光照与东海近海中肋骨条藻(Skeletonema costatum)赤潮发生季节的关系

利用船基现场培养实验和模型计算的方法,研究了光照与东海近海春夏季均能发生中肋骨条藻赤潮的关系.结果表明,中肋骨条藻生长的最适光照强度(Iopt)随水温(t)的增加呈'慢升快降'的不对称'倒V'形变化特征,在25℃左右Iopt最大,为121.6 W.m-2,Iopt-t曲线符合Blanchard方程;由东海海表水温计算的中肋骨条藻Iopt的季节变化特征与东海海面光照强度、海水透明度的季节变化基本同步(R2=0.907±0.115,p<0.001),且滞后于海面光照强度2个月左右,这使春夏季海水中光照最适宜生长的水层均为全年最厚(6 m左右).可见,中肋骨条藻对光照的适应性很强,海区海水光照的适宜性是春夏季均能形成大规模中肋骨条藻赤潮的重要原因之一.

赤潮水体中胶体物质对赤潮异弯藻(Heterosigma akashiwo)和中肋骨条藻(Skeletonema costatum)生长的影响

2004年2月9~10日在胶州湾发生的柔弱几内亚藻(Guinardia delicatula)赤潮期间分别在3个典型赤潮站位采集表层水样,利用过滤(0.7μm)和切向超滤(1000Daltons)分离赤潮暴发水体中的胶体物质,分析了不同滤液及截留液的有机碳含量,并将赤潮异弯藻(Heterosigma akashiwo)和中肋骨条藻(Skeletonema costatum)在<1000Daltons的超滤液及具有不同含量胶体物质(1000Daltons^0.7μm)的截留液中进行培养。结果发现在发生柔弱几内亚藻赤潮期间水体中的溶解有机碳浓度会增加,特别是胶体有机碳浓度会成倍增长;在不同胶体含量海水中培养的赤潮异弯藻的最大生长率μmax和最大生物量Bf与对照组相比会随着胶体含量的增加而显著增大,而中肋骨条藻的最大生长率μmax和最大生物量Bf与对照组相比会随着胶体含量增加而显著降低,表明柔弱几内亚藻赤潮水体中的胶体物质对赤潮异弯藻的生长起促进作用,而对中肋骨条藻的生长起抑制作用。这说明柔弱几内亚藻在增殖过程中所产生的胶体物质具有他感作用,会影响其它微藻的生长,从而可能对柔弱几内亚藻赤潮的形成起重要作用。

粤东柘林湾中肋骨条藻(Skeletonema costatum)种群生态学

于2000年5月～2004年12月对粤东大规模养殖区柘林湾的赤潮藻中肋骨条藻（Skeletonema costatum）种群的时空分布进行了长达5a的调查。结果表明，中肋骨条藻种群密度的周年变动模式基本为双峰型，平面分布没有显著的空间差异。调查期间，中肋骨条藻种群密度的站位实测值为0～1．4×10^7cells／dm^3，总均值为3．3×10^5cells／dm^3，占浮游植物总细胞数的67．1％，为调查海区第1优势种。在总共1045份样品中，有中肋骨条藻出现的样品数为1020份。其中，种群密度大于10^6cells／dm^3的样品有65份，大于10^7cells／dm。则有4份。以大于10^6cells／dm^3为中肋骨条藻的赤潮密度标准，在调查期间至少于2000年、2003年发生4次赤潮。运用灰关联理论对中肋骨条藻种群密度与13个环境因子的关系进行排序分析发现，水温、pH值和浮游动物是影响柘林湾中肋骨条藻种群时空分布的关键因子。水温还与中肋骨条藻种群密度的对数值具极显著意义的线性关系，而达到赤潮密度的样品均落在24．5～32．0℃区间，即每年的5～9月份高温季节。由于柘林湾浮游动物的年高峰期也出现在高温季节，说明浮游动物摄食压力的存在可能是柘林湾中肋骨条藻赤潮发生的重要抑制因子。2004年调查海区中肋骨条藻种群密度和在浮游植物群落中的优势度骤然降低，可能与水体营养盐结构和Fe含量的变化有关。因此，长期调查与监测对于研究海湾生态学和赤潮发生机制是极为重要的。

塔玛亚历山大藻(Alexandrium tamarense)和中肋骨条藻(Skeletonema costatum)种间竞争及UV-B辐射胁迫对其影响

采用共培养的方法,研究了塔玛亚历山大藻和中肋骨条藻种群竞争关系对UV-B辐射增强的响应变化。结果表明,不同的接种密度对塔玛亚历山大藻和中肋骨条藻种群竞争有明显的影响。当塔玛亚历山大藻和中肋骨条藻的接种比例为A∶S=1∶4时,中肋骨条藻在竞争中占优势;当接种例为A∶S=1∶1时,虽然塔玛亚历山大藻在竞争中占优势,但也受到了中肋骨条藻的抑制;接种比例为A∶S=4∶1时,塔玛亚历山大藻的生长竞争优势更加明显。UV-B辐射增强(在预备实验的前提下,选择1.4J/m2)可改变塔玛亚历山大藻和中肋骨条藻种群竞争的关系,使塔玛亚历山大藻种群竞争能力降低,中肋骨条藻种群竞争能力大大提高,从而导致处理Ⅰ(A∶S=1∶4)中,中肋骨条藻在竞争优势更加明显,在处理Ⅱ(A∶S=1∶1)中,中肋骨条藻在竞争中占一定的优势。

The effect of UV-B radiation enhancement on the interspecific competition between Skeletonema costatum and Heterosigma akashiwo

The responses of the interspecific competition between Skeletonema costatum and Heterosigma akashiwo to UV-B radiation enhancement were studied by the co-culture method. The results showed that Heterosigma akashiwo exhibited inhibition on the growth of Skeletonema costatum, and with the increase of initial inoculation density of Heterosigma akashiwo, heavier inhibition on Skeletonema costatum appeared. Under different inoculation proportions, Heterosigma akashiwo could always be in predominance in competition with Skeletonema costatum. The UV-B radiation treatment could change the competition relationship between Skeletonema costatum and Heterosigma akashiwo, which could increase the competitive dominance of Skeletonema costatum and decrease the competitive dominance of Heterosigma akashiwo. When the inoculation proportions of Heterosigma akashiwo and Skeletonema costatum were H∶S=1∶4 and H∶S=1∶1,Skeletonema costatum was in predominance in this competition; however, Heterosigma akashiwo was in predominance when the inoculation proportion was H∶S=4∶1.

Effects of different phosphorus concentrations and N/P ratios on the growth and photosynthetic characteristics of Skeletonema costatum and Prorocentrum donghaiense

The effects of different phosphorus(P) concentrations(0.36, 3.6, and 36 μmol/L corresponding to low-, middle-, and high-P concentration groups, respectively) and nitrogen(N)/P ratios on the growth and photosynthetic characteristics of S keletonema costatum and Prorocentrum donghaiense were studied. For both species, the high-P(HP) concentration group showed the greatest algal density and highest specifi c growth rate. Changes in the maximum effi ciency of photosystem Ⅱ(F _v/F_m) were monitored under the various P and N/P conditions. The largest decrease in F _v/F_m was in the low-P(LP) group in S. costatum and in the HP group in P. donghaiense. There were high rapid light curves and photochemical quantum yields(Φ _(PSⅡ)) for S. costatum in the HP group, while the actual photosynthetic capacity was higher in P. donghaiense than in S. costatum in the MP group. Under eutrophic but relatively P-restricted conditions, P. donghaiense had higher photosynthetic activity and potential, which could cause this dinofl agellate to increasingly dominate the phytoplankton community in these conditions. Under the same P concentration and N/P ratio, P. donghaiense had a larger relative maximum rate of electron transport and higher Φ _(PSⅡ) values than those of S. costatum. These differences between P. donghaiense and S. costatum may explain the interaction and succession patterns of these two species in the Changjiang(Yangtze) River estuary from a photosynthesis perspective.

Nutrient compositions of cultured Thalassiosira rotula and Skeletonema costatum from the Jiaozhou Bay in China

Carbon, nitrogen, phosphorus, silicon composition of cultured two different sized phytoplankton common species of Thalazsiosira rotula and Skeletonema costatum from the Jiaozhou Bay were measured. Carbon, nitrogen, phosphorus, silicon contents in cell were obvious higher in T. rotula than in S. costatum, but the percents of nitrogen, phosphorus, sihcon contents in cell dry mass in T. rotula were lower than those in S. costatum. The dry mass concentrations of nitrogen,phosphorus, silicon in S. costatum were much higher than those in T. rotula, particularly silicon, the former was 6. 4 times of the latter, showing that S. costatum could more assimilate these elements. Especially, S. costatum had competitive dominance for assimilating silicon, which is beneficial to its becoming a major dominant species in relative short silicon of the Jiaozhou Bay. There were some differences in numerical value of nutrient ratios both laboratory-cultured phytoplankton and different sized suspended particulates （ mainly phytoplankton） in the Jiaozhou Bay, which was caused by the changes of environment. High contents of carbon, nitrogon and relative low phosporus, sil- icon, high molar ratio of nitrogen to phosphorus （far higher than Redfield value） and low ratio of silicon to phosphorus and silicon to nitrogen （far lower than Redfield values） in the two diatoms and different sized suspended particulates were consistent with those in the seawater. Relative short silicon in the seawater and phytoplankton showed that silicon was possibly affectting phytoplankton growth in the Jiaozhou Bay.

Estimation of growth rate of Skeletonema costatum based on relative expression amount of PCNA gene

Partial sequence of Skeletonema costatum proliferating cell nuclear antigen （PCNA） gene was obtained by reverse transcriptase PCR（RT-PCR） and 3＇ rapid amplification of cDNA ends （3＇-RACE） techniques. Based on the obtained PCNA and cytochrome b gene（ Cyt b gene） sequences, a real-time fluorescent quantitative PCR （FQ-PCR） method was developed to detect the expression S. costatum PCNA gene, and this method was applied to study the relationship between the growth rate of S. costatum and the average expression amount of PCNA gene in a single cell. The expression amount of PCNA gene had large variation in cells collected at different culture phases, and the trend was well consistent with the growth rate, which suggested that the expression amount of PCNA gene correlated well with the cell division, and the PCNA could be a promising indicator for the S. costatum cell proliferation. Furthermore, using the PCNA gene as the objective gene and the Cyt b gene as the house-keeping gene, a new method for estimating the in situ growth rate of S. costatum was established by analysis of the relative expression quantity （REQ） of the PCNA gene.

Influences of external nutrient conditions on the transcript levels of a nitrate transporter gene in Skeletonema costatum

To verify the feasibility of high-affinity nitrate transporter gene （Nrt2） as an indicator of nitrogen status, changes in the transcript levels of transcripts associated with phosphate starvation and different nitrate concentrations were studied using real-time quantitative reverse-transcription PCR （QRT-PCR） technology in batch cultures of Skeletonema costatum. The results show that compared with P-replete condition, P starvation could reduce the Nrt2 transcript levels apparently. Nrt2 transcript levels had a significant negative linear correlation with nitrate concentrations below 40 pmol/L. The results of 48 h short-term incubation experiment under different nitrate concentrations confirmed this correlation, and the following regression equation is built： y = -3.305x ＋ 98.95, R2 = 0.988, where x represents nitrate concentrations （〈40 btmol/L） and y represents the Nrt2 transcript levels.

Study on the Effect of Monochromatic Light on the Growth of the Red Tide Diatom <i>Skeletonema Costatum</i>

Effects of light intensity and quality of three kinds of LED monochromatic lights (blue, green, and red) on the growth of Skeletonema costatum are investigated in batch culture conditions. Seven light intensities (20, 30, 40, 45, 50, 60 and 80 μmol·m-2·s-1) are used to evaluate the specific growth rate, spectrum absorption coefficient and saturated light intensity of LED monochromatic light. Results show that the growth rates of Skeletonema costatum increase with the enhanced light intensity;however, the light level beyond the saturation light intensity inhibited the growth of Skeletonema costatum. Compared with red and green light, the growth rate of Skeletonema costatum under blue light is higher within saturated light intensity, and saturated light intensity of LED monochromatic light is lower under blue light and higher under green light. It is concluded that under different monochromatic light, the saturated light intensity decreases and the growth rate increases with the increasing of spectrum absorption coefficient.

Skeletonema cf.costatum Biogenic Silica Production Rate Determinated by PDMPO Method

Diatoms are the only ecological phytoplankton that require silicic acid for growth.They are also the dominant contributor of ocean's total primary productivity.Generation and circulation with silica walls,which the siliceous organisms form,is an important component of the marine biological pump.It is crucial to the study of the operational mechanisms of biological pump with different sea areas.Moreover,it is the key link to the study of global silicon cycle.This paper introduces the basic mechanism of the formation of diatom silica walls and a new way of researching silicic acid metabolism,namely the 2-(4-pyridyl)-5-((4-(2-dimethylaminoethylaminocarbamoyl)-methoxy)phenyl)oxazole(PDMPO) dyeing method.Under a fluorescence microscope after excitation with bright green fluorescence,it can combine with silicic acid to form a complex into the Si deposition within diatom cells.The advantage of this method is that it can monitor the metabolism of silicate after adding PDMPO.For experimentation and sample collection in each of the specified time points,samples were determinated through the unutilized silicic acid,silica dissoluble intracellular and Si deposition within diatom cells,not only using hot alkaline digestions method but also PDMPO dyeing method.Results showed a good linear relationship between PDMPO fluorescent value and biogenic silica concentration.It was also indicated that PDMPO had no deleterious impact on Skeletonema cf.costatum growth for 34 h and was useful for tracking newly-deposited biogenic silica in diatoms' frustules.

Isolation, characterization and implications of the bacterial communities associated with established cultures of Chattonella marina(Raphidophyceae) and Skeletonema costatum(Bacillariophyceae)

Cultivable bacteria coexisting in the cultures of two microalgal species, Chattonella marina(Raphidophyceae)and Skeletonema costatum(diatom, Bacillariophyceae), which have been maintained in the laboratory for several years, were examined in this study. Forty-eight and thirty-four cultivable bacterial strains were isolated from different growth stages of C. marina and S. costatum cultures, respectively. A total of twelve unique bacterial phylotypes were isolated. These bacterial phylotypes belonged to Alphaproteobacteria, Gammaproteobacteria,Bacteroidetes, and Actinobacteria. Alphaproteobacteria predominated in phycospheres of both microalgae, and Rhodobacteraceae was the most common family. Bacterial phylotypes were more diversified in cultures of S.costatum than in those of C. marina. Bacterial concentrations increased remarkably after the late stationary phase of C. marina, which might account for the decline in algal cells. One phylotype of S. costatum-associated bacteria had inhibitory effects on Chaetoceros curvisetus(Bacillariophyceae). However, most bacterial phylotypes from cultures of C. marina showed significant inhibition of the growth of C. curvisetus. The results suggested that bacteria associated with C. marina might have some ecological roles in its competition with diatoms.

Effects of iron on growth,degree of pigmentization and nitrogen assimilation in Skeletonema costatum

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The Effect of UV Light and CO₂in the Production of Polyunsaturated Aldehydes in <i>Skeletonema costatum</i>(Bacillariophycea)

Skeletonema costatum was submitted to two experiments using UV lights and CO2with the purpose of observing changes in the lipids profile and the synthesis of polyunsaturated aldehydes (PUA) after cell disruption. When cells receive CO2 supply, it was noticed that the production of PUA was significantly lower. The same was observed when the culture was treated with a dose of 45.9 kJ·m-2 of ultra-violet A/B ray. The premise to all experiments was the production of 2,4-heptadienal compared to the supply of EPA as substrate. As a result, the same synthesis rate was observed both when the CO2 treatment was applied and in the experiment control. On the other hand, the culture subjected to ultraviolet radiation showed a 68% greater demand with the utilization of the substrate. These observations suggested that EPA was consumed before cell disruption and was probably exuded to the surrounding environment as a sign of stress. Changes in cell morphology could be observed by the migration of the chloroplast nearby the cell wall, where PUA was produced, indicating a defense strategy.

纳米二氧化硅与汞(Hg^2＋)对中肋骨条藻(Skeletonema costatum)的联合毒性效应

随着纳米材料在日常生产生活中的广泛应用,部分纳米颗粒物不可避免地会通过废弃物排放等途径进入海洋.当纳米颗粒物与海洋中的污染物(如与重金属)共存时,因其独特的物化特性往往会成为污染物的良好载体并在生物体内累积,从而增加已有污染物和生物的相互作用,对海洋环境构成潜在的生态风险.已有的研究更多关注单一纳米材料的生态毒性效应,有关纳米颗粒物与污染物的复合生物效应的研究较少.因此,本文研究了已广泛应用的纳米Si O2与常见的重金属污染物Hg^(2+)对东海常见海洋微藻-中肋骨条藻(Skeletonema costatum)的联合毒性效应.结果表明,Hg^(2+)会抑制中肋骨条藻的生长,24 h-EC50、48 h-EC50和72 h-EC50值分别为56.3μg·L^(-1)、58.6μg·L^(-1)和36.8μg·L^(-1);低浓度的纳米Si O2(1 mg·L^(-1)和5 mg·L^(-1))未对中肋骨条藻的生长产生抑制作用,而较高浓度的纳米Si O2(≥10 mg·L^(-1))会显著(P<0.05)抑制中肋骨条藻的生长,并且提升微藻超氧化物歧化酶SOD的活性,影响微藻的抗氧化系统.添加1 mg·L^(-1)纳米Si O2会增强Hg^(2+)对中肋骨条藻的生长抑制作用,Hg^(2+)的24 h-EC50和48 h-EC50分别下降至41μg·L^(-1)和43μg·L^(-1),虽然1 mg·L^(-1)纳米Si O2本身没有对中肋骨条藻产生生长抑制作用,但是能够明显增强Hg^(2+)对中肋骨条藻的毒性.纳米Si O2对Hg^(2+)有着较强的吸附能力,在60 min时,100 mg·L^(-1)纳米Si O2对100μg·L^(-1)的Hg^(2+)的吸附率为90.08%,最大吸附量为5.92 mg·g^(-1).吸附了Hg^(2+)的纳米Si O2在中肋骨条藻内的累积可能是造成这种协同毒性的主要原因.

溶藻细菌L7(Algicidal Bacteria Strain L7)与中肋骨条藻(Skeletonema costatum)的相互作用

将6组不同初始种群密度的溶藻细菌L7（Bacillus cereus）菌悬液和添加了溶藻细菌L7胞内、外代谢产物的2216E培养液加入到中肋骨条藻（Skeletonema costatum）悬浮液中,将5组不同初始种群密度的中肋骨条藻悬浮液和添加了中肋骨条藻胞内外代谢产物的f/2-Si培养液加入到溶藻细菌L7悬浮液中,探讨溶藻细菌L7和中肋骨条藻的相互作用.在第7天时,L7胞外代谢产物使中肋骨条藻细胞数量下降95.42％,表现为间接溶藻,胞内代谢产物使藻细胞数量增长361.47％,表现为加快藻增长.L7初始种群密度为3.89×106cfu/mL和3.89 × 107cfu/mL时,在第7天藻细胞数量均下降80％以上;初始种群密度为3.89×102～3.89×104cfu/mL时,在第7天L7促进藻生长.中肋骨条藻种群密度为3.89×103 cells/L、3.89×104 cells/L及3.89×106 cells/L时,最迟于第7天,L7种群密度开始低于对照组,即中肋骨条藻能够在一段时间后抑制L7生长.从第4天开始,中肋骨条藻胞外代谢产物使L7种群密度低于对照组,即中肋骨条藻对L7产生抑制作用;胞内代谢产物对L7生长的影响不明显.

Effects of modified clay flocculation on major nutrients and diatom aggregation during Skeletonema costatum blooms in the laboratory

Harmful algal blooms(HABs) can elicit several negative effects on aquatic environment(such as depleting the oxygen, blocking the sunlight, destroying the habitats of organisms) and life health(including poisoning/killing marine mammals, birds and human). Among the various control strategies for HABs(physical manipulation needs lots of manpower and expensive equipment, chemicals treatment has some toxic byproduct and high residual, microbial agents only has limited in laboratory research), the coagulation-flocculation of HAB species by modified clay(MC) has been proven to be an effective, lowcost and environmentally friendly method that has been widely applied in the field, particularly in eastern Asia. In order to examine the long-term effects of MC treatment, this study investigated the alternations in seawater of Skeletonema costatum, a high biomass dominant HAB species along the Chinese coast, by comparing the degradation of S. costatum detritus(A1) with the application of MC treatment(A2) and MC treatment in sediment condition(A3). The low dosage of 0.25 g/L MC could efficiently remove 4×108 cells/L of S. costatum cells within 3.5 h(approximately 97% removal). In addition, the results showed that both inorganic and organic nutrients were effectively reduced from seawater by MC particles. Compared to the total nitrogen(TN) and total phosphorus(TP) concentrations in A1 seawater, 44% of TN and 93% of TP in A2 seawater, as well as 72% of TN and 93% of TP in A3 seawater were removed during the onemonth incubation period. Simultaneously, 64% of DISi in A2 and 44% of DISi in A3 significantly decreased( P <0.001). This study demonstrated that MC treatment was able to significantly increase the downward flux of nutrients and delay the release velocity of inorganic nutrient from MC-algae matrix into the overlying seawater, particularly within sediment environment.

COMBINED EFFECTS OF TEMPERATURE, IRRADIANCE AND SALINITY ON GROWTH OF DIATOM SKELETONEMA COSTATUM

factor experiment was used to study the combined effects of temperature, irradiance and salinity on the growth of an HAB species diatom Skeletonema costatum (Grev.) Cleve. The results showed that temperature (12, 19, 25, 32℃), irradiance ((0.02, 0.08, 0.3, 1.6)×10 16 quanta/(s·cm 2)) and salinity (10, 18, 25, 30, 35) significantly influenced the growth of this species. There were interactive effects between any two of and among all three physical factors on the growth. In the experiment, the most optimal growth condition for S. costatum was temparature of 25℃, salinity of 18-35 and irradiance of 1.6×10 16 quanta/(s·cm 2). The results indicated S. costatum could divide at higher rate and were more likely to bloom under high temperature and high illumination from spring to fall. It was able to distribute widely in ocean and estuary due to its adaptation to a wide range of salinities.

Influence of salinity and nitrogen content on production of dimethylsulfoniopropionate(DMSP)and dimethylsulfide(DMS)by Skeletonema costatum

The effects of changing salinity and nitrogen limitation on dimethylsulfoniopropionate(DMSP) and dimethylsulfide(DMS) concentrations were investigated in batch cultures of coastal diatom Skeletonema costatum,an ecologically important species.Changes in salinity from 20-32 caused no measurable variation in cell growth or culture yield,but increased intracellular DMSP per cell by 30%.Nitrogen limitation caused up to a two-fold increase in total DMSP per cell and up to a three-fold increase in DMS per cell.These changes in DMSP and DMS per cell in the Skeletonema costatum cultures with nitrogen limitation and changing salinity were primarily attributed to the physiological functions of DMSP as an osmolyte and an antioxidant.The data obtained in this study indicated that nitrogen limitation and salinity may play an important role in climate feedback mechanisms involving biologically derived DMS.

Allelopathic interactions between Prorocentrum micans and Skeletonema costatum or Karenia mikimotoi in laboratory cultures

Algal allelopathy is an ecological/physiological phenomenon that has focused attention on the interactions among algae and the production of algal toxins. We investigated the allelopathic interactions between the dinoflagellate genus Prorocentrum micans and diatom genus Skeletonema costatum and between P. micans and dinoflagellate genus Karenia mikimotoi using bi-algal cultures. Because the effects were species-specific and size-dependent, we evaluated the effect of different initial densities. At low densities of P. micans and high densities of S. costatum inoculated into the same medium, the growth of P. micans was weakly restrained, whereas the growth of S. costatum was significantly suppressed. S. costatum and K. mikimotoi were strongly inhibited by P. micans, in both the bi-algal cultures and enriched filtrates. Direct cell-to-cell contact was not necessary to gain a competitive advantage, thus, our results suggest that P. micans inhibited the growth of S. costatum and K. mikimotoi by the release of allelochemical(s). Last, a mathematical model was used to simulate growth and interactions between P. micans and S. costatum and between P. micans and K. mikimotoi in bi-algal cultures.