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Author |
Thomas, D.N.; Gleitz, M. |
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Title |
Allocation of photoassimilated carbon into major algal metabolite fractions: Variation between two diatom species isolated from the Weddell Sea (Antarctica) |
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Journal Article |
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Year |
1993 |
Publication |
Polar Biology |
Abbreviated Journal |
Polar Biol |
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Volume |
13 |
Issue |
4 |
Pages |
281-286 |
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Keywords |
carbon fixation; metabolites; biomass; Nitzschia curta; Chaetoceros; Psw; Weddell Sea |
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Abstract |
Distribution of photoassimilated carbon into major metabolite classes differed between two Antarctic diatom species, Nitzschia curta and a small unicellular Chaetoceros sp.. Time course uptake studies (over 54 h) revealed that¹?C allocation appeared to be equilibrated after approximately 8 h at light saturated photosynthesis. During short term dark periods (6 h), polysaccharides as well as low-molecular-weight compounds were catabolised to sustain protein synthesis in the dark, whilst lipid reserves were not mobilised for this process. Experiments with these two species were conducted at 0 and -1.5 degree C, although no difference in the distribution of radiolabel was measured between the two temperatures. It is hypothesised that under near-optimal conditions fast growing species are characterised by a high carbon turnover associated with a rapid flow of newly assimilated carbon into polymeric compound classes. On the other hand, slower growing species (such as N. curta) may store a significant amount of surplus carbon in the low-molecular-weight metabolite fraction. Species specific preferences were observed when comparing the accumulation of radiolabel into the lipid pools. |
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Springer-Verlag |
Place of Publication |
Heidelberg |
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0722-4060 |
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Notes |
Bibliogr.: 48 ref.; Marine |
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no |
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Call Number |
refbase @ admin @ Thomas+Gleitz1993 |
Serial |
760 |
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Author |
Thomas, D.N.; Kennedy, H.; Kattner, G.; Gerdes, D.; Gough, C.; Dieckmann, G.S. |
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Title |
Biogeochemistry of platelet ice: its influence on particle flux under fast ice in the Weddell Sea, Antarctica |
Type |
Journal Article |
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Year |
2001 |
Publication |
Polar Biology |
Abbreviated Journal |
Polar Biol |
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Volume |
24 |
Issue |
7 |
Pages |
486-496 |
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Abstract |
An array of four sediment traps and one current meter was deployed under a well-developed platelet layer for 15 days in the Drescher Inlet in the Riiser Larsen ice shelf, in February 1998. Traps were deployed at 10 m (just under the platelet layer), 112 m (above the thermocline), 230 m (below thermocline) and 360 m (close to sea floor). There was a substantial flux of particulate organic material out of the platelet layer, although higher amounts were collected in the traps either side of the thermocline. Material collected was predominantly composed of faecal pellets containing diatom species growing within the platelet layer. The size classes of these pellets suggest they derive from protists grazing rather than from larger metazoans. Sediment trap material was analysed for particulate organic carbon/nitrogen/phosphorus (POC/PON/POP) and ?¹³CPOC (carbon isotopic composition of POC). These were compared with organic matter in the overlying platelet layer and the water column. In turn, the biogeochemistry of the platelet layer and water column was investigated and the organic matter characteristics related to inorganic nutrients (nitrate, nitrite, ammonium, silicate, phosphate), dissolved organic carbon/nitrogen (DOC/DON), pH, dissolved inorganic carbon (DIC), oxygen and ?¹³CDIC (carbon isotopic composition dissolved inorganic carbon). |
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Springer-Verlag |
Place of Publication |
Heidelberg |
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0722-4060 |
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Call Number |
refbase @ admin @ Thomas++2001_2 |
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762 |
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Author |
Thomas, D.N.; Lara, R.J.; Eicken, H.; Kattner, G.; Skoog, A. |
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Title |
Dissolved organic matter in Arctic multi-year sea ice during winter: major components and relationship to ice characteristics |
Type |
Journal Article |
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Year |
1995 |
Publication |
Polar Biology |
Abbreviated Journal |
Polar Biol |
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Volume |
15 |
Issue |
6 |
Pages |
447-483 |
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Keywords |
sea ice; Arctic; Dom |
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Abstract |
Ice cores were collected between 10.03.93 and 15.03.93 along a 200 m profile on a large ice floe in Fram Strait. The ice was typical of Arctic multi-year ice, having a mean thickness along the profile of 2.56 ±0.53 m. It consisted mostly of columnar ice (83%) grown through congelation of seawater at the ice bottom, and the salinity profiles were characterized by a linear increase from 0 psu at the top to values ranging between 3 and 5 psu at depth. Distributions of dissolved organic carbon (DOC) and nitrogen (DON) and major nutrients were compared with ice texture, salinity and chlorophyll a. DOC, DON, dissolved inorganic nitrogen (DIN), NH?? and NO?? were present in concentrations in excess of that predicted by dilution curves derived from Arctic surface water values. Only NO?? was depleted, although not exhausted. High DOC and DON values in conjunction with high NH?? levels indicated that a significant proportion of the dissolved organic matter (DOM) was a result of decomposition/grazing of ice algae and/or detritus. The combination of high NH?? and NO?? points to regeneration of nitrogen compounds. There was no significant correlation between DOC and Chl a in contrast to DON, which had a positively significant correlation with both salinity and Chl a, and the distribution of DOM in the cores might best be described as a combination of both physical and biological processes. There was no correlation between DOC and DON suggesting an uncoupling of DOC and DON dynamics in multi year ice. |
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Springer-Verlag |
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Heidelberg |
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0722-4060 |
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Notes |
D |
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Call Number |
refbase @ admin @ Thomas++1995 |
Serial |
763 |
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Author |
Thomas, D.N.; Mock, T. |
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Title |
Life in frozen veins – coping with the cold |
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Journal Article |
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Year |
2005 |
Publication |
The Biochemist |
Abbreviated Journal |
Biochemist |
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Volume |
27 |
Issue |
1 |
Pages |
12-16 |
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Keywords |
adaptation; Antarctic; Arctic; low temperature; micro-organism; sea ice |
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Abstract |
Every autumn a fundamental transition occurs in the surface waters of Polar Oceans. The surface waters of millions of square kilometres freeze to form an ice layer that varies from a few centimetres through to several metres thick, and which effectively separates the ocean from the atmosphere above. Ice made from seawater is a porous, semi-solid matrix permeated by a labyrinth of brine channels and pores, and within these a diverse microbial assemblage, including viruses, archaea, bacteria, flagellates and unicellular algae can thrive. These assemblages can reach such high abundances that the ice becomes a rich coffee colour. The microbial assemblages are in turn a rich food source for grazing proto- and zooplankton, especially in winter when food in the water column is scarce. |
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Biochemical Society |
Place of Publication |
London |
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no |
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Call Number |
refbase @ admin @ Thomas+Mock2005 |
Serial |
765 |
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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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Notes |
Marine |
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no |
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Call Number |
refbase @ admin @ Weykam++1997 |
Serial |
767 |
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