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Author |
Mock, T.; Dieckmann, G.S.; Haas, C.; Krell, A.; Tison, J.-L.; Belem, A.L.; Papadimitriou, S.; Thomas, D.N. |
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Title |
Micro-optodes in sea ice: a new approach to investigate oxygen dynamics during sea ice formation |
Type |
Journal Article |
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Year |
2002 |
Publication  |
Aquatic Microbial Ecology |
Abbreviated Journal |
Aquat Microb Ecol |
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Volume |
29 |
Issue |
3 |
Pages |
297-306 |
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Keywords |
Fragilariopsis cylindrus; Oxygen; Methods; Micro-optodes; Sea ice; Biogeochemistry; Diatoms; Algae; Chlorophyll; Photosynthesis; Salinity effects; Sea water; Marine ecosystems; Chlorophylls; Dissolved oxygen; Gases; Epontic environment; Electrodes; Sensors; Brines; Ice-water interface; Ice formation; Bacillariophyceae |
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Abstract |
Oxygen micro-optodes were used to measure oxygen dynamics directly within the microstructure of sea ice by freezing the sensors into the ice during its formation. The experiment was conducted in a 4 m³ mesocosm filled with artificial seawater and inoculated with a unialgal culture of the common Antarctic ice diatom Fragilariopsis cylindrus (Bacillariophyceae) to a final chlorophyll a (chl a) concentration of 11 µg 1?¹. Ice growth was initiated 7 d after inoculation by reducing the air temperature to -10 plus or minus 2 degree C and terminated 17 d later. The final ice thickness was 27 cm. One optode was frozen into grease ice and 2 others into the skeletal layer of the growing ice sheet. Increasing oxygen concentrations during ice crystal formation at the water surface and the ice-water interface revealed a strong inclusion of oxygen, which was either physically trapped and/or the result of photosynthesising diatoms. The major portion of oxygen was present as gas bubbles due to super-saturation as a result of increasing salinity and oxygen production by diatoms. An increase in salinity due to a concurrent decrease in ice temperatures during subsequent sea ice development reduced the maximum concentration of dissolved oxygen within brine. Thus, dissolved oxygen concentrations decreased over time, whereas gaseous oxygen was released to the atmosphere and seawater. The sensors are a significant advance on more conventional microelectrodes, because the recordings can be temperature and salinity compensated in order to obtain precise measurements of oxygen dynamics with regard to total (dissolved and gaseous) and dissolved oxygen in sea ice. Optodes do not consume oxygen during measuremnet over a long period under extreme conditions, which is another advantage for long-term deployment in the field. |
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Publisher |
Inter-Research |
Place of Publication |
Oldendorf/Luhe |
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ISSN |
0948-3055 |
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Notes |
Marine |
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no |
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Call Number |
refbase @ admin @ Mock++2002 |
Serial |
749 |
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Author |
Carver, S.M.; Hulatt, C.J.; Thomas, D.N.; Tuovinen, O.H. |
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Title |
Thermophilic, anaerobic co-digestion of microalgal biomass and cellulose for H2 production |
Type |
Journal Article |
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Year |
2011 |
Publication |
Biodegradation |
Abbreviated Journal |
Biodegradation |
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Volume |
22 |
Issue |
4 |
Pages |
805-814 |
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Keywords |
Anaerobiosis; Biodegradation, Environmental; Biofuels; Biomass; Bioreactors; Cellulose/*metabolism; Chlorella vulgaris/*metabolism/microbiology; Chromatography, High Pressure Liquid; Fatty Acids, Volatile/biosynthesis; *Fermentation; *Hydrogen/metabolism; Microalgae/*metabolism/microbiology; Microbial Consortia |
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Abstract |
Microalgal biomass has been a focus in the sustainable energy field, especially biodiesel production. The purpose of this study was to assess the feasibility of treating microalgal biomass and cellulose by anaerobic digestion for H2 production. A microbial consortium, TC60, known to degrade cellulose and other plant polymers, was enriched on a mixture of cellulose and green microalgal biomass of Dunaliella tertiolecta, a marine species, or Chlorella vulgaris, a freshwater species. After five enrichment steps at 60 degrees C, hydrogen yields increased at least 10% under all conditions. Anaerobic digestion of D. tertiolecta and cellulose by TC60 produced 7.7 mmol H2/g volatile solids (VS) which were higher than the levels (2.9-4.2 mmol/g VS) obtained with cellulose and C. vulgaris biomass. Both microalgal slurries contained satellite prokaryotes. The C. vulgaris slurry, without TC60 inoculation, generated H2 levels on par with that of TC60 on cellulose alone. The biomass-fed anaerobic digestion resulted in large shifts in short chain fatty acid concentrations and increased ammonium levels. Growth and H2 production increased when TC60 was grown on a combination of D. tertiolecta and cellulose due to nutrients released from algal cells via lysis. The results indicated that satellite heterotrophs from C. vulgaris produced H2 but the Chlorella biomass was not substantially degraded by TC60. To date, this is the first study to examine H2 production by anaerobic digestion of microalgal biomass. The results indicate that H2 production is feasible but higher yields could be achieved by optimization of the bioprocess conditions including biomass pretreatment. |
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Department of Microbiology, Ohio State University, 484 W. 12th Ave., Columbus, OH 43210, USA. carver.84@gmail.com |
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English |
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Series Issue |
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Edition |
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ISSN |
0923-9820 |
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Notes |
PMID:20878208 |
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no |
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Call Number |
refbase @ user @ |
Serial |
12982 |
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Author |
Hulatt, C.J.; Thomas, D.N. |
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Title |
Dissolved organic matter (DOM) in microalgal photobioreactors: a potential loss in solar energy conversion? |
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Journal Article |
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Year |
2010 |
Publication |
Bioresource Technology |
Abbreviated Journal |
Bioresour Technol |
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Volume |
101 |
Issue |
22 |
Pages |
8690-8697 |
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Keywords |
Bioreactors/*microbiology; Chlorella vulgaris/*physiology; Culture Media/chemistry; *Electric Power Supplies; Energy Transfer; Organic Chemicals/*chemistry/*metabolism; Photochemistry/*instrumentation; Solubility |
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Abstract |
Microalgae are considered to be a potential alternative to terrestrial crops for bio-energy production due to their relatively high productivity per unit area of land. In this work we examined the amount of dissolved organic matter exuded by algal cells cultured in photobioreactors, to examine whether a significant fraction of the photoassimilated biomass could potentially be lost from the harvestable biomass. We found that the mean maximum amount of dissolved organic carbon (DOC) released measured 6.4% and 17.3% of the total organic carbon in cultures of Chlorellavulgaris and Dunaliella tertiolecta, respectively. This DOM in turn supported a significant growth of bacterial biomass, representing a further loss of the algal assimilated carbon. The release of these levels of DOC indicates that a significant fraction of the photosynthetically fixed organic matter could be lost into the surrounding water, suggesting that the actual biomass yield per hectare for industrial purposes could be somewhat less than expected. A simple and inexpensive optical technique, based on chromophoric dissolved organic matter (CDOM) measurements, to monitor such losses in commercial PBRs is discussed. |
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School of Ocean Sciences, College of Natural Sciences, Bangor University, Menai Bridge, Anglesey, UK. osp418@bangor.ac.uk |
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English |
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Abbreviated Series Title |
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ISSN |
0960-8524 |
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Notes |
PMID:20634058 |
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no |
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Call Number |
refbase @ user @ |
Serial |
12981 |
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Author |
Hulatt, C.J.; Thomas, D.N. |
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Title |
Productivity, carbon dioxide uptake and net energy return of microalgal bubble column photobioreactors |
Type |
Journal Article |
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Year |
2011 |
Publication |
Bioresource Technology |
Abbreviated Journal |
Bioresour Technol |
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Volume |
102 |
Issue |
10 |
Pages |
5775-5787 |
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Keywords |
*Bioreactors; Carbon Dioxide/*metabolism; Energy Metabolism; Equipment Design; Microalgae/growth & development/*metabolism; Photochemistry |
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Abstract |
This work examined the energy return of Chlorella vulgaris and Dunaliella tertiolecta cultivated in a gas-sparged photobioreactor design where the power input for sparging was manipulated (10, 20, and 50 Wm(-3)). Dry weight, organic carbon and heating values of the biomass were measured, plus a suite of variables including Fv/Fm and dissolved oxygen. A model for predicting the higher heating value of microalgal biomass was developed and used to measure the energetic performance of batch cultivations. High power inputs enhanced maximum biomass yields, but did not improve the energy return. Cultivation in 10 Wm(-3) showed up to a 39% higher cumulative net energy return than 50 Wm(-3), and increased the cumulative net energy ratio up to fourfold. The highest net energy ratio for power input was 19.3 (D. tertiolecta, 12% CO(2), 10 Wm(-3)). These systems may be a sustainable method of biomass production, but their effectiveness is sensitive to operational parameters. |
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Address |
School of Ocean Sciences, College of Natural Sciences, Bangor University, Askew Street, Menai Bridge, Isle of Anglesey LL59 5AB, UK. osp418@bangor.ac.uk |
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0960-8524 |
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Notes |
PMID:21376576 |
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no |
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Call Number |
refbase @ user @ |
Serial |
12983 |
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Author |
Hulatt, C.J.; Thomas, D.N. |
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Title |
Energy efficiency of an outdoor microalgal photobioreactor sited at mid-temperate latitude |
Type |
Journal Article |
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Year |
2011 |
Publication |
Bioresource Technology |
Abbreviated Journal |
Bioresour Technol |
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Volume |
102 |
Issue |
12 |
Pages |
6687-6695 |
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Keywords |
Biomass; *Bioreactors; Climate; Geography; Microalgae/growth & development/*metabolism; Oxygen/metabolism; Scenedesmus/growth & development/*metabolism; Seasons; Solar Energy |
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Abstract |
This work examined the energetic performance of a 6-month semi-continuous cultivation of Scenedesmus obliquus in an outdoor photobioreactor at mid-temperate latitude, without temperature control. By measuring the seasonal biomass production (mean 11.31, range 1.39-23.67 g m(-2)d(-1)), higher heating value (22.94 kJ g(-1)) and solar irradiance, the mean seasonally-averaged photosynthetic efficiency (2.18%) and gross energy productivity (0.27 MJ m(-2) d(-1)) was calculated. When comparing the solar energy conversion efficiency to the energy investment for culture circulation, significant improvements in reactor energy input must be made to make the system viable. Using the data collected to model the energetic performance of a substitute photobioreactor design, we conclude that sustainable photobioreactor cultivation of microalgae in similar temperate climates requires a short light path and low power input, only reasonably obtained by flat-panel systems. However, temperature control was not necessary for effective long-term cultivation. |
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Address |
School of Ocean Sciences, College of Natural Sciences, Bangor University, Askew Street, Menai Bridge, Anglesey LL59 5AB, UK. osp418@bangor.ac.uk |
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English |
Summary Language |
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0960-8524 |
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PMID:21511466 |
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no |
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Call Number |
refbase @ user @ |
Serial |
12984 |
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