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  • Articles  (1,026)
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  • Articles  (1,026)
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  • 1
    Publication Date: 2018-03-14
    Description: The above mentioned article was originally scheduled for publication in the special issue on Ecology of Tundra Arthropods with guest editors Toke T. Høye and Lauren E. Culler. Erroneously, the article was published in Polar Biology , Volume 40, Issue 11, November, 2017. The publisher sincerely apologizes to the guest editors and the authors for the inconvenience caused.
    Print ISSN: 0722-4060
    Electronic ISSN: 1432-2056
    Topics: Biology
    Published by Springer
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  • 2
    Publication Date: 2018-03-14
    Description: The above mentioned article was originally scheduled for publication in the special issue on Ecology of Tundra Arthropods with guest editors Toke T. Høye . Lauren E. Culler. Erroneously, the article was published in Polar Biology, Volume 40, Issue 11, November, 2017. The publisher sincerely apologizes to the guest editors and the authors for the inconvenience caused.
    Print ISSN: 0722-4060
    Electronic ISSN: 1432-2056
    Topics: Biology
    Published by Springer
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  • 3
    Publication Date: 2018-03-14
    Description: Pacific salmon ( Oncorhynchus spp. ) populations near their northern range extent in the Arctic-Yukon-Kuskokwim region of Alaska have undergone major changes in population trajectory and illuminated the lack of basic information on juvenile ecology. This study fills information gaps on the early life history of chum salmon at northern latitudes. Energy allocation was examined in the context of distribution, feeding intensity, and diet during a critical life history period for a single cohort of juvenile chum salmon ( O. keta ) as they transition from freshwater to saltwater in Kuskokwim Bay from mid-May to early June. Juvenile chum salmon were primarily captured in the river mouth and plume. Energy density (kJ g −1 dry mass) was related to fork length, timing (day-of-year), and capture location in a general additive model. The smallest fish had slightly higher energy densities, but the change in energy density with fish size was minimal and consistent with allocating energy toward somatic growth rather than lipid storage. Fish captured earlier had higher energy density, likely reflecting the presence of residual yolk lipids during early migration. Fish captured in the river mouth and plume had higher energy densities. Feeding intensity was highest among small fish captured later within the river plume. Diet was dominated by surface prey (insects and calanoid copepods) rather than epibenthic harpacticoid copepods as commonly observed. These results provide the first data on energy allocation of juvenile chum salmon during a critical life history phase and suggest that somatic growth is prioritized over storing lipid at saltwater entry.
    Print ISSN: 0722-4060
    Electronic ISSN: 1432-2056
    Topics: Biology
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  • 4
    Publication Date: 2018-03-09
    Description: Porifera dominate vast areas of the Antarctic shelves and are successfully colonized by bacteria. Quorum sensing (QS) is a cell-to-cell communication system based on bacterial population density that, enabling the coordination of group-based behaviour, plays a critical role in the successful colonization of higher organisms, also driving the formation of biofilm for adhesion to surfaces. In this study, the production of N -Acyl homoserine lactones (AHLs), signal molecules involved in the QS mechanism, was examined for 211 Antarctic sponge-associated Gram-negative bacteria. AHL production was screened by using three different AHL biodetection systems, i.e. Agrobacterium tumefaciens pZLR4, Chromobacterium violaceum CV026 and Pseudomonas putida pKR-C12 with optimal sensitivity to moderate-chain (C8–C12), short-chain (C4–C8) and long-chain (≥ C14) AHLs, respectively. 57.8% of tested isolates activated at least one of the monitor systems used and belonged mainly to bacterial genera that are known to be involved in surface colonization by biofilm production. A thin-layer chromatographic assay based on the A. tumefaciens reporter system was utilized to determine the AHL profiles of five selected positive isolates. Visible spots on thin-layer chromatography (TLC) plates were produced by Roseobacter sp. TB60 and Psychrobacter sp. TB67 (both from the sponge, Anoxycalyx joubini ). The former probably produced N -(3-oxohexanoyl)-L-homoserine lactone (similar to the standard 3-oxo-C6-HSL), whereas the isolate TB67 produced molecules that were similar to the standard N -butanoyl-homoserine lactone (C4-HSL). The obtained results demonstrated that AHL-based signalling may play a key role in sponge–bacteria interactions also in the Antarctic environment.
    Print ISSN: 0722-4060
    Electronic ISSN: 1432-2056
    Topics: Biology
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  • 5
    Publication Date: 2018-03-09
    Description: The phylum Nemertea is an important component of the benthic ecosystems of the Southern Ocean, but its biodiversity is still relatively poorly known in Antarctic waters. There are few common and well-known nemertean species occurring in the shallow Antarctic waters, and these include the congeneric Antarctonemertes valida (Bürger, 1893) and Antarctonemertes riesgoae Taboada et al., 2013, two relatively small brooding hoplonemerteans whose females lay eggs inside cocoons. A third Antarctic member of the genus, Antarctonemertes belgica (Bürger, 1904), was reported only in the original description. Here we document the existence of a fourth Antarctic member of the genus Antarctonemertes originally described as Tetrastemma unilineatum Joubin, 1910. Our phylogenetic analysis resulted into the placement of the new Antarctonemertes in a robustly supported clade –Antarctic Antarctonemertes – containing the other two congeneric Antarctic species ( A.   valida and A.   riesgoae ), and pairwise COI molecular distances between the three species ranged from 5.2 to 6.2% ( p distance). The analysis of 104 COI sequences of the three species showed star-like haplotype networks, as in other studies on Antarctic invertebrates. Antarctonemertes unilineata comb. nov. is similar in shape to its Antarctic congeneric relatives and its most prominent morphological character is a dorsal mid-longitudinal band present along the body. We also document the presence of a cocoon built by females of A.   unilineata comb. nov., a character shared with its Antarctic congeners analysed here. Although the four Antarctic Antarctonemertes species appear to overlap their distribution, A.   riesgoae , A.   valida and A. belgica appear in sympatry in the West Antarctic shores while A.   unilineata comb. nov. has been mainly found in the East Antarctic shores and sub-Antarctic Islands.
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    Electronic ISSN: 1432-2056
    Topics: Biology
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  • 6
    Publication Date: 2018-03-07
    Description: Intensive efforts are being made to find new compounds with antimicrobial activity. The search for these novel bio-products in sparsely explored environments may be the key to providing solutions for many emerging problems. Antarctic environments are valuable locations for bioprospecting. In this study, 63 cold-adapted bacterial strains of 6100 different colony morphotypes were isolated from Antarctic seawater samples around South Shetland and Deception islands. Strains were selected based on cold-active antimicrobial production and were grouped into 11 operational taxonomic units by internal spacer region-PCR and amplified ribosomal DNA restriction analysis. Isolates arbitrarily named 2D, 5D, and 6D were closely related to Halomonas titanicae , with 99.8, 98.9, and 96.7% identity according to 16S rDNA sequencing, and 99.7, 99.3, and 98.3% according to gyrB region sequence analysis, respectively. The isolate 18SH was closely related to Candida sake (99.2%) based on sequence analysis of the ITS1–5.8S rDNA–ITS2 and D1/D2 domain of 26S rDNA. Antimicrobials produced by isolates 2D, 5D, and 6D exhibited a low-molecular weight (〈 6000 Da) and stability in wide pH and temperature ranges. When tested against foodborne and phytopathogenic bacteria, selected isolates exhibited a wide spectrum of activity. This work reports the isolation and identification of cold-adapted microorganisms with the ability to produce antimicrobial compounds with potential application in the pharmaceutical or in cold-chain management in the food industry. The current results highlight the potential of the Antarctic environment as a valuable and underexploited source of new antimicrobial molecules with exceptional properties for different biotechnological applications.
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    Electronic ISSN: 1432-2056
    Topics: Biology
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  • 7
    Publication Date: 2018-03-06
    Description: The Arctic Ocean is a region particularly prone to ongoing ocean acidification (OA) and climate-driven changes. The influence of these changes on Arctic phytoplankton assemblages, however, remains poorly understood. In order to understand how OA and enhanced irradiances (e.g., resulting from sea–ice retreat) will alter the species composition, primary production, and eco-physiology of Arctic phytoplankton, we conducted an incubation experiment with an assemblage from Baffin Bay (71°N, 68°W) under different carbonate chemistry and irradiance regimes. Seawater was collected from just below the deep Chl a maximum, and the resident phytoplankton were exposed to 380 and 1000 µatm pCO 2 at both 15 and 35% incident irradiance. On-deck incubations, in which temperatures were 6 °C above in situ conditions, were monitored for phytoplankton growth, biomass stoichiometry, net primary production, photo-physiology, and taxonomic composition. During the 8-day experiment, taxonomic diversity decreased and the diatom Chaetoceros socialis became increasingly dominant irrespective of light or CO 2 levels. We found no statistically significant effects from either higher CO 2 or light on physiological properties of phytoplankton during the experiment. We did, however, observe an initial 2-day stress response in all treatments, and slight photo-physiological responses to higher CO 2 and light during the first five days of the incubation. Our results thus indicate high resistance of Arctic phytoplankton to OA and enhanced irradiance levels, challenging the commonly predicted stimulatory effects of enhanced CO 2 and light availability for primary production.
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    Electronic ISSN: 1432-2056
    Topics: Biology
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  • 8
    Publication Date: 2018-03-06
    Description: An integrative inventory of the amphipod scavenging fauna (Lysianassoidea), combining morphological identifications with DNA barcoding, is provided here for the Filchner area situated in the south-eastern Weddell Sea. Over 4400 lysianassoids were investigated for species richness and relative abundances, covering 20 different stations and using different sampling devices, including the southernmost baited traps deployed so far (76°S). High species richness was observed: 29 morphospecies of which 5 were new to science. Molecular species delimitation methods were carried out with 109 cytochrome c oxidase I gene (COI) sequences obtained during this study as well as sequences from specimens sampled in other Antarctic regions. These distance-based analyses (trees and the Automatic Barcode Gap Discovery method) indicated the presence of 42 lineages; for 4 species, several (cryptic) lineages were found. More than 96% of the lysianassoids collected with baited traps belonged to the species Orchomenella pinguides s. l. The diversity of the amphipod scavenger guild in this ice-bound ecosystem of the Weddell Sea is discussed in the light of bottom–up selective forces. In this southernmost part of the Weddell Sea, harbouring spawning and nursery grounds for silverfish and icefishes, abundant fish and mammalian food falls are likely to represent the major food for scavengers. Finally, the importance of biodiversity surveys in the context of the establishment of a marine protected area in this region (Weddell Sea MPA) is highlighted and how future studies can contribute to a better understanding the ecological role of scavengers in this system is discussed.
    Print ISSN: 0722-4060
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    Topics: Biology
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  • 9
    Publication Date: 2018-03-06
    Description: Competition between individuals of the same or different species affects spatial distribution of organisms at any given time. Consequently, a species geographical distribution is related to population dynamics through density-dependent processes. Small Arctic rodents are important prey species in many Arctic ecosystems. They commonly show large cyclic fluctuations in abundance offering a potential to investigate how landscape characteristics relates to density-dependent habitat selection. Based on long-term summer trapping data of the Norwegian lemming ( Lemmus lemmus ) in the Scandinavian Mountain tundra, we applied species distribution modeling to test if the effect of environmental variables on lemming distribution changed in relation to the lemming cycle. Lemmings were less habitat specific during the peak phase, as their distribution was only related to primary productivity. During the increase phase, however, lemming distribution was, in addition, associated with landscape characteristics such as hilly terrain and slopes that are less likely to get flooded. Lemming habitat use varied during the cycle, suggesting density-dependent changes in habitat selection that could be explained by intraspecific competition. We believe that the distribution patterns observed during the increase phase show a stronger ecological signal for habitat preference and that the less specific habitat use during the peak phase is a result of lemmings grazing themselves out of the best habitat as the population grows. Future research on lemming winter distribution would make it possible to investigate the year around strategies of habitat selection in lemmings and a better understanding of a fundamental actor in many Arctic ecosystems.
    Print ISSN: 0722-4060
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    Topics: Biology
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  • 10
    Publication Date: 2018-03-06
    Description: The original article shows TDFe in Table 1 as µmol L −1 . The correct TDFe in Table 1 should be nmol L −1 .
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    Electronic ISSN: 1432-2056
    Topics: Biology
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