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  • diatoms  (17)
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  • 1
    ISSN: 1573-5176
    Keywords: Atrazine ; redundancy analysis ; flowing waters ; periphyton communities ; diatoms ; Cyanobacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The relationship between environmental variables, community composition and the sensitivity of periphyton on artificial substrata to the herbicide atrazine (EC50 values obtained by concentration-effect curves of photosynthesis to atrazine) was studied for 20 stream and river sites on a latitudinal across Europe (Sweden, The Netherlands, Spain). Sensitivity to atrazine was higher in Swedish than in the Spanish or Dutch sites. Direct gradient analyses were used to relate diatom taxa and algal groups with environmental variables. A first redundancy analysis (RDA) based on diatom taxa showed a pollution gradient (atrazine and nutrient concentration) associated to diatom taxa that are indicators of different degrees of pollution. A second RDA based on algal groups showed that diatom-dominated communities corresponded both to sites at higher altitudes and less industrialized areas and to sites with higher atrazine concentration; Cyanobacteria were the most common in industrial areas, whereas Chlorophyceae dominated in sites with high water temperature and alkalinity. Linear regression analyses were applied to find the relationship between the ordination axes obtained and the EC50 values. First axes of both RDA showed significant or marginally significant relationship with atrazine sensitivity. Regression analyses for the Spanish sites indicated that the sensitivity to atrazine was related with light conditions (EC50 was positively correlated with light) and the percentage of different algal groups (EC50 was positively correlated with the percentage of diatoms and negatively correlated with the percentage of green algae). The results indicating that differences in sensitivity are related to environmental variables such as light, nutrients or atrazine concentration, permitted us to identify biological indicators of sensitivity to atrazine in lotic systems: Bacillariophyceae-dominated periphyton communities were more tolerant than Chlorophyceae and Chrysophyceae-dominated communities. In addition, diatom taxa found to be tolerant to atrazine in this study have been considered in the literature to be tolerant to organic pollution.
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  • 2
    ISSN: 1573-5176
    Keywords: abalone larvae ; coralline red algae ; diatoms ; early growth ; Haliotis rubra ; settlement ; Sporolithon durum ; Ulvella lens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Five diatom species were isolated from settlementplates at Southern Ocean Mariculture, Victoria,Australia (Navicula sp., Naviculajeffreyi, Cylindrotheca closterium, Cocconeis sp., Amphora sp.) and tested insettlement experiments with Haliotis rubralarvae. Settlement was very low on single speciesdiatom films and varied between 1%–6%. Depending onthe species combination larvae preferred to settle onfilms with mixed diatom species than single speciesfilms. The highest settlement was achieved with amixed film of Navicula sp. and Amphora sp.Five and ten-day-old germlings of Sporolithondurum induced settlement of the abalone Haliotisrubra. However, the settlement rate was significantlylower on germlings than on the whole thallus of thealga. Germlings inoculated with the diatom Navicula sp. induced higher settlement than films ofthe diatom species alone. High settlement of up to52% was also achieved with germlings of the greenalga Ulvella lens. Settlement was reduced onU. lens squares inoculated with the diatom Navicula sp. but higher than on films of the diatomalone. The settlement rate was higher if plates withU. lens were previously grazed by juvenileabalone.Post-larval growth rates were higher on monospecificdiatom films than on U. lens or on S.durum. The best growth rate was obtained with Navicula sp. U. lens and S. durum areboth good settlement inducers, but are notsufficient to support rapid growth of young H.rubra post-larvae. Survival was low on U. lensand on the diatom C. closterium. We suggest thatcommercial nursery plates seeded with U. lenswill result in high and consistent settlement, whilean inoculum with Navicula sp. will ensuresufficient food for rapid growth of the post-larvae.
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  • 3
    ISSN: 1573-5176
    Keywords: diatoms ; periphyton ; monitoring ; phosphate ; eutrophication ; rivers ; Urban Wastewater Treatment Directive
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A index for monitoring the trophic status of rivers based on diatom composition (‚trophic diatom index’, TDI) has been developed, in response to the National Rivers Authority (England & Wales)'s needs under the terms of the Urban Wastewater Treatment Directive of the European Community. The index is based on a suite of 86 taxa selected both for their indicator value and ease of identification. When tested on a dataset from 70 sites free of significant organic pollution, this index was more highly correlated with aqueous P concentrations than previous diatom indices. However, where there was heavy organic pollution, it was difficult to separate the effects of eutrophication from other effects. For this reason, the value of TDI is supplemented by an indication of the proportion of the sample that is composed of taxa tolerant to organic pollution. The index was tested on the R. Browney, N-E. England, above and below a major sewage discharge. TDI values indicated that the effect of inorganic nutrients on the river downstream of the discharge was slight as the river was already nutrient-rich, but there was a large increase in the proportion of organic pollution-tolerant taxa. This indicates that the river was already so eutrophic upstream of the discharge that tertiary treatment to remove P would not be effective unless other aspects of the discharge were also improved.
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  • 4
    ISSN: 1573-5176
    Keywords: amino acid ; mariculture ; microalgae ; diatoms ; Bacillariophyceae ; biochemical composition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The amino acid and gross compositions of three benthic diatoms (Cylindrotheca fusiformis Reimann and Lewin, Navicula jeffreyi Hallegraeff et Burford and Nitzschia closterium (Ehr. W. Smith) and three chain-forming diatoms (Lauderia annulata Cleve, Skeletonema costatum (Greville) Cleve and a tropical Skeletonema sp. (CS-252)), were determined during late-logarithmic growth phase. Four of the six species were rich in protein, ranging from 31% (S. costatum) to 38% (N. closterium) of the dry weight, and contained 4.9 to 6.5% carbohydrate and 9.4 to 18% ash. The other two species, C. fusiformis and L. annulata contained only 16% protein but had nearly twice the total carbohydrate (11 to 12%) and two to three times the ash (29 to 35%) of the other species. All species contained a similar percentage of lipid (18 to 20%), and a high protein quality based on their total amino acid composition. The usefulness of these diatoms for mariculture will be determined by growth rates, gross composition and acceptability to the animal. N. closterium had the fastest growth rates of the benthic mat-forming diatoms, it was rich in protein, and it may be a good candidate for abalone culture. The two Skeletonema spp. had the fastest growth rates of the chain-forming diatoms, and are already widely used for prawn larval culture in Australia. Feeding trials are now necessary to confirm the high nutritional value of these diatom species for specific animals.
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  • 5
    ISSN: 1573-5176
    Keywords: water treatment ; mariculture ; effluents ; phytoplankton ; diatoms ; Skeletonema ; Chaetoceros ; mass culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The feasibility of using fish farm effluents was evaluated as a source of inorganic nutrients for mass production of marine diatoms. Batch cultures were conducted from May to July 1995 in 16-L outdoor rectangular tanks, homogenized by gentle aeration (0.2 L air L−1 h−1). The effluents from the two fish farms studied were both characterized by high concentrations of inorganic materials (NH4-N, PO4-;P, Si(OH)4-Si) and were shown to support production of marine diatoms. Moreover, periodic measurements of inorganic matter levels in the cultures showed that clearance was efficacious (90% in 3–5 days). Water purification efficiency and culture productivity were further increased through appropriate nutrient balancing. When effluents were limited in silicate, addition of Na2SiO3 induced a significant increase in both diatom biomass and nutrient removal efficiency. In this case, up to 720 000 cell mL−1 were produced dominated bySkeletonema costatum. By contrast, in effluents loaded with silicate, adjustment of the N:P:Si ratio by NH4-N and PO4-P supplementation then gave increased biomass production. In this case, the maximum cell density found was 450 000 cell mL−1, dominated byChaetoceros spp.
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  • 6
    ISSN: 1573-5176
    Keywords: Freshwater ecotoxicology ; periphyton ; diatoms ; indoormicrocosm ; heavy metals ; methylmercury ; inorganic mercury
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of inorganic mercury (HgII) and methylmercury (MeHg) on the colonization of artificial substrates by periphytic diatoms were studied using indoor freshwater microcosms. These consisted of a mixed biotope– water column + natural sediment – with rooted macrophyte cuttings (Elodea densa) and benthic bivalve molluscs (Corbicula fluminea).The periphyton was collected on glass slides in the water column after 34and 71 days. The two Hg sources were introduced either by daily additions to the water column, or once at the beginning into the sediment, using two nominal concentrations: water column, 0.5 μgL-1 and 2 μg L-1 for both compounds: sediment, 0.5 mg kg-1 (fw) and 2 mgkg-1 (fw) for MeHg and 1 mg kg-1 (fw) and 10 mgkg-1 (fw) for HgII. Several complementary criteria were used to analyse the structural and functional perturbations induced: cell density, species richness, diatom size, relative abundance. Exposure to MeHg added to the water column resulted in reduced cell density and changes in species composition with enhancement of e.g. Fallacia pygmaea or Nitzschia palea; inorganic Hg had less effect on the population structure. After contamination via the sediment, the effects of the two compounds were less pronounced than for the water source.
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  • 7
    ISSN: 1573-5176
    Keywords: cadmium ; copper ; diatoms ; dinoflagellates ; extracellular polysaccharides ; phytochelatins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Several diatom and dinoflagellate species isolatedfrom the Adriatic Sea, grown in batch cultures in f/2medium, were exposed to two different concentrationsof Cu and Cd. The concentrations chosen caused areduction of growth, but were not lethal. Thespecies able to tolerate the highest Cu concentrations(in the order of 0.2–0.5 mg L-1) were diatoms,while some diatoms and all the dinoflagellates wereinhibited by concentrations between 0.01 and 0.05 mgCu L-1. Cadmium was less toxic in that it did notaffect diatom or dinoflagellate growth up to aconcentration of 0.2 mg L-1. Increasedproduction of extracellular polysaccharides was foundto be a general response to the presence of thepollutant. Cylindrotheca fusiformis, Achnanthesbrevipes and Prorocentrum micans wereinvestigated for their production of intracellularmetal-ligands. Molecules with Cd-binding propertiesand having a molecular weight comparable with that ofphytochelatins were found only in C.fusiformis, and their presence showed both adose- and time-dependent response. The presence orabsence of intracellular ligands in these algae isconsistent with their ability to exclude the metalextracellularly.
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  • 8
    ISSN: 1573-5176
    Keywords: blue light ; chlorophyll a ; fluorescence ; photo-acclimation ; microalgae ; diatoms ; competition ; marennine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two prominent diatoms encountered in oyster-ponds,Haslea ostrearia and Skeletonema costatum,were grown in batch and in a semi-continuous modeunder light of different spectral quality, white, blueor blue-green. The last corresponded to white lightmodified by a water-soluble pigment, marennine,produced by H. ostrearia. After acclimation tothe different light treatments, the growth rates ofboth species showed little variation with respect tolight quality. The parameters for photosynthesisvs irradiance curves were very similar in H. ostrearia grown under the three light conditions,whereas S. costatum the maximum photosyntheticcapacity (on a chlorophyll a basis) wassignificantly reduced under blue-green light. Fluorescence analyses confirmed the data forphotosynthesis, with the operational fluorescenceyield decreasing faster with increasing irradiance inS. costatum grown under blue-green light. InH. ostrearia, fluorescence yields undersaturating irradiance were closely similar in thethree light conditions. The results are discussed inrelation with the prominent development of H.ostrearia that can outcompete other diatoms inoyster-ponds.
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  • 9
    ISSN: 1573-5176
    Keywords: dialysis culture ; continuous growth ; nitrogen metabolism ; diatoms ; Phaeodactylum tricornutum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The growth kinetics and nitrogen (N)-nutrition of the marine pennate diatom Phaeodactylum tricornutum Bohlin were determined in continuous dialysis culture at different cell densities. Inflow nutrient medium was supplied as natural unenriched estuarine seawater to a dialysis culture system with a high ratio of membrane surface area/culture volume (Am/Vc). Under the experimental conditions, the supply of inorganic macronutrients (NO 3 − + NO 4 − and PO 4 −3 ) by diffusion (Nd) was markedly greater than that provided by the dilution (FfCN) of the culture (Nd ≫ FfCN), thereby establishing an inverse relationship between the cell density and the dilution rate (D). This continuous dialysis system allows for the maintenance of prolonged growth (〉 two weeks) at various cell densities (1.4 to 27.2 × 109 cells 1−1) within a range of dilution rates between 0.30 to 1.08 d−1. In high cell density cultures, where the extracellular medium was characterized as nutrient deficient, a lower growth rate (μe) was exhibited than in cultures with lower cell densities. The growth rate (μe) remained equivalent to the dilution rate (D) throughout the culture cycle, indicating that equilibrated growth was achieved. High cell density cultures yielded higher productivity (P), relative to that of cultures grown at lower cell densities, in terms of cell-N and −C produced per unit time. However, cell quotas of both N and C declined with increasing cell concentrations. Denser cultures were characterized by an enhanced N-conversion efficiency (YN) and a higher cellular N/C atomic ratio. The nutritional response of this diatom in dense cultures reveals an efficient use of N-nutrients, presumably as a result of cellular nutrient adaptation to oligotrophic conditions.
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  • 10
    ISSN: 1573-5176
    Keywords: diatoms ; Bacillariophyta ; periphyton ; monitoring ; sampling ; rivers ; water quality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Many methods for using diatoms for routine monitoring of water quality have been developed in Europe and, in some countries, these are being used to enforce environmental legislation. In order to facilitate their wider use, particularly with respect to European Union legislation, steps are being taken to harmonize methodology. In this paper, the principles and practice of sampling are described in relation to the main habitat types encountered in Europe. Although details of methods and sampling programmes have to be tailored to particular circumstances and the overall objectives of the monitoring, a number of generalizations can be made. Where available, rocks and other hard surfaces are the preferred substrates and methods for sampling these are described. If such substrata are not available, then introduced ('artificial') substrata have many applications. Various types of introduced substrata can be used successfully, so long as some basic precautions are described. Other types of substrata such as macrophytes and macroalgae may also be useful under certain circumstances, although there is less consensus in the literature on the most appropriate methods, and of the validity of comparisons between indices computed from epiphytic and epilithic communities. When designing surveys, it is recommended that as far as possible, extremes of non-water quality factors (e.g. shade, current speed, etc) are avoided, unless these are characteristic of the system under investigation. Detailed guidelines for sampling epilithon are described. Along with the recommendations for sampling other substrata, it is hoped that these provide a framework that can be adapted to most river types in Europe.
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