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  • 1
    Keywords: Hochschulschrift
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (113 Seiten = 5 MB) , Graphen
    Edition: 2020
    Language: German
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  • 2
    Keywords: Hochschulschrift
    Type of Medium: Online Resource
    Pages: Online-Ressource (191 Seiten = 6 MB) , Illustrationen, Graphen, Karten
    Language: German
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  • 3
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    AMER SOC LIMNOLOGY OCEANOGRAPHY
    In:  EPIC3Limnology and Oceanography, AMER SOC LIMNOLOGY OCEANOGRAPHY, pp. 1-20, ISSN: 0024-3590
    Publication Date: 2020-12-01
    Description: The Arctic Ocean is highly susceptible to climate change as evidenced by rapid warming and the drastic loss of sea ice during summer. The consequences of these environmental changes for the microbial cycling of organic matter are largely unexplored. Here, we investigated the distribution and composition of dissolved organic matter (DOM) along with heterotrophic bacterial activity in seawater and sea ice of the Eurasian Basin at the time of the record ice minimum in 2012. Bacteria in seawater were highly responsive to fresh organic matter and remineralized on average 55% of primary production in the upper mixed layer. Correlation analysis showed that the accumulation of dissolved combined carbohydrates (DCCHO) and dissolved amino acids (DAA), two major components of fresh organic matter, was related to the drawdown of nitrate. Nitrate‐depleted surface waters at stations adjacent to the Laptev Sea showed about 25% higher concentrations of DAA than stations adjacent to the Barents Sea and in the central Arctic basin. Carbohydrate concentration was the best predictor of heterotrophic bacterial activity in sea ice. In contrast, variability in sea‐ice bacterial biomass was largely driven by differences in ice thickness. This decoupling of bacterial biomass and activity may mitigate the negative effects of biomass loss due to ice melting on heterotrophic bacterial functions. Overall, our results reveal that changes in DOM production and inventories induced by sea‐ice loss have a high potential to enhance the bacterial remineralization of organic matter in seawater and sea ice of the Arctic Ocean.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 4
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    AMER SOC LIMNOLOGY OCEANOGRAPHY
    In:  EPIC3Limnology and Oceanography, AMER SOC LIMNOLOGY OCEANOGRAPHY, 60(4), pp. 1392-1410, ISSN: 0024-3590
    Publication Date: 2015-11-16
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 5
    Publication Date: 2015-12-14
    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.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 6
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    WILEY-BLACKWELL PUBLISHING
    In:  EPIC3Journal of Phycology, WILEY-BLACKWELL PUBLISHING, 49(5), pp. 996-1010, ISSN: 0022-3646
    Publication Date: 2019-07-16
    Description: In this study we present the first comprehensive analyses of the diversity and distribution of marine protist (micro- nano- and picoeukaryotes) in the Western Fram Strait, using 454-pyrosequencing and high-pressure liquid chromatography (HPLC) at five stations in summer 2010. Three stations (T1; T5; T7) were influenced by Polar Water, characterized by cold water with lower salinity (〈33) and different extents of ice-concentrations. Atlantic Water influenced the other two stations (T6; T9). While T6 was located in the mixed water zone characterized by cold water with intermediate salinity (~33) and high ice-concentrations, T9 was located in warm water with high salinity (~35) and no ice-coverage at all. General trends in community structure according to prevailing environmental settings, observed with both methods, coincided well. At two stations, T1 and T7, characterized by lower ice concentrations, diatoms (Fragilariopsis sp., Porosira sp., Thalassiosira spp.) dominated the protist community. The third station (T5) was ice-covered, but has been ice-free for ~4 weeks prior to sampling. At this station, dinoflagellates (Dinophyceae 1, Woloszynskia sp. and Gyrodinium sp.) were dominant, reflecting a post-bloom situation. At station T6 and T9, the protist communities consisted mainly of picoeukaryotes, e.g. Micromonas spp. Based on our results, 454-pyrosequencing has proven to be an adequate tool to provide comprehensive information on the composition of protist communities. Furthermore, this study suggests that a snap-shot of a few, but well-chosen samples can already provide an overview of community structure patterns and successions in a dynamic marine environment.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 7
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    WILEY-BLACKWELL PUBLISHING
    In:  EPIC3Journal of Eukaryotic Microbiology, WILEY-BLACKWELL PUBLISHING, ISSN: 1066-5234
    Publication Date: 2019-07-16
    Description: Investigation of marine eukaryotic picoplankton composition is limited by missing morphological features for appropriate identification. Consequently, molecular methods are required. In this study, we used 454-pyrosequencing to study picoplankton communities at four stations in the West Spitsbergen Current (WSC; Fram Strait). High abundances of Micromonas pusilla were detected in the station situated closest to Spitsbergen, as seen in surveys of picoplankton assemblages in the Beaufort Sea. At the other three stations, other phylotypes, affiliating with Phaeocystis pouchetii and Syndiniales in the phylogenetic tree, were present in high numbers, dominating most of them. The picoplankton community structures at three of the stations, all with similar salinity and temperature, were alike. At the fourth station, the influence of the East Spitsbergen Current (ESC), transporting cold water from the Barents Sea around Spitsbergen, causes different abiotic parameters that result in a significantly different picoeukaryote community composition, which is dominated by Micromonas pusilla. This observation is particularly interesting in regard to ongoing environmental changes in the Arctic. Ongoing warming of the WSC could convey a new picoplankton assemblage into the Arctic Ocean, which may come to affect the dominance of Micromonas pusilla.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 8
    Publication Date: 2023-06-21
    Description: The collection of zooplankton swimmers and sinkers in time-series sediment traps provides unique insight into year-round and interannual trends in zooplankton population dynamics. These samples are particularly valuable in remote and difficult to access areas such as the Arctic Ocean, where samples from the ice-covered season are rare. In the present study, we investigated zooplankton composition based on swimmers and sinkers collected by sediment traps at water depths of 180–280, 800–1320, and 2320–2550 m, over a period of 16 yr (2000–2016) at the Long-Term Ecological Research observatory HAUSGARTEN located in the eastern Fram Strait (79°N, 4°E). The time-series data showed seasonal and interannual trends within the dominant zooplankton groups including copepoda, foraminifera, ostracoda, amphipoda, pteropoda, and chaetognatha. Amphipoda and copepoda dominated the abundance of swimmers while pteropoda and foraminifera were the most important sinkers. Although the seasonal occurrence of these groups was relatively consistent between years, there were notable interannual variations in abundance, suggesting the influence of various environmental condi- tions such as sea-ice dynamic and lateral advection of water masses, for example, meltwater and Atlantic water. Statistical analyses revealed a correlation between the Arctic dipole climatic index and sea-ice dynamics (i.e., ice coverage and concentration), as well as the importance of the distance from the ice edge on swimmer composition patterns and carbon export.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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