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  • 1.
    Aronsson, Andreas
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Biological effects of Wood Ash Application.2004In: Journal of Environmental Quality, ISSN 0047-2425, E-ISSN 1537-2537, Vol. 33, no 5, p. 1595-1605Article in journal (Refereed)
    Abstract [en]

    The Swedish National Board of Forestry recommends recycling of wood ash for two main reasons: 1) to avoid depletion of essential soil nutrients, and 2) to reduce the harmful effects of acidification of surface waters. There is no doubt that recycling of wood ash to boreal forests will become a major industry in the near future. Much research is conducted regarding the effects of wood ash application on forest growth. Present studies show that, generally speaking, forest growth can be increased on wood ash-ameliorated peatland rich in nitrogen. On mineral soils, however, no change or even decreased growth has been reported. The effects on ground vegetation are not very clear, as well as the effects on fungi, soil microbes and soil decomposing animals. The discrepancies between different studies are for the most part explained by abiotic factors such as variation in fertility among sites, different degrees of stabilization and wood ash dosage used, and different time scales among different studies. The lack of knowledge in the field of aquatic ecosystems and their response to ash application is an important issue for future research. The few studies conducted have mainly considered changes in water chemistry. The biotoxic effects of ash application can roughly be divided into two categories: primary and secondary. Among the primary effects is toxicity deriving from compounds in the wood ash and cadmium is probably the worst among these. The secondary effects of wood ash are generally due to its alkaline capacity and a release of ions into the soil and soil water, and finally, watercourses and lakes. The present review aims to summarize current knowledge in the topic of wood ash application to boreal forest and aquatic ecosystems, and the different effects derived from these actions. ABBREVIATIONS: WAA, Wood ash application; MT, metric tonnes

  • 2.
    Aronsson, K. Andreas
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Effects on growth, photosynthesis and pigments of the freshwater moss Fontinalis antipyretica Hedw. after exposure to wood ash solution2006In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 372, no 1, p. 236-246Article in journal (Refereed)
    Abstract [en]

    The application of wood ash from biofuel sources to the forest has been suggested as a source of nutrients for trees and for restoration of acidified soils and surface waters. Studies on the effects of wood ash on aquatic organisms and ecosystems are, however, few. This study investigated the effects of wood ash (0.1 - 10 g l-1) on the freshwater moss Fontinalis antipyretica Hedw., which has previously been shown to be a sensitive test organism for assessing environmental pollution. After nine weeks of treatment with wood ash, a significant effect of enhanced stem growth was observed at the higher concentrations (1 � 10 g l-1). The concentration of wood ash was also correlated to the growth of secondary branches. Photosynthesis (oxygen evolution after 4 h of exposure to wood ash) was significantly lower in the alkaline treatments (no pH adjustment) compared to the treatments with neutral wood ash solutions (pH adjusted to 7.5). Furthermore, photosynthesis in the alkaline wood ash treatments was significantly lower compared to the control. The ratio between the optical density value before and after acidification (OD665/665a) was higher for all wood ash concentrations compared to the control. The OD665/665a values ranged from 1.52 to 1.61 and there was a difference, however not significant, between the alkaline and the neutral treatment at 10 g l-1 wood ash. This study clearly demonstrated that wood ash may be beneficial for F. antipyretica at moderate concentrations (0.5 - 5 g l-1), particularly when sudden increase in pH is avoided.

  • 3.
    Aronsson, K. Andreas
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Effects on Motile Factors and Cell Growth of Euglena gracilis After Exposure to Wood Ash Solution: Assessment of Toxicity, Nutrient Availability and pH-Dependency2005In: Water, Air and Soil Pollution, ISSN 0049-6979, E-ISSN 1573-2932, Vol. 162, no 1-4, p. 353-368Article in journal (Refereed)
    Abstract [en]

    Wood ash application (WAA) to the forest has been suggested as a resource of nutrients for trees and for restoration of acidified soils and surface waters. However, studies of the effects of WAA on aquatic systems are few. This study investigated the effects of wood ash (1-25 g L-1) on the unicellular flagellate Euglena gracilis, which has been proved to be a sensitive test organism for assessing environmental change. Long-term (7 days) growth studies and short-term (direct, 24 and 48 h) studies of different motile factors, using the automatic biological test system Ecotox, were conducted. The results show no indication of biotoxic effects due to wood ash (adjusted to neutral) treatments. However, when no adjustments of pH in wood ash solutions were made, inhibitory effects on motile factors and cell growth were observed at higher concentrations of wood ash (10-25 g L-1) due to high pH (> 8). In tests with pH adjusted to neutral, enhanced motility was observed. These results indicate that high concentration of WAA could affect freshwater environments.

  • 4.
    Aronsson, K. Andreas
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Limnological effects on a first order stream after Wood Ash Application to a boreal forest catchment in Bispgården, Sweden2008In: Forest Ecology and Management, ISSN 0378-1127, E-ISSN 1872-7042, Vol. 255, no 1, p. 245-253Article in journal (Refereed)
    Abstract [en]

    In Sweden, whole tree harvest is common practice, possibly leading to the depletion of mineral nutrients. Furthermore, the increased use of forestry residues for heat production has caused an increasingly growing amount of by-product consisting of wood ash. Therefore, the Swedish Forest Agency has recommended wood ash application (WAA) to replace the mineral nutrients removed by whole tree harvesting, as well as a means to mitigate the acidification of boreal forests and surface waters. In a multidisciplinary study during 2003-2006 in Bispgarden (Sweden), we have investigated the limnological effects on a first order stream after WAA (conducted in 2004; 3000 kg ha-1) to a 50-ha forested catchment. In general, no significant effects on an annual basis were found for acidification parameters, such as pH, alkalinity and toxic forms of aluminum (Al). There was, however, evidence of an increased pH during the spring flood, accompanied by a simultaneous decrease in the frequency of low pH-values (<5.6). Moreover, alkalinity increased in the years 2005 and 2006 compared to that of 2003, although the increase in 2006 was not statistically different from that in 2005 or 2003. High concentrations of Al repeatedly occurred in the stream, and the WAA did not affect the frequencies of high concentrations of toxic Al forms (>50 μg 1-1). The benthic diatom community did not change as a result of the wood ash treatment and the diatom-based index IPS (Indice de PulluoSensibilité) indicated no nutrient enrichment or organic pollution of the stream water. There were, however, indices of elevated concentrations of potassium (K) in the aquatic moss Fontinalis antipyretica and in leaves from Alder (Alnus incana). We conclude that wood ash treatment of a forested catchment with the dose and form of ash applied in this study did not modify the freshwater ecosystem of a first order stream.

  • 5.
    Aronsson, K. Andreas
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Respiration measurements can assess the fitness of Gammarus pulex (L.) after exposure to different contaminants: experiments with wood ash, cadmium and aluminum2005In: Archiv für Hydrobiologie, ISSN 0003-9136, Vol. 164, no 4, p. 479-491Article in journal (Refereed)
    Abstract [en]

    Wood ash application has been suggested as a means to mitigate acidification of surface waters. However little is known about the effects of wood ash to freshwater organisms. A Clark-type oxygen electrode was used to investigate the effects of wood ash, cadmium and aluminum on the respiration of the freshwater amphipod Gammarus pulex (L.). Harmful effects following wood ash addition were primarily found to be explained by elevated pH. At high concentrations (> 1 g/l) of wood ash the respiration of G. pulex decreased when no adjustment of pH was made, a response that was negatively correlated to the elevated pH (r = -0.43). An ion-related response was also detected in the pH-adjusted (pH 7) tests, although it was not statistically significant. Cadmium proved to be sublethal in the range of 0.2-0.4mg/l in a 24-h exposure. Mortality was 100% at 0.5 and 1.0mg Cd/l. No effects were detected after exposure to Al, due to the high pH (pH 7-8) of the solutions and the subsequently low concentrations of labile monomeric Al. We demonstrate that the method described in this paper could be a useful probe for the detection of sublethal concentrations of contaminants in freshwater ecosystems.

  • 6. Björn, Gunvor
    et al.
    Ekelund, Nils
    Björn, Lars Olof
    Light-induced lineardichroism in photoreversibly photochromic sensor pigments.” - IV. Lack of chromophore rotation in phycochrome b immobilized in vitro1984In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, no 60, p. 253-256Article in journal (Refereed)
  • 7. Björn, Lars Olof
    et al.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Dinoflagellater: Hopplock från livets smörgåsbord2005In: Svensk Botanisk Tidskrift, ISSN 0039-646X, Vol. 99, no 1, p. 7-16Article in journal (Refereed)
    Abstract [en]

    The dinoflagellates constitute a group within the protistan supergroup Alveolata, and can be referred neither to the plant nor the animal kingdom. They swim about using two flagella and are able to orient using various stimuli. About half the living dinoflagellate species are capable of oxygenic photosynthesis, but most of them complement this with capture of prey. Some live ebtirely by capturing small organisms, others are parasites. Some species are able to emit light. The group has a long evolutionary history, and almost as many extinct species as extant ones have been described. Most remarkable is the way the photosynthetically potent dinoflagellates have aquiered their chloroplasts by endosymbiosis with photosynthetic organisms from many different groups. In some cases repeated endosymbiontic events have taken place.

  • 8. Björn, Lars Olof
    et al.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Koraller och deras fotosyntetiska endosymbionter, zooxantellerna.2006In: Svensk Botanisk Tidskrift, ISSN 0039-646X, Vol. 100, no 4, p. 263-270Article in journal (Other (popular science, discussion, etc.))
  • 9. Björn, Lars-Olof
    et al.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Koraller och zooxantheller: ett marint partnerskap2006In: Svensk botanisk tidskrift, ISSN 0039-646X, Vol. 100, no 4, p. 263-270Article in journal (Refereed)
    Abstract [sv]

    De flesta revbildande koraller lever i ett ömsesidigt beroende med så kallade zooxanteller, encelliga alger som lever inuti koralldjuret och som med hjälp av sin fotosyntes bidrar till försörjningen.

  • 10. Braune, Wolfram
    et al.
    Ekelund, Nils
    Institutionen för Fysiologisk Botanik, Lunds Universitet.
    Phototactic responses in Haematococcus lacustris and its modification by light intensity and the carotenoid biosynthesis inhibitor Norflurazon1990In: Archives of Microbiology, ISSN 0302-8933, E-ISSN 1432-072X, Vol. 154, p. 448-452Article in journal (Refereed)
    Abstract [en]

    At fluence rates below 45 W· m-2 cells of the flagellate stage of Haematococcus lacustris react only positively phototactically with a rather high degree of orientation (indicated by r values up to 0.66 with the Rayleigh test). The directedness of orientation decreases with decreasing irradiance. The degree of directedness of the phototactic response depends on the intensity of preirradiation: Low light intensity applied after strong light application results in a dark reaction (low r values), low light given after darkness stimulates a rather high degree of directedness of positive phototaxis. Weak blue light (=483 nm; 0.4 W · m-2) stimulates positive phototactic response, whereas comparable red light (=658 nm; 0.5 W · m-2) does not.

    Cells which were grown in a medium containing 10-4 M Norflurazon (effective in inhibition of carotenoid biosynthesis) although maintaining motility completely lose the ability to react positively phototactically. The possible role of carotenoids in the phototactic orientation is discussed.

  • 11. Carlsson, F.
    et al.
    Vetterli, A.
    Pocock, Tessa
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Falk, Stefan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    A comparative study including Clamydomonas reinhardtii and Chlamydomonas raudensis Ettl. strains SAG 49.72 and UWO 241 focusing on phototaxis.2005In: Proceedings of the 6th European Workshop Biotechnology of Microalgae, 2005Conference paper (Other academic)
    Abstract [en]

    Phototaxis is movement induced by light; this phenomenon has been detected in several solitary green algae species and generally works as a balancing force against gravitaxis, creating a system for optimum vertical placing in relation to irradiance, (energy -demands/restrictions). We study phototaxis in the mesophilic green algae, Chlamydomonas reinhardtii and C. raudensis SAG 49.72, relative to phototaxis in the from Antarctica newly isolated obligate psychrophilic strain of C. Raudensis (UWO 241) (henceforth called UWO 241). This species has some unusual movement patterns (Pocock et. al 2004) which function is yet to be revealed. Phototactic movement has not earlier been monitored in the normal conditions (high salinity, low temperature) for this strain, though when exposed to extreme temperatures (25C) the organism displays movement patterns interpreted as positive phototaxis. (Pocock et. al 2004). This behaviour should lead to a more rapid destruction of the organism due to the damaging high light (high energy input). The study shows that the three species responds different to light stimuli, when temperature is set to 12 C (culturing temperature) or the respective optimum culture temperatures. Light response curves of phototaxis in the range of 0,5 to 3000 μmol quanta m-2 s-1, shows that C. raudensis SAG 49.72 produce positive phototaxis over the entire range while C. reinhardtii mainly shows negative reactions. UWO 241 seem to be unaffected by irradiance, thus showing only nondirectional behaviour. In a second set of experiments the cells were kept in Petri dishes and exposed to 3000 μmol quanta m-2 s-1 under 40 min, in a temperature range of 5C to 25C for each sample. The results show that C. reinhardtii was negatively phototactic at 5C, switching to positive phototaxis at 25C.

  • 12.
    Danilov, Roman A
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Applicability of growth rate, cell shape and motility of Euglena gracilis as physiological parameters for bioassessment at lower concentrations of toxic substances: an experimental approach.2001In: Environmental Toxicology, ISSN 1520-4081, E-ISSN 1522-7278, Vol. 16, no 1, p. 78-83Article in journal (Refereed)
    Abstract [en]

    The responses of the growth rate, motility, and cell shape in the green flagellate Euglena gracilis to different concentrations of waste water substances from the pulp and paper industry were tested in a long-term study (7 days). Samples before (uncleaned sample) and after (cleaned sample) the treatment in a cleaning system were studied. The influence of different doses of UV-B radiation on cell shape and motility was also investigated. No statistically significant effects of increasing concentrations of the waste substances both before and after the cleaning process (except inhibition by the undiluted uncleaned effluent) on the growth rate in E. gracilis were observed. Cell shape turned out to be an unreliable physiological parameter for assessing the toxicity at lower concentrations of waste water substances. No significant patterns could be observed in the response of the cell shape to the different concentrations of the waste water substances or to UV-B radiation. Motility has been concluded to be a more sensitive parameter than cell shape. However, no clear patterns were observed in the response of the motility to the different concentrations of the waste water substances studied. Increasing concentrations of the uncleaned sample demonstrated a defense against UV-B radiation, due to the high absorbance in the UV-B range, when effects on motility were examined. We conclude that contrary to the results reported in the literature earlier, cell shape and motility of E. gracilis are not universal physiological parameters for bioassessment at lower concentrations of toxic substances, including metals such as copper and zinc from the pulp and paper industry. The long-duration tests had, in general, higher significance than those of short duration.

  • 13.
    Danilov, Roman A
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Periphyton communities on natural substrata in eu-, meso- and oligotrophic lakes at higher latitude2002In: Biologia (Bratislava), ISSN 0006-3088, E-ISSN 1336-9563, Vol. 57, no 4, p. 433-436Article in journal (Refereed)
    Abstract [en]

    Natural epiphyton and epilithon communities were studied in eu-, meso- and oligotrophic lakes at latitude of 62degrees54' N in Vasternorrlands region of Sweden. The samples of epiphyton as well as epilithon (three per lake) were identical and specific for each lake studied. Both epiphytic and epilithic communities consisted of members of three classes of algae - Cyanophyceae, Chlorophyceae and Bacillariophyceae. The highest species diversity was detected within Chlorophyceae while Cyanophyceae and Bacillariophyceae contained the same amount of species. In general, epiphyton and epilithon shared 44% of species identified. However, both epiphyton and epilithon showed distinct patterns between lakes of different trophic level. Epiphyton in the eutrophic lakes were clearly dominated by Cyanophyceae (Bacillariophyceae co-dominated in one of the eutrophic lakes). Both mesotrophic and oligotrophic lakes were signed by high abundance of Chlorophyceae and almost complete absence of Bacillariophyceae and Cyanophyceae. Epilithic communities in the oligotrophic lakes had higher species diversity than those in the meso- and eutrophic lakes studied. Chlorophyceae were dominant in two eutrophic lakes and Cyanophyceae only in one eutrophic lake, Chlorophyceae as well as Bacillariophyceae were abundant in the oligotrophic lakes. Cluster analysis based on species presence-absence led to a sufficient resolution between both epiphytic and epilithic communities of eutrophic environments, on the one hand, and epiphytic and epilithic communities of meso- and oligotrophic environments, on the other.

  • 14.
    Danilov, Roman A
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Ekelund, Nils G A
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Phytoplankton communities at different depths in two eutrophic and two oligotrophic temperate lakes at higher latitude during the period of ice cover2001In: Acta Protozoologica, ISSN 0065-1583, E-ISSN 1689-0027, Vol. 40, no 3, p. 197-201Article in journal (Refereed)
    Abstract [en]

    Phytoplankton communities at different depths and at different locations within each lake were studied during the period of ice cover (from January to March) in two eutrophic and two oligotrophic lakes in North-Eastern Sweden. Cryptophyceae, Dinophyceae and Euglenophyceae were dominant during the whole period of investigation in eutrophic environments. Bacillariophyceae, Chlorophyceae, Chrysophyceae and Cyanophyceae were only occasionally found both in eutrophic and oligotrophic lakes. Both in eutrophic and oligotrophic lakes diversity as well as abundance of phytoplankton were considerably higher immediately under ice than near the bottom. No differences in horizontal distribution of phytoplankton assemblages were detected within each lake. However, vertical differences were more profound. It is speculated that both light availability and increased ion concentration under the ice cover can be viewed as main factors determining phytoplankton communities.

  • 15.
    Danilov, Roman
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Autumn phytoplankton assemblages in temperate lakes of different eutrophication level in the middle part of Sweden2000In: Nordic Journal of Botany, ISSN 0107-055X, E-ISSN 1756-1051, Vol. 20, no 2, p. 225-232Article in journal (Refereed)
    Abstract [en]

    Phytoplankton assemblages were studied during autumn 1998 in oligo-, meso- and eutrophic lakes in central Sweden (62°54'N). Differences in phytoplankton assemblages have been detected both in space and time. In eutrophic lakes coccoid Chlorophyceae dominated quantitatively during September and October. Diatoms were the most diverse group in all types of lakes in September and in meso- and oligotrophic lakes in October. In November Cryptophyceae became the most abundant group in all lakes. The total richness of species decreased in the meso- and oligotrophic environments in November compared to September and October, whilst in the eutrophic environment it remained almost unchanged. Cluster analyses, using both presence-absence and presence-absence in combination with abundance matrices, showed similar results and a good resolution between the lakes of different eutrophication conditions. We conclude that the phytoplankton assemblages of the lakes studied depended on the trophic conditions and thus they can be used for resolution between different eutrophication levels.

  • 16.
    Danilov, Roman
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Comparative studies on the usefulness of seven ecological indices for the marine coastal monitoring close to the shore on the swedish east coast2001In: Environmental Monitoring & Assessment, ISSN 0167-6369, E-ISSN 1573-2959, Vol. 66, no 3, p. 265-279Article in journal (Refereed)
    Abstract [en]

    The simultaneous behaviour of seven ecological indices (Hurlbert's, Margalef's, Menhinick's, Shannon's, species number, Jaccard's and saprobic index) was studied based on phytoplankton data close to the shore on the East coast of Sweden during the summer 1998. The sampling stations had a similar eutrophication level and were located in bays. Standard phytoplankton databases were used in calculating the indices, which were later compared using cluster analysis. Hurlbert's, Margalef's, Menhinick's, Shannon's and species number indices, as measure of community diversity, produced similar trends which often differed from those based on Jaccard's index of similarity. However, the simultaneous use of these indices was found meaningful as a possible part of the monitoring close to the shore. The application of a saprobic index lead to erroneous conclusions in the studied case.

  • 17.
    Danilov, Roman
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Comparison of usefulness of three types of artificial substrata (glass, wood and plastic) when studying settlement patterns of periphyton in lakes of different trophic status2001In: Journal of Microbiological Methods, ISSN 0167-7012, E-ISSN 1872-8359, Vol. 45, no 3, p. 167-170Article in journal (Refereed)
    Abstract [en]

    Usefulness of three types of artificial substrata (glass, wood and plastic) was tested when studying settlement patterns of periphyton in lakes of different trophic status. Strictly eu-, meso- and oligotrophic lakes in central Sweden were chosen as objects of the study. Glass slides, glass tubes, pieces of plastic (PVC) and pieces of wood of similar dimensions were placed for 9 weeks in July-August vertically 3 cm above bottom at a total depth of ca. 30 cm. Substrata were located at well-illuminated places without any other submerged objects (like macrophytes and stones), which could potentially affect colonisation patterns by algae. Periphyton communities, which colonised both the glass tubes and the pieces of wood tested, were specific enough to enable a clear classification of the lakes studied in eu-, meso- and oligotrophic. Glass tubes turned out to be the most favourable substratum when investigating settlement patterns of periphyton in this study. Although also colonised by periphytic species, wood did not support the same diversity and abundance of species as glass did. No algae were detected on the plastics studied. The plastics were covered entirely by a slime layer of bacteria. It is discussed if the nature of plastics could have some inhibitory effects on algal growth or the slime layer itself may have prevented settlement of algal spores.

  • 18.
    Danilov, Roman
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Correlation between different levels of waste substances from the forest industry and the growth rate of Euglena gracilis1998Report (Other academic)
  • 19.
    Danilov, Roman
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Effects of copper on growth rate, cell shape, motility and photosynthesis in the green flagellate Euglena gracilis in a long-term experiment2000In: Biologia (Bratislava), ISSN 0006-3088, E-ISSN 1336-9563, Vol. 55, no 4, p. 413-418Article in journal (Refereed)
    Abstract [en]

    The green flagellate Euglena gracilis was treated for seven days with concentrations of copper ranging from 0.02 mg L-1 to 2.0 mg L-1. No inhibiting effects were detected in any physiological parameters measured. In general, it seems that enhanced copper concentrations stimulated photosynthetic efficiency (PE) of E. gracilis. Concentrations of copper reported to be critical for the other algae studied (from 0.10 mg L-1 to 0.14 mg L-1) did not show any severe negative effects on E. gracilis. An unusual trend was observed where an increase in PE was followed by an increase in light irradiance necessary to achieve light compensation point. High capacity of E. gracilis to adapt to copper stress is being discussed as a possible explanation for the trends detected.

  • 20.
    Danilov, Roman
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Effects of Cu2+, Ni2+, Pb2+, Zn2+ and pentachlorophenol on photosynthesis and motility in Chlamydomonas reinhardtii in short-term exposure experiments.2001In: BMC Ecology, ISSN 1472-6785, Vol. 1, no 1Article in journal (Refereed)
    Abstract [en]

    Background: Heavy metals, especially copper, nickel, lead and zinc, have adverse effects on terrestrial and in aquatic environments. However, their impact can vary depending on the nature of organisms. Taking into account the ability of heavy metals to accumulate in sediments, extended knowledge of their effects on aquatic biota is needed. In this context the use of model organisms (often unicellular), which allows for rapid assessment of pollutants in freshwater, can be of advantage. Pentachlorophenol has been extensively used for decades as a bleaching agent by pulpand paper industry. Pentachlorophenol tends to accumulate in the nature. We aim to determine if photosynthesis and motility can be used as sensitive physiological parameters in toxicological studies of Chlamydomonas reinhardtii, a motile green unicellular alga. It is discussed if photosynthesis and motility can be used as sensitive physiological parameters in toxicological studies. Results: The concentrations studied ranged from 0.1 to 2.0 mg l-1 for copper, nickel, lead and zinc, and from 0.1 to 10.0 mg l-1 for pentachlorophenol. Exposure time was set to 24 h. Copper and pentachlorophenol turned out to be especially toxic for photosynthetic efficiency (PE) in C. reinhardtii. Conclusion: Copper and pentachlorophenol turned out to be especially toxic for PE in C. reinhardtii. Zinc has been concluded to be moderately toxic while nickel and lead had stimulatory effects on the PE. Because of high variance, motility was not considered a reliable physiological parameter when assessing toxicity of the substances using C. reinhardtii. © 2001 Danilov and Ekelund, licensee BioMed Central Ltd.

  • 21.
    Danilov, Roman
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Effects of different levels of UV-B radiation on marine epilithic communities: a short-term microcosm study2000In: Scientia Marina, ISSN 0214-8358, E-ISSN 1886-8134, Vol. 64, no 4, p. 363-368Article in journal (Refereed)
    Abstract [en]

    Epilithic communities from brackish coastal water of the east coast of Sweden were studied in order to reveal their responses to different levels of UV-B radiation. The experiment was conducted for seven days in an indoor microcosm system. The epilithic communities were exposed daily to different doses of UV-B radiation: 1, 3, 5 and 7 hours, respectively. The intensity of the UV-B radiation used was similar to that in natural environments. After seven days clear shifts both in species composition and community structure were observed. All species of diatoms showed negative correlation with enhanced levels of UV-B. On the other hand, abundance of cyanobacteria was positively correlated with enhanced levels of UV-B (Calothrix aeruginea, R=0.49;Oscillatoria amphibia, R=0.93; Pseudanabaena mucicola, R=0.26). Communities dominated by diatoms and green algae at the initial stage of the experiment did show a drastic decrease in diatom abundance under UV-B stress and finally became dominated by cyanobacteria. Among green algae the abundance of Cladophora sericea correlated positively (R=0.33) with enhanced exposure to UV-B, while Monoraphidium-species exhibited negative correlation to UV-B. Otherwise, no significant correlation between other green algae species identified and UV-B stress could be detected. We conclude that UV-B radiation, even at lower levels, is capable to induce severe changes to marine epilithic communities. The trends revealed in the present study predict a shift from communities dominated by diatoms and green algae to those dominated by cyanobacteria.

  • 22.
    Danilov, Roman
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Effects of increasing doses of UV-B radiation on photosynthesis and motility in Chlamydomonas reinhardtii2000In: Folia microbiologica (Prague), ISSN 0015-5632, E-ISSN 1874-9356, Vol. 45, no 1, p. 41-44Article in journal (Refereed)
    Abstract [en]

    Effects of increasing doses of UV-B radiation on photosynthetic efficiency (PE) and motility inChlamydomonas reinhardtii were investigated. The exposure time ranged from 10 to 120 min at 0.73 W/m2 UV-B radiation. A decrease in compensation points (CP) was followed by an increase in PE on extending the UV-B treatment up to 60 min. The subsequent increase in PE was accompanied by increasing CPs. Enhanced doses of UV-B radiation thus have a stimulatory effect on the PE inC. reinhardtii. No inhibitory effects could be detected. No statistically significant differences in motility could be observed due to an extremely high variation of values.

  • 23.
    Danilov, Roman
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Effects of pH on the growth rate, motility and photosynthesis in Euglena gracilis2001In: Folia microbiologica (Prague), ISSN 0015-5632, E-ISSN 1874-9356, Vol. 46, no 6, p. 549-554Article in journal (Refereed)
    Abstract [en]

    The influence of pH 3-10 on the growth, motility and photosynthesis in Euglena gracilis was demonstrated during a 7-d cultivation. The cells did not survive at pH <4 and >8, highest growth rate being detected at pH 7. Motility followed a similar pattern as growth rate. Photosynthetic response curves were shown to be of the same type over the whole pH range. High respiration was characteristic for cells grown at pH 5 and 6, the lowest one at 7. At high and also at low pH more active respiration was found which can be considered as a protective response on proton stress. Respiration was not completely inhibited with potassium cyanide. Photosynthesis was the most effective at pH 6; lower and higher pH decreased photosynthetic efficiency. pH affected more the growth rate than the photosynthesis.

  • 24.
    Danilov, Roman
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Effects of short-term and long-term aluminium stress on photosynthesis, respiration and reproductive capacity in a unicellular green flagellate (Euglena gracilis).2002In: Acta Hydrochimica et Hydrobiologica, ISSN 0323-4320, E-ISSN 1521-401X, Vol. 30, no 4, p. 190-196Article in journal (Refereed)
    Abstract [en]

    Effects of short-term (1 h exposure) and long-term (7 d exposure) aluminium stress on photosynthesis and reproductive capacity have been studied in Euglena gracilis strain Z. Following concentrations of Altot (added as AlCl3) were tested: 0.5 mg L-1, 1.0 mg L-1, 1.5 mg L-1, 2.5 mg L-1, 7.5 mg L-1, 10.0 mg L-1, and 15.0 mg L-1 Al, respectively. Growth rates at different aluminium concentrations did not show significant differences, except at 15.0 mg L-1 Al. Initial respiration was higher in long-term than in the short-term experiments. It is supposed that an energy-dependent mechanism of excretion of aluminium ions has been active in the stressed cells. Consequently, the cells of E. gracilis after long-term exposure to aluminium are believed to be more acclimatised to the aluminium stress. Photosynthetic efficiency (PE) has been negatively affected by aluminium in all experiments performed. Differences between control algae and those treated with aluminium were significant in all cases. PE in long-term experiments was in general significantly higher at all concentrations of aluminium studied, compared to the short-term experiments. The aluminium concentrations tested led only to a general decrease in PE while the level of decrease was not especially concentration-dependent. In general, aluminium tolerance of E. gracilis can be estimated as low, especially by short-term exposure. However, good acclimatisation capacity of this green flagellate to aluminium doses by long-term exposure can be supposed.

  • 25.
    Danilov, Roman
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Effects of solar radiation, humic substances and nutrients on phytoplankton biomass in Lake Solumsjö, Sweden.2001In: Hydrobiologia, ISSN 0018-8158, Vol. 444, no 1-3, p. 203-212Article in journal (Refereed)
  • 26.
    Danilov, Roman
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Influence of chlorophyll concentrations on the reliability of measurements with an oxygen electrode when studying photosynthetic efficiency in bioassays using microalgae2000In: Journal of Applied Phycology, ISSN 0921-8971, E-ISSN 1573-5176, Vol. 12, no 1, p. 63-67Article in journal (Refereed)
    Abstract [en]

    Euglena gracilis and Chlamydomonas reinhardtii were used as model organisms to establish the best conditions for studying photosynthetic efficiency using the Light Pipetteexperimental system, which enables sensitive detection of changes in oxygen evolution/consumption and an easy collection and digitalisation of data. Chlorophyll concentrations of 0.005, 0.025, 0.050 and 0.075 mg mL-1 were investigated using different light regimes. Cultures of E. gracilis at the same chlorophyll concentration absorbed more light (measured at 580 μmol m-2 s-1) than those of C. reinhardtii. Cell density had a considerable effect on the reliability of measurements. Chlorophyll concentrations between 0.025 mg(Chl) ml-1 and 0.050 mg(Chl) ml-1 can be recommended when applying the Light Pipette system in bioassays using microalgae.

  • 27.
    Danilov, Roman
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Influence of waste water from the paper industry and UV-B radiation on the photosynthetic efficiency of Euglena gracilis1999In: Journal of Applied Phycology, ISSN 0921-8971, E-ISSN 1573-5176, Vol. 11, p. 157-163Article in journal (Refereed)
    Abstract [en]

    The green flagellate Euglena gracilis has been used as a model organism to elucidate the possible large-scale and short-term effects of waste substances from the pulp and paper industry on photosynthetic efficiency (PE). Different concentrations of waste substances before and after treatment in a cleaning system were studied. The uncleaned sample at concentrations up to 1:10 and the cleaned sample at concentrations up to 1:5 showed stimulating effects on the PE after 7 days of incubation compared to the control. The effects of waste substances on the PE of E. gracilis were also studied in combination with short-term studies (20 and 40 min) of ultraviolet-B radiation (UV-B, 280–320 nm). It was shown that increasing concentrations of the uncleaned sample had continuously stimulating effects on the PE and worked protectively against UV-B radiation. The cleaned sample exhibited no effects, or negative effects, on the PE of E. gracilis together with UV-B radiation compared to the experiments with only UV-B radiation. At the concentration 1:1 of the cleaned sample an increase in the PE was detected due to the high concentration of the coloured substances and a decrease in the UV-B penetration. PE revealed itself to be highly sensitive for detecting toxic effects on E. gracilis and is thus very promising for use in regular toxicity tests of waste water from pulp and paper industry.

  • 28.
    Danilov, Roman
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Responses of photosynthetic efficiency, cell shape and motility in Euglena gracilis (Euglenophyceae) to short-term exposure to heavy metals and pentachlorophenol2001In: Water, Air and Soil Pollution, ISSN 0049-6979, E-ISSN 1573-2932, Vol. 132, no 1-2, p. 61-73Article in journal (Refereed)
    Abstract [en]

    Euglena gracilis was exposed for 24 hr to concentrations of copper, nickel, lead and zinc ranging from 0.1 to 2.0 mg L-1 and to pentachlorophenol ranging from 0.1 to 10.0 mg L-1. Photosynthetic efficiency (PE) was inhibited by increasing concentrations of the heavy metals. Nickel was found to be the least toxic of the metals to E. gracilis, while the other three metals exhibited similar levels of toxicity. Treatment with pentachlorophenol caused unusual responses of the photosynthetic apparatus probably due to the especially high toxicity of this substance. Both cell shape and motility turned out to be insensitive physiological parameters for the toxicity testing of the substances studied.

  • 29.
    Danilov, Roman
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Summer phytoplankton dynamics close to the shore in three brackish water bays on the East coast of Sweden (Gulf of Bothnia)2000In: Thaiszia – J. Botany, Kosice, ISSN 1210-0420, Vol. 9, p. 131-142Article in journal (Refereed)
    Abstract [en]

    Three brackish water bays between Härnösand and Sundsvall on the East coast of Sweden (Gulf of Bothnia) were investigated between June and August 1998 in order to reveal summer phytoplankton dynamics close to the coast. All samples were collected at depth of 0,5 m. The results obtained show patterns in phytoplankton dynamics. In the spring Bacillariophyceae dominated, followed by an increase in Dinophyceae and small flagellates of Prasinophyceae and Cryptophyceae. Chlorophyceae were represented during the whole period of investigation especially with species of Monoraphidium, which often dominated or subdominated. In total 84 phytoplankton species were identified. Cluster analyses based on similarities in species’ diversity and their abundance made it easy to distinguish between the bays close to Härnösand and the Bay of Sundsvall. However, no clear differences were found between the sampling stations within the Bay of Sundsvall.

  • 30.
    Danilov, Roman
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    The efficiency of seven diversity and one similarity indices based on phytoplankton data for assessing the level of eutrophication in lakes in central Sweden1999In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 234, p. 15-23Article in journal (Refereed)
  • 31.
    Danilov, Roman
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    The use of epiphyton and epilithon data as a base for calculating ecological indices in monitoring of eutrophication in lakes in central Sweden2000In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 248, p. 63-70Article in journal (Refereed)
    Abstract [en]

    Eutrophication was monitored with the aid of one similarity and seven diversity indices in the lakes of different trophic levels (eutrophic, mesotrophic and oligotrophic) in central Sweden. The ecological indices were applied separately to epiphyton and epilithon communities. Epiphyton turned out to be inappropriate for assessing eutrophication in the lakes studied. On the other hand, Hurlbert's, Simpson's and the similarity indices turned out to be promising environmental tools when applied to the data of epilithon.

  • 32.
    Danilov, Roman
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Using the green flagellate Euglena gracilis Klebs as physiological dosimeter: is a long-term bioassay more significant than a short-term one?2001In: Turkish journal of botany, ISSN 1300-008X, Vol. 25, p. 43-44Article in journal (Refereed)
    Abstract [en]

    The use of short-term tests with E. gracilis Klebs in order to assess toxicity cannot be viewed as absolutely preferable.At least in the case with wastewater from the pulp and paper industry, 7 day-tests could lead to more explanatory and significantresults.

  • 33.
    Ekelund, N. G. A.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Interactions between photosynthesis and 'light-enhanced dark respiration' (LEDR) in the flagellate Euglena gracilis after irradiation with ultraviolet radiation2000In: Journal of Photochemistry and Photobiology. B: Biology, ISSN 1011-1344, E-ISSN 1873-2682, Vol. 55, no 1, p. 63-69Article in journal (Refereed)
    Abstract [en]

    The effects of ultraviolet radiation (UV-A, 315-400 nm plus UV-B, 280-315 nm) on photosynthesis and 'light-enhanced dark respiration' (LEDR) in Euglena gracilis have been investigated by using light pulses (80 s) with increasing photon fluence rates of 59, 163, 600, 1180, 2080 and 3340 mu mol m(-2) s(-1) and dark periods between the light pulses. LEDR is estimated as the maximum rate of oxygen consumption after a period of Light minus the rate of oxygen consumption 30 s after the maximum rate. Without any exposure to UV radiation, the photosynthetic rate and LEDR increase with increasing photon fluence rate. After 20 and 40 min exposures to UV radiation, the photosynthetic rate and LEDR as functions of photon fluence rate are reduced. After a 20 min UV treatment respiration is greater than photosynthesis after the first light pulse of 59 mu mol m(-2) s(-1) radiation, and especially at higher photon fluence rates photosynthesis is lower than the control values. The inhibitory effects of UV radiation on photosynthetic rate and LEDR are greater after a 40 min UV exposure than after a 20 min exposure. Only at 600 mu mol m(-2) s(-1) is the rate of oxygen evolution greater than that of oxygen consumption after a 40 min UV treatment. Both photosynthetic rate and LEDR are inhibited by the photosynthetic inhibitor DCMU (10(-5) M) in a similar way, which indicates close regulatory interactions between photosynthesis and LEDR. Potassium cyanide (KCN) inhibits dark respiration more than it inhibits LEDR. Dark respiration is not affected to the same degree by UV radiation as are photosynthesis and LEDR.

  • 34.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Ecological and environmental knowledge of aquatic ecosystems2010In: PS public service review, ISSN 1472-3395, , p. 1p. 502-502Article in journal (Other academic)
  • 35.
    Ekelund, Nils
    Department of Plant Physiology, University of Lund.
    Effects of calcium channel blockers and DCMU on motility and the photophobic response of Gyrodinium dorsum1989In: Archives of Microbiology, ISSN 0302-8933, E-ISSN 1432-072X, Vol. 151, p. 187-190Article in journal (Refereed)
    Abstract [en]

    The effects of the calcium channel blockers, verapamil, diltiazem and lanthanum ions and the Ca2+ dependency on motility as well as the photophobic response (stop-response) of Gyrodinium dorsum were studied. At Ca2+ concentrations below 10-3 M, motility was inhibited. La3+ inhibits the stop-response, in contrast to verapamil and diltiazem. The only calcium channel blocker that increased the amount of non-motile cells was verapamil. The results indicate that motility are Ca2+ dependent and that the stop-responses of G. dorsum could be affected by extracellular Ca2+. Effects of the photosythesis inhibitor (DCMU) on the stop-response was also determined. With background light of different wavelength (614, 658 and 686 nm) the stop-response increased. DCMU inhibited this effect of background light. Negative results with the monoclonal antibody Pea-25 directed to phytochrome and the results with DCMU, indicate that the stop-response of G. dorsum is coupled to photosynthesis rather than to a phytochrome-like pigment. Oxygen evolution, but not cell movement, was completely inhibited by 10-6 M DCMU.

  • 36.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Effects of protein synthesis inhibitors on photoinhibition by UV–B (280-320 nm) radiation in the flagellate Euglena gracilis1996In: Scienta Marina, Vol. 60, no 1, p. 95-100Article in journal (Refereed)
    Abstract [en]

    Irradiation of the flagellate Euglena gracilis by UV-B radiation resulted in inhibition of photosynthesis and motility. After 2 h of UV-B radiation (1.2 W m super(-2)) the rates of photosynthesis did not completely recover until after 24 h in visible light. After 24 h in darkness the rate of photosynthesis was lower but the recovery time in darkness after UV-B radiation was about the same as in the visible light. In the presence of lincomycin, inhibitor of chloroplast protein synthesis, therecovery of photoinhibition was totally blocked for up to 16 h recovery in visible light. However, after 24 h recovery in visible light together with lincomycin, photosynthesis was partially recovered but recovery in darkness together with lincomycindid not give any reparation at all of photosynthesis. The inhibition of motility had a slower recovery phase and had not fully recovered even after 72 h in visible light.

  • 37.
    Ekelund, Nils
    Dept of Plant Physiology, Lund Univ..
    Effects of UV-B radiation on growth and motility of four phytoplankton species1990In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 78, p. 590-594Article in journal (Refereed)
    Abstract [en]

    A depletion of the stratospheric ozone layer would result in an increased UV-B radiation, which could have harmful effects on marine organisms. The aim of this study was to determine the effects of an enhanced UV-B radiation (280–320 nin) on the motility and growth in four Swedish phytoplanklon species. The different plankton species were exposed to different doses of UV-B radiation during growth. The growth of the motile dinoflagellates, Gyronidium aureolum Hulburt (Ba 6), and Prorocentrum minimum (Pav.) P. Schiller (Ba 12), was more sensitive to UV-B radiation than the non-motile diatoms Dityhim brightwellii (P. West) Grun (Ba 15) and Phaeodactylum tricornutum Bohlin (Ba 16). One week of UV-B radiation 2 h daily (159 J m−2 day−1), had a dramatic effect on the growth of the dinoflagellates, while the diatoms were nearly unaffected. On the other hand, when given higher intensity of UV-B radiation (312, 468 and 624 J m−2 day−1) during the initial phase of growth, also the growth of the diatom, D. brightwellii, was inhibited. Not only the growth but also the swimming speed of the dinoflagellates C. aureolum and P. minimum were affected by UV-B radiation. The speed decreased rapidly after 1–2 h of UV-B radiation (312 J m−2 day−1), and after longer irradiation times the dinoflagellates lost their motility. G. aureolum exposed to UV-B radiation, regained normal speed after two weeks of visible light.

  • 38.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Effekter av ozon- och klimatförändringar på växter och djur2008In: Fauna och flora : populär tidskrift för biologi, ISSN 0014-8903, Vol. 103, no 2, p. 10-16Article in journal (Other (popular science, discussion, etc.))
  • 39.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Forøget ultraviolet stråling og dens betydning for havmiljøet.”1992In: Naturens Verden, Vol. 2, p. 57-63Article in journal (Other (popular scientific, debate etc.))
  • 40.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    ”Hej då, sjöelefanter och pingviner – hoppas vi ses igen.”1998In: Senior posten, no 5Article in journal (Other (popular science, discussion, etc.))
  • 41.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Influence of UV-B radiation on light-response curves, absorption spectra and motility of four phytoplankton species1994In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 91, p. 696-702Article in journal (Refereed)
    Abstract [en]

    Several unicellular algae were exposed to artificial UV-B (280-320 nm) radiation after adaptation to high (43 W m-2) and low (19 W m-2) visible light. UV-B radiation had different effects on rates of photosynthesis. motility and absorption spectra for these species. Photosynthesis of Euglena gracilis and the diatom Phaeodactylum tricornum was more sensitive to UV-B inhibition than that of the dinoflagellates Heterocapsa triquetra and Prorocentrum minimum. Not only UV-B radiation but light had a photoinhibitory effect on photosynthesis in all four organisms. The effect on photosynthesis was observed both on the quantum yield and on the light saturation rate of photosynthesis

  • 42. Ekelund, Nils
    Ljusrörelser hos mikroorganismer1988In: Svensk Botanisk Tidskrift, ISSN 0039-646X, Vol. 82, p. 333-336Article in journal (Other (popular science, discussion, etc.))
  • 43.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Report on fieldwork at Husvik, South Georgia: October - December 1990. "Studies on the effects of ultraviolet radiation on phytoplankton of Sub-Antarctic lakes and ponds1992In: Swedish Antarctic Research Programme 1990/91, , p. 54-57Article in journal (Other (popular science, discussion, etc.))
  • 44.
    Ekelund, Nils
    Department of Plant Physiology, University of Lund.
    Studies on the effects of UV-B radiation on phytoplankton of Sub-Antarctic lakes and ponds1992In: Polar Biology, ISSN 0722-4060, E-ISSN 1432-2056, Vol. 12, p. 533-537Article in journal (Refereed)
    Abstract [en]

    Experiments were performed to determine the effects of UV-B (ultraviolet, 280–320 nm) radiation on motility and growth of phytoplankton from lakes and ponds in South Georgia. After 4 h of solar radiation and 4h artificial radiation (UV-BBE 11.6 kJ m-2 day-1, UV-B lamps) the swimming velocity of Cryptomonas sp. decreased. The growth rate of Botryococcus, Lyngbya sp. and Stauraslrum sp. did not show any significant variations between the different light conditions. The UV-B component was reduced by filtering solar radiation through glass bottles und cellulose acetate. Cloudy days had only 30% of the radiation of clear days in both the PAR (photosynthetic active radiation) and UV-B regions. The ponds contained large amounts of humic substances, which are responsible for the absorbance in the UV region.

  • 45.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    The effect of UV-B radiation and humic substances on growth and motility of the flagellate, Euglena gracilis.1993In: Journal of Plankton Research, ISSN 0142-7873, E-ISSN 1464-3774, Vol. 15, p. 715-722Article in journal (Refereed)
    Abstract [en]

    The effects of ultraviolet-B radiation (UV-B, 250–315 nm) were determined on Euglena gracilis with respect to speed, phototactic orientation, specific growth rate, and in the presence of humic substances. Humic substances had a protective effect when studying the speed and specific growth rate. However, the degree of phototactic orientation decreased in UV-B radiation both with and without humic substances. The inhibition of O2 evolution and speed was most pronounced when using cutoff filters WG280 and WG295. The photosynthetic inhibitor DCMU (10–6 M) did not have any effect on the speed, but the 02 evolution decreased to zero. The effect of different wavelengths in the UV-B region on the speed of E.gracilis showed the maximum sensitivity at 280 and 290 nm.

  • 46.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    The effects of UV-B radiation on dinoflagellates1991In: Journal of plant physiology (Print), ISSN 0176-1617, E-ISSN 1618-1328, Vol. 138, p. 274-278Article in journal (Refereed)
  • 47.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Till sjöelefanter i mittoceanen1998In: Senior posten, no 4Article in journal (Other (popular science, discussion, etc.))
  • 48.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Växter som kan simma2012In: Havsutsikt, ISSN 1104-0513, Vol. 1, no 1, p. 8-9Article in journal (Other (popular science, discussion, etc.))
  • 49.
    Ekelund, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Växters fotosyntes vid förändrade miljöförhållanden2001In: Fauna och flora : populär tidskrift för biologi, ISSN 0014-8903, Vol. 96, no 1, p. 15-24Article in journal (Other (popular science, discussion, etc.))
  • 50. Ekelund, Nils
    Öresund1989In: Kisa-Rapport. Nr. 5Article in journal (Other (popular science, discussion, etc.))
12 1 - 50 of 87
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