藻源污染物特性对高藻水微滤处理过程中膜污染的影响

采用不同生长时期的藻细胞、藻源型有机物(AOM)及原藻液进行过滤实验,研究不同生长时期的藻源污染物对膜污染的影响特性及机制。利用UMFI法分析不同生长时期的藻细胞、AOM及原藻液的污染程度;采用CRITIC分析法定量分析了不同生长时期的AOM和藻细胞在混合过滤过程中对膜污染的贡献率,同时采用混合污染堵塞模型分析了不同生长时期的原藻液不同过滤阶段的主要污染堵塞类型。结果表明, 3个生长时期的藻细胞及AOM的膜污染程度均为对数期最轻;值得注意的是,在原藻液过滤过程中藻细胞及AOM的膜污染贡献率随着生长时期的不同而有所变化,其中AOM的污染权重随着生长时期的延长不断减小,而藻细胞的污染权重随着生长时期的延长不断增大。不同生长时期的原藻液过滤过程中均呈现两段式污染堵塞类型,并且后段均为滤饼堵塞。研究不仅阐明了藻源型污染物特性对微滤处理高藻水膜污染的影响机制,同时也为改善膜污染的技术开发提供参考。     

Evaluation of strategies to prevent algal fouling on white architectural and cellular concrete

In this study, different strategies have been examined for the prevention of algal fouling on two types of concrete with different bioreceptivity, i.e. white architectural and autoclaved aerated concrete (AAC). These strategies are aimed towards the decrease of the bioreceptivity and comprised the application of water repellents and/or biocides. Both traditional (stearates, silanes, silane siloxane mixtures and a pyridine biocide) and innovative compounds (quaternary ammonium silane-based biocides, silver copper zeolites and silver nanoparticles) have been assessed for their performance by means of an accelerated water run-off test. A modular setup was designed which allowed the simultaneous evaluation of 12 different product formulations. Algal fouling was evaluated by means of colorimetric and image analysis, for which two new evaluation criteria have been proposed.For white concrete, contrary to untreated specimens which had 40% of the surface covered with algae, no fouling was observed for surface treated specimens after 12 weeks of exposure to algae under the test conditions.For AAC, the different strategies examined were unable to completely prevent the algal fouling. The use of water repellents resulted in green algal streaks along the surface. Biocide treated specimens showed a delay of onset of fouling of two to four weeks under the test conditions. The best performance was obtained with a combination of a silane-based water repellent and a chlorinated pyridine-based biocide, for which only limited fouling was observed after eight weeks of intensive fouling exposure.     

Genotypic variation in tolerance and resistance to fouling in the brown alga <Emphasis Type="Italic">Fucus vesiculosus</Emphasis>

In this study, we examined genetic variation in resistance and tolerance to fouling organisms in the brown alga Fucus vesiculosus. We first grew 30 algal genotypes in the field, where we allowed fouling organisms to colonise the genotypes at natural levels. We then conducted a manipulative experiment, where we grew 20 genotypes of algae in aquaria with or without fouling organisms. We measured host resistance as the load of fouling organisms and tolerance as the slope of the regression of algal performance on fouling level. Fouling organisms decreased host growth and contents of phlorotannins and thus have the potential to act as selective agents on algal defenses. We found significant among-genotype variation in both resistance and tolerance to fouling. We did not find a trade-off between resistance and tolerance. We found a marginally significant cost of resistance, but no cost of tolerance. Our results thus indicate that both the tolerance and resistance of F. vesiculosus can evolve as a response to fouling and that the costs of resistance may maintain genetic variation in resistance.     

Algal fouling of underwater structures at lobster farms in Nha Trang Bay (Vietnam)

The species composition and structure of algal fouling communities on the underwater artificial substrates at lobster farms in Nha Trang Bay (Vietnam) were studied for the first time. In total, 126 taxa (species and forms) of macroalgae (24% green, 16% brown, and 60% red), as well as eight species of cyanobacteria, were found. Depending on the area and quality of the substrate, fouling algae form polydominant turf communities, mono- and bidominant communities of crustose algae, or no specific communities. The flora of macroalgal fouling at lobster farms in Nha Trang Bay was similar in terms of its diversity and species composition to that of coral reefs in areas of the Indo-Pacific with a low level of pollution. This similarity might be due to the diversity and cleanness of the substrates (the absence of sediment on the surface of the underwater structures).     

Interactions between microbial biofilms and marine fouling algae: a mini review

Natural and artificial substrata immersed in the marine environment are typically colonized by microorganisms, which may moderate the settlement/recruitment of algal spores and invertebrate larvae of macrofouling organisms. This mini-review summarizes the major interactions occurring between microbial biofilms and marine fouling algae, including their effects on the settlement, growth and morphology of the adult plants. The roles of chemical compounds that are produced by both bacteria and algae and which drive the interactions are reviewed. The possibility of using such bioactive compounds to control macrofouling will be discussed.     

Coralline algal maerl frameworks-Islands within the phaeophytic kelp belt

Summary In the subtropical belt highly productive ecosystems are formed by coral reefs in oligotrophic seas. Towards more eutrophic conditions, coral reefs diminish and are subsequently replaced by highly productive kelp forests. In high latitudes framework constructing carbonate production is enhanced by the growth of branching coralline algae which predominantly generate maerl-type deposits. On a global view, these coralline algal ecosystems show an island-like distribution pattern within the phaeophytic kelp belt. Compared to kelp ecosystems, coralline-algaldominated ecosystems have low rates of productivity. Therefore, it is reasonable to seek the pronounced competitive value of the extremely slow-growing corallines. Due to their low annual growth increment, the coralline algae studied are very endangered by abiotic physical disturbances and by overgrowth of rapidly growing filamentous algae or sessile invertebrates. To overcome fouling pressure and storm-triggered physical disturbances, coralline algae thrive well in wave-sheltered headlands or skerry areas and generate characteristic ‘denuded areas’ by intense herbivory. This general distributional pattern is also true for high-boreal to subarctic coralline algal bioherms in northern Norway. Such a complex biological feedback maintains a high potential of self-regulation or self-organization in the algal reef bioherms. The different proponents involved in feedback processes include bacterial colonization, diatom microfouling and selective induction of larval metamorphosis. The negative impact of diatom microfouling and the important role of herbivores are relevant activities in the feedback system on a microscopic scale. Macroscopically, intense herbivory on coralline algae create denuded conditions, which are a widespread phenomenon in coralline algal ecosystems.     

Effect of the Spatial Orientation of a Substrate on the Formation of Early Fouling Communities in the White Sea

The formation of early fouling communities developing under different spatial orientations of substrates and various lighting conditions was studied during a field experiment. The algal predominance on the sunlit upward-oriented sides and the animal predominance on the shaded downward-oriented sides are the consequence of two processes: (1) competitive displacement of animals from the sunlit sides by algae; (2) preferential colonization of the shaded downward-oriented sides of the substrates by animals.     

Disruption-free imaging by Raman spectroscopy reveals a chemical sphere with antifouling metabolites around macroalgae

Investigations of the surface chemistry of marine organisms are essential to understand their chemically mediated interactions with fouling organisms. In this context, the concentration of natural products in the immediate vicinity of algal surfaces, as well as their biological activity, are of particular importance. However, due to lack of appropriate methods, the distribution of compounds within the chemical sphere around marine algae is unknown. This study demonstrates the suitability of confocal resonance Raman microspectroscopy for the determination of metabolites around algal surfaces with a micrometer resolution. The spatial distribution of carotenoids in the diffusion boundary layer of the brown alga Fucus vesiculosus and the green alga Ulva sp. was determined using the disruption-free optical method. A gradient of carotenoids was determined within 0 to 150 μm from the surface of the algae, thereby demonstrating the release of the non-polar metabolites involved in antifouling processes. The differences in the carotenoid composition of the brown and green algae were reflected in the spectra. Resonance Raman microspectroscopy also allowed visualization of the lateral distribution of fucoxanthin on the algal surface and localization of concentration maxima within a 50 × 50 μm(2) area. The results from this work show clearly that established dipping techniques suitable for the extraction of the diffusion boundary layer of macroalgae only provide an average of the local strongly variable concentrations of metabolites on algal surfaces.     

Extracts of seaweeds as potential inhibitors of quorum sensing and bacterial growth

Macroalgae are an important source of antimicrobial compounds. However, it is unclear if these compounds are produced by the algae themselves, by their associated bacteria, or by both. The main aim of this study was to investigate the potential of macroalgae and their associated microorganisms to inhibit bacterial quorum sensing (QS) and growth. Before extraction, half of the algal specimens were treated with 30% ethanol to remove surface associated bacteria. Canistrocarpus cervicornis extracts were able to inhibit QS of the reporter Chromobacterium violaceum CV017, where extracts with associated bacteria were more efficient than those without bacteria. However, not all algal extracts that inhibited QS of CV017 were able to inhibit bacterial attachment of Pseudomonas aeruginosas PA01, showing specific activity of algal metabolites. Only 58% of the extracts showed antibacterial activity against eight marine fouling and pathogenic bacterial strains tested. Our data suggests that algae and their associated microbiota are important sources of antimicrobial compounds which potentially can be used in future biotechnological applications.     

A seasnake's colour affects its susceptibility to algal fouling

Evolutionary transitions from terrestrial to aquatic life modify selective forces on an animal''s coloration. For example, light penetrates differently through water than air, and a new suite of predators and visual backgrounds changes the targets of selection. We suggest that an aquatic animal''s coloration may also affect its susceptibility to algal fouling. In a colour-polymorphic field population of seasnakes (Emydocephalus annulatus) in New Caledonia, black individuals supported higher algal cover than did banded conspecifics. In experimental tests, black snake models (plastic tubes) accumulated more algae than did banded models. Algal cover substantially reduced snake activity (in the field) and swimming speeds (in the laboratory). Effects of algal cover on a snake''s hydrodynamic efficiency and/or its rate of cutaneous gas exchange thus may impose selection on the colours of aquatic organisms.     

Disruption-free imaging by Raman spectroscopy reveals a chemical sphere with antifouling metabolites around macroalgae

Investigations of the surface chemistry of marine organisms are essential to understand their chemically mediated interactions with fouling organisms. In this context, the concentration of natural products in the immediate vicinity of algal surfaces, as well as their biological activity, are of particular importance. However, due to lack of appropriate methods, the distribution of compounds within the chemical sphere around marine algae is unknown. This study demonstrates the suitability of confocal resonance Raman microspectroscopy for the determination of metabolites around algal surfaces with a micrometer resolution. The spatial distribution of carotenoids in the diffusion boundary layer of the brown alga Fucus vesiculosus and the green alga Ulva sp. was determined using the disruption-free optical method. A gradient of carotenoids was determined within 0 to 150 μm from the surface of thealgae, thereby demonstrating the release of the non-polar metabolites involved in antifouling processes. Thedifferences in the carotenoid composition of the brown and green algae were reflected in the spectra. Resonance Raman microspectroscopy also allowed visualization of the lateral distribution of fucoxanthin on the algal surface and localization of concentration maxima within a 50 × 50 μm² area. The results from this work show clearly that established dipping techniques suitable for the extraction of the diffusion boundary layer of macroalgae only provide an average of the local strongly variable concentrations of metabolites on algal surfaces.     

Algal growth inhibition on cement mortar: Efficiency of water repellent and photocatalytic treatments under UV/VIS illumination

Building materials are regularly affected by the growth of microalgae. The consequences are mainly aesthetic but the colonization can cause biodeterioration of the material in the most extreme cases. This study investigates two building material treatments that can potentially inhibit or slow down such growth: photocatalytic coatings and water repellent treatments. The efficiency of these treatments in terms of biological growth inhibition was tested on the algae species Graesiella emersonii. Algal growth on building materials was investigated using two accelerated tests simulating different types of humidification (water capillary ascent and water run-off) under different lighting conditions. Mortars treated with photocatalytic coating or with water repellent were studied. The algal growth on the mortar surface was evaluated using image analysis (area covered and intensity of fouling). No slow down of the biological growth kinetics could be attributed to photocatalytic substrates. However, for mortars impregnated with a water-repellent preparation, algal growth slowed significantly under water run-off and even stopped under water capillary ascent.     

Localization of attachment area of the symbiotic Chlorella variabilis of the ciliate Paramecium bursaria during the algal removal and reinfection

Chlorella spp. and ciliate Paramecium bursaria share a mutual symbiosis. However, both alga-removed P. bursaria and isolated symbiotic algae can grow independently. Additionally, mixing them experimentally can cause algal reinfection through host phagocytosis. Although the symbiotic algal localization beneath the host cell cortex is a prerequisite phenomenon for maintenance of the relationship of their endosymbiosis, how and where the algae locate beneath the host cell cortex remains unknown. To elucidate this phenomenon, algal distribution patterns during algal removal and reinfection were observed. During algal removal, algae at the host anterior cortex were easier to remove than at the posterior and ventral or dorsal cortex areas. During algal reinfection, the algae after separation from the host digestive vacuoles tended to localize beneath the host ventral or dorsal cortex more readily than that at other cortices. Algae that reinfected trichocyst-removed paramecia didn’t show this localization. Trichocyst-discharge experiments clarified that trichocysts of the anterior cortex are difficult to remove. In 14 strains of P. bursaria, some of the paramecia lacked their symbiotic algae at the anterior cortex. These observations demonstrate that symbiotic algae of P. bursaria are difficult to localize at the anterior cortex and that they are easy to remove from the area.     

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.     

The ins and outs of algal metal transport

Metal transporters are a central component in the interaction of algae with their environment. They represent the first line of defense to cellular perturbations in metal concentration, and by analyzing algal metal transporter repertoires, we gain insight into a fundamental aspect of algal biology. The ability of individual algae to thrive in environments with unique geochemistry, compared to non-algal species commonly used as reference organisms for metal homeostasis, provides an opportunity to broaden our understanding of biological metal requirements, preferences and trafficking. Chlamydomonas reinhardtii is the best developed reference organism for the study of algal biology, especially with respect to metal metabolism; however, the diversity of algal niches necessitates a comparative genomic analysis of all sequenced algal genomes. A comparison between known and putative proteins in animals, plants, fungi and algae using protein similarity networks has revealed the presence of novel metal metabolism components in Chlamydomonas including new iron and copper transporters. This analysis also supports the concept that, in terms of metal metabolism, algae from similar niches are more related to one another than to algae from the same phylogenetic clade. This article is part of a Special Issue entitled: Cell Biology of Metals.     

环境汞污染对藻类的毒性效应及其影响因素

综述了汞污染对藻类的毒性效应及影响因素。水环境中汞主要以元素汞、无机汞和有机汞3种形式存在。藻类吸附汞主要分为胞外的快速吸附和胞内的缓慢富集,在安全浓度内,金属汞对藻生长有一定的促进作用,随着浓度增大,抑制藻生长或致死。汞进入藻体细胞后,藻类为了存活会产生一系列保护机制。藻类对汞的排斥和排出作用可能就是对汞耐性的一种重要机制。藻类也可以通过多种方式减少汞进入藻类细胞,以及通过与其他物质结合汞使其排出胞外。温度、pH、生物学因素等影响重金属对藻类的毒性作用。并就藻类对汞耐性和适应机理、利用藻类修复和监测重金属污染、藻类响应汞胁迫的信号转导途径及其保护机制等未来研究领域进行了展望。     

Benthobservatory studies of micro-flora in a Newfoundland stream.

Collections of algae growing on the windows of a benthobservatory were made between April 1974 and October 1974. Eighty-eight species of algae representing eight classes were identified. Of these, 64% were green algae, 19% were diatoms, 11% were bluegreen algae and 6% were of the remaining 4 classes. The peak of algal growth was noted near mid-July with some indications of early spring and late autumn peaks. The relationship of algal growth to the distribution of some benthic fauna is briefly discussed.     

Endosymbiosis of Chlorella species to the ciliate Paramecium bursaria alters the distribution of the host’s trichocysts beneath the host cell cortex

Each symbiotic Chlorella of the ciliate Paramecium bursaria is enclosed in a perialgal vacuole membrane derived from the host digestive vacuole membrane. Alga-free paramecia and symbiotic algae can grow independently. Mixing them experimentally can cause reinfection. Earlier, we reported that the symbiotic algae appear to push the host trichocysts aside to become fixed beneath the host cell cortex during the algal reinfection process. Indirect immunofluorescence microscopy with a monoclonal antibody against the trichocysts demonstrates that the trichocysts change their locality to form algal attachment sites and decrease their density beneath the host cell cortex through algal reinfection. Transmission electron microscopy to detect acid phosphatase activity showed that some trichocysts near the host cell cortex are digested by the host lysosomal fusion during algal reinfection. Removal of algae from the host cell using cycloheximide recovers the trichocyst's arrangement and number near the host cell cortex. These results indicate that symbiotic algae compete for their attachment sites with preexisting trichocysts and that the algae have the ability to ensure algal attachment sites beneath the host cell cortex.     

Comparative genomics reveals differences in algal galactan biosynthesis and related pathways in early and late diverging red algae

Red algae are a major source of marine sulfated galactans. In this study, orthologs and inparalogs from seven red algae were analyzed and compared with the aim to discover differences in algal galactan biosynthesis and related pathways of these algae. Red algal orthologs for putative carbohydrate sulfotransferases were found to be prevalent in Porphyridium purpureum, Florideophytes and Bangiophytes, while red algal orthologs for putative chondroitin sulfate synthases, sulfurylases, and porphyranases /carrageenases were found exclusively in Florideophytes and Bangiophytes. The acquirement of these genes could have happened after the divergence from Cyanidiales red algae. Cyanidiales red algae were found to have more number and types of putative sulfate permeases, suggesting that these genes could have been acquired in adaptation to the environmental stresses and biogeochemistry of respective habitats. The findings of this study shed lights on the evolution of different homeostasis mechanisms by the early and late diverging red algal orders.     

Preferential expulsion of dividing algal cells as a mechanism for regulating algal-cnidarian symbiosis

A wide range of both intrinsic and environmental factors can influence the population dynamics of algae in symbiosis with marine cnidarians. The present study shows that loss of algae by expulsion from cnidarian hosts is one of the primary regulators of symbiont population density. Because there is a significant linear correlation between the rate of algal expulsion and the rate of algal division, factors that increase division rates (e.g., elevated temperature) also increase expulsion rates. Additionally, 3H-thymidine is taken up to a greater extent by algae destined to be expelled than by algae retained in the host cnidarians. Taken together, data for rates of expulsion, rates of division at different temperatures, and uptake of 3H-thymidine suggest that dividing algal cells are preferentially expelled from their hosts. The preferential expulsion of dividing cells may be a mechanism for regulation of algal population density, where the rate of expulsion of algae may be an inverse function of the ability of host cells to accommodate new algal daughter cells. This kind of regulation is present in some cnidarian species (e.g., Aiptasia pulchella, Pocillopora damicornis), but not in all (e.g., Montipora verrucosa, Porites compressa, and Fungia scutaria).