微囊藻和栅列藻光吸收特性的实验研究

在室内模拟槽中,以人工灯为光源,分别检测不同密度的微囊藻和栅列藻细胞悬液的光谱衰减,检测各样品的叶绿素含量和过滤后清液的溶解性有机碳(DOC)含量,并在紫外分光光度计上检测DOC光谱吸收,然后换算成吸收系数。再根据近似的线性加和关系计算出细胞悬液中各组分(藻细胞、水、DOC)的吸收系数。结果表明,微囊藻和栅列藻光衰减的波谱特征相似,在3个较高密度下的衰减系数的变化趋势相近,其衰减系数贡献率的平均值分别为84.95%和88.15%。将衰减系数除以各自的叶绿素浓度即可得到叶绿素的比吸收系数,两种藻3个较高密度的比吸收系数的平均值具有相似的波谱特征,在380～500、660～690nm两个波段有较明显的峰值,栅列藻和微囊藻在435nm的比吸收系数峰值分别为0.1118、0.0413(m2·mg-1chla),在670nm处的峰值分别为0.075、0.032(m2·mg-1chla)。但两者的比吸收系数差异较大,三个密度栅列藻在340～800nm的平均比吸收系数是0.0573(m2·mg-1chla),而微囊藻仅为0.0234(m2·mg-1chla),且微囊藻的所有波长的比吸收系数均小于栅列藻。根据这些参数来讨论两种藻类在分光衰减中的贡献率和光谱特征方面的差异及其生态学意义,以及在浮游植物的遥感监测方面的参考价值。     

绿藻栅藻对微囊藻的抑制效应及评价

为筛选具有控制微囊藻水华潜力的绿藻, 研究基于藻类之间的化感作用, 对34株绿藻开展筛选及评价工作。结果发现, 栅藻FACHB-1229的抑制率最高, 其滤液对微囊藻FACHB-3550和FACHB-905的抑制率分别为53.95%和48.39%; 通过对滤液中的物质进行GC-MS检测, 推测该藻株的效应物质可能为邻苯二甲酸二(2-甲氧基乙基)酯。进一步对FACHB-1229生长和光合放氧、氨氮耐受等指标进行评价, 结果发现: 该藻株在孔板中的生长速率(0.38±0.06)/d高于微囊藻生长速率(0.13±0.03)/d; 栅藻FACHB-1229的光合放氧速率高于同期测定的其他绿藻光合放氧速率, 可达(229.91±10.49) μmol O₂/(mg Chl.a·h); 同时该藻株对氨氮的耐受能力最强, 在氨氮浓度为1888.60 mg/L时其生长速率可达(0.30±0.08)/d。此外, 在与微囊藻FACHB-3550进行共培养时, 栅藻FACHB-1229所占比例持续升高。综上, 栅藻FACHB-1229具备与微囊藻竞争的优势, 有望成为微囊藻水华生物控制的优选材料。     

微囊藻和栅藻共培养实验及其竞争参数的计算

以Ｌｏｔｋａ－Ｖｏｌｔｅｒｒａ的双种竞争模型为基础,进行试验设计。共培养试验中,两种藻类的增长行为是不同的,培养前期共培养中栅藻的数量大于纯培养中栅藻的数量,而在后期则相反,微囊藻则是在整个共培养过程中的数量都小于纯培养中的数量。通过纯培养取得参数Ｋ和ｒ,变模型的微分形式为差分形式,以生长曲线拐点（密度制约起始点）出现的时间作为计算竞争参数的起始时间。经模拟计算获得参数,表明微囊藻的抑制能力是栅藻     

巢湖微囊藻和浮游甲壳动物昼夜垂直迁移的初步研究

2002年10月进行了巢湖微囊藻和几种优势浮游甲壳动物的昼夜垂直变化的研究,结果表明:微囊藻具有明显的昼夜垂直变化现象。白天上层水中的微囊藻密度显著高于下层水中,夜晚逐渐下沉使得下层水中的密度相对高于上层水。微囊藻与叶绿素a、水温、溶解氧和pH等均呈显著的正相关(p<0.01)。几种优势浮游甲壳动物的昼夜垂直迁移存在较大的差异。短尾秀体溞和角突网纹溞白天在下层水(1.5m和2.5m)中的密度较高,夜晚则倾向于在上层水(0m和0.5m)中活动。相反,卵形盘肠溞白天在上层水中密度较高,象鼻溞则在11:00和15:00时各水层中的密度显著高于夜晚。汤匙华哲水蚤和广布中剑水蚤白天倾向于在下层水中活动,夜晚则逐渐迁移到上层水中。许水蚤在夜晚和凌晨3:00时各水层中的密度显著高于白天。中华窄腹剑水蚤昼夜垂直变化不明显。微囊藻与短尾秀体溞密度呈显著的负相关,而与象鼻溞和卵形盘肠溞呈显著的正相关(p<0.01)。     

宜都栅藻——栅藻属——新种

栅藻属(Scenedesmus)是1829年由Meyen建立的。到目前为止,中国已报告有50余种。在鉴定由作者和几位同事所采集的标本时,发现采于宜都县和恩施县的标本应是一个新种,经研究命名为宜都栅藻。     

水生花卉对铜绿微囊藻、斜生栅藻和小球藻生长的影响

选择黄菖蒲(Iris pseudacorus)、溪荪(I.sanguinea)、梭鱼草(Pontederia cordata)、白花水龙(Jussiaea repens)、水罂粟(Hydrocleys nymphoides)和大藻(Pistia stratiotes)6种具有较高观赏价值的水生花卉,通过将植物种植水与藻类共同培养的方式研究了不同种植时间的种植水对铜绿微囊藻(Microcystis aeruginosa)、斜生栅藻(Scenedesmus obliqnus)和小球藻(Chlorella vulgaris)生长的影响.结果表明:6种水生花卉种植水对3种藻类的化感作用具有选择性.通过6d的处理,种植水对铜绿微囊藻生长的抑制率为31.22％ ～ 96.53％,除白花水龙外,其余5种花卉的种植水对铜绿微囊藻生长的抑制率均超过70％,表现出很好的抑藻效果;种植水对斜生栅藻生长的抑制率为23.15％～77.25％;而种植水对小球藻有抑制也有促进,抑制率为-26.07％ ～75.70％,大藻、梭鱼草和溪荪抑制小球藻的生长,黄菖蒲、白花水龙表现为低促高抑,水罂粟表现为促进作用.随着种植时间的延长,种植水对3种藻类的抑制作用增强.6种水生花卉种植水对铜绿微囊藻生长的抑制作用由大到小依次为水罂粟＞黄菖蒲＞梭鱼草＞大藻＞溪荪＞白花水龙;对斜生栅藻生长的抑制作用由大到小依次为梭鱼草＞溪荪＞黄菖蒲＞水罂粟＞白花水龙＞大藻;对小球藻生长的抑制作用由大到小依次为大藻＞梭鱼草＞溪荪＞黄菖蒲、白花水龙＞水罂粟.试验表明,6种水生花卉在控制城市景观水体中的藻类水华有一定的推广价值.     

蓖齿眼子菜对栅藻和微囊藻的他感作用及其参数

主要报道篦齿眼子菜 (俗称红线草 )的种植水抽滤液对栅藻、微囊藻生长的他感作用试验。应用修正的逻辑斯谛 (Logistic)方程和Lotka Volterra种群竞争模型来计算篦齿眼子菜对藻类的他感作用参数。纯培养试验结果表明 :种植水抽滤液对栅藻生物量和生长率都有一定的促进作用。当浓度大于等于 5 0 %时 ,对栅藻生长的影响则是有抑制效应 ,他感作用效应与种植水的浓度没有明显的相关性 ,他感作用参数平均为 - 0 0 2 6。所有浓度设对照。微囊藻的生长都有明显的抑制作用 ,他感作用参数平均为 - 0 2 37。共培养试验结果表明 :篦齿眼子菜种植水抽滤液对纯培养试验结果有放大效应。所有的种植水抽滤液浓度对栅藻生长都起促进作用 ,对栅藻的生物量效应、生长率存在明显的对数正相关 ,但与他感作用参数的相关不明显 ,共培养的他感作用参数平均为 0 0 2 0 ;对微囊藻生长抑制作用更加明显 ,共培养的他感作用参数平均为 - 0 4 2 0。不管是纯培养还是共培养中 ,种植水抽滤液对栅藻的他感作用系数值都很低 ;而种植水抽滤液浓度对微囊藻的生物量效应、生长率或他感作用的参数都存在明显的线性负相关 ,并且他感作用系数值约高一个数量级     

铜绿微囊藻和四尾栅藻在不同温度下的生长特性及竞争参数计算

在实验室条件下,对铜绿微囊（Microcystis aeruginosa）和四尾栅藻（Scendesmus quadricauda）分别在温度22℃、26℃和30℃下进行了纯培养和混合培养,实验结果显示温度对两种藻类的生长和竞争都有显著影响。微囊藻在22℃、26℃和30℃纯培养下的最大生物量及平均特定增长率（μ）分别为444、1180和998（&#215;104cells/mL）及0.33、0.38和0.37/d,说明微囊藻在26℃和30℃下生长较好;混合培养下的最大生物量及平均特定增长率分别为270、778和647（&#215;104cells/mL）及0.34、0.43和0.46/d,显示微囊藻在混合培养下受到了栅藻一定程度的竞争抑制。栅藻在22℃、26℃和30℃纯培养下的最大生物量及平均特定增长率分别为830、984和464（&#215;104cells/mL）及0.36、0.34和0.32/d;混合培养下的最大生物及平均特定增长率分别为538、554和387（&#215;104cells/mL）及0.43、0.40和0.39/d,说明栅藻在温度22℃、26℃下生长较好,混合培养下栅藻的生长受微囊藻影响较大。各温度下两种藻类的生长都可以用Logistic方程拟合。微囊藻对栅藻的抑制参数α分别为1.68（22℃）、0.65（26℃）和0.76（30℃）,而栅藻对微囊藻的抑制参数β依次为0.43（22℃）、0.51（26℃）和0.25（30℃）,三个温度下α均大于β,产生这一结果的原因可能是由于微囊藻与栅藻在竞争过程中不仅表现为资源竞争,同时还存在着明显的他感作用,且可推测微囊藻对栅藻的他感作用大于栅藻对微囊藻的,且在22℃时为最大。     

铜绿微囊藻和斜生栅藻非稳态营养盐限制条件下的生长竞争特性

采用“脉冲”添加方法进行了非稳态条件下铜绿微囊藻（M.）和斜生栅藻（S.）分别在氮磷单营养盐和双营养盐限制时的共培养试验。试验结果显示：当添加频率为1d时,无论何种营养盐限制,M.均成为优势藻种。氮限制条件下,氮时均浓度范围在0.3—2.4 mg/L时,M.始终具有竞争优势。磷限制条件下,磷浓度范围在0.018—0.035 mg/L时,S.只在生长初期阶段占优。氮磷双营养盐限制条件下,添加液的氮磷质量比为35:1（设定为最优比）,添加频率为8 d时,两种藻表现出共生特征;而偏离最优比时（N:P=70:1,17:1）,在不同的添加频率下均未出现共生现象,且氮的时均浓度为0.6—4.8 mg/L时（70:1）,M.具有竞争优势,而降低为0.15—0.3 mg/L时（17:1）,S.占优。随着添加频率的变化,两种藻的细胞大小也会随之改变,S.随着营养盐浓度的降低而增大,且在双营养盐限制条件下变化更显著。上述试验结果分析表明：两种藻竞争能力与添加频率相关,在藻种浓度的变化上,按照‘拾遗－机会’交替竞争理论,M.表现出机会主义者特征,而S.则表现出拾遗者的特征,两者的共生特征也符合‘中度干扰’假说。藻细胞大小变化表明,两种藻均可以改变大小实现最大限度争夺受限营养盐。在低浓度时,S.细胞大小的变化同样也变现出了“拾遗者”的特征。     

角突网纹溞培养滤液对铜绿微囊藻和栅藻形态及生长率的影响

在藻类中,随着环境条件的变化而产生相应的单细胞和群体之间的形态转化是一种广泛存在的现象,称为表型可塑性。例如,栅藻属成员就是这些藻类的代表,在野外具有典型的群体特征,但在室内纯培养条件下栅藻常较少形成群体而是保持以单细胞形态为主。     

萼花臂尾轮虫培养滤液对铜绿微囊藻、斜生栅藻和小球藻群体形成及生长的影响

为探索浮游动物和藻类之间可能存在的信息传递,研究了萼花臂尾轮虫培养滤液对铜绿微囊藻、斜生栅藻和小球藻的生长及群体形成的影响.把萼花臂尾轮虫按1000个·L^-1的初始密度置于小球藻中培养24h后,用孔径0.15μm的微孔滤膜抽滤,得到轮虫培养滤液,此滤液中含有轮虫在生活过程中释放的一些信息化学物质.将轮虫培养滤液以20%的比例分别加入纯培养的铜绿微囊藻、斜生栅藻和小球藻中,进行为期7d的试验.结果表明,萼花臂尾轮虫培养滤液能显著地促进斜生栅藻的群体形成,而对铜绿微囊藻和小球藻在群体形成方面没有显著作用.另外,该滤液能显著提高小球藻种群的增长,对铜绿微囊藻和斜生栅藻的生长无明显影响.3种藻类对萼花臂尾轮虫的潜在牧食采取了不同的生态策略:斜生栅藻形成群体,增大摄食阻力,从而降低被摄食的风险;小球藻通过提高增长率来抵消被取食的损失;铜绿微囊藻是通过其它方式来降低被牧食(例如毒素).这些方式分别是这些藻类维持种群规模的反牧食防御策略之一.     

Vertical distribution of Microcystis population in the regulated Nakdong River, Korea

The vertical distribution of a bloom-forming Microcystis population was studied based on the relevant limnological parameters obtained from the lower Nakdong River (Mulgum) during the summer of 1994. Over three months (late June to late September), a high abundance of Microcystis population (mean ± SD, 2.9 ± 8.4 × 10⁵ cells ml⁻¹, n = 40) and algal biomass (mean ± SD, chlorophyll a, 131 ± 346 μg l⁻¹, n = 31) was persistent throughout the entire water column (0–5 m, n = 11). The vertical distribution of carbon content was uneven, with a high concentration near the surface zone (mean ± SD, total, 7.9 ± 7.8; Microcystis, 5.2 ± 8.3 μg C ml⁻¹, n = 15). Incorporating limnological and meteorological factors, a diel study of the vertical distribution of Microcystis showed that the chlorophyll a concentration was highest near the surface zone on a calm night (wind velocity, <2 m s⁻¹, 2300–700) but was evenly distributed on a windy day (>4 m s⁻¹, 1100–1900). Among many possible factors, wind velocity may have played an important role in controlling the vertical distribution of Microcystis in the lower Nakdong River. Received: July 12, 1999 / Accepted: November 15, 1999     

Modelling vertical migration of the cyanobacterium Microcystis

Computer models can be helpful tools to provide abetter understanding of the mechanisms responsible forthe complex movements of cyanobacteria resulting fromchanges in buoyancy and mixing of the water column ina lake. Kromkamp & Walsby (1990) developed a verticalmigration model for Oscillatoria, that wasbased on the experimentally determinedrelationship between the rates of density change andphoton irradiance in this cyanobacterium. To adaptthis model to Microcystis, we determinedrelated changes in carbohydrate content in cultures ofMicrocystis. Samples were incubated at variousconstant values of photon irradiance and then placedin the dark. The changes in carbohydrate content ofthe cells during these incubations were investigated.The relationship between the ratio of carbohydrate toprotein and cell density in Microcystis wasestablished to permit conversion of the rates ofcarbohydrate change to rates of density change. Byplotting the calculated rates of density changeagainst the values of photon irradiance experiencedduring the incubations, an irradiance-response curveof density change was established. The curve showed adistinct maximum at 278 µmol photons m^-2s^-1. At higher values of photon irradiance, therate of density change was strongly inhibited. Apositive linear correlation was found between celldensity and the rates of density decrease in the dark.The validity of the use of rate equations of densitychange, which are based on short-term incubations atconstant values of photon irradiance, to predictdensity changes in Microcystis in fluctuatinglight regimes was tested. This was accomplished bymeasuring the time course of change in carbohydratecontent of two continuous cultures of Microcystis, which were submitted to fluctuatinglight regimes, and comparing the results with thechanges in the carbohydrate contents of these culturespredicted by the rate equations of carbohydratechange. The results showed good agreement: the rateequations of density change were therefore introducedinto the model to simulate vertical migration of Microcystis. The model predicts that the maximummigration depth of Microcystis will increasewith colony size up to a maximum of 200 µm radius.The effect of colony size on the net increase in celldensity during the light period was also investigatedwith the model. It predicts that small colonies havea higher net increase in cell density than largecolonies, but are inhibited at high photon irradiancesat the surface.     

Occurrence of protochlorophyll and its phototransformation to chlorophyll in mutant C-2A' of Scenedesmus obliquus

The pigment mutant C-2A' of the unicellular green alga Scenedesmus obliquus accumulates protochlorophyllide and small amounts of protochlorophyll in darkness. Protochlororphyll was isolated and characterized by thin layer chromatography and absorption and fluorescence spectroscopy. The protochlorophyll was photoreduced by light to chlorophyll both in vitro and in vivo.     

Biosynthesis of chlorophyll b in pigment mutant C-2A' of Scenedesmus obliquus

It is demonstrated that chlorophyll b does not only derive from chlorophyll a , but is also formed separately from an in vivo-occurring chlorophyllide b . The branching point for the latter synthesis is at the level of chlorophyllide, since no protochlorophyllide b was detectable. We have indications that the enzyme oxidizing chlorophyll a to chlorophyll b accepts also non-phytylated 17,18 dihydroporphyrins and is not restricted to chlorophylls. Preparations of chlorophyllide a and chlorophyll a could both be transferred with the same enzyme fraction to chlorophyllide b and chlorophyll b , respectively. Preliminary experiments show this enzyme to be membrane bound and light independent. An updated scheme for chlorophyll b biosynthesis is presented.     

斜生栅藻中虾青素的积累过程及其光合活性变化

分析了斜生栅藻（Scenedesmus obliquus）在光温（30℃,180 μmol/m2·s）胁迫条件下积累虾青素的过程,观察了该过程中细胞形态及细胞光合生理的变化。胁迫条件下,细胞在48h内生成并积累了包括海胆酮、角黄素、金盏花黄素和金盏花红素在内的多种次生类胡萝卜素,并合成了虾青素及其酯。该过程中,细胞形态由两端尖细变得不规则、膨大,原来由4、8个细胞组成的定形群体变为游离的单个细胞或2个细胞组成的群体。藻细胞光合速率在24h内先下降后上升,而后又呈现下降趋势,从34.29 μmol O2/mg Chla/h迅速下降为5.21 μmol O2/mg Chla/h;呼吸速率在前24h内升高至60.37 μmol O2/mg Chla/h,而后缓慢下降到38.40 μmol O2/mg Chla/h;光合系统Ⅱ的活性随着胁迫时间的延续而逐步下降,较初始值降低了63.9％。结果表明,斜生栅藻细胞在高光照条件下可以合成虾青素,并通过调节光合速率、呼吸速率以及光合系统Ⅱ的效率来应对胁迫。