³ cells m⁻² day⁻¹ and 1.4 × 10⁴ cells m⁻² day⁻¹, respectively. For A. pacificum, the highest cell density was 7.3 × 10⁷ cells m⁻² during the month of August, and the maximum germination fluxes occurred in July and August, reaching 5.8 × 10² cells m⁻² day⁻¹. Thus, this study revealed the seasonal dynamics of A. fundyense and A. pacificum cyst germination and their bloom occurrences in the water column. Blooms occurred one to two months after peak germination, which strongly suggests that both the formation of the initial population by cyst germination and its continuous growth in the water column most likely contributed to toxic bloom occurrences of A. fundyense and A. pacificum in the bay.     

Production of Monoclonal Antibody against Scrippsiella trochoidea Cysts and Its Application to Analysis during Cyst Formation and Enzyme-linked Immunosorbent Assay

A monoclonal antibody was produced by the fusion of mouse myeloma cells with spleen cells from a mouse immunized with the cysts of Scrippsiella trochoidea, marine phytoplankton. Immunofluorescence micro-scopic observation showed that the antibody reacted with the spines on the cyst but not with the vegetative cells and cyst walls. An enzyme-linked immunosorbent assay could be used to measure the cysts in muddy bottom sediments using the purified antibody conjugated with horseradish peroxidase.     

Production of monoclonal antibody against Scrippsiella trochoidea cysts and its application to analysis during cyst formation and enzyme-linked immunosorbent assay

A monoclonal antibody was produced by the fusion of mouse myeloma cells with spleen cells from a mouse immunized with the cysts of Scrippsiella trochoidea, marine phytoplankton. Immunofluorescence microscopic observation showed that the antibody reacted with the spines on the cyst but not with the vegetative cells and cyst walls. An enzyme-linked immunosorbent assay could be used to measure the cysts in muddy bottom sediments using the purified antibody conjugated with horseradish peroxidase.