scholarly journals Distribution of short-finned squid Illex argentinus (Cephalopoda: Ommastrephidae) inferred from the diets of Southern Ocean albatrosses using stable isotope analyses

2015 ◽  
Vol 96 (6) ◽  
pp. 1211-1215 ◽  
Author(s):  
José Seco ◽  
Gustavo A. Daneri ◽  
Filipe R. Ceia ◽  
Rui Pedro Vieira ◽  
Simeon L. Hill ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Southern Ocean ◽  
Polar Front ◽  
Antarctic Polar Front ◽  
Stable Isotope Analyses ◽  
Patagonian Shelf ◽  
Illex Argentinus ◽  
Shelf Region ◽  
The Antarctic ◽  
Isotope Analyses

The diets of marine predators are a potential source of information about range shifts in their prey. For example, the short-finned squid Illex argentinus, a commercially fished species on the Patagonian Shelf in the South Atlantic, has been reported in the diet of grey-headed, Thalassarche chrysostoma; black-browed, T. melanophris; and wandering, Diomedea exulans, albatrosses breeding at Bird Island, South Georgia (54°S 28°W) in the Southern Ocean. Tracking data suggest that these birds may feed on I. argentinus while foraging in Southern Ocean waters during their breeding season. This led to the hypothesis that I. argentinus may occur south of the Antarctic Polar Front. To test this hypothesis, we used stable isotope analyses to assess the origin of I. argentinus. We compared I. argentinus beaks from the diets of the three albatross species with beaks of cephalopod species endemic to the Patagonian Shelf and others from the Southern Ocean. Our results show that I. argentinus from the diet of albatrosses at Bird Island have δ13C values in the range −18.77 to −15.28‰. This is consistent with δ13C values for Octopus tehuelchus, a typical species from the Patagonian Shelf. In contrast, Alluroteuthis antarcticus, a Southern Ocean squid, has typically Antarctic δ13C in the range −25.46 to −18.61‰. This suggests that I. argentinus originated from warmer waters of the Patagonian Shelf region. It is more likely that the albatross species obtained I. argentinus by foraging in the Patagonian Shelf region than that I. argentinus naturally occurs south of the Antarctic Polar Front.

scholarly journals Winter Biogeochemical Cycling of Dissolved and Particulate Cadmium in the Indian Sector of the Southern Ocean (GEOTRACES GIpr07 Transect)

2021 ◽  
Vol 8 ◽  
Author(s):  
Ryan Cloete ◽  
Jean C. Loock ◽  
Natasha R. van Horsten ◽  
Susanne Fietz ◽  
Thato N. Mtshali ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Biogeochemical Cycling ◽  
Polar Front ◽  
Water Masses ◽  
Antarctic Polar Front ◽  
Intermediate Water ◽  
Subtropical Zone ◽  
Near Surface ◽  
The Antarctic ◽  
Indian Sector

Winter distributions of dissolved cadmium (dCd) and particulate cadmium (pCd) were measured for the first time in the Indian sector of the Southern Ocean thereby contributing a unique spatial and seasonal dataset. Seven depth profiles, between 41°S and 58°S, were collected along the 30°E longitude during the 2017 austral winter to investigate the biogeochemical cycling of cadmium during a period characterized by contrasting upper water column dynamics compared to summer. Our results support an important role for biological uptake during winter months albeit weaker compared to summer. Distinct, biologically driven changes in cadmium cycling across the transect were observed. For example, surface ratios of pCd to phosphorus (P; pCd:P) increased from 0.37 to 1.07 mmol mol–1 between the subtropical zone (STZ) and the Antarctic zone (AAZ) reflecting increased Cd requirements for diatoms at higher latitudes which, in turn, was driven by a complex relationship between the availability of dCd and dissolved iron (dFe), zinc (dZn) and manganese (dMn). Vertical profiles of pCd:P displayed near-surface maxima consistent with (1) P occurring in two phases with different labilities and the lability of Cd being somewhere in-between and (2) increasing dCd to phosphate (PO4; dCd:PO4) ratios with depth at each station. North of the Antarctic Polar Front (APF), a secondary, deeper pCd:P maximum may reflect an advective signal associated with northward subducting Antarctic Intermediate Water (AAIW). The strong southward increase in surface dCd and dCd:PO4, from approximately 10–700 pmol kg–1 and 40–400 μmol mol–1, respectively, reflected the net effect of preferential uptake and regeneration of diatoms with high Cd content and the upwelling of Cd enriched water masses in the AAZ. Furthermore, distinct dCd versus PO4 relationships were observed in each of the intermediate and deep water masses suggesting that dCd and PO4 distributions at depth are largely the result of physical water mass mixing.

scholarly journals Habitat and trophic ecology of Southern Ocean cephalopods from stable isotope analyses

2015 ◽  
Vol 530 ◽  
pp. 119-134 ◽  
Author(s):  
M Guerreiro ◽  
RA Phillips ◽  
Y Cherel ◽  
FR Ceia ◽  
P Alvito ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Southern Ocean ◽  
Trophic Ecology ◽  
Stable Isotope Analyses ◽  
Isotope Analyses

Dissolution and Preservation of Antarctic Diatoms and the Effect on Sediment Thanatocoenoses

1989 ◽  
Vol 31 (2) ◽  
pp. 288-308 ◽  
Author(s):  
A. Shemesh ◽  
L. H. Burckle ◽  
P. N. Froelich
Keyword(s):  
Southern Ocean ◽  
Transfer Functions ◽  
Polar Front ◽  
Antarctic Polar Front ◽  
Diatom Assemblages ◽  
Differential Dissolution ◽  
Surface Ocean ◽  
Antarctic Diatoms ◽  
The Antarctic ◽  
The Last Glacial

AbstractComparison of Southern Ocean diatom populations from (i) surface ocean production, (ii) underlying Antarctic sediments, and (iii) laboratory dissolution experiments demonstrates that dissolution can account for the temporal and spatial variations in sedimentary diatom assemblages observed in Southern Ocean sediments. Increasing dissolution causes relative depletions in N. kerguelensis (K), enrichments in T. lentiginosa (L), and slight enrichments in E. antarctica (A). This reflects the relative susceptibility to dissolution of the three species that dominate Antarctic sediments. We have devised a preservation index for the Southern Ocean based on the ratio K/(K + L) to estimate relative extents of dissolution and applied it to natural assemblages. Holocene Southern Ocean sediments display increasing opal preservation toward higher latitudes, but south of the Antarctic Polar Front preservation decreases in the order: well preserved = SE Indian > S. Atlantic ∼ SW Indian > SE Pacific = poorly preserved. Dissolution also accounts for the pattern of diatom assemblages in the last glacial maximum (LGM) sediments of the Indian and Pacific sectors, but in the Atlantic, increased E. antarctica abundances at LGM must have resulted from an increase in surface ocean production of this species. Holocene and LGM diatoms in Atlantic and Pacific sector sediments are equally well preserved, but in the Indian sectors, Holocene sediments are better preserved than those of LGM age. Paleoceanographic and paleoclimatic transfer functions derived from factor analyses of variations in the sedimentary abundances of these three diatoms have ignored the effects of differential dissolution on thanatocoenosis and thus should be interpreted with caution.

scholarly journals Heard Island: Southern Ocean Sentinel

2007 ◽  
Vol 13 (2) ◽  
pp. 145
Author(s):  
William E. Davis. Jr.
Keyword(s):  
Southern Ocean ◽  
Polar Front ◽  
Antarctic Polar Front ◽  
Volcanic Origin ◽  
Introduced Plants ◽  
Antarctic Convergence ◽  
Heard Island ◽  
History Of ◽  
The Antarctic ◽  
Substantial Interest

Heard Island is one of the most remote places on earth. It is of volcanic origin (and currently volcanically active) on the submarine Kerguelen Plateau in the Southern Ocean, roughly 4 000 km south-west of Australia, 1 500 km from Antarctica, 3 750 km from Africa, and 7 500 km from India. The island is 367 km2 in area at latitude 53�S, south of the Antarctic Polar Front (Antarctic Convergence), is 70% covered with glaciers, and has a geologic, biologic and human history of substantial interest. Because of its remoteness, relative recent discovery (1853), and infrequent human visitation, it is pristine with no human-introduced plants or mammals.

Particle export and the biological pump in the Southern Ocean

2004 ◽  
Vol 16 (4) ◽  
pp. 501-516 ◽  
Author(s):  
SUSUMU HONJO
Keyword(s):  
Organic Carbon ◽  
Southern Ocean ◽  
Carbon Particle ◽  
Polar Front ◽  
Antarctic Polar Front ◽  
Biological Pump ◽  
The South ◽  
Regeneration Rate ◽  
Particle Export ◽  
The Antarctic

The organic carbon particle export to the interior layers in the Southern Ocean in the New Zealand–Tasmania Sector was approximately 170 mmolC m−2 yr−1. The export of particulate inorganic carbon in CaCO3 was 110 mmolC m−2 yr−1 and was contributed mostly by pteropods shells in the Antarctic Zones. The Si flux from biogenic opal at the sub-Antarctic Zone was 67 mmolSi m−2 yr−1 and rapidly increased to the south up to nearly 1 molSi m−2 yr−1 in the Antarctic Zone. The Antarctic Polar Front clearly demarcated the area where the biological pump was driven by CaCO3 to the north and biogenic SiO2 particle export to the south. Summer stratification caused by the sub-zero winter water layer in the Seasonal Ice Zone (SIZ) curtails the zooplankton community and hinders the replenishment of Fe. This hypothesis explains the large organic carbon export with large f- and export ratios at the SIZ and extremely large opal production at the Antarctic Circumpolar Zone. Estimated regeneration rate of CO2 from the export production and settling particulate fluxes of organic carbon in the water column between 100 m to 1 km was about 13 mmolC m−2 d−1 in the Antarctic Zone and Polar Frontal Zone.

Multi-scale factors influencing seabird assemblages in the African sector of the Southern Ocean

2013 ◽  
Vol 26 (1) ◽  
pp. 38-48 ◽  
Author(s):  
Morgan L. Commins ◽  
Isabelle Ansorge ◽  
Peter G. Ryan
Keyword(s):  
Southern Ocean ◽  
Sea Ice ◽  
Antarctic Circumpolar Current ◽  
Polar Front ◽  
Latitudinal Gradients ◽  
Antarctic Polar Front ◽  
Sea Ice Extent ◽  
Southern Boundary ◽  
Circumpolar Current ◽  
The Antarctic

AbstractOceanic fronts are important foraging areas for many top predators, but they also define biogeographical boundaries to animals in the Southern Ocean and play a role in structuring seabird assemblages. Understanding the factors driving patterns in the spatial and temporal distribution of seabirds is important to infer the likely impact of a changing climate. Latitudinal transects south of Africa in two summers indicate that fronts and sea ice extent play key roles in determining seabird assemblages. We observed 37 seabird taxa and found five seabird assemblages. The Subtropical Convergence and pack ice-edge form the strongest biogeographical boundaries, whereas the Sub-Antarctic Front and Antarctic Polar Front are less well defined. As summer progresses, the Southern Antarctic Circumpolar Current Front (the Antarctic Divergence or southern boundary of the Antarctic Circumpolar Current) becomes important, when a distinct seabird assemblage forms north of the retreating sea ice following an influx of great shearwatersPuffinus gravis(O'Reilly), blue petrelsHalobaena caerulea(Gmelin), Kerguelen petrelsLugensa brevirostris(Lesson) and southern fulmarsFulmarus glacialoides(Smith). Seabird assemblages show strong seasonality and are predictable between years. They are structured primarily by latitudinal gradients and secondarily by seasonal variation in sea-surface temperature and ice cover within their latitudinal habitat zones.

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