Biodiversity and Phylogeny of Planktic Cyanobacteria in Temperate Freshwater Lakes

Currently, the classification used for cyanobacteria is based mainly on morphology. In many cases the classification is known to be incongruent with the phylogeny of cyanobacteria. The evaluation of this classification is complicated by the fact that numerous strains are only described morphologically and have not been isolated. Moreover, the phenotype of many cyanobacterial strains alters during prolonged laboratory cultivation. In this thesis, cyanobacterial strains were isolated from lakes (mainly Lake Tuusulanjärvi) and both morphology and phylogeny of the isolates were investigated. The cyanobacterial community composition in Lake Tuusulanjärvi was followed for two years in order to relate the success of cyanobacterial phenotypes and genotypes to environmental conditions. In addition, molecular biological methods were compared with traditional microscopic enumeration and their ability and usefulness in describing the cyanobacterial diversity was evaluated. The Anabaena, Aphanizomenon, and Trichormus strains were genetically heterogeneous and polyphyletic. The phylogenetic relationships of the heterocytous cyanobacteria were not congruent with their classification. In contrast to heterocytous cyanobacteria, the phylogenetic relationships of the Snowella and Woronichinia strains, which had not been studied before this thesis, reflected the morphology of strains and followed their current classification. The Snowella strains formed a monophyletic cluster, which was most closely related to the Woronichinia strain. In addition, a new cluster of thin, filamentous cyanobacterial strains identified as Limnothrix redekei was revealed. This cluster was not closely related to any other known cyanobacteria. The cyanobacterial community composition in Lake Tuusulanjärvi was studied with molecular methods [denaturant gradient gel electrophoresis (DGGE) and cloning of the 16S rRNA gene], through enumerations of cyanobacteria under microscope, and by strain isolations. Microcystis, Anabaena/Aphanizomenon, and Synechococcus were the major groups in the cyanobacterial community in Lake Tuusulanjärvi during the two-year monitoring period. These groups showed seasonal succession, and their success was related to different environmental conditions. The major groups of the cyanobacterial community were detected by all used methods. However, cloning gave higher estimates than microscopy for the proportions of heterocytous cyanobacteria and Synechococcus. The differences were probably caused by the high 16S rRNA gene copy numbers in heterotrophic cyanobacteria and by problems in the identification and detection of unicellular cyanobacteria.

Allelopathic effects of filamentous cyanobacteria on phytoplankton in the Baltic Sea

Eutrophication and enhanced internal nutrient loading of the Baltic Sea are most clearly reflected by increased late-summer cyanobacterial blooms, which often are toxic. In addition to their toxicity to animals, phytoplankton species can be allelopathic, which means that they produce chemicals that inhibit competing phytoplankton species. Such interspecific chemical warfare may lead to the formation of harmful phytoplankton blooms and the spread of exotic species into new habitats. This is the first report on allelopathic effects in brackish-water cyanobacteria. The experimental studies presented in this thesis showed that the filamentous cyanobacteria Anabaena sp., Aphanizomenon flos-aquae and Nodularia spumigena are capable of decreasing the growth of other phytoplankton species, especially cryptophytes, but also diatoms. The detected allelopathic effects are rather transitory, and some co-occurring species show tolerance to them. The allelochemicals are excreted during active growth and they decrease cell numbers, chlorophyll a content and carbon uptake of the target species. Although the more specific modes of action or chemical structures of the allelochemicals remain to be studied, the results clearly indicate that the allelopathic effects are not caused by the hepatotoxin, nodularin. On the other hand, cyanobacteria stimulated the growth of bacteria, other cyanobacteria, chlorophytes and flagellates in a natural phytoplankton community. In a long-term data analysis of phytoplankton abundances and hydrography of the northern Baltic Sea, a clear change was observed in phytoplankton community structure, together with a transition in environmental factors, between the late 1970s and early 2000s. Surface water salinity decreased, whereas water temperature and the concentration of dissolved inorganic nitrogen increased. In the phytoplankton community, the biomass of cyanobacteria, chrysophytes and chlorophytes significantly increased, and the late-summer phytoplankton community became increasingly cyanobacteria-dominated. In contrast, the biomass of cryptophytes decreased. The increased temperature and nutrient concentrations probably explain most of the changes in phytoplankton, but my results suggest that the possible effect of chemically mediated biological interactions should also be considered. Cyanobacterial allelochemicals can cause additional stress to other phytoplankton in the nutrient-depleted late-summer environment and thus contribute to the formation and persistence of long-lasting cyanobacterial mass occurrences. On the other hand, cyanobacterial blooms may either directly or indirectly promote the growth of some phytoplankton species. Therefore, a further increase in cyanobacteria will probably shape the late-summer pelagic phytoplankton community by stimulating some species, but inhibiting others.

Lago Pellegrini. Caracteristicas limnologicas

Este trabajo trata el estudio biológico del lago Pellegrini y las características limnológicas del ambiente desde el punto de vista pesquero y turístico en el lapso 1980-1998. Se realizaron monitoreos quincenales de calidad de agua y mensuales de plancton, plaguicidas, bacteriológicos, etc. en estaciones de muestreo situadas en el lago propiamente dicho, en el afluente y alrededores. Se analizan los problemas de eutrofización presentes, en la búsqueda de ensayos que disminuyan el deterioro del ecosistema. Los resultados comprueban un proceso de eutrofización natural, agravado por la actividad humana, con florecimientos de algas cianobacterias (Géneros Microcystis y Anabaena) y una disminución de la productividad secundaria y en la población íctica.

Toxic blue-green algae: The "problem" in perspective

The incidence of blue-green algal blooms and surface scum-formation are certainly not new phenomena. Many British and European authors have been faithfully describing the unmistakable symptoms of blue-green algal scums for over 800 years. There is no disputing that blue-green algal toxins are extremely harmful. Three quite separate categories of compound have been separated: neurotoxins; hepatotoxins and lipopolysaccharides. There is a popular association between blue-green algae and eutrophication. Certainly the main nuisance species - of Microcystis, Anabaena and Aphanizomenon are rare in oligotrophic lakes and reservoirs. Several approaches have been proposed for the control of blue-green algae. Distinction is made between methods for discharging algae already present (eg algicides; straw bales; viruses; parasitic fungi and herbivorous ciliates), and methods for averting an anticipated abundance in the future (phosphorous control, artificial circulation etc).

Toxicidade e bioacumulação de cobre em micro-organismos fotoautotróficos

Microalgas e cianobactérias têm sido amplamente recomendadas para biomonitoração de metais pesados e outros poluentes, sendo considerados indicadores sensíveis às alterações ambientais e utilizados como organismos testes na regulamentação dos níveis de metal. Estes micro-organismos fotossintetizantes são produtores primários da base da cadeia alimentar aquática e são os primeiros a serem afetados pela poluição por metais pesados. O cobre é um metal normalmente considerado como nutriente essencial para a vida aquática mas pode ser tóxico para algumas espécies. Portanto, neste estudo foram avaliados o efeito tóxico e a bioacumulação de cobre (II) em quatro espécies de micro-organismos fotoautotróficos componentes do fitoplâncton dulcícola, duas cianobactérias filamentosas (Anabaena sp. e Oscillatoria sp) e duas microalgas da classe das clorofíceas (Monorraphidium sp. e Scenedesmus sp.). O meio de cultivo utilizado nos ensaios foi o ASM-1 com e sem a presença de cobre (0,6 mg/L a 12 mg Cu2+/L) onde, o efeito tóxico do metal foi monitorado por contagem celular para as microalgas e por peso seco para as cianobactérias. A bioacumulação do metal foi avaliada da mesma forma para todos os micro-organismos, através de coletas de amostras no decorrer do experimento e determinação da concentração de cobre em solução por espectrometria de absorção atômica com chama. Os resultados obtidos mostram que o efeito tóxico do metal é diretamente proporcional à concentração inicial para os micro-organismos estudados, mas que o cobre (II) foi mais tóxico para as cianobactérias que para as microalgas verdes. A bioacumulação teve uma relação direta com o efeito tóxico do metal sobre os micro-organismos. Os resultados obtidos permitem sugerir que cobre (II) tem efeito negativo no fitoplâncton, inibindo o crescimento e alterando parâmetros metabólicos como a fotossíntese. A bioacumulação do metal pode comprometer os níveis tróficos da cadeia alimentar, afetando seu transporte para seres superiores

固氮蓝藻（Nostoc spp.）基因组文库的构建及固氮酶结构基因克隆

分离自新疆干旱荒漠地区的固氮蓝藻Nostoc spp.被证明具有较高的乙炔还原活性和特异抗逆性。为了保存Nostoc spp.的优良遗传性状和今后研究所需，我们以EMBL4噬菌体为载体，以Sau3AI部分酶解的15-22kb DNA片段为供体，构建了Nostoc spp.的基因组文库。以克氏肺炎杆菌和Anabaena sp. PCC7120的nifHDK DNA片段为探针，通过三轮噬菌斑原位杂交，成功地从基因文库中分离到了六个重组噬菌体阳性克隆。Southern杂交验证插入片段含有Nostoc spp.的固氮酶结构基因序列，并对其限制酶切图谱作了初步分析。

TNFa在鱼腥藻7120中的高效表达和对宿主光合作用的影响

蓝藻分子生物学的飞速发展已使其成为生物学的前沿。近几年来，以蓝藻为宿主的基因工程发展迅速，使转基因蓝藻已有希望制备药物或处理环境问题。但迄今为止，国内外用蓝藻表达外源基因的表达效率都不高。为了使转基因蓝藻在应用上产生较好的社会效益和经济效益，必须进一步提高外源基因在蓝藻中的表速效率，以及提高光合效率、加速生长。 本研究用人肿瘤坏死因子a（Human Tumor Necrosis Factora简称hTNFa）作为外源目的基因。它是由巨噬细胞和单核细胞受到刺激后产生的一种多功能蛋白质细胞因子。hTNFcc多种生物学效应并作为信号传导体，其中最引人注目的是它对肿瘤组织和肿瘤细胞直接地、特异性和广谱性地杀伤作用，极有希望制成抗癌剩的天然因子之一。但是用大肠杆菌得到的重组产物需要严格纯化，通常用于静脉注射，但由于毒副作用大，十几年来国内外一直停留在临床实验阶段，我们研究组建议用蓝藻为宿主表达hTNFa制备口服剂，来减缓毒副作用，已经得到了转基因鱼腥藻，并测得产物具有抑瘤的生物学活性。但是表达效率一直不高，并且它的表达对蓝藻生长有些抑制。 由于蓝藻是原核生物，基因的表达调控主要是在转录水平和翻译水平。因此，寻找在蓝藻中高效的启动子，改变SD序列的结构是提高外源基因在蓝藻中表达效率的有效手段。本研究将连有不同SD序列的TNFa cDNA克隆到穿梭表达载体pRL-489的启动子（PpsbA）下游，构建2个鱼腥藻7120的穿梭表达载体（pMD-489-TNF1，2），通过三亲接合转移法分别导八鱼腥藻7120细胞。用放射免疫法定量分析TNFa在转基因蓝藻中的表达效率。结果表明，有效地提高了TNFa在鱼腥藻7120中的表达。TNFa的表达量占总可溶性蛋白的2.1 - 2.9%和0.15%，表达效率分别提高到原来的21 - 29倍和1.5倍。 在培养转基因鱼腥藻中，观测到它们在形态和生理上都发生了变化，这反应了TNFcc基因的转入和表达对宿主光合作用的影响。 光学显微镜和扫描电子显微镜的观察发现：转基因鱼腥藻比野生型异形胞数目减少约30%。转入空质粒的营养细胞比野生型略大，转TNFa基因的鱼腥藻异形胞体积明显增加，而营养细胞比正对照和野生型小。到了生长后期，转TNFa因的鱼腥藻营养细胞体积明里增大，多与异形胞相当，有的甚至比异形胞大。转pMD-489-TNFI的鱼腥藻细胞内出现明显的空腔。通过透射电子显微镜的观察发现：转基因藻中的类囊体膜片屡结构更加明显。转基因藻和野生藻的生长曲线的比较表明，转入空质粒pRL-489对宿主的生长几乎没有影响，甚至还略快于野生型;TNFa的表达对细胞的生长有一定副作用，胞内TNFa的含量高时，细胞数增长缓慢，并且平台期时细胞数有一定下降。 从光合作用光强曲线的分析可见，转TNFa因的鱼腥藻有较低的光饱和点，暗示了TNFa的表达可以增强宿主对光的敏感性;同时，TNFa的转入使宿主的呼吸作用加强，几乎比野生型和转空质粒的正对照高一倍，显示了TNFa基因的转入和表达可能给宿主带来更大的代谢负荷;在光饱和点以上，几种藻的真实光合放氧能力大致相同，表明TNFa的表达没有破坏宿主的光合反应中心。 从室温吸收光谱分析可见，转基因蓝藻有相对较高的类胡萝卜素和叶绿素a蓝峰，转TNF谌因的鱼腥藻显示了藻蓝蛋白含量有所降低。因为蓝藻的主要天线色素为藻胆蛋白，藻蓝蛋白相对含量的下降可能与宿主对光更敏感有关。 从低温荧光发射光谱分析可见，转TNFa基因的鱼腥藻7120光系统II能量分配较高。可能是TNFa基因的转入提高了藻胆蛋白的吸收和传递光能的效率。 从叶绿素荧光动力学分析可见，鱼腥藻7120在生长的过程中PSII的活性存在一个变化的过程。TNFa的转入和表达在对数后期提高了宿主的光系统II原初光能转化效率。 从转基因藻光系统I和光系统II光合放氧活性分析与TNFa表达随培养时间变化曲线表明，转TNFcc基因鱼腥藻的光合放氧活性比野生型和正对照高，尤其是显著地提高了宿主的Psn活性。 用自然界中原来不存在的转基因鱼腥藻作上述研究表明：原来只存在于高等、异养的人类和哺乳动物中的TNFa基因，一旦转入最古老的放氧光合生物后，其表达可被调控;同时TNFa的表达又能影响宿主的光合作用。它提高了宿主对光的敏感性、光系统II的活性和对光能的利用率。这似乎都表明TNFa在蓝藻细胞中起信号传导体的作用。而且，这些数据的积累，还有助于我们优化培养条件，提高TNFa的表达效率，为产业化做好准备。

Preliminary trials on the toxicity of "Algistat" to fish and algae

Preliminary toxicity trials conducted with "Algistat" (an algicide) indicated that a dose of 0,66ppm of the compound was highly toxic to fish and 0.8ppm was the general lethal level for Spirogyra sp. The blue green algae, Oscillatoria sp., Mycrocystis sp. and Anabaena sp. were adversely affected by dosages higher than 0.5 ppm Euglena sp. was not affected even at 1.0 ppm.

藻胆体的光谱特性光能传递

1．对嗜热蓝藻层理鞭枝藻(Mastigocladus laminosus)藻胆体的光谱特性和光能传递进行了研究。其完整藻胆体的吸收峰位于622 nm，室温荧光发射峰位于673 nm。在77K荧光发射光谱中，完整藻胆体的荧光峰只有一个，位于685 nm，是末端发射体1的荧光。在低浓度磷酸缓冲液中发生严重解离的藻胆体，其77K荧光发射光谱中有二个发射峰和一个发射肩。两个荧光发射峰分别位于644 nm和683 nm。前者为主峰，属于C-藻蓝蛋白的荧光，后者是次峰，属于末端发射体2的荧光。荧光发射肩位于660 nm附近，属于别藻蓝蛋白的荧光。据此，提出层理鞭枝藻藻胆体光能传递途径如下： 藻红蓝蛋白→c—藻蓝蛋白→别藻蓝蛋白→端发射体l、末端发射体2： 2．对嗜热蓝藻层理鞭枝藻藻胆体—类囊体膜的光谱特性和光能传递进行了研究。在吸收光谱中，其藻胆体——类囊体膜在可见光区域有5个峰，它们分别位于420 nm、438 nm、490 nm、624 nm和678 nm。420 nm、438 nm和678 nm为叶绿素a的吸收峰位置。490 nm是类胡罗卜素的吸收峰，624 nm是藻胆体的吸收峰。对藻胆体——类囊体膜用580 nm波长的光激发藻胆蛋白时，在室温荧光发射光谱中有一个发射峰和一个发射肩，分别位于657 nm和690 nm，前者属于藻胆蛋白的荧光，后者属于叶绿素a的荧光。这说明藻胆蛋白能将捕获的光能传递给类囊体膜上的叶绿素a。在77K荧光发射光谱中有4个峰，它们分别位于649 nm、660 nm、688 nm和730 nm。前二者属于藻胆蛋白的荧光，后二者属于叶绿素a的荧光。这同样说明藻胆蛋白能将捕获的光能传递给类囊体膜上的叶绿素a。当用436 nm波长光激发叶绿素a时，藻胆体——类囊体膜的室温荧光发射光谱中有两个荧光峰出现，位于685 nm的峰来源于光系统Ⅱ，位于713 nm的峰来源于系统I。这说明叶绿素a捕获的光能不能逆传递给藻胆体中的藻胆蛋白。在77K荧光发射光谱中也只有叶绿素a的荧光峰，位于695 nm的峰来源于光系统Ⅱ，位于730 nm的峰来源于光系统l。此结果同样说明叶绿素a捕获的光能不能逆传递给藻胆蛋白． 3．我们以多变鱼腥藻(Anabaena variabilis)为材料，对其藻胆体核心和藻蓝蛋白进行了重组实验，得到了具有光能传递效率的藻胆体核心——藻蓝蛋白复合物。在吸收光谱中，藻胆体核心有一吸收峰和一个吸收肩，分别位于654 nm和600 nm。藻蓝蛋白的吸收光谱中只有一个峰，位于620 nm．重组样品的吸收光谱有一吸收峰和一吸收肩，分别位于654 nm和620 nm．由于620 nm与654 nm的吸收比远大于核心的600 nm与654 nm的吸收比，因此，可以认为部分藻蓝蛋白已与核心重组。在室温荧光发射光谱中，藻胆体核心只有一个峰，位于676 nm。藻蓝蛋白只有一个峰，位于653 nm。重组样品有一荧光发射峰和一荧光发射肩，分别在669 nm和650 nm附近。669 nm荧光来源于核心，650 nm荧光来源于藻蓝蛋白。重组后的核心的650 nm荧光显著大于未重组的核心，这也说明部分藻蓝蛋白与核心已重组．在77K荧光发射光谱中，藻蓝蛋白只有一个峰，位于655 nm。藻胆体核心有二个峰，分别位于666 nm和686 nm。重组样品有两个荧光发射峰和一荧光发射肩，分别位于666 nm、683 nm和648 nm附近．重组的核心的别藻蓝蛋白的荧光(F666)和藻蓝蛋白的荧光(F648)都强于未重组的核心。这一结果同样说明有藻胆体——藻蓝蛋白复合物生成。 除以上研究工作之外，我们还对多变鱼腥藻藻胆体在解离过程中的光谱特性及光能传递、藻胆体——类囊体膜的光谱特性及光能传递、藻胆体解离重组、藻胆体核心在低浓度磷酸缓冲液中的光谱特性、以及温度对藻胆体核心的影响等进行了研究。研究结果有待整理。 本文编写：PBS：藻胆体;PEB：藻红胆素;PE：藻红蛋白;PUB:藻尿胆素;PEC：藻红蓝蛋白;PCB:藻蓝胆素;PC：藻蓝蛋白;PSⅡ：光系统Ⅱ;APC:别藻蓝蛋白;PS I：光系统I;TE:末端发射体

蓝藻磷脂磷酸酶基因的缺失对光合作用的影响

磷脂酰甘油(phosphatidylglycerol, PG)是类囊体膜(也叫光合膜)中唯一的一种磷脂。在蓝藻中，PG的合成途径为：磷脂酸(phosphatidic acid, PA)胞嘧啶双磷酸-二酰基甘油 (cytidine diphosphate diacylglycerol, CDP-DAG) 磷酸磷脂酰甘油 (phosphatidylglycerol phosphate, PGP)PG。其中最后一步反应是由PGP去磷酸化而生成PG，催化该反应的是PGP磷酸酶。然而迄今为止，PGP磷酸酶还没有在蓝藻和高等植物中得到克隆和鉴定。本工作在鱼腥藻Anabaena sp. PCC7120中通过将一个可能编码PGP磷酸酶的基因(alr1715)进行突变，获得缺失PG的突变体。与野生型相比，该突变体PG的含量降低了30%左右。突变后的蓝藻藻丝发黄、生长缓慢，叶绿素含量降低。整体细胞的光合作用活性、光系统II(photosystem II，PSII)的放氧活性以及PSII反应中心的光能转化效率显著下降，传递给PSII的激发能减少。

固氮蓝藻与非固氮蓝藻谷氨酰胺酶的基因克隆、表达及其特性分析

蓝藻是唯一可以进行有氧光合作用的原核生物，是水生食物链主要的初级生产者。氮素是蓝藻细胞必需的大量营养元素之一，揭示蓝藻如何应对环境中氮素的变化、维持自身碳氮平衡的分子机理，对深刻理解蓝藻与环境的相互作用、有效促进或控制蓝藻的生长与繁殖，有重要的理论和实践意义。已有的研究发现，蓝藻细胞的碳氮平衡主要是通过调控氨同化途径中的关键酶类实现。但先前的研究主要集中在固氮蓝藻谷氨酰胺合成酶（GS）-谷氨酸合成酶(GOGAT)循环的特性分析方面，而对催化谷氨酰胺水解生成谷氨酸和氨的主要酶之一谷氨酰胺酶的报道极少，其分子特性及生理学意义尚不明了。因此，本论文以模式固氮蓝藻鱼腥藻7120 和非固氮蓝藻集胞藻6803 为材料，采用分子生物学和生物化学方法，对蓝藻谷氨酰胺酶进行体外研究，并对其生物学功能进行了初步探讨，获得了如下主要结果：1）对体外重组蛋白的酶活性检测发现，两类蓝藻基因组编码的假定性谷氨酰胺酶，均具有谷氨酰胺酶催化活性，表明基因组注释是准确的；2）固氮蓝藻重组酶（All2934、All4774）与非固氮蓝藻重组酶（Slr2079）酶学特征差异显著，具有不同的最适pH、温度及底物亲和力；3）固氮蓝藻重组酶All2934 催化活性受磷酸盐的激活，而非固氮蓝藻重组酶Slr2079 在高Na+浓度下活性更高；4）RT-PCR 分析结果表明，在正常培养条件下，两类蓝藻的谷氨酰胺酶基因在细胞内均有表达；5）在缺氮培养条件下，固氮蓝藻谷氨酰胺酶基因all2934 的表达水平发生明显变化，而all4774 保持相对稳定，表明前者可能在这类细胞应对氮饥饿过程中起重要作用；6）在正常培养条件下，非固氮蓝藻谷氨酰胺酶基因的缺失突变体(Δslr2079)与野生型表型相似，但在盐胁迫条件下，突变体生长速率及光合放氧活性均高于野生型，表明该基因可能在提高非固氮蓝藻细胞高盐耐受力方面起负调控作用。上述重要发现，不仅初步揭示了光合自氧生物谷氨酰胺酶体外重组酶的分子特征，也为进一步研究谷氨酰胺酶在蓝藻细胞内的专一性功能奠定了重要基础。

The comparison of inhibitory effects of barley and rice straws to control of algae and aquatic weeds in fish ponds

Bioassays were carried out to consider the relative effect of barley and rice straw extracts on the growth of 12 problematic freshwater algae. The laboratory results demonstrated that growth of Microcystis aeruginosa; Aphanizomenon flos–aquae, Anabaena flos–aquae, Synura petersenii, and Dinobryon sertularia were all inhibited, whereas Oscillatoria tenuis, Asterionella formosa, Spirogyra sp., and Hydrodictyon reticulatum grown were stimulated by the barley straw extract. No significant effect was also found on the growth of Chlorella kessleri, Scenedesmus subspicatus, and Navicula pelliculosa.

The diversity and abundance of zooplankton in the Lake Victoria and Kyoga basins and their relationship to fish production

Biological diversity of an ecosystem is considered a reliable measure of the state of health of the ecosystem. In Uganda's large lakes, the Victoria and Kyoga, the past three decades have been characterized by profound changes in fish species composition following the introduction of the piscivorous Nile perch (Oguto-Ohwayo 1990). Over 300 haplochromine cichlid species comprising a wide range of trophic groups were lost along with a host of non-cichlid fishes which occupied virtually all available ecological niches and in the lakes (Witte 1992). A second major ecological event has been the gradual nutrient enrichment of the water bodies (eutrophication) from diffuse and point sources, while at the same time pollutants have also gained entrance into the water systems in pace with indusfrial development and human population increases in the lake basins. Eutrophication and pollution have drastically altered the physical and-chemical character of the water medium in which different fauna and flora thrive. In Lake Victoria these alterations have resulted in changes of algal species composition from pristine community dominated by chlorophytes and diatoms (Melosira etc) to one composed largely of blue-green algae or Cyanobacteria (Microcystis, Anabaena, Planktolyngbya etc) (Mugidde 1993, Hecky 1993).

Trophic interrelationships and food-webs among the fishes in ecosystems of the Victoria and Kyoga lake basin

The Victoria and Kyoga lake basins had a high fish species diversity with many fish species that were found only in these lakes. Two Tilapiines species Oreochromis esculentus and Oreochromis variabilis were the most important commercial species in these lakes and were found nowhere else on earth except in the Victoria and Kyoga lake basins (Graham 1929, Worthington 1929). Lakes Kyoga and Nabugabo also had endemic haplochromine species (Worthington 1929, Trewavas 1933, Greenwood 1965, 1966). As stocks of introduced species increased, stocks of most of the native species declined rapidly or disappeared altogether. The study was carried out on Lakes Victoria and Kyoga, River Nile, some selected satellite lakes from the two basins namely Lakes Mburo, Kachera, Wamala, Kayanja, Kayugi, Nabugabo, Victoria, Victoria nile and River Sio(Victoria lake basin). Lakes Kyoga (Iyingo), Nawampasa, Nakuwa, Gigati, Nyaguo, Agu, Kawi and Lemwa (Kyoga lake basin). Species composillon and relative abundance of fishes were estimated by detennining the overall average total number of each species encountered. A trophic consists of species using the same food category. Shannon-Weaver Index of diversity H (Pielou, 1969) and number of trophic groups, were used to estimate the Trophic diversity of various fish species in the lakes. Food analysis has been done on some fishes in some of the sampled lakes and is still going on, on remaining fishes and in some lakes. Generally fish ingested detritus, Spirulina, Melosira, filamentous algae, Planktolyngbya, Microcysists, Anabaena, Merismopedia, Spirogyra, higher plant material, rotifers, Ostracodes, Chironomid larvae and pupae, Choaborus larvae, Odonata, Povilla, Insect remains, Caridina, fish eggs and fish. Eight trophic groups were identified from thes food items ingestes. These included detritivores, algae eaters, higher plant eaters, zooplanktivores, insectivores, molluscivores, prawn eaters, paedophages and piscivores. Trophic diversity by number of trophic groups was highest in Lake Kyoga (6) followed by lakes Kayugi, Nabugabo, River Nile and Mburo (3) and the lowest number was recorded in kachera (2).

复合藻-菌净化系统处理麦秆造纸废液初步研究

在室内模拟条件下,采用正交设计法建立了一种由蛋白核小球藻(Chlorella pyrenoidosa)、鱼腥藻7120(Anabaena sp.PCC7120)、硝化细菌(Nitrate bacteria)和荚膜红假单胞菌(Rhodopseudomonas capsulata)组成的复合藻-菌净化系统去除造纸废液中有机质和氨态氮的最优化模型,确定了藻类与细菌的最优化数量配比关系为蛋白核小球藻∶鱼腥藻7120∶硝化细菌∶荚膜红假单胞菌=1∶2.17∶2.83∶5.09.比较了复合藻-菌净化系统最优化模型与单