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  • 1
    Publication Date: 2019-02-01
    Description: Time-series studies of arctic marine ecosystems are rare. This is not surprising since polar regions are largely only accessible by means of expensive modern infrastructure and instrumentation. In 1999, the Alfred Wegener Institute, Helmholtz-Centre for Polar and Marine Research (AWI) established the LTER (Long-Term Ecological Research) observatory HAUSGARTEN crossing the Fram Strait at about 79° N. Multidisciplinary investigations covering all parts of the open-ocean ecosystem are carried out at a total of 21 permanent sampling sites in water depths ranging between 250 and 5500 m. From the outset, repeated sampling in the water column and at the deep seafloor during regular expeditions in summer months was complemented by continuous year-round sampling and sensing using autonomous instruments in anchored devices (i.e., moorings and free-falling systems). The central HAUSGARTEN station at 2500 m water depth in the eastern Fram Strait serves as an experimental area for unique biological in situ experiments at the seafloor, simulating various scenarios in changing environmental settings. Long-term ecological research at the HAUSGARTEN observatory revealed a number of interesting temporal trends in numerous biological variables from the pelagic system to the deep seafloor. Contrary to common intuition, the entire ecosystem responded exceptionally fast to environmental changes in the upper water column. Major variations were associated with a Warm-Water-Anomaly evident in surface waters in eastern parts of the Fram Strait between 2005 and 2008. However, even after 15 years of intense time-series work at HAUSGARTEN, we cannot yet predict with complete certainty whether these trends indicate lasting alterations due to anthropologically-induced global environmental changes of the system, or whether they reflect natural variability on multiyear time-scales, for example, in relation to decadal oscillatory atmospheric processes.
    Type: Article , PeerReviewed
    Format: text
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  • 2
    Publication Date: 2014-10-07
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
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  • 3
    Publication Date: 2014-10-07
    Description: The export and composition of particles has been measured by means of annually moored sediment traps at the AWI long-term observatory HAUSGARTEN in Fram Strait (79°/4°E) in 200-300m depth since the year 2000. The area of investigation west of Spitsbergen at a water depth of 2500m is temporally covered by sea ice during the course of the year. It is further influenced by the inflow of warm Atlantic waters at the surface as well as recirculating of the warm waters modified by out-flowing cold arctic waters. With our study we aim at tracing effects of environmental changes in pelagic system structure and impacts on the fate of organic matter produced in the upper water column in a region that is anticipated to react very sensible to climate change. We present data on the export of total particulate matter (TPM), particulate organic carbon and nitrogen (POC/PON), biogenic particulate silica (bPSi), carbonate (CaCO3) and protist composition achieved during the period 2000 - 2009. We observed a bimodal seasonal sedimentation pattern for almost all flux components. Annual fluxes showed greatest variation for TPM and CaCO3 (3-5 fold), and a drastic decrease in bPSi, a proxy for diatoms. The export of organic carbon and total biogenic matter on the other hand hardly showed any variation (1-2 fold) since the begin of the measurements in the year 2000. The results obtained during the 9 year period of the study are compared to the findings of sediment trap studies conducted in the Fram Strait during the end of the eighties and we will discuss our findings in regard to the changing environmental conditions in the area.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
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  • 4
    Publication Date: 2018-02-16
    Description: Phytoplankton community analysis is important with respect to natural or humaninduced changes in the marine environment. Because of the efforts involved and the limitations of traditional methods, molecular sensing approaches are becoming more popular. Among others, microarray techniques targeting ribosomal 18S sequences have been successfully applied for phytoplankton investigation. In this contribution, we compared the results of two microarray methods targeting 18S rDNA and 18S rRNA with the results obtained from microscopy, HPLC and flow cytometry. On a qualitative basis, the microarrays showed similar or potentially better performance than the non-molecular methods. Quantitatively, our data suggest that microarray signals obtained from 18S rDNA provide relatively rough estimates of phytoplankton abundance. In contrast, when targeting 18S rRNA instead, a robust linear relationship (r2 ¼ 0.68) between molecular sensing signal and microscopic cell counts could be demonstrated using a probe specific to the genus Pseudo-nitzschia as an example. Thus, for both qualitative and quantitative purposes, microarray techniques can be valuable additions to traditional methods for phytoplankton analysis. Routine monitoring approaches in particular could benefit from advantages like reduced effort, higher taxonomic resolution and a potential for automation.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 5
    Publication Date: 2015-03-05
    Description: Protists in the central Arctic Ocean are adapted to the harsh environmental conditions of its various habitats. During the Polarstern cruise ARK-XXVI/3 in 2011, at one sea ice station, large aggregates accumulated at the bottom of the melt ponds. In this study, the protist assemblages of the bottom layer of the sea ice and melt pond aggregate were investigated using flow cytometry and 454-pyrosequencing. The objective is to provide a first molecular overview of protist diversity in these habitats and to consider the overlaps and/or differences in the community compositions. Results of flow cytometry pointed to a cell size distribution that was dominated by 3-10 µm nanoflagellates. The phylogenetic classification of all sequences was conducted at a high taxonomic level, while a selection of abundant (≥1% of total reads) sequences was further classified at a lower level. On the high taxonomic level, both habitats showed very similar community structures, dominated by chrysophytes and chlorophytes. On the lower taxonomic level, dissimilarities in the diversity of both groups were encountered in the abundant biosphere. While sea ice chlorophytes and chrysophytes were dominated by Chlamydomonas/Chloromonas spp and Ochromonas spp, the melt pond aggregate was dominated by Carteria sp., Ochromonas spp. and Dinobryon faculiferum. We suppose that the relatively high similarity in diversity is a consequence of melt pond freshwater seeping through porous sea ice in late summer. Differences in the abundant biosphere nevertheless indicate that differences in both habitats are also strong enough to select for different dominant species.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 6
  • 7
    Publication Date: 2014-10-07
    Description: Since about fifteen years the Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung (AWI) conducts time-series observations in the transition zone between the North-Atlantic and the Arctic Ocean. Activities are focused on water mass exchange through Fram Strait and ecosystem studies at the deep-sea observatory HAUSGARTEN. The location in Fram Strait – being the sole deep connection between the North-Atlantic and the Arctic Ocean – is of special interest with respect to the exchange of heat and freshwater between the Arctic and lower latitudes. The Fram Strait ecosystem is expected to be particularly vulnerable to Global Change related variations in environmental conditions, including the progressive sea-ice retreat. Obtained time series of physical and biological observations demonstrate the tight connection between abiotic habitat properties and ecosystem characteristics. These findings clearly advocate for a multidisciplinary and multi-scale approach that combines fixed-point and region-wide time-series observations. There are motivated plans for the extension of the current observations and the transition towards the integrated deep-sea observatory FRAM (FRontiers in Arctic marine Monitoring). In addition to the integration of existing physical and ecosystem observation components to fully exploit synergies, strategies for FRAM also include the implementation of novel instruments (e.g., ice-tethered platforms, profiling moorings, benthic crawlers, biooptical instrumentation) to extend observation-capacities in space and time – including periods of limited access due to permanent ice-coverage. FRAM represents a key site of the European Multidisciplinary Seafloor and Water Column Observatory EMSO, and a member of the Long-Term Ecological Research - Network (LTER). FRAM contributes to the ESFRI projects SIOS (Svalbard Integrated Arctic Earth Observing System) and ICOS (Integrated Carbon Observation System). As part of the Fixed-point Open Ocean Observatory network FixO3 (7th framework EU-program; www.fixo3.eu), the FRAM infrastructure provides coordinated, free-of-charge access to external users under the objective of Transnational Access (TNA).
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
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  • 8
    Publication Date: 2014-11-12
    Description: Planktonic algae are the most abundant photosynthetic organisms. They are the basis of the marine food web, and changes in phytoplankton communities generally provide an early indication for climate-driven modifications of marine food webs and the whole ecosystem. Harmful algal blooms (HAB) are a subset of planktonic algal species that have negative impacts on humans and aquatic environments. The formation of HABs depends on several multifactorial climate and environmental drivers that influence timing and frequency of these algal blooms. There is some evidence that the occurrence of HAB might become more intense, widespread, frequent and unexpected in future decades due to climate variability. In North ocean regions the global climate change is reflected by changing environmental parameter, such as increasing sea surface temperature, modified water mass stratification and rising freshwater content in the Arctic realm. Within this study the occurrence, abundance and dispersal of toxic algae species is analysed in Nordic seas and the Arctic Ocean, based on molecular detection with a nucleic acid biosensor. Alongside with this it will be assessed whether biosensor systems can serve as an early warning system for human health policies in the field of water resource management.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed , info:eu-repo/semantics/conferenceObject
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  • 9
    Publication Date: 2014-11-12
    Description: To understand function and stability of ecosystems it is crucial to gain insights into their species composition, particulary in the face of global warming. Next Generation Sequencing (NGS) is the method of choice for getting fast overviews of species diversity in a high number of samples. Currently, there are lively discussions about bioinformatic techniques to enhance the quality of sequencing outputs and how to post process these data in order to estimate the “real” diversity as precisely as possible. In this study, we analyzed the protist composition of three water samples, collected in the Fram Strait in 2010. We compared different potential sequencing error corrected and uncorrected datasets, which were generated with widely used open-source software: QIIME, mothur and PhyloAssigner. Relative abundance of protist phyla was hardly affected by the choice of the software, quality filtering and error correction. However, the outputs differed strongly in relative abundance of diatom genera and were not comparable to dominant diatoms observed with light microscopy. Our main findings are beneficial for the enhancement of study design, data preparation and interpretation and gives insights into the optimization potential of NGS experiments in general.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed , info:eu-repo/semantics/conferenceObject
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  • 10
    Publication Date: 2015-03-20
    Description: This talk is based on recent discoveries regarding spatial biogeography of Phaeocystis spp. via molecular monitoring in the North Sea, North Atlantic, Fram Strait and Central Arctic Ocean. The cosmopolitan micro algal genus Phaeocystis plays a crucial role in the ecology and biogeochemistry in nearly all marine ecosystems. It harbors three bloom- and colony-forming species, two cold and one `warm` water species. All three species: P. pouchetii in the Arctic, P. antarctica in the Southern Ocean and P. globosa in cold/warm temperate and tropical waters, are known to be key species within their habitats. P. pouchetii and P. globosa are believed to be species complexes. P. globosa has been physiologically widely studied, indicating eurythermal features due to a broad temperature span from -4 °C to more than +20 °C. This arises the question if present day populations of P. globosa could be dispersed via oceanic current regimes into the Arctic Ocean which is known to be an open oceanic system. Does P. globosa have the guts to enter the Arctic?
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
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