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Author |
Raike, A.; Kortelainen, P.; Mattsson, T.; Thomas, D.N. |
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Title |
36 year trends in dissolved organic carbon export from Finnish rivers to the Baltic Sea |
Type |
Journal Article |
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Year |
2012 |
Publication |
The Science of the Total Environment |
Abbreviated Journal |
Sci Total Environ |
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Volume  |
435-436 |
Issue |
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Pages |
188-201 |
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Keywords |
Baltic States; Carbon/*chemistry; Finland; Hydrology; Oceans and Seas; Rivers/*chemistry; Seasons; Soil/chemistry |
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Abstract |
Increasing dissolved organic carbon (DOC) concentrations in lakes, rivers and streams in northern mid latitudes have been widely reported during the last two decades, but relatively few studies have dealt with trends in DOC export. We studied the export of DOC from Finnish rivers to the Baltic Sea between 1975 and 2010, and estimated trends in DOC fluxes (both flow normalised and non-normalised). The study encompassed the whole Finnish Baltic Sea catchment area (301,000 km(2)) covering major land use patterns in the boreal zone. Finnish rivers exported annually over 900,000 t DOC to the Baltic Sea, and the mean area specific export was 3.5 t km(-2). The highest export (7.3t km(-2)) was measured in peat dominated catchments, whereas catchments rich in lakes had the lowest export (2.2 t km(-2)). Inter-annual variation in DOC export was high and controlled mainly by hydrology. There was no overall trend in the annual water flow, although winter flow increased in northern Finland over 36 years. Despite the numerous studies showing increases in DOC concentrations in streams and rivers in the northern hemisphere, we could not find any evidence of increases in DOC export to the northern Baltic Sea from Finnish catchments since 1975. |
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Address |
Finnish Environment Institute (SYKE), P.O. Box 140, FI-00251, Helsinki, Finland. antti.raike@ymparisto.fi |
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English |
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ISSN |
0048-9697 |
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Notes |
PMID:22854090 |
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Call Number |
refbase @ user @ |
Serial |
12986 |
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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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ISSN |
0036-8075 |
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Review |
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no |
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Call Number |
refbase @ admin @ Thomas+Dieckmann2002_2 |
Serial |
759 |
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Author |
Kattner, G.; Thomas, D.N.; Haas, C.; Kennedy, H.; Dieckmann, G.S. |
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Title |
Surface ice and gap layers in Antarctic sea ice: highly productive habitats |
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Journal Article |
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Year |
2004 |
Publication |
Marine Ecology Progress Series |
Abbreviated Journal |
Mar Ecol Prog Ser |
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Volume |
277 |
Issue |
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Pages |
1-12 |
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Keywords |
Antarctic sea ice; Gap layers; Biogeochemistry; Particulate organic matter; Dissolved organic matter; Chlorophyll a; Nutrients |
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Abstract |
Biogeochemical investigations of the upper layers of sea ice were made on layered summer ice floes collected from the Weddell Sea, Antarctica, from mid-February to March 1997. The surface layers had a clearly defined bottom layer immediately overlying a gap filled with seawater. Generally the gap covered rotten sea ice below. Using differences in algal biomass, mostly in the bottom layer of the surface ice overlying the gap, the floes were classified as low, moderate or high biomass. In addition, a floe with a re-frozen gap layer was studied. In the floes with the highest biomass, particulate organic carbon (POC) and nitrogen (PON) reached concentrations of up to 6000 µMC and 600 µMN in the bottom layer. In the upper part of the surface ice layer and the gap water, particulate and dissolved organic matter concentrations (POM, DOM) were clearly lower. High concentrations of POM were generally accompanied by high values of DOM although POM values generally exceeded DOM. All C and N contents of organic matter were significantly correlated. In gap waters, POM was low but still clearly higher than in the surrounding seawater, whereas DOM was in the range of seawater concentrations. Most POC/PON and C/chlorophyll a ratios pointed to an actively growing algae community, whereas the higher and more variable DOC/DON ratios reflected the various sources influencing DOM composition. Nitrate and silicate closely followed the signature of salinity, reaching in some gap water samples values similar to seawater concentrations. In some samples, in particular from the upper part of the surface ice layer, nitrate was totally exhausted. The distribution of the regenerated nutrients ammonium and phosphate was totally different from that of nitrate and silicate, reaching values of up to 15.9 and 9.08 µM, respectively. The bottom ice layer of the floe with the re-frozen gap layer had a high biomass similar to that of the high-biomass ice floe. DOC concentrations were lower, and DON maximum was not clearly linked with DOC maximum, but instead was associated with high ammonium and phosphate concentrations. The significant correlations between POM and DOM as well as between nitrate and silicate and between the regenerated nutrients ammonium and phosphate indicate that the gap-layer floes are semi-enclosed, highly productive habitats that still maintain high biomass during freezing. They are ubiquitous in the Antarctic pack-ice zone and important features that support high algae standing stocks. |
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Publisher |
Inter-Research |
Place of Publication |
Oldendorf/Luhe |
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ISSN |
0171-8630 |
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no |
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Call Number |
refbase @ admin @ Kattner++2004 |
Serial |
745 |
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Author |
Kennedy, H.; Thomas, D.N.; Kattner, G.; Haas, C.; Dieckmann, G.S. |
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Title |
Particulate organic matter in Antarctic summer sea ice: concentration and stable isotopic composition |
Type |
Journal Article |
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Year |
2002 |
Publication |
Marine Ecology Progress Series |
Abbreviated Journal |
Mar Ecol Prog Ser |
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Volume |
238 |
Issue |
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Pages |
1-13 |
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Keywords |
Pom; Anarctic sea ice; ice microalgae; carbon isotopic composition |
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Abstract |
The chemical and isotopic data from sea ice collected over a wide area of the Weddell Sea, Antarctica, during the austral summer/early autumn illustrate the range of environmental conditions under which ice algae grow. A range of ice types and features were sampled including intact and layered ice floes and surface ponds. Sea ice communities were found in all these environments but the highest biomasses were found either at the base of ice floes, or in the interior of layered floes with quasi-continuous horizontal gaps at or shortly below the water level. In the layered floes, particulate organic carbon (POC) measured in the ice layer immediately overlying the gap water (280 to 6014 µmol dm?³) was in excess of what would be predicted if algal growth had occurred in a closed environment. The chemical composition of the gap water was strongly affected by biological activity in the overlying ice, which acts as a physical support for the algae retained within its matrix. The lowest range of POC (27 to 739 µmol dm?³) conformed to predictions of algal growth in a closed system and samples were collected from the interior of ice floes where there was essentially no potential for nutrient exchange. The surface ponds displayed nitrate (NO³?) exhaustion and total dissolved inorganic carbon (?CO?) reductions consistent with nutrient limited algal growth. The stable carbon isotopic composition of the particulate organic matter (POM) across all habitat types sampled (?¹³CPOC -10.0 to -27.3?) displayed a wide range but was much less variable than the range of POC concentrations might have implied. The assumption that the highest biomass of algae in sea ice will result in the most positive ?¹³CPOC values cannot be generally applied. The isotopic composition of dissolved inorganic carbon (?¹³C?CO?) in gap waters and surface ponds varied from 0.15 to 3.0? and was shown to be commensurate with the changes predicted from NO³? deficits caused by algal growth. |
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Publisher |
Inter-Research |
Place of Publication |
Oldendorf/Luhe |
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ISSN |
0171-8630 |
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Notes |
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no |
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Call Number |
refbase @ admin @ Kennedy++2002 |
Serial |
746 |
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Author |
Gleitz, M.; Thomas, D.N. |
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Title |
Variation in phytoplankton standing stock, chemical composition and physiology during sea-ice formation in the southeastern Weddell Sea, Antarctica |
Type |
Journal Article |
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Year |
1993 |
Publication |
Journal of Experimental Marine Biology and Ecology |
Abbreviated Journal |
J Exp Mar Biol Ecol |
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Volume |
173 |
Issue |
2 |
Pages |
211-230 |
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Keywords |
Antarctic; ecophysiology; ice algae; phytoplankton; primary production; sea-ice formation; biochemical composition; plant physiology; Psw; Weddell Sea; population number; sea ice; algae; standing crop |
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Abstract |
Changes in physico-chemical conditions, phytoplankton biomass, biochemical composition and primary productivity were investigated during autumnal sea-ice formation in the southeastern Weddell Sea, Antarctica. During sea-ice growth, brine salinities gradually increased with decreasing temperature. Nutrient concentrations in the brine of sea ice older than 2 weeks were lower than calculated from initial surface seawater values. The concomittant accumulation of phytoplankton biomass could not be explained solely by physical enrichment. We suggest that several microalgal species retained the capacity to assimilate nutrients and continued to grow in newly formed sea ice. However, nutrient depletions were moderate, and biochemical analyses did not indicate nutrient stress of algal metabolism. Relative abundance of smaller diatom species increased during ice growth, suggesting that pore space available for colonization in conjunction with physiological acclimation capacity were major factors determining successional patterns in recently formed sea ice. Even though ice algal assemblages apparently sustained the capacity to acclimate to reduced irradiances brought about by ice growth and increasing snow cover, maximum primary production was considerably lower than values usually reported from spring and summer ice communities. Therefore, autumnal primary production in newly formed sea ice may not add greatly to total annual production, but may provide an important food source for ice-associated grazers during the winter period, when phytoplankton biomass in the water column is extremely low. |
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Publisher |
Elsevier Science B.V. |
Place of Publication |
Amsterdam |
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ISSN |
0022-0981 |
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Call Number |
refbase @ admin @ Gleitz+Thomas1993 |
Serial |
734 |
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