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Author |
Krell, A.; Schnack-Schiel, S.B.; Thomas, D.N.; Kattner, G.; Zipan, W.; Dieckmann, G.S. |
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Title |
Phytoplankton dynamics in relation to hydrography, nutrients and zooplankton at the onset of sea ice formation in the eastern Weddell Sea (Antarctica) |
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Journal Article |
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Year |
2005 |
Publication |
Polar Biology |
Abbreviated Journal |
Polar Biol |
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Volume |
28 |
Issue |
9 |
Pages |
700-713 |
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Keywords  |
Weddell Sea; Asf; Hydrography; Phytoplankton; Seasonal change; Community composition; Primary production; Zooplankton |
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Abstract |
The quantitative and qualitative distribution of phytoplankton was investigated along five North–South transects in the eastern Weddell Sea during the transition from late autumn to winter. Relationships with the regional hydrography, progressing sea ice coverage, nutrient distribution and zooplankton are discussed and compared with data from other seasons. To the north of the Antarctic Slope Front (ASF) a remnant temperature minimum layer was found above the primary pycnocline throughout summer. Surface waters had not entirely acquired typical winter characteristics. While temperature was already in the winter range, this was not the case for salinity. Highest biomass of phytoplankton, with the exception of the first transect, was found in the region adjoining the ASF to the north. Absolute chlorophyll a (Chl a) concentrations dropped from 0.35 to 0.19 µg/1. Nutrient pools exhibited a replenishing tendency. Ammonium concentrations were high (0.75–2 µmol/1), indicating extensive heterotrophic activity. The phytoplankton in the ASF region was dominated by nanoflagellates, particularly Phaeocystis spp.. North of the ASF the abundance of diatoms increased, with Fragilariopsis spp., F. cylindrus and Thalassiosira spp. dominating. Community structure varied both due to hydrographical conditions and the advancing ice edge. The phytoplankton assemblage formed during late autumn were very similar to the ones found in early spring. A POC/PON ratio close to Redfield, decreasing POC concentration and a high phaeophytin/ Chl a ratio, as well as a high abundance of mesozooplankton indicated that a strong grazing pressure was exerted on the phytoplankton community. A comparison between primary production (PP) in the water column and the sea ice showed a shift of the major portion of PP into the ice during the period of investigation. |
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Springer-Verlag |
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Heidelberg |
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0722-4060 |
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Isi:000231421200006 |
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Call Number |
refbase @ admin @ Krell++2005 |
Serial |
747 |
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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 |
Thomas, D.N.; Dieckmann, G.S. (eds) |
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Title |
Sea ice – an introduction to its physics, chemistry, biology and geology |
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Book Whole |
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Year |
2003 |
Publication |
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Keywords |
zoology; sea ice |
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Abstract |
Sea ice, which covers up to 7% of the planets surface, is a major component of the worlds oceans, partly driving ocean circulation and global climate patterns... |
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Blackwell Science Ltd |
Place of Publication |
Oxford |
Editor |
Thomas, D.N.; Dieckmann, G.S. |
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0-632-05808-0 |
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Call Number |
refbase @ user @ Thomas+Dieckmann2003 |
Serial |
845 |
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Author |
Thomas, D.N.; Dieckmann, G.S. (eds) |
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Title |
Sea ice – an introduction to its physics, chemistry, biology and geology |
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Book Whole |
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Year |
2003 |
Publication |
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Keywords |
zoology; sea ice |
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Abstract |
Sea ice, which covers up to 7% of the planets surface, is a major component of the worlds oceans, partly driving ocean circulation and global climate patterns... |
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Publisher |
Blackwell Science Ltd |
Place of Publication |
Oxford |
Editor |
Thomas, D.N.; Dieckmann, G.S. |
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0-632-05808-0 |
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no |
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Call Number |
refbase @ user @ Thomas+Dieckmann2003 |
Serial |
849 |
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Author |
Thomas, D.N.; Dieckmann, G.S. (eds) |
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Title |
Sea ice – an introduction to its physics, chemistry, biology and geology |
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Book Whole |
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Year |
2003 |
Publication |
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Abbreviated Journal |
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Issue |
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Keywords |
zoology; sea ice |
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Abstract |
Sea ice, which covers up to 7% of the planet's surface, is a major component of the world's oceans, partly driving ocean circulation and global climate patterns. It provides a habitat for a rich diversity of marine organisms, and is a valuable source of information in studies of global climate change and the evolution of present day life forms. Increasingly, sea ice is being used as a proxy for extraterrestrial ice covered systems. Sea Ice provides a comprehensive review of our current available knowledge of polar pack ice, the study of which is severely constrained by the logistic difficulties of working in such harsh and remote regions of the earth. The book's editors, Drs Thomas and Dieckmann have drawn together an impressive group of international contributing authors, providing a well-edited and integrated volume, which will stand for many years as the standard work on the subject. Contents of the book include details of the growth, microstructure and properties of sea ice, large-scale variations in thickness and characteristics, its primary production, micro-and macrobiology, sea ice as a habitat for birds and mammals, sea ice biogeochemistry, particulate flux, and the distribution and significance of palaeo sea ice. |
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Publisher |
Blackwell Science Ltd |
Place of Publication |
Oxford |
Editor |
Thomas, D.N.; Dieckmann, G.S. |
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0-632-05808-0 |
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no |
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Call Number |
refbase @ admin @ Thomas+Dieckmann2003 |
Serial |
15290 |
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