不同起始密度对3种赤潮微藻种间竞争的影响

通过共培养的方法,研究了不同起始密度对赤潮异弯藻和中肋骨条藻、塔玛亚历山大藻和赤潮异弯藻、塔玛亚历山大藻和中肋骨条藻之间种间竞争的影响。结果表明1赤潮异弯藻对中肋骨条藻的生长有一定的抑制作用,随着初始接种时赤潮异弯藻细胞密度的提高,这种抑制作用愈加明显。2塔玛亚历山大藻和中肋骨条藻与塔玛亚历山大藻和赤潮异弯藻之间的种间竞争结果相类似,即起始密度比例为A∶S(H)=1∶4时,中肋骨条藻和赤潮异弯藻分别在竞争中占优势;当起始密度比例为A∶S(H)=1∶1和A∶S(H)=4∶1,塔玛亚历山大藻在竞争中占优势。     

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。     

塔玛亚历山大藻对黑褐新糠虾存活、生长以及种群繁殖的影响

通过塔玛亚历山大藻 ( Alexandrium tamarense)对黑褐新糠虾 ( N eomysis awatschensis)的急性和慢性毒性作用研究 ,发现塔玛亚历山大藻对黑褐新糠虾的存活、生殖、生长等有不利影响 ,影响程度随塔玛亚历山大藻藻细胞密度的增加而增加。在 96 h急性毒性实验中 ,塔玛亚历山大藻对黑褐新糠虾的半致死密度为 70 0 0 cells/ml,去藻过滤液中糠虾的死亡率为 2 5 %。在 6 2 d的慢性毒性实验中 ,密度为 90 0 cells/ml的塔玛亚历山大藻对黑褐新糠虾的繁殖有严重影响 ,在此影响下的实验组亲虾产幼虾总数只有 2 7尾 ,仅为对照组产幼虾数目的 1 6 .4 % ;其总产幼虾天数、日最高产幼数分别只有对照的 32 %、4 1 % ,其初次产虾日期也推迟了 3d,并出现了 3次生殖中断。塔玛亚历山大藻对黑褐新糠虾亲虾的存活、生长也有一定的影响 ,处在密度为 90 0 cells/ml塔玛亚历山大藻中的黑褐新糠虾亲虾的存活率只有对照的 6 3% ,糠虾亲虾的体长和体重分别为对照组亲虾的 95 .6 %和 81 .9% ,但差异尚不显著 ( P>0 .0 5 )     

营养盐限制条件下塔玛亚历山大藻对东海原甲藻的化感作用研究

为明确塔玛亚历山大藻(Alexandrium tamarense)对东海原甲藻(Prorocentrum donghaiense)生长的化感作用,研究了在N、P限制及正常营养盐条件下(又称富营养)塔玛亚历山大藻无细胞滤液对东海原甲藻生长的影响,并探讨了3种不同营养盐条件下两种藻共培养时的生长状况。结果表明,半连续培养时,营养盐限制下,塔玛亚历山大藻无细胞滤液对东海原甲藻的生长均有一定影响。N限制下,5 d后东海原甲藻藻密度显著低于未加滤液的对照组,藻密度为1.02×107 cells L-1,对照组为1.7×107 cells L-1;P限制下,东海原甲藻藻密度与对照组差异不显著,5 d后藻密度为1.44×107 cells L-1;富营养条件下,东海原甲藻藻密度与对照组无明显区别。共培养时,塔玛亚历山大藻对东海原甲藻生长的抑制作用更为显著,N、P限制下,4 d后东海原甲藻全部死亡,且聚集成团形成沉淀;富营养条件下,仍有少量东海原甲藻存活(藻密度3.3×104 cells L-1)。这表明,塔玛亚历山大藻对东海原甲藻的生长有一定的化感作用。营养盐限制可促进塔玛亚历山大藻化感物质的合成和释放,化感作用是塔玛亚历山大藻抑制东海原甲藻生长的原因之一。     

我国东南沿海亚历山大藻休眠孢囊的分布和萌发研究

对4个海域的塔玛亚历山大藻(Alerandrium tamarense)和链状亚历山大藻(A．catenella)休眠孢囊的分布及萌发进行了研究．结果表明,厦门港仅在X1和X2站位有分布,且密度很小(0．4个·g-1);广西只在G2站位有发现,密度较少(2．5个·g-1泥样)．闽江口有3个站位有分布,M4站位的4～6cm层密度最大,达到6个·g-1泥样;长江口的孢囊分布广、密度大,DG-26站位的8～10cm层孢囊密度达到了23．2个·g-1泥样．孢囊的分布与沉积物底质类型、沉积速率、海流都有一定的关系．光照对孢囊萌发没有影响,温度升高导致萌发率和存活率均增大,而萌发时间缩短;在低氧条件下(0．01mgO2L-1),孢囊萌发率为0．亚历山大藻孢囊在合适的环境条件下终年都会萌发     

浙江南麂海域塔玛亚历山大藻种群动态及其与环境因子的关系

基于2006年4月至2007年3月在浙江南麂海域的调查结果,对南麂海域塔玛亚历山大藻的种群动态及其与环境因子的关系进行了研究.结果表明：塔玛亚历山大藻在南麂海域仅出现在春季（4—6月）;藻细胞密度在春季呈规则的单峰曲线,表层水体中藻细胞密度的最高值（12250 cells·L^-1）出现在5月8日;塔玛亚历山大藻集中出现在水温18.5 ℃～19.5℃、盐度29.5‰～31.0‰的水体中;较高的藻细胞密度与较低的磷酸盐浓度相对应,氮盐浓度的变化与藻细胞密度之间没有明显的对应关系.逐步线性回归结果表明,塔玛亚历山大藻细胞密度与N∶P存在显著的正相关关系.     

有毒赤潮甲藻塔玛亚历山大藻（香港株Ⅱ）的生长特性研究

在室内条件下研究温度、N和P、维生素、抗生素对有毒赤潮甲藻塔玛亚历山大藻(香港株Ⅱ生长的影响。结果表明,塔玛亚历山大藻的适宜生长温度和N、P浓度分别为21-25℃,882-1765μmol／L和18-72μmol／L。复合维生素B的加入有利于塔玛亚历山大藻的生长,而50Uml^-1以上的抗生素则对其有明显的抑制作用。     

N、P营养盐对塔玛亚历山大藻（Alexandrium tamarense）生长的影响

模拟自然海水营养盐浓度状况,在N、P浓度分别为10-500μg L-1 N和0.74-74μg L-1 P时,研究N、P双因子限制(N、P浓度同时降低,N:P固定为15:1)及单因子限制(保持N或P为最高浓度,只降低一种营养盐浓度)对有毒赤潮藻塔玛亚历山大藻(Alexandrium tamarense)生长的影响。结果表明,塔玛亚历山大藻细胞能较快进入对数生长期,但N、P双因子限制能明显影响其生长,在N、P浓度分别低于100μg L-1 N和15μg L-1 P时,细胞密度无明显增长;而N或P分别受限时,生长态势明显优于N、P同时受到限制的试验组,而且N、P单因子中度限制对生长影响较小。结果说明塔玛亚历山大藻对单因子营养元素限制较强的适应能力,可使其在常常出现单营养因子限制的自然水体中维持一定生长速率和细胞密度,并有助于滤食该藻的贝类体内麻痹性贝类毒素的积累。     

特丁基三嗪对两种赤潮藻去除的实验研究

研究了特丁基三嗪(tertbutyl triazille)对塔玛亚历山大藻和球形棕囊藻两种赤潮生物的杀灭和控制作用。结果表明,特丁基三嗪能有效地控制和杀灭塔玛亚历山大藻和球形棕囊藻,其中96h杀灭塔玛亚历山大藻的有效浓度为0．2mgL^-1,杀灭球形棕囊藻的有效浓度为0.3mgL^-1。特丁基三嗪具有高效、作用时效长的特点,可能是一种比较理想的赤潮藻去除剂。     

有害赤潮藻种塔玛亚历山大藻的研究进展

塔玛亚历山大藻(Alexandrium tamarense)是一种全球分布的有毒涡鞭毛藻,在中国的渤海、东海和南海海域均有分布。塔玛亚历山大藻是一种主要的有毒赤潮原因种,而且它能产生可经食物链传递后在贝类、鱼类等生物体内大量蓄积的麻痹性贝毒素,对水域环境和人类健康都具有极大的危害。因此,针对塔玛亚历山大藻的产生、发展以及毒素的特征等开展了广泛而深入的研究。本文主要从塔玛亚历山大藻的生长环境、分子鉴定、藻际竞争关系以及治理等方面进行了综述,为研究塔玛亚历山大藻的利弊和监控提供参考。     

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.     

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.       

大亚湾海域锥状斯氏藻孢囊形成与萌发的季节变化

锥状斯氏藻(Scrippsiella trochoidea)是南海大亚湾海域优势甲藻。为了解该藻孢囊形成和萌发动态及其对营养细胞种群动态的影响,2001年1月-2002年1月在大亚湾澳头海域用沉积物捕捉器及TFO重力采泥器对其孢囊进行每月一次的周年监测,同时对浮游植物、水温、盐度、溶解氧等也进行了监测。孢囊形成和萌发分别以沉积物捕捉器中的孢囊形成率以及上表层沉积物中空孢囊的百分比来表示。钙质孢囊和非钙质孢囊年平均形成率分别为1.11×104 cysts m-2d-1和2.13×105 cysts m-2d-1。前者在冬季大量形成,而后者在夏季形成较多。孢囊多在春秋季节萌发,夏季萌发较少,而冬季几乎不萌发。在5月份和10月份营养细胞数量峰形成前,孢囊的萌发出现了高峰,而表层沉积物中的孢囊数量及孢囊形成率则在营养细胞数量峰后大幅度上升。由此可见,大亚湾沉积物中该藻孢囊的萌发给水体提供了丰富的营养细胞,反之水体中高密度营养细胞又促使孢囊的大量形成,从而造成了锥状斯氏藻赤潮在大亚湾海域接连发生。     

Modelling the population dynamics of the toxic dinoflagellate Alexandrium tamarense in Hiroshima Bay, Japan. II. Sensitivity to physical and biological parameters

Using the numerical model developed in a previous paper [Yamamotoet al. (2002c) J. Plankton Res., 24, 33–47], the sensitivityof population dynamics of Alexandrium tamarense to physicaland biological parameters was analysed. Horizontal and verticaldiffusions led to the dispersion of dense A. tamarense populationsin the surface layer of the innermost portion of the bay. Temperatureand salinity influenced the timing of the A. tamarense bloomdue to its stenothermal and stenohaline characteristics. Althoughincreasing the light intensity caused the bloom of A. tamarenseto begin earlier, it lowered the cell density at the bloom peakas a result of phosphate depletion in the ambient water. Bothincreasing the cyst density and the excystment rate had littleinfluence on the population dynamics of A. tamarense vegetativecells. Increasing the phosphate concentration led to increasesin cell density of A. tamarense, indicating that growth is phosphate-limited.Oysters, which are cultured intensively in this bay, appearto stimulate the bloom of A. tamarense through the regenerationof phosphorus from their faeces/pseudofaeces. The phosphorusreduction measure that has been taken since 1980 and the recentconstruction of a large dam are discussed as important factorsthat may influence the population dynamics of A. tamarense.     

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．     

Dinoflagellate cyst records in recent sediments from Daya Bay, South China Sea

Nine sediment cores of 8–26 cm in length were collected from two basins of Daya Bay, the South China Sea, by Tokyo University Fisheries Oceanography Laboratory core sampler in August 2001 to investigate the distribution of dinoflagellate resting cysts. In the present study, 51 different cyst morphotypes representing 22 genera were identified from 65 sediment samples. Among them, there were 21 autotrophic species and 30 heterotrophic ones. Cyst species richness in each sample varied from 12 to 29, while the values of Shannon‐Weaver diversity index (H′) were between 0.15 and 4.13. There were an obvious increase in both species richness and values of H′in 2–6 cm sediments. Cyst concentrations varied from 154 to 113 483 cysts per gram dry weight sediment, and were much higher in upper sediments. Scrippsiella trochoidea was the most dominant cyst type, which took up over 90% of cyst assemblages in the upper sediments. The abrupt increase of S. trochoidea cysts in the surface sediments reflected the bloom of this species in Daya Bay in 2000. The results from cyst assemblages showed some trend of changes in water quality in this area, and indicated a typical type of pollution caused by cultural eutrophication, which started in the 1980s and greatly accelerated in the middle of 1990s. Cysts of Alexandrium, mainly those of Alexandrium catenella and Alexandrium tamarense complex, occurred frequently and abundantly in this area, with the highest concentration and relative frequency of 503 cysts per gram dry weight sediment and 22.3%, respectively. The high abundance of Alexandrium cysts provided rich ‘seed bed’ for Alexandrium blooms and was also an important source of paralytic shellfish poisoning toxins, especially in winter.     

Influences of sedimentation and hydrodynamics on the spatial distribution of Alexandrium catenella/tamarense resting cysts in a shellfish farming lagoon impacted by toxic blooms

Since resting cysts are a potential seeding source for blooms, the presence of these cysts in sediments is a marker of an established population for a number of harmful algal species. The spatial patterns of cyst density in relation to sediment characteristics and hydrodynamics are still largely misunderstood. This study investigated the spatial distribution of resting cysts belonging to the Alexandrium tamarense species complex (Dinophyceae) in sediments of a Mediterranean coastal lagoon (Thau Lagoon, France). This lagoon, hosting shellfish farming, is regularly impacted by toxic Alexandrium catenella blooms. The average cyst density across the whole lagoon was rather low, <20 cysts g⁻¹ of dry sediment (DS). However, densities varied widely among sampled stations, with the highest density (∼440 cysts g⁻¹ DS) recorded in a shallow cove named Crique-de-l’Angle, which is the only area where dense blooms of A. catenella and A. tamarense have been recorded in the years preceding this survey. An analysis using spatial autoregressive models demonstrated that cyst densities were highly spatially autocorrelated (indicating that close stations tended to have more similar cyst densities) with accumulation sites. With respect to sediment characteristics (5 granulometric fractions <2 mm and biochemical components), the highest densities were found in silty sediments containing high proportions of water and organic matter. Nevertheless, the linkage between cyst density and sediment structure was not always verified; this reflected the influence of hydrodynamics on the sedimentation of cysts and sediment particles, and on the dispersal of cysts away from the bloom area by wind-induced currents, suggesting that hydrodynamics was responsible for the spatially autocorrelated distribution of cyst densities.     

Observations on Alexandrium tamarense (Lebour) Balech and Other Dinoflagellate Populations in Golfo Nuevo, Patagonia (Argentina)

The toxic dinoflagellate Alexandrium tamarense and other dinoflagellatespecies were studied, along with water temperature and nutrientconcentrations, from September 1995 to December 1998 in theGolfo Nuevo, Chubut, Argentina. Nutrient concentrations werelow, showing a peak of high concentration in winter and a phaseof depletion in late spring and summer. Dinoflagellates tendedto be abundant during spring and summer, when Prorocentrum micanswas the most important species. Other dinoflagellates were Pyrophacushorologium and Dinophysis acuminata. Ceratium tripos, C. fususand C. horridum were present during the autumn, and a C. tripospeak up to 5.9 x 10³ cell l^–1 was observed in May 1997.Alexandrium tamarense showed strong interannual variation, thehighest concentration being found in spring (September–October)1995, with densities up to 15 x 10³ cells l^–1. The secondA.tamarense peak was observed during October–November1998 with maximal densities up to 5 x 10³ cells l^–1. Moderatelyhigh A. tamarense cyst densities, up to 300 cysts cm^–3of sediment, were found in the deep zone of the Golfo Nuevobasin. Among meteorolog-ical variables, increased late winterrain and higher solar radiation during spring may have influencedA. tamarense blooms.     

Coupling planktonic and benthic shifts during a bloom of Alexandrium catenella in southern Chile: Implications for bloom dynamics and recurrence

Cell abundances and distributions of Alexandrium catenella resting cysts in recent sediments were studied along time at two locations in the Chilean Inland Sea exposed to different oceanographic conditions: Low Bay, which is much more open to the ocean than the more interior and protected Ovalada Island. The bloom began in interior areas but maximum cyst concentrations were recorded in locations more open to the ocean, at the end of the Moraleda channel. Our results showed a time lapse of around 3 months from the bloom peak (planktonic population) until the number of resting cysts in the sediments reached a maximum. Three months later, less than 10% of the A. catenella cysts remained in the sediments. Maximum cyst numbers in the water column occurred one month after the planktonic peak, when no cells were present. The dinoflagellate assemblage at both study sites was dominated by heterotrophic cysts, except during the A. catenella bloom. CCA analyses of species composition and environmental factors indicated that the frequency of A. catenella blooms was associated with low temperatures, but not with salinity, chlorophyll a concentration, and predator presence (measured as clam biomass). However, resting cyst distribution was only related to cell abundance and location. The occurrence of A. catenella cysts was also associated with that of cysts from the toxic species Protoceratium reticulatum. By shedding light on the ecological requirements of A. catenella blooms, our observations support the relevance of encystment as a mechanism of bloom termination and show a very fast depletion of cysts from the sediments (<3 months), which suggest a small role for resting cyst deposits in the recurrence of A. catenella blooms in this area.