Medical research by the British Antarctic Survey

first_imgThere is a long record of medical research and observation in the Antarctic, almost as long as the record of exploration. The early expeditions usually had a medical officer who described the medical hazards of the Antarctic. In this article, an account will be given of the research undertaken by medical officers of the Falkland Islands Dependencies Survey (FIDS) and, subsequently, of the British Antarctic Survey (BAS). A more detailed report will be found in the chapter entitled “Man and the environment” in Antarctic research (Priestley et al. eds, 1964).last_img read more

A comparison of the ammonite faunas of the Antarctic Peninsula and Magallanes Basin

first_imgAmmonite-bearing Jurassic and Cretaceous sedimentary successions are well developed in the Antarctic Peninsula and the Magallanes Basin of Patagonia. Faunas of middle Jurassic-late Cretaceous age are present in Antarctica but those of Patagonia range no earlier than late Jurassic. Although the late Jurassic perisphinctid-dominated faunas of the Antarctic Peninsula show wide-ranging Gondwana affinities, it is not yet possible to effect a close comparison with faunas of similar age in Patagonia because of the latter’s poor preservation and our scant knowledge of them. In both regions the Neocomian is not well represented in the ammonite record, although uninterrupted sedimentary successions appear to be present. Lack of correspondence between the Aptian and Albian faunas of Alexander I. and Patagonia may be due to major differences in palaeogeographical setting. Cenomanian-Coniacian ammonite faunas are known only from Patagonia, although bivalve faunas indicate that rocks of this age are present in Antarctica. Kossmaticeratid faunas mark the late Cretaceous in both regions. In Antarctica these have been classified as Campanian, whereas in Patagonia it is generally accepted, perhaps incorrectly, that these also range into the Maestrichtian.last_img read more

Sampling biological characteristics of krill: Effect of heterogeneous nature of swarms

first_imgAn effect of the very patchy distribution of Antarctic krill (Euphausia superba Dana) in various forms of aggregation is that a single swarm may not provide an unbiased estimate of population parameters such as mean length of krill in the local area. Here, we analyse the number of samples required to estimate the characteristics of a local population as precisely as if there were no differences between krill swarms in terms of their biological composition. Krill were intensively sampled over different spatial and temporal scales around South Georgia in 1981 and 1982, and in the Bransfield Strait in 1985. These varied from replicate hauls at a single station over 24 h and repeat sampling in restricted areas over periods of 6 to 14 d to regional surveys around South Georgia and in the Bransfield Strait. Various biological characteristics were measured such as length, maturity, moult stage and feeding state. Depending upon the biological characteristic examined and the area covered by the sampling programme, the number of samples needed to obtain the same degree of precision as would be found in the absence of heterogeneity varied from 3 to > 80 samples. This has important implications for the design of net-sampling programme for monitoring krill populations.last_img read more

Seasonal stratification and tidal current profiles along Ronne Ice Front

first_imgThroughout much of the year a coastal polynya along Ronne Ice Front in the southern Weddell Sea is maintained by winds blowing from Ronne Ice Shelf and tidal divergence [Foldvik et al., 2001; Renfrew et al., 2002]. In wintertime, the coastal polynya is the focus of intense heat loss, as relatively warm water is exposed to the cold atmosphere, causing the seawater to cool to itssurface freezing point, with further heat loss resulting in sea ice production. Sustained sea ice production is maintained as newly formed sea ice is transported northward away from the polynya by offshore winds. Production rates are 1 or 2 orders of magnitude higher than for thesurrounding sea ice, with typically 6.1 % of the entire Weddell Sea ice production focused within the polynya that makes up only 0.013 % of the Weddell Seas area [Renfrew et al., 2002]. The associated High Salinity Shelf Water (HSSW) production will be equally intense within the polynya resulting in convective overturning of the entire underlying water column during winter [Foldvik et al., 2001; Nicholls et al., 2003] and a strong seasonal signal in the water column properties. Any changes in seasonal stratification are likely to significantly affect the tidal current profile in this region [Makinson, 2002]. It is the strongly depth dependent semi-diurnal tidal currents,associated with the proximity of the critical latitude [Foldvik et al., 2001; Foldvik et al., 1990],that are sensitive to these changes. The northern most part of the Ronne Ice Front region lies near the M2 critical latitude (74° 28′ 18″S), which can give rise to a thick bottom boundary layer that may occupy the entire water column. Along the ice front, early observations of tidal currents and water column properties were confined to short summer observations and hence no seasonal data was available. However, four moorings with records greater than one year have been successfully recovered from the Ronne Ice Front coastal polynya [Foldvik et al., 2001; Woodgate et al., 1998]. Initial analysis by Makinson and Schröder [2004] has shown that during periods of stratification,the tidal current profile is notably different from those during the winter. The data from these moorings forms the basis of the work presented here and their locations are shown in Figure 1.last_img read more

Anthropogenic and biophysical contributions to increasing atmospheric CO2 growth rate and airborne fraction

first_imgWe quantify the relative roles of natural and anthropogenic influences on the growth rate of atmospheric CO2 and the CO2 airborne fraction, considering both interdecadal trends and interannual variability. A combined ENSO-Volcanic Index (EVI) relates most (similar to 75%) of the interannual variability in CO2 growth rate to the El-Nino-Southern-Oscillation (ENSO) climate mode and volcanic activity. Analysis of several CO2 data sets with removal of the EVI-correlated component confirms a previous finding of a detectable increasing trend in CO2 airborne fraction (defined using total anthropogenic emissions including fossil fuels and land use change) over the period 1959-2006, at a proportional growth rate 0.24% y(-1) with probability similar to 0.9 of a positive trend. This implies that the atmospheric CO2 growth rate increased slightly faster than total anthropogenic CO2 emissions. To assess the combined roles of the biophysical and anthropogenic drivers of atmospheric CO2 growth, the increase in the CO2 growth rate (1.9% y(-1) over 1959-2006) is expressed as the sum of the growth rates of four global driving factors: population (contributing + 1.7% y(-1)); per capita income (+ 1.8% y(-1)); the total carbon intensity of the global economy (-1.7% y(-1)); and airborne fraction (averaging + 0.2% y(-1) with strong interannual variability). The first three of these factors, the anthropogenic drivers, have therefore dominated the last, biophysical driver as contributors to accelerating CO2 growth. Together, the recent (post-2000) increase in growth of per capita income and decline in the negative growth (improvement) in the carbon intensity of the economy will drive a significant further acceleration in the CO2 growth rate over coming decades, unless these recent trends reverse.last_img read more

Contrasting phylogeographical patterns for springtails reflect different evolutionary histories between the Antarctic Peninsula and continental Antarctica

first_imgWe examined the genetic structure among populations and regions for the springtails Cryptopygus antarcticus antarcticus and Gomphiocephalus hodgsoni (Collembola) to identify potential historical refugia and subsequent colonization routes, and to examine population growth/expansion and relative ages of population divergence. Location Antarctic Peninsula for C. a. antarcticus; Antarctic continent (southern Victoria Land) for G. hodgsoni. Methods Samples were collected from 24 and 28 locations across the Antarctic Peninsula and southern Victoria Land regions for C. a. antarcticus and G. hodgsoni, respectively. We used population genetic, demographic and nested clade analyses based on mitochondrial DNA (cytochrome c oxidase subunit I and subunit II). Results Both species were found to have population structures compatible with the presence of historical glacial refugia on Pleistocene (2 Ma-present) time-scales, followed by post-glacial expansion generating contemporary geographically isolated populations. However, G. hodgsoni populations were characterized by a fragmented pattern with several ‘phylogroups’ (likely ancestral haplotypes present in high frequency) retaining strong ancestral linkages among present-day populations. Conversely, C. a. antarcticus had an excess of rare haplotypes with a much reduced volume of ancestral lineages, possibly indicating historical founder/bottleneck events and widespread expansion. Main conclusions We infer that these differences reflect distinct evolutionary histories in each locality despite the resident species having similar life-history characteristics. We suggest that this has predominantly been influenced by variation in the success of colonization events as a result of intrinsic historical glaciological differences between the Antarctic Peninsula and continental Antarctic environments.last_img read more

Global Collembola on Deception Island

first_imgThree new non-indigenous springtail species are recorded in recent collections made on Deception Island, South Shetland Islands, maritime Antarctic: Deuteraphorura (Deuteraphorura)cebennaria (Gisin) (Collembola: Onychiuridae), Mesaphorura macrochaeta Rusek (Tullbergiidae), and Proisotoma minuta Axelson (Isotomidae). One of these, D. (D.) cebennaria,is described. Additionally, two new indigenous species, Mesaphorura macrochaeta Rusek and Proisotoma minuta Axelson, are also recorded. The total number of Collembola species now known from the island is 14, comprised of eight native species and six non-indigenous species. This number of non-indigenous species recorded at Deception Island compares with only a single non-indigenous springtail recorded at any other maritime or continental Antarctic location. The reason underlying this high level of occurrence of non-indigenous species on Deception Island islikely to be a combination of the island’s high level of human visitation and the presence of relatively benign terrestrial habitats associated with areas of geothermal activity. Two of the new records represent species recently assessed as being of the highest risk to become invaders in the less extreme environments of the subantarctic, thereby emphasising the importance and urgency of adopting and applying effective biosecurity measures to protect the unique and vulnerable ecosystems of this region. Also documented are the impacts on the soil fauna of the island from human trampling, which drastically reduced densities of both native and non-indigenous species to 1% of the abundance typical of non-trampled sites.last_img read more

Extreme variation in migration strategies between and within wandering albatross populations during their sabbatical year, and their fitness consequences

first_imgMigratory behavior, routes and zones used during the non-breeding season are assumed to have been selected to maximize fitness, and can lead to genetic differentiation. Yet, here we show that migration strategies differ markedly between and within two genetically similar populations of wandering albatross Diomedea exulans from the Crozet and Kerguelen archipelagos in the Indian Ocean. Wandering albatrosses usually breed biennially if successful, and during the sabbatical year, all birds from Kerguelen migrate to the Pacific Ocean, whereas most from Crozet are sedentary. Instead of taking the shortest routes, which would involve a return against headwinds, migratory birds fly with the westerly winds, requiring detours of 10,000 s km. In total, migrants circumnavigate Antarctica 2 to 3 times, covering more than 120,000 km in a single sabbatical year. Our results indicate strong links between migratory behavior and fitness; all birds from Kerguelen breed biennially, whereas a significant proportion of those from Crozet, especially females, are sedentary and breed in consecutive calendar years. To breed annually, these females temporarily change mate, but return to their original partner in the following year. This extreme variation in migratory behavior has important consequences in term of life history evolution and susceptibility to climate change and fisheries.last_img read more

The seasonal cycle of ocean-atmosphere CO2 flux in Ryder Bay, west Antarctic Peninsula

first_imgApproximately 15 million km2 of the Southern Ocean is seasonally ice covered, yet the processes affecting carbon cycling and gas exchange in this climatically important region remain inadequately understood. Here, 3 years of dissolved inorganic carbon (DIC) measurements and carbon dioxide (CO2) fluxes from Ryder Bay on the west Antarctic Peninsula (WAP) are presented. During spring and summer, primary production in the surface ocean promotes atmospheric CO2 uptake. In winter, higher DIC, caused by net heterotrophy and vertical mixing with Circumpolar Deep Water, results in outgassing of CO2 from the ocean. Ryder Bay is found to be a net sink of atmospheric CO2 of 0.59–0.94 mol Cm−2 yr−1 (average of 3 years). Seasonal sea ice cover increases the net annual CO2 uptake, but its effect on gas exchange remains poorly constrained. A reduction in sea ice on the WAP shelf may reduce the strength of the oceanic CO2 sink in this region.last_img read more

Leapfrog migration and habitat preferences of a small oceanic seabird, Bulwer’s petrel (Bulweria bulwerii)

first_imgAim Our current understanding of migratory strategies and the reasons for their high variability along the phylogenetic tree remains relatively poor. Most of the hypotheses relating to migration have been formulated for terrestrial taxa; classically, oceanic migrations were considered as merely dispersive because of the scarcity of observations in the open ocean. We describe for the first time, the migration strategy of a small seabird, the Bulwer’s petrel (Bulweria bulwerii), and provide new insights into the ecology and evolution of long-distance marine migrations. Location Subtropical and tropical Atlantic Ocean. Methods Using cutting-edge geolocators, we examined the year-round distribution and at-sea activity patterns of adult Bulwer’s petrels sampled at five localities throughout the species’ breeding range in the Atlantic, within the Azores, Salvages, Canary and Cape Verde archipelagos. We assessed the migratory connectivity of the species and its habitat use at population and metapopulation scales. Results Our results provide the first evidence of an oriented leapfrog migration in oceanic seabirds. Ecological niche models based on breeding-season data effectively predicted that subtropical waters of the South Atlantic would be the preferred habitat for the northern populations of Bulwer’s petrels during the non-breeding season. Habitat modelling also highlighted similarities in distributions between the breeding and non-breeding periods for the southern populations. Data on at-sea activity patterns suggested that birds from the northern and southern populations behave differently during the breeding season, as well as in the northern and southern non-breeding ranges during the non-breeding period. Main conclusions These results indicate that specific habitat preferences, presumably related to differences in prey availability, explain the observed distributions and hence the pattern of leapfrog migration described for Bulwer’s petrel. Our study demonstrates the utility of integrating diverse tracking data from multiple populations across international boundaries, and habitat modelling, for identifying important areas common to many marine species in the vast oceanic environments.last_img read more