不同营养条件对东海原甲藻和中肋骨条藻竞争参数的影响

以东海原甲藻和中肋骨条藻为研究对象,采用室内单种培养和混合培养,设置不同的氮、磷营养条件,研究了不同营养条件对两种微藻的生长状况和种间竞争参数的影响.结果表明:随着氮、磷浓度的增加,两种藻的最大生物量均呈增加趋势,混合培养中两种微藻的比生长率低于单独培养.在混合培养中,生长前期中肋骨条藻是优势种,随着培养时间的延长,东海原甲藻成为优势种,且优势种发生变化的时间与营养条件有关.混合培养中,东海原甲藻拐点出现时间在0.5 ～4.9 d,中肋骨条藻为0～2.6d,东海原甲藻拐点出现时间晚于中肋骨条藻.在各营养条件下,东海原甲藻对中肋骨条藻的竞争抑制参数β均高于中肋骨条藻对东海原甲藻的竞争抑制参数α,当N为128μmol·L-1、P为32 μmol·L-1时,东海原甲藻的竞争能力是中肋骨条藻的3.8倍,两者差异最为明显.     

东海原甲藻与中肋骨条藻的种间竞争特征

对东海原甲藻和中肋骨条藻按照起始Chl-a比1∶5、1∶1和5∶1进行了f/2条件下的共培养实验,以探讨这两种藻的种间竞争特征。实验结果表明在共培养体系中,中肋骨条藻完全占优势,而东海原甲藻的生长受到明显的抑制。应用Lotka-Volterra种间竞争模型对共培养实验进行模拟的结果表明,东海原甲藻与中肋骨条藻的种间竞争结果与初始密度配比无关,中肋骨条藻总会竞争胜过东海原甲藻。为了探讨他感作用对东海原甲藻和中肋骨条藻种间竞争的影响,采用了中肋骨条藻的无藻细胞滤液来进行培养实验。实验结果显示,中肋骨条藻滤液对东海原甲藻及其本身的生长均无明显影响,这表明他感作用并非中肋骨条藻获得优势的主要竞争方式。     

东海原甲藻与中肋骨条藻的种间竞争数值模拟

研究探讨了两个零维箱式模型在东海典型赤潮藻东海原甲藻和中肋骨条藻竞争与演替研究中的应用。模型在采用不同接种密度下的单种培养实验数据进行参数校正后,被用来模拟不同N/P条件下单种培养实验以及两藻种共培养竞争实验,并以实验数据对其结果进行了验证。模拟结果表明,在单种培养条件下,模型能够较好地重现两种藻在不同N/P环境中的生长及对营养盐的利用;共培养实验的模拟结果显示,在所有初始细胞密度比例条件下,中肋骨条藻的最终密度均会超过东海原甲藻,且PO4的消耗主要源于中肋骨条藻的利用,与实验结果一致,表明模型能够很好地体现两种藻的竞争结果及对营养盐的竞争关系;由于模型不足以模拟除营养盐竞争以外的藻间相互作用,模拟结果未体现东海原甲藻细胞数迅速衰减这一现象,有待进一步研究。     

鼠尾藻对赤潮异弯藻和中肋骨条藻的抑制作用

通过共培养的方法,研究了鼠尾藻（Surgassum thunbergii）培养水的过滤液、新鲜组织、干粉末、水溶性抽提液对赤潮异弯藻（Heterosigma akashiwo）和中肋骨条藻（Skeletonema costatum）生长的抑制效应,建立了分隔共培养系统并证明了抑制物质的存在,排除了细胞直接接触抑制的可能性.结果表明,在共培养实验中,鼠尾藻新鲜组织、干粉末及水溶性抽提液对赤潮异弯藻和中肋骨条藻的生长具有显著的抑制作用,且在较高浓度下对两种赤潮微藻的生长具有致死效应.在一次性及半连续培养方式下,鼠尾藻培养水过滤液对赤潮异弯藻的生长无抑制效应,而对中肋骨条藻的生长具有显著的抑制效应.     

敌百虫对中肋骨条藻生长的影响

研究了有机磷农药敌百虫对中肋骨条藻Skeletonema costatum生长的影响。相对于水生甲壳类和鱼类,敌百虫对中肋骨条藻毒性较低,72 h半抑制浓度(EC₅₀)为84.8 mg/L。在31 d的亚慢性暴露下,低浓度组(≤10 mg/L)藻细胞生长趋势与对照组相似;50 mg/L的敌百虫在暴露初期对骨条藻的生长具有明显抑制作用,但在暴露15 d后,该浓度组藻细胞密度仍保持增长,最大细胞密度为2.77×10⁷ cells/mL,是对照组的137.7%。100 mg/L则能完全抑制藻细胞的生长。本实验结果说明敌百虫等有机磷农药的广泛使用可能会刺激浮游植物的生长,从而增加引发赤潮的风险。     

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。     

不同光照条件下米氏凯伦藻和东海原甲藻生长的温度生态幅

米氏凯伦藻和东海原甲藻是我国东南沿海地区赤潮的主要优势种。为定量获取米氏凯伦藻和东海原甲藻生长的温度生态幅,根据3个光照水平(28.32,75.06,111.66μmol m~(-2)s~(-1))条件下4个温度水平(18,22,25,28℃)对米氏凯伦藻和东海原甲藻生长特性的室内培养实验结果,并结合Shelford耐受性定律建立了基于温度的米氏凯伦藻和东海原甲藻比生长率的耐受性模型,最后根据前期的研究成果分别获取了米氏凯伦藻和东海原甲藻生长的最适温度、适温范围及耐受温度范围。结果表明,无论是米氏凯伦藻还是东海原甲藻,在相同培养光照条件下,在设定的温度水平范围内,分别存在一个适宜米氏凯伦藻和东海原甲藻的最适生长温度T_(opt),且当T≤T_(opt)时,米氏凯伦藻和东海原甲藻细胞密度和比生长率随着温度的升高而显著增大;而当T≥T_(opt)时,米氏凯伦藻和东海原甲藻细胞密度和比生长率随着温度的升高而显著减小。随着培养光照强度的升高,米氏凯伦藻和东海原甲藻细胞密度和比生长率均呈现"先升后降"的变化趋势。建立的藻类生长温度耐受性模型与谢尔福德耐受定律较为吻合,定量获取米氏凯伦藻在3个光照水平(28.32,75.06,111.66μmol m~(-2)s~(-1))下的最适生长温度分别为22.48,22.37,22.33℃;适温范围分别为17.93—27.03,17.82—26.92,17.78—26.88℃;耐受温度范围分别为13.38—31.58,13.27—31.47,13.23—31.43℃;东海原甲藻在3个光照水平(28.32,75.06,111.66μmol m~(-2)s~(-1))下的最适生长温度分别为22.10,21.99,21.93℃;适温范围分别为17.59—26.61,17.48—26.5,17.42—26.44℃;耐受温度范围分别为13.08—31.12,12.97—31.01,12.91—30.95℃。     

米氏凯伦藻与东海原甲藻共培养条件下的种群竞争

米氏凯伦藻(Karenia mikimotoi)与东海原甲藻(Prorocentrum donghaiense)为有害赤潮生物,两者经常形成复合型赤潮.该文设置东海原甲藻的起始密度为400 cells·mL-1,米氏凯伦藻分别为200 cells·mL-1、400 cells·mL-1和800 cells·mL-1,通过共培养实验,初步研究米氏凯伦藻和东海原甲藻的种间关系.结果表明:共培养条件下,受到东海原甲藻的影响,米氏凯伦藻的生长受到抑制.米氏凯伦藻不同的起始密度对东海原甲藻的生长有不同的影响,较低的起始密度(200 cells·mL-1、400cells·mL-1)促进东海原甲藻的生长,使其增长率提高,生长曲线达到拐点的时间提前;高的起始密度(800 cells·mL-1)对东海原甲藻的生长有一定的抑制作用,使其增长率降低,生长曲线达到拐点的时间推迟.     

三种典型赤潮藻产生与消耗二甲基硫化物的速率估算

采用抑制剂加入法估算了中肋骨条藻、棕囊藻和东海原甲藻在不同生长期内二甲基硫化物的产生与消耗速率.结果表明:颗粒态二甲基巯基丙酸(DMSPp)和颗粒态二甲亚砜(DMSOp)在3种藻类的不同生长期内均为净消耗,溶解态二甲基巯基丙酸(DMSPd)和溶解态二甲亚砜(DMSOd)的含量受藻类产生与细菌病毒消耗控制,在藻类不同生长期内存在不同的产生与消耗速率,而二甲基硫(DMS)在3种藻不同生长期内均为净产生.同一种藻在不同生长期内以及不同藻在相同生长期内二甲基硫化物的产生与消耗速率均存在较大差异,表明藻类的生理状态和种间差异均对二甲基硫化物的产生与消耗速率产生影响.     

尿素对中肋骨条藻与米氏凯伦藻生长的影响

采用实验室一次性培养,研究了尿素对我国东海赤潮优势藻中肋骨条藻(Skeletonema costatum)和米氏凯伦藻(Karenia mikimotoi)生长的影响。结果表明,中肋骨条藻和米氏凯伦藻均能在不同比例尿素的条件下较好地生长。随着培养液中尿素比例的增大,中肋骨条藻细胞生长速率(0.91—0.82/d)逐渐减小,平台期最大生物量(2.0×10~5—1.2×10~5个/m L)也逐渐减小,而米氏凯伦藻细胞的生长速率(0.36—0.51/d)逐渐增大,最大生物量基本不变(约1.1×10~4个/m L)。在平台期中肋骨条藻培养液中氮盐浓度最低下降到2.5μmol/L左右维持不变,而米氏凯伦藻氮盐浓度最低下降到1.0μmol/L左右。在指数生长期,随着细胞的生长溶解有机氮(DON,Dissolved Organic Nitrogen)含量迅速增加,中肋骨条藻介质中DON的浓度达到最大值(5—6μmol/L),然后浓度基本不变。米氏凯伦藻介质中DON在指数生长阶段达到最大值(2—3μmol/L)后开始下降。中肋骨条藻单细胞颗粒氮的含量(约为10~(-6)μmol,平台期约为10~(-7)μmol)要远远小于米氏凯伦藻(指数期约为10~(-4)μmol,平台期约为10~(-6)μmol)。研究表明,两种藻对尿素的吸收利用存在明显差异,在较低的溶解无机氮和较高的溶解有机氮环境中,甲藻有更好的适应性,该研究对于解释我国长江口春季硅藻和甲藻赤潮的演替有借鉴的意义。     

凤眼莲浸出液对东海原甲藻生长的抑制作用

研究了凤眼莲浸出液对赤潮藻东海原甲藻生长的影响。浸出液浓度以单位体积溶液中所含凤眼莲鲜重表示。结果显示,在浸出液浓度大于2g·L^-1时,活体凤眼莲浸出液和干凤眼莲浸出液对东海原甲藻的生长都有明显的抑制作用。在浸出液浓度达到8g·L^-1时,活体凤眼莲浸出液和干凤眼莲浸出液对东海原甲藻都具有杀灭作用,东海原甲藻全部死亡出现的时间分别为培养后的第4t和第5t。经121℃高温处理20min后的活体凤眼莲浸出液对东海原甲藻的抑制作用仍然存在,抑制作用并没有显著减弱。研究结果表明凤眼莲的抑藻物质具有用来控制赤潮生物东海原甲藻的潜在价值。     

不同无机氮源对东海原甲藻生长的影响

在实验室条件下,研究了不同浓度、不同形态的氮(NaNO₃、NH₄Cl和NaNO₂)对东海原甲藻(Prorocentrum donghaiense)生长的影响。结果表明:在NH₄Cl浓度为5.20μmol·L^-1(N/P为8)时藻的比生长率最高,而N/P为32和100时,藻的生长明显受到抑制。在NaNO₃为氮源时,最适N/P为12(氮浓度为7.80μmol·L^-1)。而NaNO₂作氮源,N/P为16(10.40μmol·L^-1)时藻的比生长率最高,N/P为32和100时藻的生长也明显受到抑制。研究显示,东海原甲藻对无机氮NH₄Cl和NaNO₃和NaNO₂都可以利用,最适生长的N/P比范围在8～20之间,相对高的N/P(32、100)不利于东海原甲藻的生长。     

Comparative studies on the allelopathic effects of two different strains of Ulva pertusa on Heterosigma akashiwo and Alexandrium tamarense

Allelopathic effects of fresh tissue and dry powder of a nonsexual and a sexual strain of the macroalga Ulva pertusa on the growth of the microalgae Heterosigma akashiwo and Alexandium tamarense were evaluated using long-term coexistence culture systems in which several concentrations of macroalga fresh tissue and dry powder were used. The effects of macroalga culture medium filtrate on the two HAB algae were also investigated. Moreover, isolation co-culture systems were built to confirm the existence of allelochemicals and preclude the growth inhibition by direct contact. Short-term algicidal effect assays of macroalgae on H. akashiwo were carried out to measure the rate of algal cell lysis. The results of the coexistence assays showed that the growth of H. akashiwo and A. tamarense was strongly inhibited by fresh tissue and by dry powder of both strains of U. pertusa. The allelochemicals were lethal to H. akashiwo at relatively higher concentrations. The macroalga culture medium filtrate exhibited no apparent growth inhibitory effect on the two HAB algae under initial or semicontinuous filtrate addition, which suggested that continuous release of small quantities of rapidly degradable allelochemicals from the fresh tissue of both strains of U. pertusa was essential to effectively inhibit the growth of H. akashiwo and A. tamarense.     

Effects of Prorocentrum donghaiense and Alexandrium catenella on the material transfer in a simulated marine food chain

The biochemical composition of Prorocentrum donghaiense was analyzed and the effects of P. donghaiense and Alexandrium catenella on the transport of materials through a simulated marine food chain were investigated. The results showed that the content of phenylalanine, histidine and lysine in P. donghaiense was obviously lower than that in other dietary microalgae. Fed with P. donghaiense solely, the gross conversion efficiencies (GCEs) of A. salina increased gradually when the algal densities were lower than 4 × 104 cells/ml, and decreased gradually at higher densities. When fed with the mixture of P. donghaiense and the diatom Nitzschia. closterium, A. salina preferred grazing on P. donghaiense to grazing on N. closterium, and the GCEs of A. salina decreased with the increasing density of P. donghaiense. Exposed to A. catenella, A. salina lost weight and no Chlorophyll a was detected in the guts, which indicated that A. salina did not ingest the algal cells. When the re-suspended cells and cell-free medium of A. catenella were mixed with N. closterium or P. donghaiense, respectively, the grazing and GCEs of A. salina were all diminished. Consequently, the large-scale blooms of P. donghaiense and A. catenella in the East China Sea could adversely affect zooplankton owing to insufficient food or nutrition, and therefore impact the material transfer efficiency through the food chain.     

24-表油菜素内酯和盐度对浒苔生长和生理活性的影响

为探讨低温条件下外源植物激素和盐度变化对浒苔光合生理的影响,本文选取浒苔为供试材料,研究24-表油菜素内酯和盐度对其生长、光合色素、叶绿素荧光参数、抗氧化活性和可溶性蛋白含量的影响.结果表明: 与正常盐度(近岸海水盐度为25)相比,浒苔的生长在盐度10处理下显著增加,增幅为45.9%,但在盐度5处理下显著降低.盐度5处理的浒苔比其他盐度处理具有较高的Chl a和可溶性蛋白.24-表油菜素内酯(0.2 mg·L^-1)的加入显著抑制了浒苔的生长,尤其在盐度25处理下,浒苔呈现负增长的趋势,并大量释放孢子(配子),有效光化学效率、超氧化物歧化酶酶活性和可溶性糖含量明显降低,但可溶性蛋白含量显著增加.即在温度15 ℃条件下,可通过适当降低盐度促进浒苔的生长;在盐度25条件下,可通过添加24-表油菜素内酯促进孢子(配子)释放,为浒苔的大规模养殖提供原材料.     

Allelopathic effect of aqueous extracts of three weed species on the growth and leaf chlorophyll content of bread wheat

The purpose of this study was to evaluate the allelopathic effect of weeds (Avena fatua, Melilotus officinalis and Polypogon hissaricus) on germination, growth, dry biomass and chlorophyll concentration of three cultivars of wheat (Ata Habib, Pirsabaq and Serin). In germination test, different concentrations of aqueous extracts (5, 10 and 15?g/l) of the three weeds significantly reduced percent germination; however, 15?g/l extract of M. officinalis resulted in complete failure of germination of cultivar Pirsabaq. In pot culture, root and shoot length, chlorophyll concentration and seedling dry biomass of the three wheat varieties showed differential responses to different weeds. Aqueous extract at 15?g/l of A. fatua increased root and shoot length and dry biomass of cultivar Pirsabaq; however, these parameters were significantly retarded in other two wheat cultivars by extract of weeds. Moisture content of the cultivars did not show any response to allelopathic stress of the weeds. In contrast, chlorophyll concentration in Pirsabaq and Serin was significantly increased by aqueous extract of all the weeds but reduced it in cultivar Ata Habib by 50%. In general, Ata Habib was found to be the most sensitive cultivar to the imposed allelopathic stress. The phytotoxic potential of three weeds was found in the order of A. fatua?>?M. officinalis?>?P. hissaricus.     

Influences of light and UV-B on growth and sporulation of the green alga Ulva pertusa Kjellman

The cosmopolitan presence of Ulva spp. is partly due to its great reproductive ability, but relatively little information is available for the radiation conditions triggering reproduction. In the present study, we investigated the effect of photon irradiance, photoperiod, and spectral qualities of light on growth and reproduction of Ulva pertusa.During 8-day culture of discs cut from marginal parts of the thallus of U. pertusa, the size of the thallus discs was greatest at 10 μmol m⁻² s⁻¹, while saturation of reproduction occurred at 30 μmol m⁻² s⁻¹. The minimum photon irradiance allowing growth and reproduction was 5 and 10 μmol m⁻² s⁻¹, respectively. Rapid increases in the size and subsequent initiation of sporulation were observed in samples transferred to saturating irradiance from 5 μmol m⁻² s⁻¹ or darkness for 9 days. When exposed to different photoperiods (8:16-, 12:12-, 16:8-h LD and continuous light regimes) combined with different photon irradiances (10 and 100 μmol m⁻² s⁻¹), U. pertusa thallus showed that the thallus size attained at the low irradiance was similar in daylengths longer than 12 h per day, while the surface area increased in parallel with increasing light duration at the high irradiance. The degree of sporulation at 10 μmol m⁻² s⁻¹ varied, ranging from no sporulation in 8:16-h LD to 80% in 16:8-h LD and continuous light. On the other hand, there was no remarkable difference in the degree of sporulation between the photoperiods except for slightly smaller percentage sporulation in 8:16-h LD at 100 μmol m⁻² s⁻¹.At 5 μmol m⁻² s⁻¹, the growth of U. pertusa was markedly lower in green than in blue or red light, but there was no sporulation in any spectral quality. The degree of sporulation at 20 μmol m⁻² s⁻¹ was almost twice as much in blue or red as in green light.The size of plants irradiated with 1.0 W m⁻² of UV-B for 20-40 min increased by 18-21% relative to control, whereas higher UV irradiance caused inhibition of growth. There was a significantly lower incidence of sporulation in UV-B-irradiated plants with the degree of reduction being greater in those exposed to higher UV doses. The total biologically effective UV-B dose for 50% inhibition of sporulation was 0.085 Dose_eff kJ m⁻². The time required to achieve 50% inhibition would be longer than 13 h at depths below 1 m in Ahnin coastal waters. The vertical attenuation coefficient of PAR (λ=400-700 nm) and UV-B (λ=300-320 nm) in April 1998 at Ahnin on the eastern coast of Korea was 0.21 m⁻¹ for K_PAR and 0.54 m⁻¹ for K_UV-B. A large reduction of light quantity and rapid disappearance of blue wavelength occurred by shading from overlying thalli.Percentage inhibition of sporulation was only 14-18% at 150-200 μmol m⁻² s⁻¹ compared with 70% at 10 μmol m⁻² s⁻¹, when plants were incubated under different irradiances of PAR immediately after UV-B exposures.These different photoadaptive strategies for sporulation may in part account for the great ecological success of U. pertusa.