Concordance of interannual fluctuations in acoustically estimated densities of Antarctic krill around South Georgia and Elephant Island: biological evidence of same-year teleconnections across the Scotia Sea

1999 ◽  
Vol 134 (4) ◽  
pp. 675-681 ◽  
Author(s):  
A. S. Brierley ◽  
D. A. Demer ◽  
J. L. Watkins ◽  
R. P. Hewitt
Keyword(s):  
Antarctic Krill ◽  
Scotia Sea ◽  
South Georgia ◽  
Biological Evidence ◽  
Interannual Fluctuations ◽  
Elephant Island

scholarly journals Experimental determination of reflectance spectra of Antarctic krill (Euphausia superba) in the Scotia Sea

2021 ◽  
pp. 1-13
Author(s):  
Anna Belcher ◽  
Sophie Fielding ◽  
Andrew Gray ◽  
Lauren Biermann ◽  
Gabriele Stowasser ◽  
...  
Keyword(s):  
Antarctic Krill ◽  
Euphausia Superba ◽  
Reflectance Spectra ◽  
Spectral Signature ◽  
Absorption Feature ◽  
Scotia Sea ◽  
Surface Ocean ◽  
Measuring Surface ◽  
Ground Truthing

Abstract Antarctic krill are the dominant metazoan in the Southern Ocean in terms of biomass; however, their wide and patchy distribution means that estimates of their biomass are still uncertain. Most currently employed methods do not sample the upper surface layers, yet historical records indicate that large surface swarms can change the water colour. Ocean colour satellites are able to measure the surface ocean synoptically and should theoretically provide a means for detecting and measuring surface krill swarms. Before we can assess the feasibility of remote detection, more must be known about the reflectance spectra of krill. Here, we measure the reflectance spectral signature of Antarctic krill collected in situ from the Scotia Sea and compare it to that of in situ water. Using a spectroradiometer, we measure a strong absorption feature between 500 and 550 nm, which corresponds to the pigment astaxanthin, and high reflectance in the 600–700 nm range due to the krill's red colouration. We find that the spectra of seawater containing krill is significantly different from seawater only. We conclude that it is tractable to detect high-density swarms of krill remotely using platforms such as optical satellites and unmanned aerial vehicles, and further steps to carry out ground-truthing campaigns are now warranted.

scholarly journals The Effects of Combined Ocean Acidification and Nanoplastic Exposures on the Embryonic Development of Antarctic Krill

2021 ◽  
Vol 8 ◽  
Author(s):  
Emily Rowlands ◽  
Tamara Galloway ◽  
Matthew Cole ◽  
Ceri Lewis ◽  
Victoria Peck ◽  
...  
Keyword(s):  
Embryonic Development ◽  
Southern Ocean ◽  
Ocean Acidification ◽  
Antarctic Krill ◽  
Gravid Female ◽  
Limb Bud ◽  
Global Ocean ◽  
Plastic Pollution ◽  
Atlantic Sector ◽  
Scotia Sea

In aquatic environments, plastic pollution occurs concomitantly with anthropogenic climate stressors such as ocean acidification. Within the Southern Ocean, Antarctic krill (Euphausia Superba) support many marine predators and play a key role in the biogeochemical cycle. Ocean acidification and plastic pollution have been acknowledged to hinder Antarctic krill development and physiology in singularity, however potential multi-stressor effects of plastic particulates coupled with ocean acidification are unexplored. Furthermore, Antarctic krill may be especially vulnerable to plastic pollution due to their close association with sea-ice, a known plastic sink. Here, we investigate the behaviour of nanoplastic [spherical, aminated (NH2), and yellow-green fluorescent polystyrene nanoparticles] in Antarctic seawater and explore the single and combined effects of nanoplastic (160 nm radius, at a concentration of 2.5 μg ml–1) and ocean acidification (pCO2 ∼900, pHT 7.7) on the embryonic development of Antarctic krill. Gravid female krill were collected in the Atlantic sector of the Southern Ocean (North Scotia Sea). Produced eggs were incubated at 0.5 °C in four treatments (control, nanoplastic, ocean acidification and the multi-stressor scenario of nanoplastic presence, and ocean acidification) and their embryonic development after 6 days, at the incubation endpoint, was determined. We observed that negatively charged nanoplastic particles suspended in seawater from the Scotia Sea aggregated to sizes exceeding the nanoscale after 24 h (1054.13 ± 53.49 nm). Further, we found that the proportion of embryos developing through the early stages to reach at least the limb bud stage was highest in the control treatment (21.84%) and lowest in the multi-stressor treatment (13.17%). Since the biological thresholds to any stressors can be altered by the presence of additional stressors, we propose that future nanoplastic ecotoxicology studies should consider the changing global ocean under future climate scenarios for assessments of their impact and highlight that determining the behaviour of nanoplastic particles used in incubation studies is critical to determining their toxicity.

Changes in seabird species abundance near South Georgia during a period of rapid change in sea surface temperature

1992 ◽  
Vol 4 (1) ◽  
pp. 15-22 ◽  
Author(s):  
G.L. Hunt ◽  
J. Priddle ◽  
M.J. Whitehouse ◽  
R.R. Veit ◽  
R.B. Heywood
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Rapid Change ◽  
Species Abundance ◽  
Sea Surface ◽  
Resident Species ◽  
Seabird Species ◽  
Scotia Sea ◽  
South Georgia ◽  
Time Observation

During a three month research cruise near the island of South Georgia, sea surface temperature (SST) increased from c. 2°C to over 4°C. Satellite derived SST show that this corresponded to a rapid southward and eastward shift of isotherms in the northern Scotia Sea, which could have resulted from changes in the wind field. At the same time, observation from the ship of seabirds close to the island indicated changes in the abundance of some non-resident species, whereas resident breeders from South Georgia, such as black-browed albatrosses (Diomedea melanophris) and prions (Pachyptila spp.) which were foraging locally, were present at consistent density in both halves of the survey. Blue petrels (Halobaena caerulea) left the area after breeding, so were associated only with the low water temperatures during the first part of the cruise. In contrast, great shearwaters (Puffinus gravis) and soft-plumaged petrels (Pterodroma mollis) migrated into the area later in the survey. These birds were almost certainly non-breeders which were feeding in the warmer water which had moved towards the island.

scholarly journals Diel vertical migration of Antarctic krill (Euphausia superba) is flexible during advection across the Scotia Sea

2009 ◽  
Vol 31 (10) ◽  
pp. 1265-1281 ◽  
Author(s):  
K. A. Cresswell ◽  
G. A. Tarling ◽  
S. E. Thorpe ◽  
M. T. Burrows ◽  
J. Wiedenmann ◽  
...  
Keyword(s):  
Vertical Migration ◽  
Diel Vertical Migration ◽  
Antarctic Krill ◽  
Euphausia Superba ◽  
Scotia Sea ◽  
Antarctic Krill Euphausia Superba

scholarly journals Spatial and temporal variability in the structure of aggregations of Antarctic krill (Euphausia superba) around South Georgia, 1997–1999

2011 ◽  
Vol 68 (3) ◽  
pp. 489-498 ◽  
Author(s):  
Martin J. Cox ◽  
Jonathan L. Watkins ◽  
Keith Reid ◽  
Andrew S. Brierley
Keyword(s):  
Temporal Variability ◽  
Antarctic Krill ◽  
Marine Ecosystem ◽  
Euphausia Superba ◽  
Spatial And Temporal Variability ◽  
Dual Frequency ◽  
South Georgia ◽  
Estimation System ◽  
Antarctic Krill Euphausia Superba

Abstract Cox, M. J., Watkins, J. L., Reid, K., and Brierley, A. S. 2011. Spatial and temporal variability in the structure of aggregations of Antarctic krill (Euphausia superba) around South Georgia, 1997–1999. – ICES Journal of Marine Science, 68: . Antarctic krill are important in the South Georgia (54°S 35°W) marine ecosystem. They form aggregations that vary widely in packing density (<1 to 1000 s of individuals m−3), length (tens to thousands of metres), and height (tens of metres). Acoustic surveys are often used to estimate krill biomass and provide data that give insight into aggregation structure. Using dual-frequency (38 and 120 kHz) acoustic data collected during six surveys conducted around South Georgia during the 1997, 1998, and 1999 austral summers, we isolated 2990 aggregations by applying the Shoal Analysis and Patch Estimation System algorithm in Echoview and a krill-length-dependent acoustic identifier (ΔSv120–38). Multivariate cluster (partition) analysis was applied to metrics from each of the aggregations, resulting in three aggregation types with an overall proportional split of 0.28:0.28:0.44. Types 1 and 3 had low mean densities (<2 g m−3), whereas Type 2 had a mean density of 94 g m−3. Intersurvey differences were found between the effort-corrected numbers of aggregation types (p = 2.5e−6), and between on- and off-continental shelf areas (p = 1.5e−7), with a greater number of Type 2 aggregations being found on-shelf. The findings suggest intersurvey variation in krill catchability, with krill being more likely to be caught on-shelf.

scholarly journals From strategic ambiguity to technical reference points in the Antarctic krill fishery: the worst journey in the world?

2013 ◽  
Vol 40 (4) ◽  
pp. 394-405 ◽  
Author(s):  
SIMEON L. HILL
Keyword(s):  
Antarctic Krill ◽  
Drake Passage ◽  
Simulation Models ◽  
Reference Points ◽  
Multiple Predators ◽  
Scotia Sea ◽  
Current State ◽  
Management Measures ◽  
Spatial Subdivision ◽  
Ecosystem State

SUMMARYThe goals of ecosystem based management (EBM) are strategically ambiguous, meaning that they require interpretation to identify objectives for ecosystem state. Ecosystem states that are useful for achieving such objectives are known as reference points. Soft reference points specify both a state and a probability of the ecosystem being in that state. They are used with simulation models to identify management measures for which the risk of the ecosystem entering an undesirable state is below a specified level. The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) is responsible for the EBM of Antarctic krill fisheries. CCAMLR used soft reference points for the krill stock in the Scotia Sea and southern Drake Passage to set a regional catch limit. However, this catch limit needs spatial subdivision to protect predators from localized depletion. Model-based evaluations of different options for subdividing the catch limit used illustrative reference points to assess the depletion risk to multiple predators. This study demonstrates that the apparent risk is sensitive to the choice of reference point and method for aggregating modelled predators. EBM practitioners and stakeholders need to be aware that these factors could therefore bias comparisons of management measures. Nonetheless, qualitative distinctions between different spatial subdivision options are relatively consistent except at high levels of aggregation and extreme reference points. This study also demonstrates a lack of generality in the relationship between current and future ecosystem state. Thus, the EBM goal of maintaining ecosystem resilience implies different reference points for the current state of different ecosystem components. Despite early progress in defining soft reference points for the krill stock, CCAMLR has not yet defined reference points for krill predators. Structured dialogue aimed at identifying collective objectives might be necessary to achieve further progress in CCAMLR and other EBM organizations.

scholarly journals Recruitment of Antarctic krill Euphausia superba in the South Georgia region: adult fecundity and the fate of larvae

2007 ◽  
Vol 331 ◽  
pp. 161-179 ◽  
Author(s):  
GA Tarling ◽  
J Cuzin-Roudy ◽  
SE Thorpe ◽  
RS Shreeve ◽  
P Ward ◽  
...  
Keyword(s):  
Antarctic Krill ◽  
Euphausia Superba ◽  
The South ◽  
South Georgia ◽  
Antarctic Krill Euphausia Superba
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