Critical conditions for ferric chloride-induced flocculation of freshwater algae

The effects of algae concentration, ferric chloride dose, and pH on the flocculation efficiency of the freshwater algae Chlorella zofingiensis can be understood by considering the nature of the electrostatic charges on the algae and precipitate surfaces. Two critical conditions are identified which, when met, result in flocculation efficiencies in excess of 90% for freshwater algae. First, a minimum concentration of ferric chloride is required to overcome the electrostatic stabilization of the algae and promote bridging of algae cells by hydroxide precipitates. At low algae concentrations, the minimum amount of ferric chloride required increases linearly with algae concentration, characteristic of flocculation primarily through electrostatic bridging by hydroxide precipitates. At higher algae concentrations, the minimum required concentration of ferric chloride for flocculation is independent of algae concentration, suggesting a change in the primary flocculation mechanism from bridging to sweep flocculation. Second, the algae must have a negative surface charge. Experiments and surface complexation modeling show that the surface charge of C. zofingiensis is negative above a pH of 4.0 ± 0.3 which agrees well with the minimum pH required for effective flocculation. These critical flocculation criteria can be extended to other freshwater algae to design effective flocculation systems.     

Digestion of Added Homologous Algae by Chlorella-Bearing Paramecium bursaria

SYNOPSIS. Endosymbiotic algae from Paramecium bursaria when added to the culture medium are ingested by Chlorella -bearing P. bursaria at a rate of 2,000 algae/organism/day. That the ingested algae are digested and assimilated by the ciliates is suggested by the more rapid growth of Paramecium when algae are added to the medium ( G = 40 hr with algae compared to 190 hr without). The digestion by the ciliates of exogenous algae contrasts with the survival of these algae under normal growth conditions. It is suggested that the protection of the endogenous algae is related to their location in peripheral perialgal vacuoles.     

兰州五泉山的藻类及其分布

以兰州五泉山为该地藻种资源库,对其中水生、陆生生境中藻类的种类多样性、群落结构、分布特点进行了研究。结果发现该地藻类植物65种(含4变种),包括蓝藻、绿藻、硅藻和红藻,其中硅藻种类最多(29种),其它依次为蓝藻(24种)、绿藻(11种)和红藻(1种)。水体中共42种,硅藻最多,有26种,其次蓝藻8种,绿藻7种,红藻1种,不同水体中优势种和亚优势种不同。土壤生境中发现20种,蓝藻13种,绿藻4种,硅藻3种,且非洲席藻和小球藻分为优势种和亚优势种。7个种类在水、陆两大生境都有分布,而且它们主要是丝状蓝藻。     

Marine macroalgae as foods for fishes: an evaluation of potential food quality

Synopsis A revitalized view of feeding by herbivorous marine fishes is sought through two questions. First, What characteristics of major taxa of algae identify them as predictably high or low quality foods? Second, are marine algae valuable foods for fishes which do not mechanically disrupt cell walls and do not harbor specialized enzymes or microbes capable of lysing cell walls? Energy, ash and nutrient content of 16 species of marine algae were employed to assess food quality of fleshy red, green, brown and calcareous red algae. On the basis of ash, calories, total protein and total lipid content, fleshy algae should be superior to calcareous algae as foods for fishes; in addition, green algae should be superior to brown algae and brown algae superior to red algae. When the probable digestibility of storage and extracellular carbohydrates is considered, green and red algae are predicted superior to brown algae as food. Two species of damselfishes (Pomacentridae) from the Gulf of California,Eupomacentrus rectifraenum andMicrospathodon dorsalis, eat red and green algae and ignore brown and calcareous algae. They feed, therefore, in a fashion consistent with predictions based only on algal chemistry. These fishes absorb at least 20–24% of the biomass, 57–67% of the protein, 46–56% of the lipid and 37–44% of the carbohydrate contained in algae eaten in the wild. Since these damselfishes do not masticate their food, it appears that herbivorous fishes can digest major fractions of algal nutrients without mechanical destruction of algal cells.     

古尔班通古特沙漠生物结皮藻类的组成和生态分布研究

通过对新疆古尔班通古特沙漠中9个样地73份生物结皮土样藻类的培养和鉴定,分析了古尔班通古特沙漠中生物结皮藻类的种类组成和生态分布特点。结果表明．该沙漠中有藻类植物49属121种．隶属于蓝藻门、绿藻门、硅藻门和裸藻门。其中监藻83种,绿藻20种,硅藻11种。裸藻7种。蓝藻占总种数的68．60％,其中又以丝状种类为优势．占66．27％;绿藻则以单细胞种类为主。在古尔班通古特沙漠不同地带中,其藻类物种多样性和群落组成均有所不同,中部藻类物种最为丰富,北部和南部次之。而东部和西部则明显减少。在沙垄不同部位的分布中,少数种类对地貌部位的选择性不明显,但有些种类在不同地貌部位分布有差异。藻类在结皮不同层次的分布不同,在结皮层中藻类的种类和数量都较丰富．且以丝状种类较多,而在结皮下层藻类的种类和数量明显减少。     

The Response of Experimental Rocky Shore Communities to Nutrient Additions

The aim of this study was to determine whether the experimental nutrient enrichment of littoral rocky shore communities would be followed by a predicted accumulation of fast-growing opportunistic algae and a subsequent loss of perennial benthic vegetation. Inorganic nitrogen (N) and potassium (P) was added to eight concrete mesocosms inhabited by established littoral communities dominated by fucoids. The response to nutrient enrichment was followed for almost 2 1/2 years. Fast-growing opportunistic algae (periphyton and ephemeral green algae) grew significantly faster in response to nutrient enrichment, but the growth of red filamentous algae and large perennial brown algae was unaffected. However, these changes were not followed by comparable changes in the biomass and composition of the macroalgae. The biomass of opportunistic algae was stimulated only marginally by the nutrient enrichment, and perennial brown algae (fucoids) remained dominant in the mesocosm regardless of nutrient treatment level. Established rocky shore communities thus seem able to resist the effects of heavy nutrient loading. We found that the combined effects of the heavy competition for space and light imposed by canopy-forming algae, preferential grazing on opportunistic algae by herbivores, and physical disturbance, succeeded by a marked export of detached opportunistic algae, prevented the fast-growing algae from becoming dominant. However, recruitment studies showed that the opportunistic algae would become dominant when free space was available under conditions of high nutrient loading and low grazing pressure. These results show that established communities of perennial algae and associated fauna in rocky shore environments can prevent or delay the accumulation of bloom-forming opportunistic algae and that the replacement of long-lived macroalgae by opportunistic species at high nutrient loading may be a slow process. Nutrient enrichment may not, in itself, be enough to stimulate structural changes in rocky shore communities.     

藻类的光控发育

藻类发育的许多方面受光的调控,且多种多样的光受体参与藻类的光形态建成过程。本文就近年来藻类光形态建成领域的研究进展简要综述,内容以海洋藻类为主,主要包括光周期、非光周期控制的藻类发育类型,以及藻类的光受体的种类及分子特性,并兼顾与高等植物的相关特性进行比较。     

Development of microalgae communities in the Phytotelmata of allochthonous populations of Sarracenia purpurea (Sarraceniaceae)

The phytotelmata of the North American pitcher plant Sarracenia purpurea are colonised by a great variety of aquatic organisms and, thus, provide an ideal model to study trophic interactions in small freshwater ecosystems. Although algae are discussed as a potential food source for predators, little is known about the structure of algae coenoses in pitchers of S. purpurea. This study aims to elucidate temporal shifts in the algae community structure in pitchers of an allochthonous population of S. purpurea in Saxony, Germany. A total of 78 algae taxa was found in the pitchers. Mean algae abundances in new and old pitchers were similar (2.6 x 10(5) and 2.3 x 10(5) algae ml(-1), respectively). Taxa from the orders Chlamydomonadales, Chlorococcales, and Ochromonadales were the primary colonisers. With increasing age of the pitchers the filamentous green algae from the order Klebsormidiales became more abundant. In contrast, pennate diatoms dominated the algae coenoses in the fen. Algae community structure in vase-shaped 50 ml Greiner tubes was similar to those of natural pitchers. Differences in the temporal patterns of algae coenoses in individual pitchers suggested a colonisation of the pitchers by algae via trapped insects, air and rain water rather than via the surrounding fen. Biomass of algae approximated 0.3 mg C ml(-1), which corresponds to 82.8 % of the living biomass (bacteria, heterotrophic nanoflagellates, algae, protozoans and rotifers). Rotifers were abundant in new pitchers; nematodes and mites were seldom found in all pitchers. A similar qualitative and quantitative composition of the aquatic biocoenoses was observed in pitchers of another allochthonous S. purpurea population growing in Blekinge, Sweden. Biomass of algae represented nearly one quarter of the total organic matter content in the pitchers. Thus, nitrogen and phosphorus compounds present in the algae biomass might be used by the carnivorous S. purpurea plant as additional food source in allochthonous populations in Europe lacking top predators.     

Retrospective analysis of the marine flora of Vostok Bay,Sea of Japan

A general list of the flora of Vostok Bay (Sea of Japan) compiled on the basis of original and literature data includes 161 species, among them 25 green algae, 42 brown algae, 90 red algae, and 4 species of seagrass. In the period from 2000 to 2004, 114 species of macrophytes (19 green algae, 29 brown algae, 63 red algae, and 3 species of seagrass) were found in Vostok Bay; 19 species of algae were first records for this bay. On the whole, the flora of Vostok Bay is dominated by warm-water species, among which Asian low-boreal species occupy the leading position. The flora of Vostok Bay is changing under the influence of global climatic and local anthropogenic factors. In recent years, there is a tendency for the proportion of warm-water species to increase. The local anthropogenic influence on the flora of Vostok Bay has caused changes in the species composition of plant communities.     

A symbiosome membrane is not required for the actions of two host signalling compounds regulating photosynthesis in symbiotic algae isolated from cnidarians

In many cnidarians, symbiotic algae live within host-derived symbiosomes. We determined whether a symbiosome membrane alters the response of isolated symbiotic algae to two signalling compounds that regulate algal carbon metabolism. Host release factor (HRF), which stimulates photosynthate release, and photosynthesis inhibiting factor (PIF), which inhibits photosynthetic carbon fixation, are found in homogenised tissue of the scleractinian coral Plesiastrea versipora. Compared with seawater controls, photosynthate release from isolated algae incubated in P. versipora homogenate for 2 h in the light was: 6 to 19-fold higher from its own algae (free of symbiosomes); 19 to 32-fold higher from Zoanthid robustus algae (within symbiosomes) and 3 to 24-fold higher from Z. robustus algae (free of symbiosomes); and from cultured algae (free of symbiosomes) was seven-fold higher from Montipora verrucosa and four-fold higher from Cassiopeia xamachana. Incubation of algae in P. versipora homogenate inhibited photosynthesis by: 33-49% in P. versipora algae; 29-47% in Z. robustus algae (regardless of whether or not the symbiosome was present); and 25% in M. verrucosa algae. In C. xamachana algae, photosynthesis increased. We conclude that the symbiosome is not essential for, yet does not block, the effects of HRF and PIF.     

Effect of seaweed preparations on murine immunocytes

During a screening programme for new medical agents, many aqueous extracts from 59 species of seaweed were found to possess bioactivity against murine immunocytes. Thirty-eight extracts (8 green, 12 brown, 18 red algae) showed suppressive effects on the mitogenic response. Furthermore, 16 extracts (2 green, 6 brown, 8 red algae) suppressed the production of Interleukin 1 (1L-1) from murine macrophage. Using the murine mixed lymphocyte reaction assay, suppressive effects were observed in 4 red algae, but none in green or brown algae. Nine seaweed extracts suppressed the production of secondary antibody (IgG, IgM). Extracts of 3 red algae suppressed strongly the proliferation of bone marrow cells, but 2 other red algae caused stimulation above 200%. This is apparently the first report showing immunosuppressive activity from marine algae.     

江苏省灌西盐场盐藻及其β—胡萝卜素资源调查

为了开发利用富含β-胡萝卜素的江苏沿海盐田盐藻(Dunaliellasalina)资源,我们采用常规调查方法,对江苏省灌西盐场的天然盐藻进行调查,并推算出约有259公斤左右的β-胡萝卜素年产量。而且,藻数量和β-胡萝卜素含量都受到光照、温度、雨水等气候因素影响。本调查为灌西盐场盐藻资源开发提供了一个可靠的依据,为其它盐场估计本场资源量提供了一个参考。     

A critical review of soil algae as a crucial soil biological component of high ecological and economic significance

Aero-terrestrial algae are ecologically and economically valuable bioresources contributing to carbon sequestration, sustenance of soil health, and fertility. Compared to aquatic algae, the literature on subaerial algae is minimal, including studies of distinctive habitats such as forest soils, agricultural fields, deserts, polar regions, specific subaerial zones, artificial structures, and tropical soils. The primary goal here was to identify the gaps and scope of research on such algae. Accordingly, the literature was analyzed per sub-themes, such as the “nature of current research data on terrestrial algae,” “methodological approaches,” “diversity,” “environmental relationships,” “ecological roles,” and “economic significance.” The review showed there is a high diversity of algae in soils, especially members belonging to the Cyanophyta (Cyanobacteria) and Chlorophyta. Algal distributions in terrestrial environments depend on the microhabitat conditions, and many species of soil algae are sensitive to specific soil conditions. The ecological significance of soil algae includes primary production, the release of biochemical stimulants and plant growth promoters into soils, nitrogen fixation, solubilization of minerals, and the enhancement and maintenance of soil fertility. Since aero-terrestrial habitats are generally stressed environments, algae of such environments can be rich in rare metabolites and natural products. For example, epilithic soil algae use wet adhesive molecules to fix them firmly on the substratum. Exploring the ecological roles and economic utility of soil and other subaerial algae could be helpful for the development of algae-based industries and for achieving sustainable soil management.     

Relative Contributions of Various Cellular Mechanisms to Loss of Algae during Cnidarian Bleaching

When exposed to stress such as high seawater temperature, corals and other cnidarians can bleach due to loss of symbiotic algae from the host tissue and/or loss of pigments from the algae. Although the environmental conditions that trigger bleaching are reasonably well known, its cellular and molecular mechanisms are not well understood. Previous studies have reported the occurrence of at least four different cellular mechanisms for the loss of symbiotic algae from the host tissue: in situ degradation of algae, exocytic release of algae from the host, detachment of host cells containing algae, and death of host cells containing algae. The relative contributions of these several mechanisms to bleaching remain unclear, and it is also not known whether these relative contributions change in animals subjected to different types and/or durations of stresses. In this study, we used a clonal population of the small sea anemone Aiptasia, exposed individuals to various precisely controlled stress conditions, and quantitatively assessed the several possible bleaching mechanisms in parallel. Under all stress conditions tested, except for acute cold shock at 4°C, expulsion of intact algae from the host cells appeared to be by far the predominant mechanism of bleaching. During acute cold shock, in situ degradation of algae and host-cell detachment also became quantitatively significant, and the algae released under these conditions appeared to be severely damaged.     

Delayed light action spectra of several algae in visible and ultraviolet light

Action spectra for delayed light production by several algae were determined from 250 to 750 mµ incident light. In the visible portion of the spectrum the action spectra resemble those reported by previous workers for photosynthesis and light emission. Blue-green algae had a maximum at 620 mµ, red algae at 550 mµ, whereas green and brown algae have action spectra corresponding to chlorophyll and carotenoid absorption. In the ultraviolet portion of the spectrum delayed light is emitted by algae down to 250 mµ incident light. The action spectra of the different algae are not alike in the ultraviolet portion of the spectrum. This indicates that pigments other than chlorophyll must be sensitizing or shielding the algae in the ultraviolet region.     

The effects of nutrient enrichment and herbivore abundance on the ability of turf algae to overgrow coral in the Caribbean

Turf algae are multispecies communities of small marine macrophytes that are becoming a dominant component of coral reef communities around the world. To assess the impact of turf algae on corals, we investigated the effects of increased nutrients (eutrophication) on the interaction between the Caribbean coral Montastraea annularis and turf algae at their growth boundary. We also assessed whether herbivores are capable of reducing the abundance of turf algae at coral-algae boundaries. We found that turf algae cause visible (overgrowth) and invisible negative effects (reduced fitness) on neighbouring corals. Corals can overgrow neighbouring turf algae very slowly (at a rate of 0.12 mm 3 wk⁻¹) at ambient nutrient concentrations, but turf algae overgrew corals (at a rate of 0.34 mm 3 wk⁻¹) when nutrients were experimentally increased. Exclusion of herbivores had no measurable effect on the rate turf algae overgrew corals. We also used PAM fluorometry (a common approach for measuring of a colony''s “fitness”) to detect the effects of turf algae on the photophysiology of neighboring corals. Turf algae always reduced the effective photochemical efficiency of neighbouring corals, regardless of nutrient and/or herbivore conditions. The findings that herbivores are not capable of controlling the abundance of turf algae and that nutrient enrichment gives turf algae an overall competitive advantage over corals together have serious implications for the health of Caribbean coral reef systems. At ambient nutrient levels, traditional conservation measures aimed at reversing coral-to-algae phase shifts by reducing algal abundance (i.e., increasing herbivore populations by establishing Marine Protected Areas or tightening fishing regulations) will not necessarily reduce the negative impact of turf algae on local coral communities. Because turf algae have become the most abundant benthic group on Curaçao (and likely elsewhere in the Caribbean), new conservation strategies are required to mitigate their negative impact on coral communities.     

球状绿藻的隐性生物多样性及其分类学进展

球状绿藻主要指绿藻门中多为单细胞, 形状为球形、近球形, 或由球形衍生出来的其他形状的藻类。球状绿藻分布广泛, 遍布全球, 生活于淡水、海水和亚气生等生境中, 其相似的简单形态下隐藏着复杂的物种多样性。球状绿藻分类学上主要位于绿藻门的两纲四目及其一些独立支系的类群。球状绿藻分类学正由传统的基于形态特征向基于分子信息的复合分类方法转变。球状绿藻隐性的物种多样性涉及约40属, 其中15属是依据新标本材料而建立的新属, 12个属是依据新证据建立的新组合。本文重点介绍了1998年以后在共球藻纲和绿藻纲中新发现和命名的单细胞球状绿藻, 介绍了它们的形态特征、分类学迁移及理由, 特别对常见的小球藻属和栅藻属的分类学概念变迁作了详细介绍, 对一些尚没有中文名的拉丁学名给出了中文命名。另外, 本文讨论了基于DNA的分类学方法在球状绿藻分类学中的应用, 目前系统发育位置的不同已经成为球状绿藻分类的主要依据。目前球状绿藻分类面临的问题是大多分类位置未用分子系统发育方法的验证。 未来, 球状绿藻分类学家应用系统发育研究结合形态学研究探索单细胞球状绿藻的生物多样性。     

海藻多糖生物活性及分子修饰

简要介绍了近年来有关海藻多糖抗病毒、抗肿瘤、免疫促进、免疫抑制等生理活性的最新研究 ,重点介绍了不同种类海藻多糖的不同生理活性机理的研究进展。对多糖与生理活性之间的构效关系进行了阐述 ,在构效关系基础上进行多糖分子结构修饰是提高海藻多糖生理活性、降低毒副作用的有效手段。进一步介绍了目前多糖分子修饰常用方法 ,并对修饰后分子的生理活性改变进行了阐述。     

Levels of zinc, cadmium and lead in some marine algae from Aqaba-Red Sea

Jordan has witnessed a rapid industrial development in the last twenty years. This has lead to the release of waste materials or pollutants into the marine environment, particularly nearby Aqaba Port. The present study investigates the levels of zinc, cadmium and lead in four brown algae, three red algae and four green algal species collected from Aqaba. Three different levels of lead and zinc concentrations were found: the highest level of both metals is exhibited among brown algae; intermediate level is exhibited among red algae and the lowest level is seen among the green algae. Very low concentrations of cadmium were found in all examined algal species. The results indicate that the brown algal species Cystosira myrica, Sargassum asperifolium, Sargassum neglectum, and Sargassum subrepandum always contain the highest concentrations of lead and zinc, but these algae are less contaminated than brown algae from industrial European seas.     

Comparative chemical composition of the Barents Sea brown algae

Comparative study of phytochemical compositions of the most widespread brown algae species (one laminarian and four fucoid algae) from Barents Sea has been performed. A modified technique for mannitol determination in brown algae is proposed. It was revealed that fucus algae (fam. Fucaceae) contain 3% (of total dry weight) less mannitol than laminaria (Laminaria saccharina). The contents of alginic acid and laminaran in the Barents Sea fucoids are more than 10% less compared to laminaria. The alga L. saccharina contains almost two times more iodine than the species of fam. Fucaceae. The amounts of fucoidan and sum lipids in the Barents Sea fucoid algae is higher than in Laminaria saccharina (4-7% and 1-3%, respectively). In terms of contents of main biologically active compounds, fucus and laminarian algae from Barents Sea are inferior to none of the Far-Eastern species. The Barents Sea algae may become an important source of biologically active compounds.