Sandwich Islands Research Articles

The Falklands War

The 1982 Falklands War had a decisive outcome, that is the restoration of British control over the Falkland Islands, South Georgia and the South Sandwich Islands, but failed to end the long-running Anglo-Argentine dispute about the Falklands/Malvinas issue. The fundamental sovereignty problem remains today, as evidenced by Argentina's occasional withdrawal of overflying rights for flights between Chile and the Falklands. Although the Falklands/Malvinas question has now returned to the margins of international affairs, the 1982 war continues to attract the interest of historians, as highlighted by the recent publication of D. George Boyce's The Falklands War and Sir Lawrence Freedman's two-volume The Official History of the Falklands Campaign (2005) (rev. supra, 260–4). Moreover, in 2005 the new FOI provisions yielded additional evidence, most notably the release of the logbook of HMS Conqueror (The Times, 10 Oct. 2005), the submarine responsible for sinking the Belgrano. Undoubtedly, the war's twenty-fifth anniversary in 2007 will prompt even more publications. Drawing upon a wide range of sources, including Argentine publications, Boyce provides a useful synthesis of the secondary literature with particular reference to the interaction between war and diplomacy. Readers are offered by way of background a clear view of pre-war developments, including the fundamental sovereignty issue, the clash between popular and territorial sovereignty, and the complications arising from the ‘immobilism’ of the Falkland islanders. Inevitably, the ‘mistakes and inconsistencies’ of British policymakers figure prominently; thus they are accused of not only failing to balance the demands of defence and deterrence but also giving the wrong signals to an increasingly impatient Argentine military regime beset by escalating domestic unrest. Intelligence inadequacies represent a major part of what Boyce describes as Britain's pre-war ‘failure of the imagination’. Regarding the 74-day war itself, Boyce's account is adequate, even if the text glosses over episodes—these include the presence of SAS forces in Chile (May) by way of preparing for action against Rio Grande airfield across the border in Argentina—warranting fuller coverage. Of course, as Boyce points out, the sinking of the General Belgrano, a heavily armoured cruiser, was, and remains, ‘the most controversial action of the whole Falklands War’ (p. 104), given the allegations of Arthur Gavshon and Desmond Rice (The Sinking of the Belgrano, 1984), among others, that HMS Conqueror's attack was intended largely to torpedo Peruvian-inspired peace initiatives. Boyce, whose conclusions are echoed by Freedman's official history (Freedman, Vol. II, 736–46), dismisses such claims (pp. 101–09), while acknowledging the complications resulting from the government's inaccurate reporting of events. Inevitably, several sections of the book would benefit from updating to take account of both Freedman's privileged access to closed public records and recent FOI revelations. For example, whereas Boyce writes that the battle of Goose Green ‘seems’ to be a ‘classic example of political demands forcing the military pace’ (p. 126), Freedman felt able to be far more definite in stressing its political motivation, that is to meet the desire of politicians to show that British forces still held the military initiative (Freedman, Vol. II, 555–6, 577). Nevertheless, Boyce's book compares favourably with Freedman's official history in terms of its coverage of the myriad faces of the conflict, particularly the way in which the artistic, literary and photographic representations of war signalled a strong sense of ‘public and political commitment’ (p. 190). Taking advantage of the broader historical perspective, Boyce offers useful insights into Thatcher's Britain, while urging readers to appreciate that this small war, though easily dismissed as both a military anomaly and an imperial irrelevance, possessed important consequences for both Britain's role in the world and the conduct of war. Even so, Boyce could contribute more to the emerging reappraisal of the war's military significance. In 1982 the Falklands War, characterised as demonstrating more traditional military features, was overshadowed by a Cold War underpinned by nuclear weapons. As Freedman argues on the closing page of his official history, however, perhaps this 1982 conflict should be viewed rather as ‘one of the first of the coming post cold-war era’ (Freedman, Vol. II, 747). Generally speaking, Boyce's history offers a clear and concise text for students likely to be deterred by the 1,100-page official history. For this reason, occasional factual errors are to be regretted. For example, the British plan to recapture South Georgia was code-named ‘Operation Paraquat’, not ‘Operation Parquet’ (pp. 87, 98)! Nor will readers be helped by the repeated misspelling of the names of, say, the American Secretary of Defense (Caspar Weinberger) or Virginia Gamba-Stonehouse, Freedman's Argentine collaborator for Signals of War (1990).

Geothermal bryophyte habitats in the South Sandwich Islands, maritime Antarctic

AbstractQuestion: How does geothermal activity influence terrestrial plant colonization, species composition and community development in the Antarctic?Location: South Sandwich Islands, maritime Antarctic.Methods: Bryophytes were documented during a biological survey of the archipelago in January and February 1997. Particular attention was given to sites under current or recent influence of geothermal activity. Temperature profiles obtained across defined areas of activity on several islands were linked with the presence of specific bryophytes.Results: Greatest bryophyte richness was associated with geothermally influenced ground. Of 35 moss and nine liverwort species recorded, only four mosses were never associated with heated ground, while eight of the liverworts and 50% of the mosses were found only on actively or recently heated ground. Some species occur in unheated sites elsewhere in the maritime Antarctic, but were absent from such habitats on the South Sandwich Islands. Several species occurred in distinct zones around fumaroles. Maximum temperatures recorded within the upper 0.5 cm of the vegetation surface were 40 ‐ 47 °C, with only Campylopus introflexus tolerating such temperatures. Maximum temperatures 2.5 or 5 cm below the vegetation surface of this moss reached 75 °C. Other bryophytes regularly present in zoned vegetation included the mosses Dicranella hookeri, Sanionia georgico‐uncinata, Pohlia nutans and Notoligotrichum trichodon, and the liverworts Cryptochila grandiflora and Marchantia berteroana. Surface temperatures of 25 ‐ 35 °C and subsurface temperatures of 50 ‐ 60 °C were recorded in these species.Conclusions: These exceptional plant communities illustrate the transport of viable propagules into the Antarctic. Individually ephemeral in nature, the longer term existence of geothermal habitats on islands along the Scotia Arc may have provided refugia during periods of glacial expansion, facilitating subsequent recolonization of Antarctic terrestrial habitats.

“Evolutionist and Missionary,” The Reverend John Thomas Gulick (1832–1923). Part I: cumulative segregation—geographical isolation

During the late 19th and early 20th centuries, the American missionary and naturalist John Thomas Gulick (1832-1923) was one of the most well-known and influential evolutionists, anticipating in his research and writing, later proposals of geographical isolation, population genetics, genetic drift, and the founder principle in speciation. In over 20 publications based on studies of non-adaptive geographical variation in several hundred species of snails in the genus Achatinella, collected in the valleys of Oahu in the Sandwich Islands (Hawaii), Gulick provided evidence for the formation of new species from varieties and the importance of geographical (non-adaptive) isolation in species diversification. Gulick's theory of the species-differentiating effects of isolation was regarded by many as a more complete theory of speciation than Darwin's, and by others as correcting a fundamental deficiency in Darwin's theory, namely how groups of organisms diversify one from another. Gulick also saw organisms as active participants in, and in interaction with, their environment, for which he coined the term coincident selection, anticipating the Baldwin effect/organic selection. With his concepts of cumulative segregation (geographical isolation), indiscriminate isolation (the Founder effect) and coincident selection (the Baldwin effect), we should recognize Gulick as one of the earliest and most original and innovative evolutionary biologists.

Geothermal bryophyte habitats in the South Sandwich Islands, maritime Antarctic

Abstract Question: How does geothermal activity influence terrestrial plant colonization, species composition and community development in the Antarctic? Location: South Sandwich Islands, maritime Antarctic. Methods: Bryophytes were documented during a biological survey of the archipelago in January and February 1997. Particular attention was given to sites under current or recent influence of geothermal activity. Temperature profiles obtained across defined areas of activity on several islands were linked with the presence of specific bryophytes. Results: Greatest bryophyte richness was associated with geothermally influenced ground. Of 35 moss and nine liverwort species recorded, only four mosses were never associated with heated ground, while eight of the liverworts and 50% of the mosses were found only on actively or recently heated ground. Some species occur in unheated sites elsewhere in the maritime Antarctic, but were absent from such habitats on the South Sandwich Islands. Several species occurre...

Аналіз магнітудної чутливості сейсмічного комплексу, встановленого на УАС Академік Вернадський для сейсмічних подій з району Сандвічевих островів

Аналіз магнітудної чутливості сейсмічного комплексу, встановленого на УАС Академік Вернадський для сейсмічних подій з району Сандвічевих островів

Tardigrade fauna of the South Sandwich Islands, maritime Antarctic

Tardigrade fauna of the South Sandwich Islands, maritime Antarctic

Distribution, reproductive and energetic conditions of decapod crustaceans along the Scotia Arc (Southern Ocean)

SUMMARY: Studies on decapod distribution patterns and reproductive and energetic conditions were carried out along the islands and shallows of the Scotia Arc (Southern Ocean) during the RV “Polarstern” LAMPOS expedition (ANT XIX/5) between April and May 2002. A clear biogeographic zonation was found. The Subantarctic Magellan-South Atlantic decapod fauna consisting of both “natant” (caridean) and “reptant” (astacidean, anomuran, and brachyuran) decapods appeared along the northern branch of the Scotia Arc to South Georgia, where Subantarctic and Antarctic faunas were found overlapping. An impoverished caridean shrimp fauna was found along the islands of the southern branch, from the South Sandwich Islands to the Antarctic Peninsula. Differences in the reproductive traits of the two most abundant species were detected. The reproductive cycle of Notocrangon antarcticus at South Georgia was more advanced than that at the South Orkney Islands, probably due to temperature differences between the two locations. Although the oogenesis and the reproductive cycle of Munida subrugosa seem to be in phase at Burdwood Bank and in the Beagle Channel, the oocyte number is probably lower at the former location. A new index was used to measure the energy devoted to reproduction by relating the energy contents of the egg mass/ovary plus hepatopancreas and the energy content of the whole body. This index revealed that the energy investment in reproduction was (1) independent of the sampling location, (2) species-specific, and (3) larger in caridean shrimps than in galatheid crabs.

Thoughts on controls on evolution and dispersal of benthos in the Magellan-Scotia Sea region: a workshop proposal

The Scotia Arc and the Scotia Sea comprise a geologically young feature of the Earth’s surface that evolved over the last 40 million years (Ma) or so, between the southern tip of South America and the northern tip of the Antarctic Peninsula. With the notable exception of the much younger South Sandwich Islands, the islands, banks and seamounts of the arc represent dispersed fragments of a previous continental link between southern South America (Magellan region) and the Antarctic Peninsula. The benthic marine shelf faunas of the region are the focus of the IBMANT (Investigacion Biolologica Marina en Magallanes relacionada con la Antartida) programme, and those of the surrounding oceanic deeps are the focus of ANDEEP (Antarctic Benthic Deep-Sea Biodiversity). Elucidating the potential relationships between the faunas of the region and the profound geographical, oceanographic and climatic changes undergone by the region in later Cenozoic time is hampered by significant unknowns in the geological history, the expense of further geoscientific exploration to fill these, and a general lack of communication between the biological and geological science communities. It is suggested that the time is opportune for a truly multidisciplinary workshop at which all the involved science communities have much to gain from the others.

Light rare earth element depleted to enriched basaltic flows from 2.8 to 2.7 Ga greenstone belts of the Uchi Subprovince, Ontario, Canada

A compositionally diverse group of basaltic flows are present in the 2.7 Ga St. Joseph assemblage of the St. Joseph greenstone belt, Uchi Subprovince. A spectrum of light rare earth element (LREE) depleted to enriched patterns corresponds to low-, medium- and high-K series (LKS, MKS, HKS) basalts, shoshonites and leucitites of some modern arcs. More primitive, tholeiitic LKS and MKS basalts plot with counterparts from modern intraoceanic arcs, such as the South Sandwich Islands, and show no evidence of contamination by continental crust. Consequently they are interpreted to have erupted in an oceanic setting. There is an array from low Nb with high Zr/Nb (29) to high Nb but lower Zr/Nb (15) indicative of a mantle wedge similar to average mid ocean ridge basalts (MORB; average Zr/Nb = 32). These basalts also show positive to negative Nb, Hf and Zr anomalies. Negative anomalies are interpreted as the product of first stage melting, where LREE and MREE are added to the mantle wedge from dehydration of the slab, leaving a residue with high Nb/La, Hf/Nd and Zr/Nd. Second stage melts inherit the high HFSE/REE ratios. Within the Birch–Uchi greenstone belt, basalts of the ∼2.8 Ga Woman assemblage includes both LKS and HKS. These are characterized by similar Nb–Zr/Nb and HFSE/REE systematics, signifying that these are general features of sub-arc mantle wedges that developed over 100 Ma in Uchi subprovince arcs. Enriched St. Joseph assemblage basaltic rocks cannot stem from sediment melting on the slab, as Th/Ce ratios are generally < 0.1. Neither can they derive from an ocean island basalt component because Nb anomalies do not correlate with La/Yb n. Rather, the trend from primitive LKS through MKS to HKS, leucitite and shoshonite is interpreted to reflect progressively lower degrees of partial melting at increasing depths and/or less depleted mantle wedge.

Tardigrade fauna of the South Sandwich Islands, maritime Antarctic

The maritime Antarctic South Sandwich Islands are an isolated oceanic archipelago of volcanic origin lying between 56º18'S, 27º34'W and 59º27'S, 27º22'W. All the islands are of recent origin (maximum ages 0.5–3 million years) with many still exhibiting some form of volcanic activity. The islands are part of the Scotia Arc, lying on a crustal upwarp extending from South Georgia through the South Sandwich Islands to the South Shetland Islands that connects the Andean chain of South America to the Antarctic Peninsula. As part of an extensive biological survey completed during early 1997, samples were collected from 10 of the 11 major islands in the archipelago from which the tardigrade fauna has subsequently been extracted. We report the composition of this fauna, and discuss its biogeographical relationships. Tardigrade species richness was low (6 taxa), in keeping with the recent formation and isolation of these islands. However, as reported previously for the terrestrial arthropod fauna and bryophyte flora, there is indication of both suband maritime Antarctic origin.

Topographical Survey and Mapping of British Antarctic Territory, South Georgia and the South Sandwich Islands 1944–1986

The Photogrammetric RecordVolume 20, Issue 111 p. 307-308 Topographical Survey and Mapping of British Antarctic Territory, South Georgia and the South Sandwich Islands 1944–1986 A. Wright, A. WrightSearch for more papers by this author A. Wright, A. WrightSearch for more papers by this author First published: 05 September 2005 https://doi.org/10.1111/j.1477-9730.2005.00333_4.xRead the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume20, Issue111September 2005Pages 307-308 RelatedInformation

Inner Core Differential Motion Confirmed by Earthquake Waveform Doublets

We analyzed 18 high-quality waveform doublets with time separations of up to 35 years in the South Sandwich Islands region, for which the seismic signals have traversed the inner core as PKP(DF). The doublets show a consistent temporal change of travel times at up to 58 stations in and near Alaska, and they show a dissimilarity of PKP(DF) coda. Using waveform doublets avoids artifacts of earthquake mislocations and contamination from small-scale heterogeneities. Our results confirm that Earth's inner core is rotating faster than the mantle and crust at about 0.3 degrees to 0.5 degrees per year.

First recorded eruption of Mount Belinda volcano (Montagu Island), South Sandwich Islands

The MODVOLC satellite monitoring system has revealed the first recorded eruption of Mount Belinda volcano, on Montagu Island in the remote South Sandwich Islands. Here we present some initial qualitative observations gleaned from a collection of satellite imagery covering the eruption, including MODIS, Landsat 7 ETM+, ASTER, and RADARSAT-1 data. MODVOLC thermal alerts indicate that the eruption started sometime between 12 September and 20 October 2001, with low-intensity subaerial explosive activity from the island’s summit peak, Mount Belinda. By January 2002 a small lava flow had been emplaced near the summit, and activity subsequently increased to some of the highest observed levels in August 2002. Observations from passing ships in February and March 2003 provided the first visual confirmation of the eruption. ASTER images obtained in August 2003 show that the eruption at Mount Belinda entered a new phase around this time, with fresh lava effusion into the surrounding icefield. MODIS radiance trends also suggest that the overall activity level increased significantly after July 2003. Thermal anomalies continued to be observed in MODIS imagery in early 2004, indicating a prolonged low-intensity eruption and the likely establishment of a persistent summit lava lake, similar to that observed on neighboring Saunders Island in 2001. Our new observations also indicate that lava lake activity continues on Saunders Island.

John Rae and Thorstein Veblen

(2004). John Rae and Thorstein Veblen. Journal of Economic Issues: Vol. 38, No. 3, pp. 765-786.

Biological and physical processes structuring deep-sea surface sediments in the Scotia and Weddell Seas, Antarctica

Abstract Five deep-sea transects were sampled in the Scotia Sea and Weddell Sea from the Drake Passage to the South Sandwich Islands, Antarctica, with depths ranging from 767 to 6333 m. A combination of sediment surface and sediment profile imaging was used to characterize the physical and biological processes structuring the benthic boundary layer and surface sediments from the sediment–water interface (SWI) to as much as 17 cm below the SWI. The factors structuring surface sediments were related to distance from Antarctic landmasses, which are the main source of sediment, and deposition of water-column or sea-ice primary productivity. Stations near the continental shelf and slope tended to have coarse (granule to cobble) sediments derived from melting sea-ice. Input of fine sediments was estimated to be low at these stations because many of the coarse sediment grains appeared to be manganese coated. At the deepest stations in the Ona Basin, South Shetland Trench, and South Sandwich Trench, sediment appeared to be primarily hemipelagite silt-clay but were varved with as many as four distinct color laminations. These layers varied in thickness fom 0.6 to 10.6 cm and may have been related to turbidite flows. While geology and physical processes that deliver sediment to the bottom were the primary factors dictating substratum characteristics, biological processes were, to varying degrees, important in structuring the SWI and sediment fabric. Biological processes, primarily in the form of bioturbation, were most prominent at fine-grained stations but were also obvious even on rock substratum on top of the Shackleton Fracture Zone. There were gradients between the degree of bioturbation and type of biogenic structure present with depth. At depths 75% of the sediment bioturbated) the structure of surficial sediments at 5 of 13 stations. At depths >2000 m, biological processes were overall less diverse but dominated at 8 of 11 stations.

Benthic infaunal communities across the Weddell Sea Basin and South Sandwich Slope, Antarctica

Abstract The present study represents the first quantitative investigation of deep-sea benthic infauna in Antarctica. Box cores and multicores were used to collect sediment from 12 stations across the slope and abyssal basin of the Weddell Sea and the slope off the South Sandwich Islands, including sites in the South Sandwich Trench (6300 m). The multicore was a more efficient sampler than the box core. Nine phyla of invertebrates were found, dominated by annelids (67%), crustaceans (20%); other phyla (13%). A total of 117 taxa were identified to the species level: 72 were polychaetes; 45 were crustaceans. Many taxa are new to science. Highest densities were at the 1000 m depth on the western slope of the Weddell Sea (260 individuals per 0.1 m−2) and at ca. 2200 m on the South Sandwich Slope (132 individuals per 0.1 m−2); lowest densities were in the central Weddell Sea Basin (39 individuals per 0.1 m−2). Species richness and rarefaction analysis suggest that the fauna is undersampled. The 117 species identified in this study were represented by only 237 specimens, indicating that species were being added at a rate of one species for every two specimens collected. Rarefaction curves do not begin to reach an asymptote supporting high estimates of diversity. Some species appear to be limited to distinct zones in upper and middle slope depths, other species extend from the slope to the abyssal basin, and at least two species appear to be restricted to the abyssal basin. In general, the densities of infauna on the slopes surrounding the Weddell Sea Basin have lower densities than well-studied areas off North America. However, abyssal populations in Antarctica appear to have denser infaunal populations than those from off New England and the North Pacific Gyre. Productive surface waters of the Weddell Sea and subsequent sinking of phytoplankton to the seabed are probable reasons for the higher benthic productivity in Antarctic abyssal sediments. Similarity analyses were not informative because so few species were collected. Two stations in the Weddell Abyssal Basin were the only ones to exhibit a high level of similarity due to two shared polychaetes. Data on reproductive status of some polychaetes suggest that species limited to abyssal depths are reproducing there. Other species with broader depth ranges may be receiving recruits from slope depths. The results suggest that the deep-water infauna in Antarctica is largely endemic, but has some components that occur along other continental margins and adjacent abyssal basins.

Diversity of Southern Ocean deep-sea Isopoda (Crustacea, Malacostraca) — a comparison with shelf data

Samples were taken during the expeditions ANDEEP I & II (ANT XIX/3-4) (ANtarctic benthic DEEP-sea biodiversity, colonisation history and recent community patterns) with RV Polarstern for the analysis of the Southern Ocean (SO) deep-sea isopod biodiversity in the Drake Passage, off Elephant Island, along the South Shetland Islands, in the northwestern Weddell Sea, and at the South Sandwich Islands. In total 5525 specimens of Isopoda were sampled and 317 species were discriminated. Isopoda were the most abundant peracarid taxon, with 38% of all Peracarida, 98% of the Isopoda belonging to the suborder Asellota. Species richness was highest in the northwestern Weddell Sea; diversity and evenness were relatively high at all stations. The Munnopsididae were the most dominant isopod family, with 61% of the specimens, 118 species divided among 28 genera; the Haploniscidae comprised 15% of all isopods with 36 species from four genera, followed by the Ischnomesidae with 7% and 30 species from five genera. The families Desmosomatidae, Macrostylidae and Nannoniscidae comprised 10% of the isopod specimens. The Desmosomatidae were the second most diverse family, with 48 species from 12 genera. Species of the suborder Valvifera or the family Serolidae were much rarer in the SO deep-sea than on the shelf. 141 of isopod species (46% of the total number) were rare, occurring only at one of the 21 epibenthic-sledge stations. A cluster analysis showed no clear relation between isopod communities and geographic area. Depth was the most important factor for differences in isopod community patterns. The species accumulation curve shows that the SO deep sea was not sampled representatively during ANDEEP I & II and further sampling is necessary. The SO deep-sea differs in faunal composition from the shelf.

Deep-water sedimentary environments of the northwestern Weddell Sea and South Sandwich Islands, Antarctica

Abstract Two transects have been sampled using short cores (multi and box), seabed photography, video sequences, and sediment profile images across the northwestern Weddell Sea and South Sandwich Forearc, Antarctica. A total of 12 core stations were examined for sediment structure, texture and composition to determine their depositional history. Four of the core stations from the Weddell Continental Slope, Abyssal Plain and South Sandwich Forearc and Trench were further examined for trace metal analysis (Ba, U, Mn and Pb) for sediment source and palaeoproductivity, and 210Pb for age profiles and depth of mixing by bioturbation. The 3055 m station at the base of the Weddell Continental Slope, recovered laminated muddy–silty contourites with a surface layer of hemipelagites with abundant ice-rafted debris, possibly originating from the 1995 Larsen A and 2002 Larsen B ice shelf disintegration. This is interpreted as a moderate-energy depositional environment influenced by Weddell Sea Bottom Water along-slope current, reworking sediment. Sediment sources to this station include the direct input of clastic material from ice with variation in sediment sources from in situ current winnowing and along-slope transport reflected in the Mn/Li and Ba/Li ratios. The 4760 m station on the Weddell Abyssal Plain recovered hemipelagites, interpreted as a low-energy depositional environment with sediment supplied both from direct ice-rafting and pelagic settling during productive seasonally ice-free periods. The 210Pb profiles indicate a sedimentation rate of 0.024 cm/year−1, with the 206/207Pb isotope ratios suggesting a principle sediment source from ice-rafting. The 2292 and 6326 m stations from the slope and floor of the South Sandwich Forearc recovered pelagic and turbiditic sediments. This is interpreted as a high-energy down-slope depositional environment, with high surface biogenic productivity and sediment supply leading to localised down-slope mass-movements on the slope and floor. High levels of Mn/Li and elevated U/Li ratios demonstrate a strong concentration of Mn in organic-poor sediment. The Mn redoxcline is present at 10 cm depth. The high Ba/Li (500 ppm) in the forearc floor core reflects some limited enhanced productivity. Source sediment for the forearc may, in part, be derived from the northwest Weddell Abyssal Plain, based on the 206/207Pb isotope ratios reflecting transport by Weddell Sea Bottom Water.

Mesozooplankton community structure in the Scotia Sea during the CCAMLR 2000 survey: January–February 2000

An analysis of mesozooplankton community structure in the Scotia Sea was carried out, based on 123 RMT1 double oblique hauls (0–200 m) taken during the CCAMLR 2000 Survey. Standardized sample data (log abundance per 1000 m3) were grouped into taxonomic categories and subjected to cluster analysis and multi-dimensional scaling. Two ordinations were performed, the first based on a reduced taxonomic dataset (31 categories out of a full 120) obtained by pooling ontogenetic stages within species and by including only those taxa that contributed at least 4% to total abundance at any one station. This disclosed two major station groups, which separated north and south, forming ‘warm’ and ‘cold’ water communities respectively, whereas four minor groups were mainly associated with stations around the Antarctic Peninsula and within the Weddell Scotia Confluence. Mean zooplankton abundance (238 000 individuals per 1000 m3) within the northerly group G1 was up to 12 times higher than in other groups. The second ordination using all taxonomic categories disclosed an additional intermediate group (G1a), which was geographically consistent with the southern part of the northern group 1 from the previous ordination. However, because of taxonomic similarities between all the major station groups it was concluded that they represented a single community, which differed only in its phenological development and the mass occurrence of patchily distributed organisms such as krill larvae. Testing the relationships of station groups with the position of water masses and frontal boundaries indicated that the Weddell Front was broadly coincident with the boundary of the northern and southern communities over much of its length. However, the presence of stations belonging to group G2, to the north of the Weddell Front, to the west of the Antarctic Peninsula, and around the South Sandwich Islands, was consistent with the distribution of ice-influenced surface water. Low zooplankton abundance and species developmental composition suggested that this ‘community’ was largely in an over-wintered state. Copepods and euphausiids dominated the mesozooplankton throughout the study area with small copepods (Oithona spp., Ctenocalanus spp. and Metridia spp.) particularly abundant.

Modeling the krill transport pathways in the Scotia Sea: spatial and environmental connections generating the seasonal distribution of krill

Abstract A coupled physical–biological model analysis was undertaken to examine the seasonal development of the distribution of antarctic krill (Euphausia superba Dana) in the Scotia Sea. The origin and fate of krill observed during the CCAMLR 2000 survey were studied using output from the OCCAM model. Lagrangian particle tracking for the period prior to the survey showed the expected dominance of the west to east flow of material associated with the main direction of the current flow, but there was no simple association of particle transport with any of the fronts of the Antarctic Circumpolar Current. Most of the krill were associated with areas to the south of the Antarctic Circumpolar Current in the Weddell–Scotia Confluence (WSC) and farther east in Weddell Sea-influenced waters. Examining the pathways of krill transport in relation to satellite-derived sea-ice distributions suggests that particles present in the high krill biomass regions in January would have come from areas that were covered by sea-ice during late winter/early spring (September–October). The results of Eulerian grid-based simulations of the development of the biomass distribution after the survey period showed transport of particles around South Georgia, probably in association with the Southern Antarctic Circumpolar Current Front. However, many of the krill encountered in the eastern Scotia Sea would have exited toward the east, passing north of the South Sandwich Islands, probably in association with the Southern Boundary of the Antarctic Circumpolar Current and Weddell Sea waters that penetrate to the north in this area. These krill may return to more southern regions where further spawning is possible in later years. Simulations of particle tracks that included diurnal vertical migration showed that krill behavior could modify the pathways of transport, although the current flows probably dominate the movement of krill in open ocean regions. This study suggests that the summer distribution of krill in the Scotia Sea is connected to the winter sea-ice distribution and probably to the pattern and rate of the spring sea-ice retreat. Many of the krill in the survey region in the summer of 1999/2000 came from under the sea-ice in the eastern Scotia Sea, the southern Scotia Arc, and the northern Weddell Sea. This highlights that the spatial association of the sea-ice with the Weddell–Scotia Confluence and frontal regions of the Antarctic Circumpolar Current during winter and spring will be crucial in determining the summer krill distribution. Variation in the extent and timing of sea-ice retreat, and fluctuations in Weddell–Scotia Confluence and Scotia Sea flows, will change the pathways of transport resulting in large changes in the distribution of the krill during summer.