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  • Articles  (6)
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  • 1
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    Sea-ice habitat minimizes grazing impact and predation risk for larval Antarctic krill (2021)
    In:  EPIC3Polar Biology, ISSN: 0722-4060
    Details
    Publication Date: 2021-05-19
    Description: Survival of larval Antarctic krill (Euphausia superba) during winter is largely dependent upon the presence of sea ice as it provides an important source of food and shelter. We hypothesized that sea ice provides additional benefits because it hosts fewer competitors and provides reduced predation risk for krill larvae than the water column. To test our hypothesis, zooplankton were sampled in the Weddell-Scotia Confluence Zone at the ice-water interface (0–2 m) and in the water column (0–500 m) during August–October 2013. Grazing by mesozooplankton, expressed as a percentage of the phytoplankton standing stock, was higher in the water column (1.97 ± 1.84%) than at the ice-water interface (0.08 ± 0.09%), due to a high abundance of pelagic copepods. Predation risk by carnivorous macrozooplankton, expressed as a percentage of the mesozooplankton standing stock, was significantly lower at the ice-water interface (0.83 ± 0.57%; main predators amphipods, siphonophores and ctenophores) than in the water column (4.72 ± 5.85%; main predators chaetognaths and medusae). These results emphasize the important role of sea ice as a suitable winter habitat for larval krill with fewer competitors and lower predation risk. These benefits should be taken into account when considering the response of Antarctic krill to projected declines in sea ice. Whether reduced sea-ice algal production may be compensated for by increased water column production remains unclear, but the shelter provided by sea ice would be significantly reduced or disappear, thus increasing the predation risk on krill larvae.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
    Format: application/pdf
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  • 2
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    Size and stage composition of age class 0 Antarctic krill (Euphausia superba) in the ice-water interface layer during winter/early spring (2016)
    SPRINGER
    In:  EPIC3Polar Biology, SPRINGER, 39(9), pp. 1515-1526, ISSN: 0722-4060
    Details
    Publication Date: 2016-08-30
    Description: The condition and survival of Antarctic krill (Euphausia superba) strongly depends on sea ice conditions during winter. How krill utilize sea ice depends on several factors such as region and developmental stage. A comprehensive understanding of sea ice habitat use by krill, however, remains largely unknown. The aim of this study was to improve the understanding of the krill's interaction with the sea ice habitat during winter/early spring by conducting large-scale sampling of the ice-water interface (0-2 m) and comparing the size and developmental stage composition of krill with the pelagic population (0-500 m). Results show that the population in the northern Weddell Sea consisted mainly of krill that were less than one year old (age class 0; AC0), and that it was comprised of multiple cohorts. Size per developmental stage differed spatially, indicating that the krill likely were advected from various origins. The size distribution of krill differed between the two depth strata sampled. Larval stages with a relatively small size (mean 7 to 8 mm) dominated the upper two meter layer of the water column, while larger larvae and AC0 juveniles (mean 14 to 15 mm) were proportionally more abundant in the 0-500 m stratum. Our results show that, as krill mature, their vertical distribution and utilization of the sea ice appears to change gradually. This could be the result of changes in physiology and/or behaviour, as e.g. the krill's energy demand and swimming capacity increase with size and age. The degree of sea ice association will have an effect on large-scale spatial distribution patterns of AC0 krill and on predictions of the consequences of sea ice decline on their survival over winter.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 3
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    The winter pack-ice zone provides a sheltered but food-poor habitat for larval Antarctic krill (2017)
    Springer Nature
    In:  EPIC3Nature Ecology & Evolution, Springer Nature, 1, pp. 1853-1861, ISSN: 2397-334X
    Details
    Publication Date: 2018-01-03
    Description: A dominant Antarctic ecological paradigm suggests that winter sea ice is generally the main feeding ground for krill larvae. Observations from our winter cruise to the southwest Atlantic sector of the Southern Ocean contradict this view and present the first evidence that the pack-ice zone is a food-poor habitat for larval development. In contrast, the more open marginal ice zone provides a more favourable food environment for high larval krill growth rates. We found that complex under-ice habitats are, however, vital for larval krill when water column productivity is limited by light, by providing structures that offer protec- tion from predators and to collect organic material released from the ice. The larvae feed on this sparse ice-associated food during the day. After sunset, they migrate into the water below the ice (upper 20 m) and drift away from the ice areas where they have previously fed. Model analyses indicate that this behaviour increases both food uptake in a patchy food environment and the likelihood of overwinter transport to areas where feeding conditions are more favourable in spring.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 4
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    Seasonal changes in the vertical distribution and community structure of Antarctic macrozooplankton and micronekton (2014)
    PERGAMON-ELSEVIER SCIENCE LTD
    In:  EPIC3Deep-Sea Research Part I: Oceanographic Research Papers, PERGAMON-ELSEVIER SCIENCE LTD, 84, pp. 127-141, ISSN: 0967-0637
    Details
    Publication Date: 2019-07-16
    Description: The macrozooplankton and micronekton community of the Lazarev Sea (Southern Ocean) was investigated at 3 depth layers during austral summer, autumn and winter: (1) the surface layer (0–2 m); (2) the epipelagic layer (0–200 m); and (3) the deep layer (0–3000 m). Altogether, 132 species were identified. Species composition changed with depth from a euphausiid-dominated community in the surface layer, via a siphonophore-dominated community in the epipelagic layer, to a chaetognath-dominated community in the deep layer. The surface layer community predominantly changed along gradients of surface water temperature and sea ice parameters, whereas the epipelagic community mainly changed along hydrographical gradients. Although representing only 1% of the depth range of the epipelagic layer, mean per-area macrofauna densities in the surface layer ranged at 8% of corresponding epipelagic densities in summer, 6% in autumn, and 24% in winter. Seasonal shifts of these proportional densities in abundant species indicated different strategies in the use of the surface layer, including both hibernal downward and hibernal upward shift in the vertical distribution, as well as year-round surface layer use by Antarctic krill. These findings imply that the surface layer, especially when it is ice-covered, is an important functional node of the pelagic ecosystem that has been underestimated by conventional depth-integrated sampling in the past. The exposure of this key habitat to climate-driven forces most likely adds to the known susceptibility of Antarctic pelagic ecosystems to temperature rise and changing sea ice conditions.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
    Format: application/pdf
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  • 5
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    Gelatinous and soft-bodied zooplankton in the Northeast Pacific Ocean: Phosphorus content and potential resilience to phosphorus limitation (2021)
    In:  EPIC3Hydrobiologia, ISSN: 0018-8158
    Details
    Publication Date: 2022-01-07
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 6
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    Status, Change, and Futures of Zooplankton in the Southern Ocean (2022)
    In:  EPIC3Frontiers in Ecology and Evolution, 9(624692)
    Details
    Publication Date: 2022-07-20
    Description: In the Southern Ocean, several zooplankton taxonomic groups, euphausiids, copepods, salps and pteropods, are notable because of their biomass and abundance and their roles in maintaining food webs and ecosystem structure and function, including the provision of globally important ecosystem services. These groups are consumers of microbes, primary and secondary producers, and are prey for fishes, cephalopods, seabirds, and marine mammals. In providing the link between microbes, primary production, and higher trophic levels these taxa influence energy flows, biological production and biomass, biogeochemical cycles, carbon flux and food web interactions thereby modulating the structure and functioning of ecosystems. Additionally, Antarctic krill (Euphausia superba) and various fish species are harvested by international fisheries. Global and local drivers of change are expected to affect the dynamics of key zooplankton species, which may have potentially profound and wide-ranging implications for Southern Ocean ecosystems and the services they provide. Here we assess the current understanding of the dominant metazoan zooplankton within the Southern Ocean, including Antarctic krill and other key euphausiid, copepod, salp and pteropod species. We provide an overview of observed and potential future responses of these taxa to a changing Southern Ocean and the functional relationships by which drivers may impact them. To support future ecosystem assessments and conservation and management strategies, we also identify priorities for Southern Ocean zooplankton research.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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