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  • 1
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    Regional variation in the life cycle of Rhincalanus gigas (Copepoda Calanoid) in the Atlantic sector of the Southern Ocean - re-examination of existing data (1928-1993) (1997)
    In:  EPIC3Marine ecology-progress series, 157, pp. 261-275
    Details
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 2
    Electronic Resource
    Electronic Resource
    Sampling biological characteristics of krill: Effect of heterogeneous nature of swarms (1990)
    Springer
    Marine biology 107 (1990), S. 409-415 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An effect of the very patchy distribution of Antarctic krill (Euphausia superba Dana) in various forms of aggregation is that a single swarm may not provide an unbiased estimate of population parameters such as mean length of krill in the local area. Here, we analyse the number of samples required to estimate the characteristics of a local population as precisely as if there were no differences between krill swarms in terms of their biological composition. Krill were intensively sampled over different spatial and temporal scales around South Georgia in 1981 and 1982, and in the Bransfield Strait in 1985. These varied from replicate hauls at a single station over 24 h and repeat sampling in restricted areas over periods of 6 to 14 d to regional surveys around South Georgia and in the Bransfield Strait. Various biological characteristics were measured such as length, maturity, moult stage and feeding state. Depending upon the biological characteristic examined and the area covered by the sampling programme, the number of samples needed to obtain the same degree of precision as would be found in the absence of heterogeneity varied from 3 to 〉 80 samples. This has important implications for the design of net-sampling programme for monitoring krill populations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01313422
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  • 3
    Electronic Resource
    Electronic Resource
    Antarctic krill aggregation characteristics from acoustic observations in the Southwest Atlantic Ocean (1993)
    Springer
    Marine biology 117 (1993), S. 171-183 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The distributional features and physical characteristics of 4830 krill (Euphausia superba Dana) aggregations detected acoustically in the Southwest Atlantic between 26 January and 21 February 1981 are described. Results are compared with aggregations detected in the Indian Ocean. Aggregations in the Atlantic were larger, closer to the surface and to each other than in the Indian Ocean. Similar patterns in the distribution of aggregation spacing along survey transects were found in the two areas, although the pattern of spacings in the Atlantic indicates differences in the scale of aggregation. Serial interdependence of aggregation variables was minimal in the Atlantic, with aggregation thickness, length and spacing showing weak inter-relationships. Weak functional association, between water depth and aggregation thickness was evident. Investigation of variability in aggregation structure in relation to prevailing environmental conditions gave equivocal results and no clear association between any aggregation variable and prevailing hydrography was observed. The implications of these results for future studies on krill aggregation are discussed in relation to a conceptual framework which was developed from the present results and aimed at linking krill aggregation characteristics to environmental features.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00346440
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  • 4
    Electronic Resource
    Electronic Resource
    Cephalopod prey of the grey-headed albatrossDiomedea chrysostoma (1990)
    Springer
    Marine biology 104 (1990), S. 353-362 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cephalopod remains were collected, at regular intervals throughout the fledging period, from the stomach contents of chicks of the grey-headed albatrossDiomedea chrysostoma at Bird Island, South Georgia, in 1984 and 1986 and from regurgitations of adults at the nest in 1986. The 1984 sample was taken during a season characterised by abnormal local oceanographic conditions in which the breeding success was very low; in 1986 conditions were normal and breeding success was high. Cephalopod beaks (289 from adults; 5 651 from chicks) were identified, and allometric equations were used to estimate the biomass represented. Five cephalopod species belonging to five families (Gonatidae, Onychoteuthidae, Psychroteuthidae, Ommastrephidae and Cranchiidae) contributed 98% by number and 97% of the biomass fed to chicks. The most important species was the ommastrephidMartialia hyadesi, contributing 68.9 to 77.4% by number and 72.5 to 79.3% of the total biomass fed to chicks. The relative proportions of cephalopod species in the chicks' diet were similar between 1984 and 1986, but the total number and biomass was significantly less in 1984. There is evidence of growth ofM. hyadesi between January and June.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01314337
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  • 5
    Electronic Resource
    Electronic Resource
    Layers of Antarctic krill, Euphausia superba : are they just long krill swarms? (1998)
    Springer
    Marine biology 131 (1998), S. 237-247 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Antarctic krill, Euphausia superba Dana, a major component in the southern ocean food web, typically occur in aggregations that range from small, discrete swarms and schools through to layers and superswarms that extend horizontally for several kilometres. A large Longhurst–Hardy plankton recorder has been used to obtain high-resolution serial samples from within two layers (up to 4 km in length) that were found near Elephant Island, north of the Antarctic Peninsula. Krill length, sex and maturity stage, net and acoustic estimates of number density are shown to vary significantly within these large layers. The variation occurring within a single layer is comparable with that occurring in a set of 38 swarms sampled contemporaneously with the layers. Thus, unlike a krill swarm, a whole krill layer may account for a substantial amount of the variation in the local krill population, although individual parts of the layer cannot be considered in this way. The layers play an important role in the ecology of the krill within the area. Firstly, these large layers may contain a significant proportion of the biomass within an area. Secondly, the structure of the layers gives some insight into the ways in which krill swarm formation and dispersal may be occurring.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050316
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  • 6
    Electronic Resource
    Electronic Resource
    Cephalopod prey of the wandering albatross Diomedea exulans (1987)
    Springer
    Marine biology 96 (1987), S. 1-10 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cephalopod beaks from the stomach contents of “wandering albatross” (Diomedea exulans L.) chicks from Bird Island, South Georgia, were sampled between May and September in 1983 and 1984. Lower beaks were identified and measured, and allometric data were used to calculated mantle length and biomass of the species consumed. A total of 3421 lower beaks were examined, representing 35 species in the 1983 sample and 45 species in the 1984 sample. Eight of the twenty families contributed over 95% of the biomass. In 1984 there were less Onychoteuthidae and more Ommastrephidae than in 1983 and a decrease in the number of species known to occur south of the Antarctic Polar Front. There was a difference in the size-frequency distribution of the cephalopod diet in the two years; in 1984 there was a higher frequency of intermediate-sized specimens, reflecting the greater importance of ommastrephids, especially Illex sp. The energy content of cephalopods in 1984 may have been greater than in 1983. Serial sampling of cephalopod beaks during the austral winter did not reveal evidence of growth. By the age of 200 d, wandering albatross chicks have consumed a total of approximately 100 kg wet weight of cephalopods each.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00394833
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  • 7
    Electronic Resource
    Electronic Resource
    Digestion rate, gut passage time and absorption efficiency in the Antarctic spiny plunderfish (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 57 (2000), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The absolute gut evacuation rate (GER) (g day−1) of Harpagifer antarcticus increased with increasing ration mass, fish mass only influenced the absolute GER at a daily ration level of 0·3% wet fish mass (approximately a maintenance ration). The relative GER (% of meal fed day−1) was also affected differently by fish and ration mass depending on the relative ration level being fed; at rations of 0·7% wet fish mass or above the relative GER decreased with increasing fish or ration mass (in such a way that the absolute GER remained constant and unaffected by fish mass). At maintenance (0·3% wet fish mass) rations the relative GER was not affected by fish size or ration mass. Thus, there appears to be a ration threshold above which the digestion physiology alters. Mass-specific GER (% g fish−1 day−1) decreased with increasing fish mass. Within a set relative ration level (% wet fish mass) an increase in fish mass decreased the mass-specific GER. At a fixed ration mass, an increase in fish mass (i.e. a reduction in the ration expressed as % fish mass) resulted in a decrease in mass-specific GER. Gut evaluation time (GET) decreased and absorption efficiency (A) increased with increasing absolute GER. The effect of ration and fish mass on the absolute and relative GER followed the same pattern irrespective of the diet, however the A and GER (% day−1 and g day−1) were higher and the GET shorter when the fish were fed shelled krill rather than amphipods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.2000.tb02201.x
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  • 8
    Electronic Resource
    Electronic Resource
    Response of two Antarctic bryophytes to stratospheric ozone depletion (2002)
    Oxford, UK : Blackwell Science Ltd
    Global change biology 8 (2002), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: We report a study which measured changes to the radiative environment arising from stratospheric O3 depletion at Rothera Point on the western Antarctic Peninsula (67°S, 68°W) and subsequent associations between these changes and the pigmentation and maximum quantum yield of photochemistry (Fv/Fm) of two Antarctic bryophytes, the liverwort Cephaloziella varians and the moss Sanionia uncinata. We found a strong relationship between O3 column depth and the ratio of UV-B to PAR irradiance (FUV-B/FPAR) recorded at ground level. Weaker, but significant, associations were also found between O3 column depth and noon irradiances and daily doses of unweighted and biologically effective UV-B radiation received at ground level. Regression analyses indicated that FUV-B/FPAR and daily dose of unweighted UV-B were best predictors for concentrations of total carotenoids and UV-B screening pigments extracted from bryophyte tissues. Concentrations of these pigments were loosely but significantly positively associated with O3-dependent irradiance parameters. HPLC analyses of carotenoids also suggested that both species increased the synthesis of neoxanthin during periods of O3 depletion. Violaxanthin, lutein, zeaxanthin and b,bββ-carotene concentrations were also apparently influenced by O3 reduction, but not consistently across both bryophyte species. Concentrations of chlorophylls a and b were apparently unaffected by O3 depletion.No direct associations between Fv/Fm and O3-dependent irradiance parameters were found. However stepwise multiple regression analyses suggested that the production of UV-B screening pigments conferred protection from elevated FUV-B/FPAR on Fv/Fm in both species and that carotenoids conferred protection on Fv/Fm in Sanionia. Our data suggest that changes to the radiative environment associated with stratospheric O3 depletion influence the pigmentation of two Antarctic bryophytes, but that Fv/Fm is unaffected, at least in part because of rapid synthesis of protective pigments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2486.2002.00509.x
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  • 9
    Electronic Resource
    Electronic Resource
    Growth and tissue mass cycles in the infaunal bivalve Yoldia eightsi at Signy Island, Antarctica (2000)
    Springer
    Polar biology 23 (2000), S. 420-428 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Shell growth in Yoldia eightsi was measured over an austral summer and winter in 1992. In specimens 〈 12 mm length, growth was not significantly different between summer and winter periods, and the fastest recorded rate, 6.3 μm day−1 was for 5-mm individuals during the winter. In summer, specimens of all lengths grew significantly, but in winter bivalves 〉 27 mm length did not increase in length. Tissue dry and ash-free dry mass (AFDM) cycles were assessed at monthly intervals between December 1988 and January 1991. ANCOVA indicated significant interannual and seasonal effects on this cycle. Tissue mass increased in the summer, coinciding with the phytoplankton bloom and the period of maximum sedimentation of organic material from the water column. A standard 20-mm-length animal reached a maximum AFDM of 114 mg in February 1990. The minimum value (68 mg AFDM) throughout the 2 years of measurements was in early December 1988, at the end of the austral winter. Periods of tissue mass increase were, therefore, decoupled from shell growth, at least in juveniles. Tissue mass was significantly higher in 1990 than 1989, which was mainly due to high organic contents in the summer (January to May). This was not consistent with the pattern of organic content in the sediments at the study site, but was in phase with the cycle in sediment chlorophyll a content. Tissue mass increase depended on major resource input during the summer, but Y. eightsi was capable of maintaining winter condition from stocks of benthic microalgae in years of poor ice cover. Tissue mass declined between April and July each year. This was accompanied by large falls in tissue ash content, and coincided with the spawning period in early June. These are the first monthly tissue mass data collected over a 2-year period for an Antarctic mollusc. They are the first such data indicating seasonal variation in tissue mass and showing a decoupling of shell and tissue growth in a polar bivalve. The P/B ratio calculated from these data was 0.106, which is slightly lower than previous values found for this species, but is in line with general values for Antarctic marine benthos.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003000050463
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  • 10
    Electronic Resource
    Electronic Resource
    The summer zooplankton community at South Georgia: biomass, vertical migration and grazing (1995)
    Springer
    Polar biology 15 (1995), S. 195-208 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Zooplankton abundance and biomass were determined during January 1990 at two stations to the north-west of South Georgia using a Longhurst Hardy Plankton Recorder (LHPR). At both shelf and oceanic station sites, zooplankton biomass, (excluding Euphausia superba), was found to be ca. 13 g dry mass m−2. Copepods and small euphausiids dominated the catches. These estimates are over 4 times higher than values generally reported for the Southern Ocean and may reflect firstly, the high productivity of the study area, secondly, the time of year, summer, when biomass for many species is maximal, and thirdly, the high sampling efficiency of the LHPR. Principal components analysis disclosed similarities and differences between adjacent depth strata in terms of abundance, biomass and species composition. At both stations most variability occurred in the mixed layer (0–60 m) and thermocline (60–120 m) with depth horizons below this being more homogeneous. Diel migrations were observed for most taxa with abundance increasing in the mixed layer at night. At the oceanic station, species and higher taxa belonging to the mesopelagic community were generally well spread throughout this domain and, with the exception of Pleuromamma robusta and Metridia curticauda, showed little evidence of migration. The grazing impact of the epipelagic community (copepods and small euphausiids) was estimated to remove 3–4% of the microbial standing stock day−1 and a conservative 25% and 56% of daily primary production at the oceanic and shelf stations respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239059
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