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  • 2015-2019  (28)
  • 2010-2014  (35)
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  • 1
    Keywords: Hochschulschrift
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (102 Blatt = 7 MB) , Illustrationen, Diagramme, Karten
    Language: English
    Note: Zusammenfassung in deutscher und englischer Sprache
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  • 2
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    PANGAEA
    In:  Supplement to: Fadeev, Eduard; Salter, Ian; Schourup-Kristensen, Vibe; Nöthig, Eva-Maria; Metfies, Katja; Engel, Anja; Piontek, Judith; Boetius, Antje; Bienhold, Christina (2018): Microbial Communities in the East and West Fram Strait During Sea Ice Melting Season. Frontiers in Marine Science, 5, https://doi.org/10.3389/fmars.2018.00429
    Publication Date: 2023-01-28
    Description: Here we present a comparative study of polar summer microbial communities in the ice-free (eastern) and ice-covered (western) hydrographic regimes at the LTER HAUSGARTEN in Fram Strait, the main gateway between the Arctic and North Atlantic Oceans. Based on measured and modeled biogeochemical parameters, we tentatively identified two different ecosystem states (i.e., different phytoplankton bloom stages) in the distinct regions. Using Illumina tag-sequencing, we determined the community composition of both free-living and particle-associated bacteria as well as microbial eukaryotes in the photic layer.
    Keywords: ARK-XXVIII/2; Bacteria; Bacterial production; Bacterial production, standard deviation; CTD/Rosette; CTD-RO; Date/Time of event; DEPTH, water; Event label; HG_I; HG_IX; HGIV; Latitude of event; Longitude of event; N4; North Greenland Sea; Polarstern; PS85; PS85/411-2; PS85/424-1; PS85/426-1; PS85/429-1; PS85/437-1; PS85/444-1; PS85/455-2; PS85/460-1; PS85/465-1; PS85/469-1; PS85/470-1; PS85/473-6; PS85/482-1
    Type: Dataset
    Format: text/tab-separated-values, 222 data points
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  • 3
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    PANGAEA
    In:  Supplement to: Nöthig, Eva-Maria; Bracher, Astrid; Engel, Anja; Metfies, Katja; Niehoff, Barbara; Peeken, Ilka; Bauerfeind, Eduard; Cherkasheva, Alexandra; Gäbler-Schwarz, Stefanie; Hardge, Kristin; Kilias, Estelle; Kraft, Angelina; Mebrahtom Kidane, Yohannes; Lalande, Catherine; Piontek, Judith; Thomisch, Karolin; Wurst, Mascha (2015): Summertime plankton ecology in Fram Strait—a compilation of long- and short-term observations. Polar Research, 34, 18 pp, https://doi.org/10.3402/polar.v34.23349
    Publication Date: 2023-06-21
    Description: Between Greenland and Spitsbergen, Fram Strait is a region where cold ice-covered Polar Water exits the Arctic Ocean with the East Greenland Current (EGC) and warm Atlantic Water enters the Arctic Ocean with the West Spitsbergen Current (WSC). In this compilation, we present two different data sets from plankton ecological observations in Fram Strait: (1) long-term measurements of satellite-derived (1998-2012) and in situ chlorophyll a (chl a) measurements (mainly summer cruises, 1991-2012) plus protist compositions (a station in WSC, eight summer cruises, 1998-2011); and (2) short-term measurements of a multidisciplinary approach that includes traditional plankton investigations, remote sensing, zooplankton, microbiological and molecular studies, and biogeochemical analyses carried out during two expeditions in June/July in the years 2010 and 2011. Both summer satellite-derived and in situ chl a concentrations showed slight trends towards higher values in the WSC since 1998 and 1991, respectively. In contrast, no trends were visible in the EGC. The protist composition in the WSC showed differences for the summer months: a dominance of diatoms was replaced by a dominance of Phaeocystis pouchetii and other small pico- and nanoplankton species. The observed differences in eastern Fram Strait were partially due to a warm anomaly in the WSC. Although changes associated with warmer water temperatures were observed, further long-term investigations are needed to distinguish between natural variability and climate change in Fram Strait. Results of two summer studies in 2010 and 2011 revealed the variability in plankton ecology in Fram Strait.
    Keywords: AWI_BioOce; Biological Oceanography @ AWI
    Type: Dataset
    Format: application/zip, 24 datasets
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  • 4
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    PANGAEA
    In:  Supplement to: Piontek, Judith; Lunau, Mirko; Händel, Nicole; Borchard, Corinna; Wurst, Mascha; Engel, Anja (2010): Acidification increases microbial polysaccharide degradation in the ocean. Biogeosciences, 7(5), 1615-1625, https://doi.org/10.5194/bg-7-1615-2010
    Publication Date: 2023-11-15
    Description: With the accumulation of anthropogenic carbon dioxide (CO2), a proceeding decline in seawater pH has been induced that is referred to as ocean acidification. The ocean's capacity for CO2 storage is strongly affected by biological processes, whose feedback potential is difficult to evaluate. The main source of CO2 in the ocean is the decomposition and subsequent respiration of organic molecules by heterotrophic bacteria. However, very little is known about potential effects of ocean acidification on bacterial degradation activity. This study reveals that the degradation of polysaccharides, a major component of marine organic matter, by bacterial extracellular enzymes was significantly accelerated during experimental simulation of ocean acidification. Results were obtained from pH perturbation experiments, where rates of extracellular alpha- and beta-glucosidase were measured and the loss of neutral and acidic sugars from phytoplankton-derived polysaccharides was determined. Our study suggests that a faster bacterial turnover of polysaccharides at lowered ocean pH has the potential to reduce carbon export and to enhance the respiratory CO2 production in the future ocean.
    Keywords: alpha-glucosidase activity per cell; Bacteria; Bacteria, abundance, standard deviation; beta-glucosidase activity per cell; Carbon, organic, particulate; Carbon, organic, particulate, standard deviation; Cell-specific glucosidase activity; Cell-specific glucosidase activity, standard deviation; Combined glucose loss; Combined glucose loss, standard deviation; Element analyser CNS, EURO EA; EPOCA; European Project on Ocean Acidification; Experimental treatment; FACSCalibur flow-cytometer (Becton Dickinson); High Performance anion-exchange chromatography; Light:Dark cycle; Measured; Particulate organic carbon loss; Particulate organic carbon loss, standard deviation; pH; Polysacchrides loss; Polysacchrides loss, standard deviation; Radiation, photosynthetically active; Sample ID; see reference(s); Temperature, water; Time, incubation; WTW 340i pH-analyzer and WTW SenTix 81-electrode
    Type: Dataset
    Format: text/tab-separated-values, 452 data points
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  • 5
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    PANGAEA
    In:  GEOMAR - Helmholtz Centre for Ocean Research Kiel | Supplement to: Engel, Anja; Piontek, Judith; Grossart, Hans-Peter; Riebesell, Ulf; Schulz, Kai Georg; Sperling, Martin (2014): Impact of CO2 enrichment on organic matter dynamics during nutrient induced coastal phytoplankton blooms. Journal of Plankton Research, 36(3), 641-657, https://doi.org/10.1093/plankt/fbt125
    Publication Date: 2024-02-01
    Description: A mesocosm experiment was conducted to investigate the impact of rising fCO2 on the build-up and decline of organic matter during coastal phytoplankton blooms. Five mesocosms (~38 m³ each) were deployed in the Baltic Sea during spring (2009) and enriched with CO2 to yield a gradient of 355-862 µatm. Mesocosms were nutrient fertilized initially to induce phytoplankton bloom development. Changes in particulate and dissolved organic matter concentrations, including dissolved high-molecular weight (〉1 kDa) combined carbohydrates, dissolved free and combined amino acids as well as transparent exopolymer particles (TEP), were monitored over 21 days together with bacterial abundance, and hydrolytic extracellular enzyme activities. Overall, organic matter followed well-known bloom dynamics in all CO2 treatments alike. At high fCO2, higher dPOC:dPON during bloom rise, and higher TEP concentrations during bloom peak, suggested preferential accumulation of carbon-rich components. TEP concentration at bloom peak was significantly related to subsequent sedimentation of particulate organic matter. Bacterial abundance increased during the bloom and was highest at high fCO2. We conclude that increasing fCO2 supports production and exudation of carbon-rich components, enhancing particle aggregation and settling, but also providing substrate and attachment sites for bacteria. More labile organic carbon and higher bacterial abundance can increase rates of oxygen consumption and may intensify the already high risk of oxygen depletion in coastal seas in the future.
    Keywords: BIOACID; Biological Impacts of Ocean Acidification; SOPRAN; Surface Ocean Processes in the Anthropocene
    Type: Dataset
    Format: application/zip, 2 datasets
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  • 6
    Publication Date: 2024-03-15
    Keywords: 19-Butanoyloxyfucoxanthin; 1-Iodoethane; 1-Iodopropane; 2-Iodopropane; Algae, biomass as carbon; Algae, fatty acids; Algae abundance; Alkaline phosphatase; Alkalinity, Gran titration (Gran, 1950); Alkalinity, total; Alloxanthin; alpha-Carotene, beta,epsilon-Carotene; Ammonium; Aphanizophyll; Aragonite saturation state; Arctic; Bacteria; Bacteria, biomass as carbon; Bacteria, fatty acids; Bacteria, high DNA fluorescence; Bacteria, low DNA fluorescence; Bacterial/community respiration, oxygen, ratio; Bacterial biomass production of carbon; Bacterial biomass production of carbon, standard deviation; Bacterial production; Bacterial production, standard deviation; beta-Carotene, beta,beta-Carotene; Bicarbonate ion; BIOACID; Biogenic silica; Biological Impacts of Ocean Acidification; Biomass/Abundance/Elemental composition; Bromochloromethane; Bromoiodomethane; Calanus finmarchicus, δ13C; Calcite saturation state; Calculated; Calculated from linear regression; Calculated using CO2SYS; Calculated using seacarb after Nisumaa et al. (2010); Carbon, inorganic, dissolved; Carbon, inorganic, particulate; Carbon, organic, dissolved; Carbon, organic, particulate; Carbon, total, particulate; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Carbon dioxide, flux per mesocosm; Chloroiodomethane; Chlorophyll a; Chlorophyll a, areal concentration; Chlorophyll b; Chlorophyll c1+c2; Chlorophyll c3; Chlorophytes; Cirripedia, larvae, δ13C; Coast and continental shelf; Community composition and diversity; Coulometry; Cryptophytes; Cyanobacteria, biomass per area; DATE/TIME; delta 13C labeling method; Diadinoxanthin; Diatoxanthin; Dibromochloromethane; Dibromomethane; Diiodomethane; Dimethyl sulfide, dissolved; Dimethylsulfoniopropionate; Entire community; EPOCA; EUR-OCEANS; European network of excellence for Ocean Ecosystems Analysis; European Project on Ocean Acidification; Exudation as determined by 14C DOC production; Exudation as determined by 14C DOC production, standard deviation; Field experiment; Flow cytometry; Fucoxanthin; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Gas chromatography - Mass spectrometry (GC-MS); GC-PFPD; Gross community production of oxygen; Hand-operated CTD (Sea&Sun Technology, CTD 60M); High Performance Liquid Chromatography (HPLC); Identification; Iodomethane; Kongsfjorden-mesocosm; MESO; Mesocosm experiment; Mesocosm or benthocosm; Myxoxanthophyll; Nanoplankton; Neoxanthin; Net community production, standard deviation; Net community production of carbon dioxide; Net community production of oxygen; Nitrate; Nitrite; Nitrogen, organic, dissolved; Nitrogen, organic, particulate; Nitrous oxide; OA-ICC; Ocean Acidification International Coordination Centre; Other metabolic rates; Oxygen; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Pelagos; Peridinin; pH; Phosphate; Phosphorus, organic, dissolved; Phosphorus, organic, particulate; Phytoplankton, biomass per area; Picophytoplankton; Polar; Prasinoxanthin; Primary production/Photosynthesis; Primary production of POC as determined by 14C POC production; Primary production of POC as determined by 14C POC production, standard deviation; Pulsed flame photometric detector - gas chromatography; Respiration; Respiration, oxygen, bacterial; Respiration, oxygen, bacterial, standard error; Respiration, oxygen, community; Respiration, oxygen, community, standard error; Salinity; Sample comment; Sigmas; Silicon; Svalbard; Temperature, water; Thymidine incorporation; Time, incubation; Transfer velocity, carbon dioxide; Transfer velocity, dimethyl sulfide; Transfer velocity, nitrous oxide; Tribromomethane; Turbidity (Formazin Turbidity Unit); Violaxanthin; Viral abundance; Virus/bacteria ratio; Viruses; Water content of mesocosm; Zeaxanthin; Δδ13C; δ13C, algae; δ13C, bacteria; δ13C, dissolved inorganic carbon; δ13C, dissolved organic carbon; δ13C, particulate organic carbon
    Type: Dataset
    Format: text/tab-separated-values, 35076 data points
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  • 7
    Publication Date: 2020-06-18
    Description: Transparent exopolymer particles (TEP) are a class of marine gel particles and important links between surface ocean biology and atmospheric processes. Derived from marine microorganisms, these particles can facilitate the biological pumping of carbon dioxide to the deep sea, or act as cloud condensation and ice nucleation particles in the atmosphere. Yet, environmental controls on TEP abundance in the ocean are poorly known. Here, we investigated some of these controls during the first multiyear time-series on TEP abundance for the Fram Strait, the Atlantic gateway to the Central Arctic Ocean. Data collected at the Long-Term Ecological Research observatory HAUSGARTEN during 2009 to 2014 indicate a strong biological control with highest abundance co-occurring with the prymnesiophyte Phaeocystis pouchetii. Higher occurrence of P. pouchetii in the Arctic Ocean has previously been related to northward advection of warmer Atlantic waters, which is expected to increase in the future. Our study highlights the role of plankton key species in driving climate relevant processes; thus, changes in plankton distribution need to be accounted for when estimating the ocean’s biogeochemical response to global change.
    Type: Article , PeerReviewed
    Format: text
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  • 8
    Publication Date: 2020-06-18
    Description: In marine oxygen (O2) minimum zones (OMZs), the transfer of particulate organic carbon (POC) to depth via the biological carbon pump might be enhanced as a result of slower remineralisation under lower dissolved O2 concentrations (DO). In parallel, nitrogen (N) loss to the atmosphere through microbial processes, such as denitrification and anammox, is directly linked to particulate nitrogen (PN) export. However it is unclear (1) whether DO is the only factor that potentially enhances POC transfer in OMZs, and (2) if particle fluxes are sufficient to support observed N loss rates. We performed a degradation experiment on sinking particles collected from the Baltic Sea, where anoxic zones are observed. Sinking material was harvested using surface-tethered sediment traps and subsequently incubated in darkness at different DO levels, including severe suboxia (〈0.5 mg l−1 DO). Our results show that DO plays a role in regulating POC and PN degradation rates. POC(PN) degradation was reduced by approximately 100% from the high to low DO to the lowest DO. The amount of NH4+ produced from the pool of remineralising organic N matched estimations of NH4+ anammox requirements during our experiment. This anammox was likely fueled by DON degradation rather than PON degradation.
    Type: Article , PeerReviewed
    Format: text
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  • 9
    Publication Date: 2021-02-08
    Description: Climate models project that the Arctic Ocean may experience ice-free summers by the second half of this century. This may have severe repercussions on phytoplankton bloom dynamics and the associated cycling of carbon in surface waters. We currently lack baseline knowledge of the seasonal dynamics of Arctic microbial communities, which is needed in order to better estimate the effects of such changes on ecosystem functioning. Here we present a comparative study of polar summer microbial communities in the ice-free (eastern) and ice-covered (western) hydrographic regimes at the LTER HAUSGARTEN in Fram Strait, the main gateway between the Arctic and North Atlantic Oceans. Based on measured and modeled biogeochemical parameters, we tentatively identified two different ecosystem states (i.e., different phytoplankton bloom stages) in the distinct regions. Using Illumina tag-sequencing, we determined the community composition of both free-living and particle-associated bacteria as well as microbial eukaryotes in the photic layer. Despite substantial horizontal mixing by eddies in Fram Strait, pelagic microbial communities showed distinct differences between the two regimes, with a proposed early spring (pre-bloom) community in the ice-covered western regime (with higher representation of SAR11, SAR202, SAR406 and eukaryotic MALVs) and a community indicative of late summer conditions (post-bloom) in the ice-free eastern regime (with higher representation of Flavobacteria, Gammaproteobacteria and eukaryotic heterotrophs). Co-occurrence networks revealed specific taxon-taxon associations between bacterial and eukaryotic taxa in the two regions. Our results suggest that the predicted changes in sea ice cover and phytoplankton bloom dynamics will have a strong impact on bacterial community dynamics and potentially on biogeochemical cycles in this region.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
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  • 10
    Publication Date: 2021-02-08
    Description: Sea-ice ecosystems are among the most extensive of Earth’s habitats; yet its autotrophic and heterotrophic activities remain poorly constrained. We employed the in situ aquatic eddy-covariance (AEC) O2 flux method and laboratory incubation techniques (H14CO3−, [3H] thymidine and [3H] leucine) to assess productivity in Arctic sea-ice using different methods, in conditions ranging from land-fast ice during winter, to pack ice within the central Arctic Ocean during summer. Laboratory tracer measurements resolved rates of bacterial C demand of 0.003–0.166 mmol C m−2 day−1 and primary productivity rates of 0.008–0.125 mmol C m−2 day−1 for the different ice floes. Pack ice in the central Arctic Ocean was overall net autotrophic (0.002–0.063 mmol C m−2 day−1), whereas winter land-fast ice was net heterotrophic (− 0.155 mmol C m−2 day−1). AEC measurements resolved an uptake of O2 by the bottom-ice environment, from ~ − 2 mmol O2 m−2 day−1 under winter land-fast ice to~ − 6 mmol O2 m−2 day−1 under summer pack ice. Flux of O2-deplete meltwater and changes in water flow velocity masked potential biological-mediated activity. AEC estimates of primary productivity were only possible at one study location. Here, productivity rates of 1.3 ± 0.9 mmol O2 m−2 day−1, much larger than concurrent laboratory tracer estimates (0.03 mmol C m−2 day−1), indicate that ice algal production and its importance within the marine Arctic could be underestimated using traditional approaches. Given careful flux interpretation and with further development, the AEC technique represents a promising new tool for assessing oxygen dynamics and sea-ice productivity in ice-covered regions.
    Type: Article , PeerReviewed
    Format: text
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