Seals and whales of the Southern Ocean

1977 ◽  
Vol 279 (963) ◽  
pp. 81-96 ◽  
Keyword(s):  
Southern Ocean ◽  
Marine Mammals ◽  
Deep Ocean ◽  
Euphausia Superba ◽  
The Body ◽  
The Arctic ◽  
Individual Species ◽  
Baleen Whales ◽  
Fur Seals ◽  
The Antarctic

There are fewer species of marine mammals in the Antarctic than in the Arctic, probably because of the wide deep ocean with no geographical barriers to promote speciation. The stocks are substantially larger in the Antarctic and the body sizes of individual species are larger, probably owing to a more abundant food supply. Seasonal changes in the environment in the Southern Ocean are marked and food available to baleen whales is very much greater in summer. Ecological interactions of the consumers, principally in relation to krill Euphausia superba , are discussed and attention drawn to some of the ways in which ecological separation is achieved, both within and between species. Estimates of abundances, biomasses and food requirements are given for the seals and large whales. The original numbers of whales in the Antarctic were far greater than in other oceans, but the stocks have been severely reduced by whaling. This may have increased the availability of krill to other consumers by as much as 150 million tonnes annually. Increased growth rates, earlier maturity and higher pregnancy rates have been demonstrated for baleen whale species, and earlier maturity for the crabeater seal. While it has not been possible to demonstrate increases in the populations of any of these species, the stocks of fur seals and penguins have been monitored and show significant population increases. A key question is whether the original balance of this ecosystem can be regained with appropriate management.

Fishing down the food web of the Antarctic continental shelf and slope

Polar Record ◽  
2013 ◽  
Vol 50 (1) ◽  
pp. 92-107 ◽  
Author(s):  
David G. Ainley ◽  
Daniel Pauly
Keyword(s):  
Southern Ocean ◽  
Food Web ◽  
Antarctic Peninsula ◽  
Continental Margin ◽  
Marine Mammals ◽  
Marine Ecosystem ◽  
Euphausia Superba ◽  
The Commons ◽  
By Catch ◽  
The Antarctic

ABSTRACTThe history of biotic exploitation for the continental margin (shelf and slope) of the Antarctic Large Marine Ecosystem (LME) is reviewed, with emphasis on the period from 1970 to 2010. In the Antarctic Peninsula portion, marine mammals were decimated by the 1970s and groundfish by the early 1980s. Fishing for Antarctic krill Euphausia superba began upon the demise of groundfish and now is the only fishing that remains in this region. Surveys show that cetacean and most groundfish stocks remain severely depressed, harvest of which is now prohibited by the International Whaling Commission and the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). On the other hand, krill fishing in this region is underway and in recent years has contributed up to 72% of the Southern Ocean catch, depending on fishing conditions and the CCAMLR conservation measures in force. Elsewhere along the Antarctic continental margin, marine mammals were also severely depleted by the 1970s, followed directly by relatively low-level fisheries for krill that continued until the early 1990s. Recently in these areas, where fin-fishing is still allowed, fisheries for Antarctic toothfish Dissostichus mawsoni have been initiated, with one of this fish's main prey, grenadiers Macrourus spp., being taken significantly as by-catch. Continental margin fishing currently accounts for ~25% of the total toothfish catch of the Southern Ocean. Fishing along the Antarctic continental margin, especially the Antarctic Peninsula region, is a clear case of both the tragedy of the commons and ‘fishing down the food web’.

scholarly journals The role of marine mammals in the Barents Sea foodweb

2019 ◽  
Vol 76 (Supplement_1) ◽  
pp. i37-i53 ◽  
Author(s):  
Marie-Anne Blanchet ◽  
Raul Primicerio ◽  
André Frainer ◽  
Susanne Kortsch ◽  
Mette Skern-Mauritzen ◽  
...  
Keyword(s):  
Marine Mammals ◽  
Barents Sea ◽  
Phylogenetic Group ◽  
The Arctic ◽  
Phylogenetic Groups ◽  
Baleen Whales ◽  
Trophic Links ◽  
The Barents Sea ◽  
Network Modularity

Abstract Marine mammals are important players in the Barents Sea ecosystem but their structural role in the foodweb has been little explored. We compare foodweb-related characteristics within and between phylogenetic groups for 19 marine mammals. As a group, they directly connect to the most central species (i.e cod and haddock) in the Barents Sea (i.e. cod and haddock) and consume over half of the available species. Pinnipeds are the most homogenous phylogenetic group with high omnivory and high prey richness. Mysticetes are split between well-connected species with high omnivory like the humpback whale, and peripheral specialists like the blue whale. Based on foodweb-derived indices some species consistently cluster together forming two groups, suggesting topological redundancy within them. One is dominated by Arctic seals and the other includes most of the baleen whales. Marine mammals generally contribute to network modularity as their trophic links are mainly within their own module. However, Atlantic species such as the grey seal act as a module connector decreasing modularity. This might negatively affect ecosystem robustness with perturbation effects spreading further and quicker in the foodweb. In the Arctic reaches of the Barents Sea, climate warming is likely to bring about extensive changes in the foodweb structure through a redistribution of species.

Francis Charles Fraser, 16 June 1903 - 21 October 1978

1979 ◽  
Vol 25 ◽  
pp. 287-317
Keyword(s):  
Natural History ◽  
Southern Ocean ◽  
British Museum ◽  
Euphausia Superba ◽  
Main Task ◽  
Baleen Whales ◽  
Life And Death ◽  
Personal Qualities

Francis Charles Fraser, internationally respected as a leading authority on whales, dolphins and porpoises, spent most of his career (1933-69) in the British Museum (Natural History). His introduction to cetology could not have been better. From 1925 to 1933 he was a zoologist on ‘ Discovery Investigations’, charged with the main task of studying the life and death of whales in relation to their physical and biological surroundings in the Southern Ocean. Fraser’s Discovery research, as will be seen, was considerably more than that represented in his definitive study on the development of krill ( Euphausia superba ), the food of the large baleen whales. His publications from the Museum were almost entirely concerned with cetaceans. That he was able to pursue this research, despite the heavy and increasing demands of museum and other duties, was due to his adroitness as an organizer and the disciplined way he divided his time. There was also his determination, which matched his sturdy figure. His personal qualities will emerge as this memoir proceeds. But it is right now to say that many remember him with affection and miss the warmth of his company.

scholarly journals Coccolithophore populations and their contribution to carbonate export during an annual cycle in the Australian sector of the Antarctic zone

2018 ◽  
Vol 15 (6) ◽  
pp. 1843-1862 ◽  
Author(s):  
Andrés S. Rigual Hernández ◽  
José A. Flores ◽  
Francisco J. Sierro ◽  
Miguel A. Fuertes ◽  
Lluïsa Cros ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Ocean Acidification ◽  
Deep Ocean ◽  
Sediment Traps ◽  
Global Ocean ◽  
Field Observations ◽  
Scotia Sea ◽  
Allochthonous Species ◽  
Circumpolar Current ◽  
The Antarctic

Abstract. The Southern Ocean is experiencing rapid and relentless change in its physical and biogeochemical properties. The rate of warming of the Antarctic Circumpolar Current exceeds that of the global ocean, and the enhanced uptake of carbon dioxide is causing basin-wide ocean acidification. Observational data suggest that these changes are influencing the distribution and composition of pelagic plankton communities. Long-term and annual field observations on key environmental variables and organisms are a critical basis for predicting changes in Southern Ocean ecosystems. These observations are particularly needed, since high-latitude systems have been projected to experience the most severe impacts of ocean acidification and invasions of allochthonous species. Coccolithophores are the most prolific calcium-carbonate-producing phytoplankton group playing an important role in Southern Ocean biogeochemical cycles. Satellite imagery has revealed elevated particulate inorganic carbon concentrations near the major circumpolar fronts of the Southern Ocean that can be attributed to the coccolithophore Emiliania huxleyi. Recent studies have suggested changes during the last decades in the distribution and abundance of Southern Ocean coccolithophores. However, due to limited field observations, the distribution, diversity and state of coccolithophore populations in the Southern Ocean remain poorly characterised. We report here on seasonal variations in the abundance and composition of coccolithophore assemblages collected by two moored sediment traps deployed at the Antarctic zone south of Australia (2000 and 3700 m of depth) for 1 year in 2001–2002. Additionally, seasonal changes in coccolith weights of E. huxleyi populations were estimated using circularly polarised micrographs analysed with C-Calcita software. Our findings indicate that (1) coccolithophore sinking assemblages were nearly monospecific for E. huxleyi morphotype B/C in the Antarctic zone waters in 2001–2002; (2) coccoliths captured by the traps experienced weight and length reduction during summer (December–February); (3) the estimated annual coccolith weight of E. huxleyi at both sediment traps (2.11 ± 0.96 and 2.13 ± 0.91 pg at 2000 and 3700 m) was consistent with previous studies for morphotype B/C in other Southern Ocean settings (Scotia Sea and Patagonian shelf); and (4) coccolithophores accounted for approximately 2–5 % of the annual deep-ocean CaCO3 flux. Our results are the first annual record of coccolithophore abundance, composition and degree of calcification in the Antarctic zone. They provide a baseline against which to monitor coccolithophore responses to changes in the environmental conditions expected for this region in coming decades.

Circumpolar occurrence of eugregarinid protozoanCephaloidophora pacificaassociated with Antarctic krill,Euphausia superba

2008 ◽  
Vol 20 (5) ◽  
pp. 437-440 ◽  
Author(s):  
Kunio T. Takahashi ◽  
Masaki Kobayashi ◽  
So Kawaguchi ◽  
Junko Saigusa ◽  
Atsushi Tanimura ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Antarctic Krill ◽  
Geographical Location ◽  
Protozoan Parasite ◽  
Euphausia Superba ◽  
Maturity Stage ◽  
Syowa Station ◽  
Frequency Distributions ◽  
The Mean ◽  
The Antarctic

AbstractThe geographical distribution of protozoan parasiteCephaloidophora pacificaAvdeev (Order Eugregarininda) associated with Antarctic krill,Euphausia superba, was examined in samples collected from the vicinity of the Antarctic Peninsula, near Syowa Station, and Pacific and Indian sectors of the Southern Ocean.Cephaloidophora pacificawas found at all stations around the Antarctic, with 96.4% of the euphausiids infected (n = 195). The numbers ofC. pacificaper krill ranged from 0 to 8089 krill-1, and the average was 350.0 ± 787.8 (mean ± SD). The frequency distributions ofC. pacificashowed an overdispersed parasite population (i.e. the variance was greater than the mean) at all locations. Statistical analysis showed that whilst the geographical location did not have a significant effect on intensity ofC. pacificathe maturity stage of krill did, with an increasing intensity of infection as krill matures. The infestation ofE. superbaby eugregarinid protozoan is considered to be a circum-Antarctic phenomenon, and it occurs equally throughout the Southern Ocean.

scholarly journals Metabolic and enzymatic adaptations in northern krill,Meganyctiphanes norvegica, and Antarctic krill,Euphausia superba

2000 ◽  
Vol 57 (S3) ◽  
pp. 115-129 ◽  
Author(s):  
Friedrich Buchholz ◽  
Reinhard Saborowski
Keyword(s):  
Antarctic Krill ◽  
Citrate Synthase ◽  
Enzyme Regulation ◽  
Euphausia Superba ◽  
Food Sources ◽  
The Arctic ◽  
Ligurian Sea ◽  
Meganyctiphanes Norvegica ◽  
The Antarctic ◽  
Antarctic Krill Euphausia Superba

The Antarctic krill, Euphausia superba, is restricted to the Antarctic Ocean. The northern krill, Meganyctiphanes norvegica, is extremely widely distributed from the arctic North Atlantic to the warm Mediterranean. Respiration measurements showed no seasonal differences in rates determined in krill from the thermally stable Clyde Sea (Scotland) and the cooler but variable Danish Kattegat. In the warm Ligurian Sea, where temperatures are stable, krill showed higher rates in April than in September, indicating reactions to the short but intensive productive season. Krill can passively benefit from enhancements of overall metabolism when ascending into upper, warmer water strata during their pronounced diel vertical migration. Michaelis-Menten constants (Km) of citrate synthase (CS) were compared. In terms of respiration and enzyme regulation, krill from the Ligurian Sea stand apart: temperature and nutrition appear to be of different influence, relatable to genetic differentiation in the species. In contrast, Kmof CS in E. superba is temperature independent, highlighting the species' stenothermal physiology. A basal level of activity of digestive enzymes ensures immediate utilization of patchy food sources. Specific induction, including that of chitinases, indicating omnivory in both species, underlines krill's exceptional capacity to adapt to highly variable trophic environments. Processes of moult, growth, and reproduction are locally and seasonally adjusted.

scholarly journals Implications of shortwave cloud forcing and feedbacks in the Southern Ocean

2006 ◽  
Vol 44 ◽  
pp. 15-22 ◽  
Author(s):  
Erica L. Key ◽  
Peter J. Minnett
Keyword(s):  
Southern Ocean ◽  
Radiative Forcing ◽  
Heat Budget ◽  
The Arctic ◽  
Cloud Forcing ◽  
Clear Sky ◽  
A Value ◽  
Atmospheric Transmissivity ◽  
The Antarctic ◽  
Surface Heat Budget

AbstractMeasurements of the incident solar radiation taken during the Antarctic Remote Ice Sensing Experiment (ARISE) aboard the R/V Aurora Australis in the Southern Ocean and springtime Antarctic ice pack are analyzed together with all-sky cloud imagery to determine the incident shortwave cloud radiative forcing at the surface. For most solar zenith angles (Z<82˚) in this dataset, the primary shortwave cloud effect is to induce cooling of the surface; as the sun approaches the horizon, however, the shortwave effects become negligible or even positive. The clear-sky atmospheric transmissivity over the length of the cruise is 0.91, a value comparable to those derived from measurements taken at various locations in the Arctic during daylight periods. Although the presence of clouds has a great effect on the surface heat budget and provides a negative shortwave feedback that may stabilize the polar atmosphere, the effect on the photosynthetically active radiation available to ice algae is relatively small in comparison to the effects of even small amounts of snow on sea ice.

Fur seal skull from sealers' quarters at Sandy Bay, Macquarie Island, Southern Ocean

Polar Record ◽  
1991 ◽  
Vol 27 (162) ◽  
pp. 245-248 ◽  
Author(s):  
K. Townrow ◽  
P. D. Shaughnessy
Keyword(s):  
Southern Ocean ◽  
Arctocephalus Gazella ◽  
Archaeological Excavation ◽  
Antarctic Fur Seal ◽  
Macquarie Island ◽  
Fur Seals ◽  
Fur Seal ◽  
Antarctic Research ◽  
The Antarctic ◽  
Specific Identity

AbstractFur seals were exterminated from Macquarie Island about 20 years after discovery of the island in 1810. Their specific identity is unknown. Few fur seals were reported at the island until it was occupied by the Australian National Antarctic Research Expeditions in 1948. Fur seal numbers are now increasing. An archaeological excavation at a sealers' quarters at Sandy Bay in 1988 revealed the fragmented skull of a young Antarctic fur sealArctocephalus gazella1.1 m below the surface in a layer dated in the 1870s and 1880s. This period coincides with the recovery of fur seal populations in the South Atlantic Ocean following earlier harvesting. Elsewhere it has been argued that the Antarctic fur seal is unlikely to have been the original fur seal at Macquarie Island because few individuals of that species are ashore in winter, which is the season when the island was discovered and fur-seal harvesting began. It is concluded that the Sandy Bay skull is from a vagrant animal.

Lipids, trophic relationships, and biodiversity in Arctic and Antarctic krill

2000 ◽  
Vol 57 (S3) ◽  
pp. 178-191 ◽  
Author(s):  
Stig Falk-Petersen ◽  
Wilhelm Hagen ◽  
Gerhard Kattner ◽  
Andrew Clarke ◽  
John Sargent
Keyword(s):  
Fatty Acids ◽  
Neutral Lipids ◽  
Critical Factor ◽  
Euphausia Superba ◽  
High Ratio ◽  
Wax Esters ◽  
Trophic Relationships ◽  
The Arctic ◽  
Lower Ratio ◽  
The Antarctic

Environmental seasonality is a critical factor in structuring polar marine ecosystems. The extensive data now available on the lipids of Arctic and Antarctic euphausiids show that all species are characterised by a seasonally high lipid content, and neutral lipids, whether wax esters or triacylglycerols, are primarily accumulated for reproduction. The Arctic Thysanoessa inermis and the Antarctic Euphausia crystallorophias contain high levels of wax esters and higher concentrations of 18:4(n-3) and 20:5(n-3) and a lower ratio of 18:1(n-9)/(n-7) fatty acids in their neutral lipids than the Arctic Thysanoessa raschii and the Antarctic Thysanoessa macrura and Euphausia superba. Large amounts of phytol in the lipids of T. raschii and E. crystallorophias during winter suggest the ingestion of decaying algae originating in sedimenting material or in sea ice. Thysanoessa raschii, T. macrura, and E. superba have a high ratio of 18:1(n-9)/ (n-7) fatty acids, indicating animal carnivory. We conclude that T. inermis and E. crystallorophias are true high polar herbivores, while T. raschii, T. macrura, and E. superba are omnivores with a more boreal distribution. The Arctic species Thysanoessa longicaudata and Meganyctiphanes norvegica are carnivores feeding on Calanus, as indicated by high amounts of 20:1(n-9) and 22:1(n-11) fatty acids.

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