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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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no |
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Call Number |
refbase @ admin @ Weykam++1997 |
Serial |
767 |
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Author |
Thomas, D.N.; Dieckmann, G.S. |
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Title |
Antarctic sea ice – a habitat for extremophiles |
Type |
Journal Article |
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Year |
2002 |
Publication |
Science |
Abbreviated Journal |
Science |
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Volume |
295 |
Issue |
5555 |
Pages |
641-644 |
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Keywords |
Microorganisms; Sea ice; Ecosystems; Polar zones; Antarctic zone; Epontic organisms; Sea ice ecology; Antarctic sea ice; Marine microorganisms; Marine ecosystems; Bacteria; Algae; Psychrophilic bacteria; extremophiles; Ps; Antarctica |
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Abstract |
The pack ice of Earth's polar oceans appears to be frozen white desert, devoid of life. However, beneath the snow lies a unique habitat for a group of bacteria and microscopic plants and animals that are encased in an ice matrix at low temperatures and light levels, with the only liquid being pockets of concentrated brines. Survival in these conditions requires a complex suite of physiological and metabolic adaptations, but sea-ice organisms thrive in the ice, and their prolific growth ensures they play a fundamental role in polar ecosystems. Apart from their ecological importance, the bacterial and algae species found in sea ice have become the focus for novel biotechnology, as well as being considered proxies for possible life forms on ice- covered extraterrestrial bodies. |
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American Association for the Advancement of Science |
Place of Publication |
Washington, DC |
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0036-8075 |
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Review |
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no |
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Call Number |
refbase @ admin @ Thomas+Dieckmann2002_2 |
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759 |
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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 |
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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 |
Place of Publication |
Heidelberg |
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ISSN |
0722-4060 |
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D |
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no |
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Call Number |
refbase @ admin @ Thomas++1995 |
Serial |
763 |
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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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ISSN |
0722-4060 |
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no |
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Call Number |
refbase @ admin @ Thomas++2001_2 |
Serial |
762 |
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Author |
Schnack-Schiel, S.B.; Dieckmann, G.S.; Kattner, G.; Thomas, D.N. |
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Title |
Copepods in summer platelet ice in the eastern Weddell Sea, Antarctica |
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Journal Article |
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Year |
2004 |
Publication |
Polar Biology |
Abbreviated Journal |
Polar Biol |
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Volume |
27 |
Issue |
8 |
Pages |
502-506 |
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Abstract |
Copepods in platelet-ice layers underlying fast ice and in the water column below were studied at Drescher Inlet, eastern Weddell Sea in February 1998. Three copepod species were found: Drescheriella glacialis and Paralabidocera antarctica occurred in platelet-ice layers, while Stephos longipes was only present in the water column. The distribution of all species varied considerably between station and depth. D. glacialis dominated the platelet-ice community and occurred at all five platelet-ice sampling sites, except one, with numbers of up to 26 ind. l?¹. In contrast, P. antarctica was only found in low numbers (up to 2 ind. l?¹) at one site. The total copepod abundance in the platelet ice was not associated with algal biomass, although it was strongly correlated with high ammonium concentrations (up to 9 µM) in the interstitial water between the platelets. This is the first indirect evidence to support the hypothesis that zooplankton excretion can partly account for the high ammonium values often found in platelet-ice layers. |
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Springer-Verlag |
Place of Publication |
Heidelberg |
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0722-4060 |
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Notes |
Short note |
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Call Number |
refbase @ admin @ Schnack-Schiel++2004 |
Serial |
752 |
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