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Author |
Thomas, D.N. |
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Title |
Photosynthetic microbes in freezing deserts |
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Journal Article |
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Year |
2005 |
Publication |
Trends in Microbiology |
Abbreviated Journal |
Trends Microbiol |
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Volume |
13 |
Issue |
3 |
Pages |
87-88 |
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Abstract |
Polar deserts are not devoid of life despite the extreme low temperature and scarcity of water. Recently, patterned stone fields – caused by periglacial activity – have been surveyed in the Arctic and Antarctic. It was found that the productivity of the cyanobacteria and algae (hypoliths) that colonise the underside of the stones is strongly related to the pattern of the stones. The hypolith assemblages were in some cases as productive as lichens, bryophytes and plants that resided nearby. |
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Elsevier Science B.V. |
Place of Publication |
Amsterdam |
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Language |
English |
Summary Language |
English |
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0966-842X |
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Call Number  |
refbase @ admin @ Thomas2005 |
Serial |
755 |
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Author |
Weykam, G.; Thomas, D.N.; Wiencke, C. |
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Title |
Growth and photosynthesis of the Antarctic red algae Palmaria decipiens (Palmariales) and Iridaea cordata (Gigartinales) during and following extended periods of darkness |
Type |
Journal Article |
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Year |
1997 |
Publication |
Phycologia |
Abbreviated Journal |
Phycologia |
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Volume |
36 |
Issue |
5 |
Pages |
395-405 |
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Keywords |
Winter; Polar waters; Photosynthesis; Antarctic zone; Ice cover; Seaweeds; Light effects; Plant physiology; Growth; Palmariales; Gigartinales; Iridaea cordata; Palmaria decipiens; Ps; Antarctica |
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Abstract |
Physiological and developmental responses during and following long-term exposure to darkness were investigated in the Antarctic red algae Palmaria decipiens and Iridaea cordata. Thalli were kept in darkness for a period of 6 mo, simulating winter sea ice cover. Subsequently, they were grown illuminated under seasonally fluctuating Antarctic daylengths. During darkness, P. decipiens, an Antarctic endemic, rapidly lost its ability to photosynthesize although chlorophyll a content remained fairly constant. The amount of floridean starch decreased gradually in the dark, with a sudden drop simultaneous with the development of new blades. After reexposure to light there was a rapid increase in photosynthetic oxygen production, whereas the rate of carbon assimilation increased more slowly, resulting in high apparent photosynthetic quotients. The increase in growth rate showed a close relation to carbon assimilation, suggesting that carbon is utilized first for growth, then for floridean starch accumulation. In contrast to P. decipiens, the photosynthetic rate of the Antarctic cold-temperate I. cordata was still about half of the initial rate after a dark period of 6 mo, i.e. the alga maintained functionality of its photosynthetic apparatus during winter. After reexposure to light there was a continuous increase in specific growth rate due to increasing photosynthetic activity. Iridaea cordata also accumulated floridean starch during summer, although in smaller amounts than P. decipiens. Together with the ability to photosynthesize, starch accumulation facilitates survival during extended dark periods in winter. The early development of blade initials and the rapid increase in photosynthetic capability after illumination may permit P. decipiens to use the period of high water transparency optimally in Antarctic spring. Iridaea cordata seems better able to survive prolonged dark periods in areas with less predictable light conditions. Both physiological patterns are well suited to the highly seasonal light conditions in Antarctica. |
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0031-8884 |
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Marine |
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Call Number |
refbase @ admin @ Weykam++1997 |
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767 |
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Author |
Stedmon, C.A.; Thomas, D.N.; Granskog, M.; Kaartokallio, H.; Papadimitriou, S.; Kuosa, H. |
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Title |
Characteristics of dissolved organic matter in Baltic coastal sea ice: allochthonous or autochthonous origins? |
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Journal Article |
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Year |
2007 |
Publication |
Environmental Science & Technology |
Abbreviated Journal |
Environ Sci Technol |
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Volume |
41 |
Issue |
21 |
Pages |
7273-7279 |
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Keywords |
Carbon/analysis; *Humic Substances; Ice Cover/*chemistry; Nitrogen/analysis; Oceans and Seas; Spectrometry, Fluorescence |
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Abstract |
The origin of dissolved organic matter (DOM) within sea ice in coastal waters of the Baltic Sea was investigated using parallel factor (PARAFAC) analysis of DOM fluorescence. Sea ice DOM had distinctly different fluorescence characteristics than that of the underlying humic-rich waters and was dominated by protein-like fluorescence signals. PARAFAC analysis identified five fluorescent components, all of which were present in both sea ice and water. Three humic components were negatively correlated to salinity and concluded to be terrestrially derived material. Baltic Sea ice DOM was found to be a mixture of humic material from the underlying water column incorporated during ice formation and autochthonous material produced by organisms within the ice. Dissolved organic carbon (DOC) and nitrogen (DON) concentrations were correlated to the humic fluorescence, indicating that the majority of the organic carbon and nitrogen in Baltic Sea ice is bound in terrestrial humic material trapped within the ice. This has implications for our understanding of sea ice carbon cycling in regions influenced by riverine input (e.g., Baltic and Arctic coastal waters), as the susceptibility of DOM to degradation and remineralization is largely determined by its source. |
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Address |
Department of Marine Ecology, National Environmental Research Institute, University of Aarhus, Frederiksborgvej 399, 4000 Roskilde, Denmark. cst@dmu.dk |
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0013-936X |
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PMID:18044499 |
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Call Number |
refbase @ user @ |
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12979 |
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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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ISSN |
0960-8524 |
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PMID:20634058 |
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Call Number |
refbase @ user @ |
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12981 |
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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 |
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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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0923-9820 |
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PMID:20878208 |
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refbase @ user @ |
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12982 |
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