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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 conditions 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.

Due to the increasing amount of data produced in science, concepts for data reusability are of immense importance. One aspect is the publication of data in a way that ensures that it is findable, reusable, traceable and comparable (FAIR1 principles). However, putting these principles into practice often causes significant difficulties for researchers. Therefore some repositories accept datasets described only with the minimum metadata required for DOI allocation. Unfortunately, this contains not enough information to conform to the FAIR principles - many research data cannot be reused despite having a DOI. In contrast, other repositories aid the researchers by providing advice and strictly controlling the data and their metadata. To simplify the process of defining the needed amount of metadata and of controlling the data and metadata, the AtMoDat2 (Atmospheric Model Data) project developed a detailed standard for the FAIR publication of atmospheric model data.For this purpose we have developed a concept for the “ideal” description of atmospheric model data. A prerequisite for this is the data publication with a DataCite DOI. The ATMODAT standard3 was developed to implement this concept. The standard defines the data format as NetCDF, mandatory metadata (for DOI, landing page and data header), and naming conventions used in climate research - the Climate and Forecast conventions (CF-conventions4). However, many variable names used in urban climate research, for example, are not part of the CF-conventions. For this, standard names have to be defined together with the community and the inclusion in the list of CF-conventions has to be requested. Furthermore we developed and published Python routines which allow data producers as well as repositories to check model output data against the standard. The ATMODAT standard will first be applied by the project partners of the two participating universities (University of Hamburg and Leipzig). Here, climate model data are processed with a post-processor in preparation for publication. Subsequently, the files including the specified metadata for the DataCite metadata schema will be published by the World Data Center for Climate5 (WDCC). Data fulfilling the AtMoDat standard will be marked at the landing page by a special EASYDAB6 (Earth System Data Branding) logo. EASYDAB is a currently developed branding for FAIR and open data from the Earth System Sciences. This indicates to future data users that the dataset is a verified dataset that can be easily reused. The standardization of the data and the further steps are easily transferable to data from other disciplines.1 Wilkinson, M., Dumontier, M., Aalbersberg, I. et al.: The FAIR Guiding Principles for scientific data management and stewardship. Sci Data 3, 160018 (2016). https://doi.org/10.1038/sdata.2016.18 2 https://www.atmodat.de/3 https://cera-www.dkrz.de/WDCC/ui/cerasearch/entry?acronym=atmodat_standard_en_v3_04 https://cfconventions.org/5 https://cera-www.dkrz.de/WDCC/ui/cerasearch/6 https://www.easydab.de/

As in many scientific disciplines, there are a variety of activities in Earth system sciences that address the important aspects of good research data management. What has not been sufficiently investigated and dealt with so far is the easy discoverability and re-use of quality-checked data. This aspect is taken up by the EASYDAB label.EASYDAB1 is a currently developed branding for FAIR and open data from the Earth System Sciences. The branding can be adopted by institutions running a data repository which stores data from the Earth System Sciences. EASYDAB is always connected to a research data publication with DataCite DOIs. Data published under EASYDAB are characterized by a high maturity, extensive metadata information and compliance with a comprehensive discipline-specific standard. For these datasets, the EASYDAB logo is added to the landing page of the data repository. Thereby, repositories can indicate their efforts to publish data with high maturity.The first standard made for EASYDAB is the ATMODAT standard2, which has been developed within the AtMoDat3 project (Atmospheric Model Data). It incorporates concrete recommendations and requirements related to the maturity, publication and enhanced FAIRness of atmospheric model data. The requirements are for rich metadata with controlled vocabularies, structured landing pages, file formats (netCDF) and the structure within files. Human- and machine-readable landing pages are a core element of the ATMODAT standard and should hold and present discipline-specific metadata on simulation and variable level. The ATMODAT standard includes checklists for the data producer and the data curator so that the compliance with the standard can easily be obtained by both sides. To facilitate automatic checking of the netCDF files headers, a checker program will also be provided and published with DOI. Moreover, a checker for the compliance with the requirements for the DOI Metadata will be developed and made openly available. The integration of standards from other disciplines in the Earth System Sciences, such as oceanography, into EASYDAB is helpful and desirable to improve the re-use of reviewed, high-quality data. 1www.easydab.de2https://cera-www.dkrz.de/WDCC/ui/cerasearch/entry?acronym=atmodat_standard_en_v3_03www.atmodat.de

Bei Klimasimulationen werden große Mengen an Daten erzeugt. Aus diesem Grund können in der Regel nicht alle Ergebnisse einer Simulation eines Klimamodells von einer Forschungsgruppe alleine ausgewertet werden. Beim Coupled Model Intercomparison Projekt (CMIP) wird daher ein Fokus darauf gelegt, dass auch andere Forschungsgruppen die Daten auswerten können. Deshalb gibt es genaue Vorgaben, wie diese Daten zu beschreiben und zu formatieren sind. Zudem werden viele dieser Datensätze mit einem DOI (Digital Object Identifier) versehen. Dies alles erleichtert die Suche und Weiterverarbeitung der Daten.Allerdings gibt es weitaus mehr als CMIP Daten, die für die Klimaforschung wichtig sind. Viele Ergebnisse von z.B. regionalen Klimamodellen oder Stadtklimamodellen werden nicht veröffentlicht, obwohl von den Datenerzeugern nur ein Bruchteil der Ergebnisse ausgewertet werden kann. Deshalb drängen viele Förderer auf eine Veröffentlichung der Daten in einem Repositorium. Aber auch in diesem Fall können sie oft nicht weiterverwendet werden. Die Gründe sind vielfältig: Unzureichende Metadaten Mangelnde Auffindbarkeit, z.B. durch Suchmaschinen Fehlende Rechte zur Weiterverarbeitung Fehlende Qualitätskontrolle Das BMBF geförderte Projekt AtMoDat (https://www.ATMODAT.de) wurde 2019 gestartet, um die Veröffentlichung von Atmosphärischen Modelldaten zu stärken und zu verbessern. Eine Methode ist dabei die Einhaltung der FAIR-Prinzipien - Findable, Accessible, Interoperable, Reusable (siehe Wilkinson et al., 2016). Zudem sollten alle Daten mit einem DataCite DOI veröffentlicht werden, um die Auffindbarkeit und Zitierbarkeit zu verbessern. Eine Anleitung, wie man dabei vorgehen sollte, findet sich in dem Standard, der im AtMoDat-Projekt entwickelt wurde. Der ATMODAT-Standard ist leicht umzusetzen und beinhaltet genaue Vorgaben für die Metadaten des DOI, die Landing Page und die Header der netCDF-Dateien. Daten, die diesem Standard genügen und dessen Einhaltung vom jeweiligen Repositorium geprüft wurde, können mit dem Earth System Data Branding (EASYDAB) versehen werden. Durch dieses Branding kann eine angemessene Qualitätssicherung der Daten durch die Nutzer sehr leicht nachvollzogen werden. Im Vortrag werden der Standard und EASYDAB vorgestellt.

Within the AtMoDat project (Atmospheric Model Data, www.atmodat.de), a standard has been developed which is meant for improving the FAIRness of atmospheric model data published in repositories. Atm...

The generation of high quality research data is expensive. The FAIR principles were established to foster the reuse of such data for the benefit of the scientific community and beyond. Publishing research data with metadata and DataCite DOIs in public repositories makes them findable and accessible (FA of FAIR). However, DOIs and basic metadata do not guarantee the data are actually reusable without discipline-specific knowledge: if data are saved in proprietary or undocumented file formats, if detailed discipline-specific metadata are missing and if quality information on the data and metadata are not provided. In this contribution, we present ongoing work in the AtMoDat project, -a consortium of atmospheric scientists and infrastructure providers, which aims on improving the reusability of atmospheric model data. Consistent standards are necessary to simplify the reuse of research data. Although standardization of file structure and metadata is well established for some subdomains of the earth system modeling community – e.g. CMIP –, several other subdomains are lacking such standardization. Hence, scientists from the Universities of Hamburg and Leipzig and infrastructure operators cooperate in the AtMoDat project in order to advance standardization for model output files in specific subdomains of the atmospheric modeling community. Starting from the demanding CMIP6 standard, the aim is to establish an easy-to-use standard that is at least compliant with the Climate and Forecast (CF) conventions. In parallel, an existing netCDF file convention checker is extended to check for the new standards. This enhanced checker is designed to support the creation of compliant files and thus lower the hurdle for data producers to comply with the new standard. The transfer of this approach to further sub-disciplines of the earth system modeling community will be supported by a best-practice guide and other documentation. A showcase of a standard for the urban atmospheric modeling community will be presented in this session. The standard is based on CF Conventions and adapts several global attributes and controlled vocabularies from the well-established CMIP6 standard. Additionally, the AtMoDat project aims on introducing a generic quality indicator into the DataCite metadata schema to foster further reuse of data. This quality indicator should require a discipline-specific implementation of a quality standard linked to the indicator. We will present the concept of the generic quality indicator in general and in the context of urban atmospheric modeling data.

Regarding the development of complex new technological processes, research data management systems are of major importance to support scientist in large collaborative projects and allow project teams to take advantage of a research organized according to the FAIR data principles. At the example of the CRC 1153, where an interdisciplinary team researches novel process chains for the manufacturing of hybrid components, an approach to organize the research data management process using a research data and knowledge management system and a domain specific vocabulary is being developed.

Digitization of the research (data) lifecycle has created a galaxy of data nodes that are often characterized by sparse interoperability. With the start of the European Open Science Cloud in November 2018 and facing the upcoming call for the creation of the National Research Data Infrastructure (NFDI), researchers and infrastructure providers will need to harmonize their data efforts. In this article, we propose a recently initiated proof-of-concept towards a network of semantically harmonized Research Data Management (RDM) systems. This includes a network of research data management and publication systems with semantic integration at three levels, namely, data, metadata, and schema. As such, an ecosystem for agile, evolutionary ontology development, and the community-driven definition of quality criteria and classification schemes for scientific domains will be created. In contrast to the classical data repository approach, this process will allow for cross-repository as well as cross-domain data discovery, integration, and collaboration and will lead to open and interoperable data portals throughout the scientific domains. At the joint lab of L3S research center and TIB Leibniz Information Center for Science and Technology in Hanover, we are developing a solution based on a customized distribution of CKAN called the Leibniz Data Manager (LDM). LDM utilizes the CKAN’s harvesting functionality to exchange metadata using the DCAT vocabulary. By adding the concept of semantic schema to LDM, it will contribute to realizing the FAIR paradigm. Variables, their attributes and relationships of a dataset will improve findability and accessibility and can be processed by humans or machines across scientific domains. We argue that it is crucial for the RDM development in Germany that domain-specific data silos should be the exception, and that a semantically-linked network of generic and domain-specific research data systems and services at national, regional, and organization levels should be promoted within the NFDI initiative.

Disziplinübergreifendes Forschungsdatenmanagement für Hochschulbibliotheken und Projekte zu vereinfachen und zu etablieren – das ist das Ziel von RADAR. Im Sommer 2016 geht mit ‚RADAR – Research Data Repository‘ ein Service an den Start, der Forschenden, Institutionen verschiedener Fachdisziplinen und Verlagen eine generische Infrastruktur für die Archivierung und Publikation von Forschungsdaten anbietet. Zu den Dienstleistungen gehören u. a. die Langzeitverfügbarkeit der Daten mit Handle oder Digital Object Identifier (DOI), ein anpassbares Rollen- und Zugriffsrechtemanagement, eine optionale Peer-Review-Funktion und Zugriffsstatistiken. Das Geschäftsmodell ermutigt Forschende, die anfallenden Nutzungsgebühren des Repositoriums in Drittmittelanträge und Datenmanagementpläne zu integrieren. Publizierte Daten stehen als Open Data zur Nachnutzung wie etwa Data Mining, Metadaten-Harvesting und Verknüpfung mit Suchportalen zur Verfügung. Diese Vernetzung ermöglicht ein nachhaltiges Forschungsdatenmanagement und die Etablierung von Dateninfrastrukturen wie RADAR., The goal of RADAR is to simplify and establish inter-disciplinary research data management for university libraries and projects. In summer 2016‚ ‘RADAR – Research Data Repository‘ starts as a service that offers researchers, institutions of different disciplines and publishers a generic infrastructure for archiving and publishing their research data. Among others, services are long-term data availability with Handle or Digital Object Identifier (DOI), an adaptable role and access rights management, an optional peer review function and access statistics. The business model encourages researchers to integrate arising charges for using the repository into applications for Third-Party funding and data management plans. Published data are available as Open Data to be used by Data Mining, metadata harvesting or linking with search portals. This interlinking enables a sustainable research data management and the establishment of data infrastructures like RADAR.

Forschungsergebnisse und die zugehorigen Rohdaten so zu archivieren, dass Wissenschaftler sie finden und weiternutzen konnen, erfordert eine Infrastruktur. Damit auch kleinere Forschungseinrichtungen eine solche aufbauen konnen, haben mehrere Forschungsinstitute zusammengearbeitet und ein entsprechendes System entwickelt.

The demand of reproducible results in the numerical simulation of optoelectronic devices or more general in mathematical modeling and simulation requires the (long-term) accessibility of data and software that were used to generate those results. Moreover, data visualizations such as videos are useful to present those results in a comprehensible manner. Persistent identifiers can be used to ensure the permanent connection of these different digital objects thereby preserving all information in the right context. Here we give an overview over the state-of-the art of data preservation, data and software citation and illustrate the benefits and opportunities of enhancing publications with visual simulation data by showing a use case from optoelectronics.

Pteropods are an important component of the zooplankton community and hence of the food web in the Fram Strait. They have a calcareous (aragonite) shell and are thus sensitive in particular to the effects of the increasing CO2 concentration in the atmosphere and the associated changes of pH and temperature in the ocean. In the eastern Fram Strait, two species of thecosome pteropods occur, the cold water-adapted Limacina helicina and the subarctic boreal species Limacina retroversa. Both species were regularly observed in year-round moored sediment traps at ~ 200–300 m depth in the deep-sea long-term observatory HAUSGARTEN (79°N, 4°E). The flux of all pteropods found in the trap samples varied from 50 m− 2 d− 1). This picture completely changed after 2005/6 when L. retroversa became dominant and total pteropod numbers in the trap samples increased significantly. Concomitant to this shift in species composition, a warming event occurred in 2005/6 and persisted until the end of the study in 2009, despite a slight cooling in the upper water layer after 2007/8. Sedimentation of pteropods showed a strong seasonality, with elevated fluxes of L. helicina from August to November. Numbers of L. retroversa usually increased later, during September/October, with a maximum at the end of the season during December/January. In terms of carbonate export, aragonite shells of pteropods contributed with 11–77% to the annual total CaCO3 flux in Fram Strait. The highest share was found in the period 2007 to 2009, predominantly during sedimentation events at the end of the year. Results obtained by sediment traps occasionally installed on a benthic lander revealed that pteropods also arrive at the seafloor (~ 2550 m) almost simultaneous with their occurrence in the shallower traps. This indicates a rapid downward transport of calcareous shells, which provides food particles for the deep-sea benthos during winter when other production in the upper water column is shut down. The results of our study highlight the great importance of pteropods for the biological carbon pump as well as for the carbonate system in Fram Strait at present, and indicate modifications within the zooplankton community. The results further emphasize the importance of long-term investigation to disclose such changes.

Pelagic zooplankton were monitored from 2000 to 2012 at a permanent location near the Svalbard archipelago, at the boundary between the central Arctic Ocean and the Greenland Sea in the eastern Fram Strait. The temporal results reveal the first evidence of successful reproduc- tion in Arctic waters by an Atlantic pelagic crustacean from temperate waters. The Atlantic hyperid amphipod Themisto compressa is shown to have expanded its range from more southerly and warmer waters from 2004 onwards. Successful reproductive activity by T. compressa in Arctic waters was confirmed in 2011, indicated by the presence of a complete temporal series of develop- mental stages including ovigerous females and recently hatched juveniles. The Arctic amphipod community is currently in transition and a continuing northward spread of southern invaders could cause a biodiversity shift from large Arctic to smaller Atlantic species.

Life-cycle characteristics of the free-swimming lysianassoid amphipod Cyclocaris guilelmi were investigated and compared to those of other regularly appearing amphipods in the Arctic deep-sea community. In this context we analysed time-series data of meso- and bathypelagic amphipods collected as swimmers in moored sediment traps from 2004-2008 at the deep-sea long-term observatory HAUSGARTEN (79°N/4°E) in the eastern Fram Strait, Arctic Ocean. Six mesopelagic and three bathypelagic deep-sea amphipod species regularly occurred in the traps. The lysianassoid C. guilelmi showed a stable interannual population size and seasonal peaks in its occurrence from August to February during the five-year sampling period. The investigation of its population structure and reproduction ecology indicated year-round breeding behavior of this species. Up to 4 cohorts consisting mainly of juvenile and female C. guilelmi were observed. We conclude that C guilelmi plays an important role within the Arctic amphipod deep water community.

The pelagic amphipods Themisto abyssorum and Themisto libellula represent important links between the herbivore zooplankton community and higher trophic levels of the Arctic marine food webs. Large double structured eyes of both of these hyperiid species are assumed to be used for visual prey detection. However, no information is available on the feeding strategies of these visually searching predators for the period of the polar night, a time of year with no or very low levels of daylight. Here, we report on the stomach and gut content of both Themisto species collected during a January expedition around Svalbard (78° to 81°N). Results indicate that T. abyssorum and T. libellula feed actively during the Arctic winter. The major food source of both amphipods consisted of calanoid copepods, most frequently Calanus finmarchicus.

Time series length-frequency data are presented for Themisto amphipods collected as swimmers by moored sediment traps since 2000 at the AWI deep-sea observatory HAUSGARTEN (79°N/4°E) in the eastern Fram Strait. Amphipod occurrences increased significantly from 2000 to 2009 at 200–300 m depth, and the North Atlantic species Themisto compressa was continuously present in the samples starting in 2004. We present year-round records of large adult Themisto amphipods, including the appearance of Themisto libellula with a total body length of up to 56.7 mm and juveniles starting from 4.0 mm. The length of Themisto abyssorum ranged from 4.2 to 25.6 mm, whereas it varied for Themisto compressa from 8.8 to 24.4 mm. Length-frequency analysis indicated a life span of 2 years for T. abyssorum and at least 3 years for T. libellula . The absence of juveniles for T. compressa suggested its reproduction in southern subarctic areas and its occasional northward migration with warmer Atlantic water into the eastern Fram Strait. The seasonal and long-term size structures of the three pelagic species were consistent over the course of the study, indicating no changes occurred in cohort development due to increasing abundances or warming water temperatures.

Populations of Platorchestia platensis (Krøyer, 1845) and Orchestia grillus Bosc, 1802 (Amphipoda, Talitroidea) show variations in body size throughout their range in the Gulf of Mexico and along the Atlantic coast of North America. For each species we describe an intraspecific correlation between median body size and degrees of latitude north, such that in populations progressively further north from the equator, the median body size becomes larger. This growth and development pattern is consistent with the metabolic theory of ecology and appears to be general among Talitridae, with a few exceptions.

Since 2000, sediment traps have been deployed at the HAUSGARTEN (a long-term observatory established by the Alfred-Wegener-Institute for Polar and Marine Research in 1999) in the Fram Strait, (west of Spitsbergen at a water depth of 2,500 m, located in the confluence zone of the warm saline Atlantic water and water masses of polar origin) in order to investigate seasonal and inter-annual fluctuation of particle flux and the various contribution of zooplankton swimmers. Amongst these swimmers, amphipods are regularly observed occurring in a recurrent pattern and they dominate the biomass. Thus, we present data on amphipods regarding their seasonal and regional distribution pattern throughout the period 2000–2007. The most frequently observed amphipod species are Themisto libellula, T. abyssorum and T. compressa. While Themisto libellula is considered a true Arctic species associated to polar water masses, the boreal-Atlantic species Themisto abyssorum is imported into the Arctic by Atlantic water. A third species, Themisto compressa, occurred in 2004 and has been continually observed in the samples since then. The latter species has its main distribution in the warm regions of the North Atlantic and its occurrence in the Fram Strait points to the increased influence of warm Atlantic water masses. During 2000–2007, the amphipod composition in the samples has changed in favor of T. abyssorum and T. compressa. These shifts could suggest a northward movement of Atlantic species in the seasonally ice-covered area, a region of the ocean anticipated to react very sensitively to global warming.

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.

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: Plankton; ecology; biogeochemistry; Fram Strait; Arctic Ocean; climate change.(Published: 1 December 2015)Citation: Polar Research 2015, 34, 23349, http://dx.doi.org/10.3402/polar.v34.23349To access the supplementary material for this article, please see supplementary files in the column to the right (under Article Tools).

Polar regions are characterized by a strong seasonality in primary production and distinct fluctuations in food supply. The storage of energy in the form of lipids is expected to follow a seasonal pattern; however, year-round observations are lacking. The seasonal variations of lipid classes and fatty acid compositions of four pelagic amphipods have been investigated. Individuals were collected at various depths during summer and winter expeditions to the Fram Strait and Svalbard archipelago (788–818N). Our results show a year-round dominance of wax esters and triacylglycerols over phospholipids for Themisto abyssorum, Themisto libellula, Themisto compressa and Cyclocaris guilelmi. High levels of the Calanus-marker fatty acids 20:1 and 22:1 (both isomers) during summer and winter indicated that all four species are part of the Calanus-based food web. Specific fatty acid trophic markers for diatoms and flagellates indicated that the lipid-based energy transfer could be traced back to the respective algal sources.We found a distinct difference between animals collected from very deep and shallow waters, which indicates that the lipid reservoir of these amphipods and their biochemical modifications seem to buffer seasonal variations in available prey and to allow an active, predatory life-style year-round in Arctic waters.

Indications accumulate that the Arctic Ocean is in transition towards a new, warmer state. With this development, we expect shifts in the composition of Arctic zooplankton communities, as well as adaptations in the life-cycle history of established species. In the Arctic marine food web, carnivorous pelagic amphipods are an important link between herbivorous mesozooplankton and higher trophic levels such as planktivorous fish and seabirds. The present study closely investigates the community patterns of three important epipelagic amphipods Themisto abyssorum, T. libellula and T. compressa, and the deep-water amphipod Cyclocaris guilelmi. The objectives of this work focus on the year-round life-cycle characteristics of pelagic amphipods and on their function in the food web structure at study sites between Greenland and the Svalbard archipelago. In this thesis, three publications address the year-round life-cycle characteristics of Themisto spp. and C. guilelmi sampled by moored sediment traps in the northeastern Fram Strait. The sediment traps are deployed in a long-term observatory, the HAUSGARTEN, which is maintained by the Alfred Wegener Institute for Polar and Marine Research at the boundary between the central Arctic Ocean and the Greenland Sea since 2000. In the epipelagic trap samples hyperiids of the genus Themisto represent the dominant taxa among the collected amphipod community. Length-frequency analyses of year-round samples from 2000 to 2009 indicate a life span of two years for the sub-arctic species T. abyssorum and at least three years for the typical Arctic amphipod T. libellula. From 2004 to 2008, the meso- and bathypelagic amphipod communities in the sediment traps from 800 to 2700 m depth show the prevalent appearance of the deep-water amphipod C. guilelmi. Two other studies focus on the winter feeding strategies of Themisto spp. and C. guilelmi. The results from the gut content analyses indicate for the first time that T. abyssorum and T. libellula are active predators during the Arctic winter, with calanoid copepods as their major prey. In addition, a comparison of summer and winter fatty acid profiles shows a dominance of copepod biomarkers of the genus Calanus in the four investigated amphipod species, indicating that T. abyssorum, T. libellula, T. compressa and C. guilelmi are all part of Calanus-based food web and perform a business-as-usual feeding-mode during the polar night. To conclude, I show that long-term observations and a detailed knowledge of species specific ecology are of high importance for the identification of possible shifts within zooplankton community patterns and to predict their consequences in the food web structure of Arctic ecosystems.