Month: May 2021

Biological research by the British Antarctic Survey

first_imgThe Antarctic Peninsula, the islands rising from the Scotia Ridge, and the Falkland Islands are a key area for biologists interested in the origin, relationships, and adaptations of the Antarctic flora and fauna. Of all Antarctic regions, furthermore, this has perhaps been the most intensively studied. The pioneer observations of J. R. and J. G. Forster during Cook’s circumnavigation in 1772–75, and of James Eights in 1833 (Caiman, 1937), supplemented by the less systematic accounts of those engaged in early nineteenth-century sealing and whaling voyages (Weddell, 1825; Allen, 1899) paved the way for the thorough scientific programmes of more modern expeditions. The first of these, the Belgica expedition under de Gerlache, 1897–99, yielded much general information and brought back an apterous fly {Belgica antarctica),the first higher insect to be discovered in the true Antarctic. Soon afterwards, the Swedish South Polar Expedition led by Nordenskjold, 1901–04, brought to the Antarctic an outstanding botanist, the late C. J. F. Skottsberg, whose botanical researches on Antarctic and sub-Antarctic themes were to last for over half a century (Skottsberg, 1963). During the following decade the two French expeditions led by Charcot, 1903–05 and 1908–10, contributed important microbiological and ornithological information, and in 1902–04 the Scottish National Antarctic Expedition under Bruce made the first study of the South Orkney Islands and provided a general evaluation of botanical and biogeographical problems (Rudmose Brown, 1912). All these expeditions made general collections of flora and fauna which revealed that the Antarctic Peninsula and its adjacent islands were the richest area, biologically speaking, of the whole Antarctic region. Farther north, the Swedish Magellanic Expedition, led by Skottsberg in 1907–09, provided what is still the only published account of the vegetation of the Falkland Islands and information vital to the evaluation of biogeographical relationships between the Scotia Ridge, the Antarctic Peninsula, and the Magellanic region of South America. Skottsberg (1912) also described the vegetation of South Georgia, where pioneer work had been done by Will during the German International Polar Year expedition, 1882–83. The botanical work on this island, up to 1964, has recently been comprehensively reviewed by Greene (1964a).last_img read more

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Fish prey of the Wandering Albatross Diomedea exulans at South Georgia

first_imgThe fish diet (45% of total diet by weight) of Wandering Albatrosses rearing chicks at South Georgia during the austral winters of 1983 and 1984 was investigated using otoliths retrieved from regurgitations. These provide the first quantitative data for this species and for any albatross. By number of identified otoliths (32% could be identified only as ?Macrouridae and ?Moridae), Pseudochaenichthys georgianus (35%), Muraenolepis microps (33%) and Chaenocephalus aceratus (20%) predominated, with Notothenia gibberifrons, Pagothenia hansoni and Champsocephalus gunnari (together 12%) also present. Composition by weight (estimated from otolith length) of the main species was Pseudochaenichthys 51%, Muraenolepis 14%, Chaenocephalus 27%; if digestion and wear had reduced otoliths by 10% the values would be Pseudochaenichthys 54%, Chaenocephalus 25%, Muraenolepis 13%. Composition by weight (actual or corrected values) was almost identical between years but epipelagic fish were significantly more abundant in 1983 than 1984. All identified fish eaten by Wandering Albatrosses are common on the South Georgia continental shelf and most of them are caught in the commercial fishery there. However, two of the three main target species of this fishery in 1983–1984, Notothenia rossii and Champsocephalus were not, or rarely, caught by Wandering Albatrosses. It seems unlikely, therefore, that the albatrosses depend greatly on the fishery for acquisition of fish prey but how they catch several species, including Muraenolepis, which are mainly benthic in habit is unknown.last_img read more

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The ratio of MSA to non-sea-salt sulphate in Antarctic Peninsula ice cores

first_imgMethane sulphonic acid (MSA) in an ice core from Dolleman Island (70°35′S, 60°56′W) shows significantly high concentrations (typically 1-2 µm, but up to 5 µm) compared to values recorded in ice cores and in snowfall from elsewhere in Antarctica. MSA data from two other higher altitude Antarctic Peninsula ice cores, Dyer Plateau (70°31′S, 65°01′W) and Gomez Nunatak (74°01′S, 70°38′W), show that the high concentrations measured at Dolleman Island are not representative of the Peninsula region as a whole. However the mean molar MSA/nss-SO42− ratios at the three sites are similar (Dolleman Is, 0.46; Gomez, 0.37; Dyer, 0.32). Exceptionally high concentrations observed at Dolleman Island may be related to its proximity to the biologically productive Weddell Sea, an important source of dimethyl sulphide (DMS), the precursor of MSA. The MSA data from this site are further unusual in that in deeper sections of this core they demonstrate a well defined seasonal maximum in winter rather than in summer and are out of phase with non sea-salt sulphate, another product of the decomposition of DMS. In contrast, in a near-surface section, MSA variations are in phase with non sea-salt sulphate, with a maximum concentration in the summer layer. A change in the season of deposition of MSA from winter to summer in the recent past is not considered likely. An alternative explanation is that there has been a relocation of the MSA from summer to winter layers during burial.last_img read more

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Plasma progesterone concentrations measured using a enzyme-linked immunosorbent assay useful for diagnosing pregnancy in harbour seal (Phoca vitulina)

first_imgWild-caught female harbor seals (Phoca vitulina) were classified as sexually mature or immature on the basis of standard body length ( 125 cm mature) and plasma progesterone concentrations measured using an enzyme-linked immunosorbent assay (ELISA), a technique usable in the field. Sexually mature females were classified as pregnant or non-pregnant on the basis of their plasma progesterone concentrations. Of 28 wild mature female harbor seals caught in the Moray Firth, N.E. Scotland, between the end of February and the end of May, 79% had plasma progesterone concentrations greater than 60 nmol liter−1, the lowest plasma progesterone concentration measured in one of eight females later observed with a pup, and were diagnosed as pregnant. A linear discriminant function, calculated to provide a method of distinguishing pregnant and non-pregnant females, predicted 100% of non-pregnant females and 95.8% of pregnant females using plasma progesterone concentration, standard length, and month of capture as parameters. Plasma progesterone concentrations were less than 30 nmol liter−1 in all mature and immature males and immature females. In mature females plasma progesterone concentrations ranged from 0-318 nmol liter−1.last_img read more

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Diversity of Antarctic terrestrial protozoa

first_imgHeterotrophic protozoa have a global distribution in terrestrial habitats. The functional groups significantly represented are zooflagellates, cillates, gymnamoebae and testate amoebae. Their range extends into the Antarctic zone, but the species richness of the communities is rarely of the same order of magnitude as those in temperate latitudes. Species diversity is usually very low owing to dominance of the communities by single, or a few, species which are best adapted to the Antarctic terrestrial environment. This is characterized by seasonal, diurnal or unpredictable fluctuations in moisture, temperature and bacterial food supply of high amplitude. The fauna shows pauperization with latitude and climatic severity. Nearly all records of species distribution are consistent with the model that community composition is determined by local conditions. An important exception is the distribution of the testate amoeba genus Nebela whose species distribution is influenced by biogeographical factors. Successional changes in community composition in fellfield habitats are characterized by the sequence: pioneer microflagellate colonizers, larger flagellates and small ciliates, and finally testate amoebae. The succession is most closely correlated with the accumulation of organic matter. A model of the strategies of dominant microflagellate species can be constructed by ordinating them on a two-dimensional habitat template of A-r-K selection continuum. The globally ubiquitous microflagellate Heteromita globosa emerges as the most strongly A-selected and K-selected. The occurrence of terrestrial protozoa near their latitudinal limits of distribution can serve as sensitive indicators of the biological effects of climatic change. Having short generation times and effective means of cyst dispersal, changes in the gross distribution can provide rapid warning of critical changes in thermal regimes.last_img read more

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Survey of marine birds and mammals of the South Sandwich Islands

first_imgDuring January and February 1997, two separate surveys of the birds and seals of the South Sandwich Islands archipelago were made, with further data obtained from the northern islands during February 1998. Together, these surveys provide the most recent and accurate estimates of breeding populations of most species, their distributions, and their habitat. Observations were made (1) from a small vessel operating close inshore, which surveyed approximately 92% of the archipelago’s coastline, in addition to making shore counts at selected locations; (2) during a six-week shorebased field camp on Candlemas Island; and (3) opportunistically during helicopter-supported landings and airborne operations over all islands in the archipelago. The surveys recorded 16 species of breeding birds, including the first confirmation of breeding by black-bellied storm petrels (Fregetta tropica) and Antarctic terns (Sterna vittata), the second record of incubating king penguins (Aptenodytes patagonicus), and the location of many previously unrecorded seabird breeding sites. The population of chinstrap penguins (Pygoscelis antarctica), at approximately 1.5 x 10 pairs is considerably less than the estimate of 5 x 10 pairs currently in use, and represents about 30% of the world population. Populations of chinstrap penguins, Antarctic fulmars (Fulmarus glacialoides), cape petrels (Daption capense), and snow petrels (Pagodroma nivea) in the South Sandwich Islands are of global significance. Five species of seals were recorded. At the time of the surveys, only Antarctic fur seals (Arctocephalus gazella) were confirmed to be breeding, and several new breeding sites were located. Pup numbers showed a small increase compared with the few earlier records, but the population has not undergone the large increases seen on South Georgia and at sites in the maritime Antarctic. The other four species recorded are considered highly likely to breed either within the archipelago or amongst pack ice that seasonally surrounds the islands.last_img read more

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Impacts of local human activities on the Antarctic environment

first_imgWe review the scientific literature, especially from the past decade, on the impacts of human activities on the Antarctic environment. A range of impacts has been identified at a variety of spatial and temporal scales. Chemical contamination and sewage disposal on the continent have been found to be long-lived. Contemporary sewage management practices at many coastal stations are insufficient to prevent local contamination but no introduction of non-indigenous organisms through this route has yet been demonstrated. Human activities, particularly construction and transport, have led to disturbances of flora and fauna. A small number of non-indigenous plant and animal species has become established, mostly on the northern Antarctic Peninsula and southern archipelagos of the Scotia Arc. There is little indication of recovery of overexploited fish stocks, and ramifications of fishing activity oil bycatch species and the ecosystem could also be far-reaching. The Antarctic Treaty System and its instruments, in particular the Convention for the Conservation of Antarctic Marine Living Resources and the Environmental Protocol, provide a framework within which management of human activities take place. In the face of the continuing expansion of human activities in Antarctica, a more effective implementation of a wide range of measures is essential, in order to ensure comprehensive protection of the Antarctic environment, including its intrinsic, wilderness and scientific values which remains a fundamental principle of the Antarctic Treaty System. These measures include effective environmental impact assessments, long-term monitoring, mitigation measures for non-indigenous species, ecosystem-based management of living resources, and increased regulation of National Antarctic Programmes and tourism activities.last_img read more

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Impact of atmospheric forcing on Antarctic continental shelf water masses

first_imgThe Antarctic continental shelf seas feature a bimodal distribution of water mass temperature, with the Amundsen and Bellingshausen Seas flooded by Circumpolar Deep Water that is several degrees Celsius warmer than the cold shelf waters prevalent in the Weddell and Ross Seas. This bimodal distribution could be caused by differences in atmospheric forcing, ocean dynamics, ocean and ice feedbacks, or some combination of these factors. In this study, a highly simplified coupled sea ice–mixed layer model is developed to investigate the physical processes controlling this situation. Under regional atmospheric forcings and parameter choices the 10-yr simulations demonstrate a complete destratification of the Weddell Sea water column in winter, forming cold, relatively saline shelf waters, while the Amundsen Sea winter mixed layer remains shallower, allowing a layer of deep warm water to persist. Applying the Weddell atmospheric forcing to the Amundsen Sea model destratifies the water column after two years, and applying the Amundsen forcing to the Weddell Sea model results in a shallower steady-state winter mixed layer that no longer destratifies the water column. This suggests that the regional difference in atmospheric forcings alone is sufficient to account for the bimodal distribution in Antarctic shelf-sea temperatures. The model prediction of mixed layer depth is most sensitive to the air temperature forcing, but a switch in all forcings is required to prevent destratification of the Weddell Sea water column.last_img read more

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East Weddell Sea echinoids from the JR275 expedition

first_imgInformation regarding the echinoids in this dataset is based on the Agassiz Trawl (AGT) and epibenthic sledge (EBS) samples collected during the British Antarctic Survey cruise JR275 on the RRS James Clark Ross in the austral summer 2012. A total of 56 (1 at the South Orkneys and 55 in the Eastern Weddell Sea) Agassiz Trawl and 18 (2 at the South Orkneys and 16 in the Eastern Weddell Sea) epibenthic sledge deployments were performed at depths ranging from ~280 to ~2060 m. This presents a unique collection for the Antarctic benthic biodiversity assessment of an important group of benthic invertebrates. In total 487 specimens belonging to six families, 15 genera, and 22 morphospecies were collected. The species richness per station varied between one and six. Total species richness represents 27% of the 82 echinoid species ever recorded in the Southern Ocean (David et al. 2005b, Pierrat et al. 2012, Saucède et al. 2014). The Cidaridae (sub-family Ctenocidarinae) and Schizasteridae are the two most speciose families in the dataset. They comprise seven and nine species respectively. This is illustrative of the overall pattern of echinoid diversity in the Southern Ocean where 65% of Antarctic species belong to the families Schizasteridae and Cidaridae (Pierrat et al. 2012).last_img read more

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Evidence for a palaeo-subglacial lake on the Antarctic continental shelf

first_imgSubglacial lakes are widespread beneath the Antarctic Ice Sheet but their control on ice-sheet dynamics and their ability to harbour life remain poorly characterized. Here we present evidence for a palaeo-subglacial lake on the Antarctic continental shelf. A distinct sediment facies recovered from a bedrock basin in Pine Island Bay indicates deposition within a low-energy lake environment. Diffusive-advection modelling demonstrates that low chloride concentrations in the pore water of the corresponding sediments can only be explained by initial deposition of this facies in a freshwater setting. These observations indicate that an active subglacial meltwater network, similar to that observed beneath the extant ice sheet, was also active during the last glacial period. It also provides a new framework for refining the exploration of these unique environments.last_img read more

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