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  • 11
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    Seawater carbonate chemistry and hatch rates of Antarctic krill (2013)
    PANGAEA
    In:  Supplement to: Kawaguchi, So; Ishida, Akio; King, Rob; Raymond, Ben; Waller, N; Constable, A; Nicol, Steven; Wakita, M; Ishimatsu, Atsushi (2013): Risk maps for Antarctic krill under projected Southern Ocean acidification. Nature Climate Change, 3(9), 843-847, https://doi.org/10.1038/nclimate1937
    Details
    Publication Date: 2024-03-15
    Description: Marine ecosystems of the Southern Ocean are particularly vulnerable to ocean acidification. Antarctic krill (Euphausia superba; hereafter krill) is the key pelagic species of the region and its largest fishery resource. There is therefore concern about the combined effects of climate change, ocean acidification and an expanding fishery on krill and ultimately, their dependent predators-whales, seals and penguins. However, little is known about the sensitivity of krill to ocean acidification. Juvenile and adult krill are already exposed to variable seawater carbonate chemistry because they occupy a range of habitats and migrate both vertically and horizontally on a daily and seasonal basis. Moreover, krill eggs sink from the surface to hatch at 700-1,000 m, where the carbon dioxide partial pressure (pCO2) in sea water is already greater than it is in the atmosphere. Krill eggs sink passively and so cannot avoid these conditions. Here we describe the sensitivity of krill egg hatch rates to increased CO2, and present a circumpolar risk map of krill hatching success under projected pCO2 levels. We find that important krill habitats of the Weddell Sea and the Haakon VII Sea to the east are likely to become high-risk areas for krill recruitment within a century. Furthermore, unless CO2 emissions are mitigated, the Southern Ocean krill population could collapse by 2300 with dire consequences for the entire ecosystem.
    Keywords: Alkalinity, total; Animalia; Antarctic; Aragonite saturation state; Arthropoda; Bicarbonate ion; Bottles or small containers/Aquaria (〈20 L); Calcite saturation state; Calculated using seacarb after Nisumaa et al. (2010); Carbon, inorganic, dissolved; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Eggs; Eggs, hatched; Eggs, unhatched; Euphausia superba; EXP; Experiment; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Identification; Laboratory experiment; OA-ICC; Ocean Acidification International Coordination Centre; Open ocean; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Pelagos; pH; pH, standard deviation; Polar; Potentiometric; Potentiometric titration; Replicate; Reproduction; Salinity; Salinity, standard deviation; Single species; Southern_Ocean_OA; Species; Temperature, standard deviation; Temperature, water; Treatment; Zooplankton
    Type: Dataset
    Format: text/tab-separated-values, 9576 data points
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    DATA PANGAEA
  • 12
    Electronic Resource
    Electronic Resource
    Green krill, the indicator of micro- and nano-size phytoplankton availability to krill (1999)
    Springer
    Polar biology 22 (1999), S. 133-136 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Size-fractionated chlorophyll-a concentrations of surface seawater were measured for pico-, nano-, and micro-size fractions (〈2 μm, 2–10 μm, and 〉10 μm respectively) during commercial krill fishery operations in the waters north of the South Shetland Islands. The proportion of green krill (individuals discoloured due to active feeding on phytoplankton) had significant regressions with chlorophyll-a concentrations in micro- and nano-size fractions. Between these two fractions, chlorophyll-a concentration in the micro-size fraction showed the higher partial regression coefficient. This result shows the importance of phytoplankton larger than nano-phytoplankton, especially micro-phytoplankton, in terms of a phytoplanktonic food source for Antarctic krill in the natural environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003000050400
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    Paper (German National Licenses)
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  • 13
    Electronic Resource
    Electronic Resource
    Antarctic krill (Euphausia superba dana) eat salps (1996)
    Springer
    Polar biology 16 (1996), S. 479-481 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Feeding behaviour of Antarctic krill (Euphausia superba) on salps was observed in shipboard experiments during the 1994/1995Kaiyo Maru Antarctic Ocean research cruise. The feeding rate was more than 0.5 salp/krill per day. When offered ethanol extracts of four prey types, salps, phytoplankton, krill and polychaetes, krill preferred the salp extracts. This evidence implies that the substances extracted from salps were most attractive to krill. These results might indicate a tight ecological relationship between krill and salps.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02329066
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  • 14
    Electronic Resource
    Electronic Resource
    Microzooplankton grazing in the surface water of the Southern Ocean during an austral summer (1997)
    Springer
    Polar biology 18 (1997), S. 240-245 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Microzooplankton grazing was investigated in surface waters of the Indo-Pacific and Atlantic sectors of the Southern Ocean by the dilution method. Phytoplankton growth varied mainly between 0.1 and 0.4 day−1, and microzooplankton grazing between 0.0 and 0.3 day−1. Great fluctuations in phytoplankton growth rate were observed at one station within 3 weeks and between closely spaced stations. Microzooplankton grazing rates were similar to phytoplankton growth rate despite the variation of phytoplankton growth rates, although in some cases, phytoplankton growth overwhelmed microzooplankton grazing. These observations suggest that microzooplankton are the main consumers of primary producers, and that steady state between phytoplankton growth and microzooplankton grazing is usually established in the Southern Ocean in austral summer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003000050184
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  • 15
    Electronic Resource
    Electronic Resource
    Discovery of ciliates reproducing in the gut of Antarctic krill (1997)
    Springer
    Polar biology 18 (1997), S. 158-160 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract During a recent Antarctic research cruise (December 1994/February 1995), dissection of fresh Antarctic krill (Euphausia superba) on board ship revealed live motile ciliates in the gut of krill. Further observation of gut samples by scanning electron microscopy indicated that the ciliates were symbionts located within the gut. We inferred that the ciliates may have enabled the krill to digest a wider range of food items, and as a consequence, this had became an important strategy for Antarctic krill's survival in the Antarctic ecosystem.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003000050171
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  • 16
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    Light regime affects the seasonal cycle of Antarctic krill (Euphausia superba): impacts on growth, feeding, lipid metabolism, and maturity (2018)
    In:  EPIC3Canadian Journal of Zoology, 96(11), pp. 1203-1213, ISSN: 0008-4301
    Details
    Publication Date: 2019-05-08
    Description: Light regime is an important zeitgeber for Antarctic krill (Euphausia superba Dana, 1850), which seems to entrain an endogenous timing system that synchronizes its life cycle to the extreme light conditions in the Southern Ocean. To understand the flexibility of Antarctic krill’s seasonal cycle, we investigated its physiological and behavioural responses to different light regimes and if an endogenous timing system was involved in the regulation of these seasonal processes. We analysed growth, feeding, lipid content, and maturity in a 2-year laboratory experiment simulating the latitudinal light regimes at 52°S and 66°S and constant darkness under constant food level. Our results showed that light regime affected seasonal cycles of growth, feeding, lipid metabolism, and maturity in Antarctic krill. Seasonal patterns of growth, feeding, and maturity persisted under constant darkness, indicating the presence of an endogenous timing system. The maturity cycle showed differences in critical photoperiods according to the simulated latitudinal light regime. This suggests a flexible endogenous timing mechanism in Antarctic krill, which may determine its response to future environmental changes.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 17
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    The Seasonal Metabolic Activity Cycle of Antarctic Krill (Euphausia superba): Evidence for a Role of Photoperiod in the Regulation of Endogenous Rhythmicity (2018)
    FRONTIERS MEDIA SA
    In:  EPIC3FRONTIERS IN PHYSIOLOGY, FRONTIERS MEDIA SA, 9(1715), ISSN: 1664-042X
    Details
    Publication Date: 2019-02-13
    Description: Antarctic krill (Euphausia superba), a key species in the Southern Ocean, reduce their metabolism as an energy saving mechanism in response to the harsh environmental conditions during the Antarctic winter. Although the adaptive significance of this seasonal metabolic shift seems obvious, the driving factors are still unclear. In particular, it is debated whether the seasonal metabolic cycle is driven by changes in food availability, or if an endogenous timing system entrained by photoperiod might be involved. In this study, we used different long-term photoperiodic simulations to examine the influence of light regime and endogenous rhythmicity on the regulation of krill seasonal metabolic cycle. Krill showed a seasonal cycle of growth characterized by null-to-negative growth rates during autumn-winter and positive growth rates during spring-summer, which was manifested also in constant darkness, indicating strong endogenous regulation. Similar endogenous cycles were observed for the activity of the key-metabolic enzyme malate dehydrogenase (MDH) and for the expression levels of a selection of metabolic-related genes, with higher values in spring-summer and lower values in autumn-winter. On the other side, a seasonal cycle of oxygen consumption was observed only when krill were exposed to simulated seasonal changes in photoperiod, indicating that light-related cues might play a major role in the regulation of krill oxygen consumption. The influence of light-regime on oxygen consumption was minimal during winter, when light-phase duration was below 8 h, and it was maximal during summer, when light-phase duration was above 16 h. Significant upregulation of the krill clock genes clk, cry2, and tim1, as well as of the circadian-related opsins rh1a and rrh, was observed after light-phase duration had started to decrease in early autumn, suggesting the presence of a signaling cascade linking specific seasonal changes in the Antarctic light regime with clock gene activity and the regulation of krill metabolic dormancy over the winter.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 18
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    Successful ecosystem-based management of Antarctic krill should address uncertainties in krill recruitment, behaviour and ecological adaptation (2020)
    Nature Publishing Group
    In:  EPIC3Communications Earth & Environment, Nature Publishing Group, 1(28), ISSN: 2662-4435
    Details
    Publication Date: 2020-11-12
    Description: Antarctic krill, Euphausia superba, supports a valuable commercial fishery in the Southwest Atlantic, which holds the highest krill densities and is warming rapidly. The krill catch is increasing, is concentrated in a small area, and has shifted seasonally from summer to autumn/winter. The fishery is managed by the Commission for the Conservation of Antarctic Marine Living Resources, with the main goal of safeguarding the large populations of krill-dependent predators. Here we show that, because of the restricted distribution of successfully spawning krill and high inter-annual variability in their biomass, the risk of direct fishery impacts on the krill stock itself might be higher than previously thought. We show how management benefits could be achieved by incorporating uncertainty surrounding key aspects of krill ecology into management decisions, and how knowledge can be improved in these key areas. This improved information may be supplied, in part, by the fishery itself.
    Repository Name: EPIC Alfred Wegener Institut
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  • 19
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    The importance of Antarctic krill in biogeochemical cycles (2019)
    In:  EPIC3Nature Communications, 10(4742)
    Details
    Publication Date: 2020-01-21
    Description: Antarctic krill (Euphausia superba) are swarming, oceanic crustaceans, up to two inches long, and best known as prey for whales and penguins – but they have another important role. With their large size, high biomass and daily vertical migrations they transport and transform essential nutrients, stimulate primary productivity and influence the carbon sink. Antarctic krill are also fished by the Southern Ocean’s largest fishery. Yet how krill fishing impacts nutrient fertilisation and the carbon sink in the Southern Ocean is poorly understood. Our synthesis shows fishery management should consider the influential biogeochemical role of both adult and larval Antarctic krill.
    Repository Name: EPIC Alfred Wegener Institut
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  • 20
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    Analysis of the circadian transcriptome of the Antarctic krill Euphausia superba (2019)
    In:  EPIC3Scientific Reposrts, 9(13894)
    Details
    Publication Date: 2020-01-21
    Description: Antarctic krill (Euphausia superba) is a high latitude pelagic organism which plays a central role in the Southern Ocean ecosystem. E. superba shows daily and seasonal rhythms in physiology and behaviour, which are synchronized with the environmental cycles of its habitat. Recently, the main components of the krill circadian machinery have been identified and characterized. However, the exact mechanisms through which the endogenous timing system operates the control and regulation of the overt rhythms remains only partially understood. Here we investigate the involvement of the circadian clock in the temporal orchestration of gene expression by using a newly developed version of a krill microarray platform. The analysis of transcriptome data from krill exposed to both light-dark cycles (LD 18:6) and constant darkness (DD), has led to the identification of 1,564 putative clock-controlled genes. A remarkably large proportion of such genes, including several clock components (clock, period, cry2, vrille, and slimb), show oscillatory expression patterns in DD, with a periodicity shorter than 24 hours. Energy-storage pathways appear to be regulated by the endogenous clock in accordance with their ecological relevance in daily energy managing and overwintering. Our results provide the first representation of the krill circadian transcriptome under laboratory, free-running conditions.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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