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Author |
Gomez, I.; Thomas, D.N.; Wiencke, C. |
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Title |
Longitudinal profiles of growth, photosynthesis and light independent carbon fixation in the Antarctic brown alga Ascoseira mirabilis |
Type |
Journal Article |
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Year |
1995 |
Publication |
Botanica Marina |
Abbreviated Journal |
Bot Mar |
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Volume |
38 |
Issue |
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Pages |
157-164 |
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Abstract |
Thallus growth, photoynthetic oxygen evolution and rates of carbon fixation were determinedalong the lamina of the endemic Antarctic brown alga Ascoseira mirabilis (Ascoseirales), grown under simulated Antarctic condtions. The meristem is basally located and forms new blade tiddue under spring-conditions. Light saturated net photosynthesis (P,ax), measures as O? production, was higher in ther intermediate region of the plant (9..8 µmol O? g?¹ fw h?¹). In general, photosynthetic parameters such as dark respiration, gross photosynthesis, photosynthetic efficiency (?) and photosynthetic light compensation (Ic) increased significantly towards the distal region. Carbon-fixation in A. mirabilis also showed thllus-dependent variation. Rates of light and light independent (dark) carbon fixation increased towards the distal regions ranging between 7.6-9.5 and 1.2-2.0 µmol C g?¹ fw h?¹ respectively. The percentage of light independent carbon fixation (in relation to light ¹?C-fixation) also increased from the basal to the distal parts reaching 24% in the distal region of the thallus. he contents of Chl a and Chl c, were close to 0.37 and 0.14 mg g?¹ fw respectively and were notably uniform along the lamina. The results indicate that the formation of the blade by a basal meristem and the increase of light carbon fixation rates from base to the distal regions in A. mirabilis are similar compared with certain Laminariales, especially members of the genus Laminaria. However, light independent carbon fixation is highest in the meristem of Laminaria, opposite to the results obtained here for A. mirabilis |
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de Gruyter |
Place of Publication |
Berlin, New York |
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Call Number |
refbase @ admin @ Gomez++1995 |
Serial |
736 |
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Author |
Krell, A.; Ummenhofer, C.; Kattner, G.; Naumov, A.; Evans, D.; Dieckmann, G.S.; Thomas, D.N. |
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Title |
The biology and chemistry of land fast ice in the White Sea, Russia – A comparison of winter and spring conditions |
Type |
Journal Article |
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Year |
2003 |
Publication |
Polar Biology |
Abbreviated Journal |
Polar Biol |
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Volume |
26 |
Issue |
11 |
Pages |
707-719 |
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Abstract |
Various abiotic and biotic parameters, including phytoplankton distribution, were studied to investigate seasonal changes within the fast-ice cover in Chupa Inlet, a freshwater-influenced Arctic-like fjord in Kandalaksha Bay (White Sea). Sea ice and under-ice water were collected along transects in the inlet in February and April 2002. Ice-texture analysis, salinity and δ18O values indicated that the complete ice sheet had transformed within 2 months. This resulted from an upward growth of snow ice and subsequent melting at the underside of the ice, which makes a comparison between the two sampling periods difficult in terms of defining temporal developments within the ice. Nutrients, DOC and DON concentrations in the under-ice water were typical for Russian Arctic rivers. Concentrations of nitrate, silicate and DOC in the ice were lower, which is attributed to a loss as the ice forms. The concentrations were also modified by biological activity. In February, there was a strong correspondence between the distribution of biological parameters, including particulate and dissolved organic carbon and nitrogen (POC and PON, DOC and DON) and inorganic nutrients (nitrate, nitrite, phosphate and silicate), which was not the case in April. The correlation between both DOC and DON with ammonium indicates heterotrophic activity within the winter ice collected in February. Sea-ice organisms were distributed throughout the ice, and several assemblages were found in surface layers of the ice. In April, a more typical distribution of biomass in the ice was measured, with low values in the upper part and high algal concentrations in the lower sections of the ice, characteristic of a spring ice-algal bloom. In contrast to the February sampling, there was evidence that the ice-algal assemblage in April was nitrogen-limited, with total inorganic nitrogen concentrations being <1 µ mand a mean inorganic nitrogen to phosphorus ratio of 2.8. The ice assemblages were dominated by diatoms (in particular, Nitzschia spp.). There were temporal shifts in the assemblage composition: in February, diatoms accounted for 40% and in April for >98% of all organisms counted. |
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Springer-Verlag |
Place of Publication |
Heidelberg |
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0722-4060 |
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Call Number |
refbase @ user @ Krell++2003 |
Serial |
290 |
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Author |
Gleitz, M.; Rutgers v d Loeff, M.; Thomas, D.N.; Dieckmann, G.S.; Millero, F.J. |
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Title |
Comparison of summer and winter inorganic carbon, oxygen and nutrient concentrations in Antarctic sea ice brine |
Type |
Journal Article |
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Year |
1995 |
Publication |
Marine Chemistry |
Abbreviated Journal |
Mar Chem |
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Volume |
51 |
Issue |
2 |
Pages |
81-91 |
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Keywords |
dissolved oxygen; inorganic compounds; summer; winter; nutrients (mineral); Antarctic zone; sea ice; brines; carbon; chemical composition; Psw; Weddell Sea; polar zones; polar regions; nutrients |
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Abstract |
During summer (January 1991) and winter (April 1992) cruises to the southern Weddell Sea (Antarctica), brine samples were collected from first year sea ice and analysed for salinity, temperature, dissolved oxygen and major nutrient concentrations. Additionally, the carbonate system was determined from measurements of pH and total alkalinity. During winter, brine chemical composition was largely determined by seawater concentration in the course of freezing. Brine temperatures ranged from -1.9 to -6.7 °C. Precipitation of calcium carbonate was not observed at the corresponding salinity range of 34 to 108. Removal of carbon from the total inorganic carbon pool (up to 500 µmol Ct kg?¹) was related to reduced nutrient concentrations, indicating the presence of photosynthetically active ice algal assemblages in the winter sea ice. However, nutrient and inorganic carbon concentrations did generally not reach growth limiting levels for phytoplankton. The combined effect of photosynthesis and physical concentration resulted in O? concentrations of up to 650 µmol kg?¹. During summer, brine salinities ranged from 21 to 41 with most values >28, showing that the net effect of freezing and melting on brine chemical composition was generally slight. Opposite to the winter situation, brine chemical composition was strongly influenced by biological activity. Photosynthetic carbon assimilation resulted in a Ct depletion of up to 1200 µmol kg?¹, which was associated with CO? (aq) exhaustion and O? concentrations as high as 933 µmol kg?¹. The concurrent depletion of major nutrients generally corresponded to uptake ratios predicted from phytoplankton biochemical composition. Primary productivity in summer sea ice is apparently sustained until inorganic resources are fully exhausted, resulting in brine chemical compositions that differ profoundly from those of surface waters. This may have important implications for pathways of ice algal carbon acquisition, carbon isotope fractionation as well as for species distribution in the open water phytoplankton. |
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Elsevier Science B.V. |
Place of Publication |
Amsterdam |
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0304-4203 |
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no |
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Call Number |
refbase @ admin @ Gleitz++1995 |
Serial |
733 |
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Author |
Dieckmann, G.S.; Eicken, H.; Haas, C.; Garrison, D.L.; Gleitz, M.; Lange, M.; Nöthig, E.-M.; Spindler, M.; Sullivan, C.W.; Thomas, D.N.; Weissenberger, J. |
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Title |
A compilation of data on sea ice algal standing crop from the Bellingshausen, Amundsen and Weddell Seas from 1983 to 1994 |
Type |
Book Chapter |
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Year |
1998 |
Publication |
Antarctic sea ice: Biological processes, interactions and variability |
Abbreviated Journal |
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Pages |
85-92 |
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Keywords |
Algae; Biomass; Ecology; Ice composition; Antarctica; Bellingshausen Sea; Amundsen Sea; Weddell Sea |
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Abstract |
Algal standing stock as chlorophyll a in sea ice was compiled from 448 cores collected during 13 U.S. and German research cruises to Antarctica between 1983 and 1994. The data have a high variability and show no clear relationships with other parameters such as core length. However, seasonal variations in standing stock are discernable. The authors recommend that due to the high variability in the data and inconsistency of sampling methods, the data be used with caution, since they do not represent all sea ice habitats. We provide the data due to the current need for such information for the parameterization of models. |
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American Geophysical Union |
Place of Publication |
Washington, DC |
Editor |
Lizotte, M.P.; Arrigo, K.R. |
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Antarctic Research Series |
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Series Volume |
73 |
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0-87590-901-9 |
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no |
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Call Number |
refbase @ admin @ Dieckmann++1998 |
Serial |
731 |
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Author |
Arrigo, K.R.; Thomas, D.N. |
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Title |
Large scale importance of sea ice biology in the Southern Ocean |
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Journal Article |
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Year |
2004 |
Publication |
Antarctic Science |
Abbreviated Journal |
Antarct Sci |
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Volume |
16 |
Issue |
4 |
Pages |
471-486 |
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Keywords |
algae; Antarctic; biogeochemistry; carbon cycle; primary production; Full Data Records |
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Abstract |
Despite being one of the largest biomes on earth, sea ice ecosystems have only received intensive study over the past 30 years. Sea ice is a unique habitat for assemblages of bacteria, algae, protists, and invertebrates that grow within a matrix dominated by strong gradients in temperature, salinity, nutrients, and UV and visible radiation. A suite of physiological adaptations allow these organisms to thrive in ice, where their enormous biomass makes them a fundamental component of polar ecosystems. Sea ice algae are an important energy and nutritional source for invertebrates such as juvenile krill, accounting for up to 25% of total annual primary production in ice-covered waters. The ability of ice algae to produce large amounts of UV absorbing compounds such as mycosporine-like amino acids makes them even more important to organisms like krill that can incorporate these sunscreens into their own tissues. Furthermore, the nutrient and light conditions in which sea ice algae thrive induce them to synthesize enhanced concentrations of polyunsaturated fatty acids, a vital constituent of the diet of grazing organisms, especially during winter. Finally, sea ice bacteria and algae have become the focus of biotechnology, and are being considered as proxies of possible life forms on ice-covered extraterrestrial systems. An analysis of how the balance between sea ice and pelagic production might change under a warming scenario indicates that when current levels of primary production and changes in the areas of sea ice habitats are taken into account, the expected 25% loss of sea ice over the next century would increase primary production in the Southern Ocean by approximately 10%, resulting in a slight negative feedback on climate warming. |
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Cambridge University Press |
Place of Publication |
Cambridge |
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0954-1020 |
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no |
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Call Number |
refbase @ admin @ Arrigo+Thomas2004 |
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729 |
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