Rothera Point Research Articles

Delayed arm regeneration in the Antarctic brittle star Ophionotus victoriae

We describe the levels of natural arm damage in the Antarctic brittle star Ophionotus victoriae and the rate of arm regeneration over the period of 1 yr, as measured in our aquarium facil- ities at Rothera Point, West Antarctic Peninsula. The natural incidence of arm damage in O. victoriae is high (97% of individuals examined). The rate of regeneration was 0.44 mm wk -1 , which is slow, but within the range of data from temperate brittle stars and also in line with data from the literature showing a general trend of decreasing arm regeneration rate with temperature. The Q10 for arm regeneration rate of 2.6 across brittle stars is within the expected biological range. However, O. victo- riae arm regeneration experiences a lag phase of up to 5 mo before reproducible amounts of new tissue are produced. Such a long lag phase has not been documented for any other brittle star species and produces a range of Q10 values from 3.6 (when compared to the slowest documented lag phase for a temperate brittle star) to exceptionally high Q10 values of 14.9 and 15.4 (when either fastest or average regeneration times are considered for temperate brittle stars and this Antarctic species). This indicates that the initial process of arm regeneration in O. victoriae is either different to that of other brittle stars or it is dependent on factors other than the effects of temperature on enzyme-mediated biochemical reactions, such as gonadal cycles and seasonality.

Metabolic recovery of the Antarctic liverwort Cephaloziella varians during spring snowmelt

We measured the responses of pigments and chlorophyll a fluorescence parameters of the Antarctic leafy liverwort Cephaloziella varians to snowmelt during austral spring 2005 at Rothera Point on the western Antarctic Peninsula. Although no changes to the concentrations of UV-B photoprotective pigments were detected during snowmelt, chlorophyll and carotenoid concentrations and maximum photosystem (PS)II yield (F v /F m) were respectively 88, 60 and 144% higher in the tissues of the liverwort that had recently emerged from snow than in those under a 10 cm depth of snow. A laboratory experiment similarly showed that effective PSII yield increased rapidly within the first 45 min after plants sampled from under snow were removed to an illuminated growth cabinet. The pigmentation and PSII yields of plants during snowmelt were also compared with those of plants in January, during the middle of the growing season at Rothera Point. During snowmelt, plants had lower F v /F m values, chlorophyll a/b ratios and concentrations of UV-B photoprotective pigments and carotenoids than during mid-season, suggesting that although there is some recovery of PSII activity and increases in concentrations of photosynthetic pigments during snowmelt, the metabolism of C. varians is restricted during this period.

Effect of Antarctic solar radiation on sewage bacteria viability

The majority of coastal Antarctic research stations discard untreated sewage waste into the near-shore marine environment. However, Antarctic solar conditions are unique, with ozone depletion increasing the proportion of potentially damaging ultraviolet-B (UV-B) radiation reaching the marine environment. This study assessed the influence of Antarctic solar radiation on the viability of Escherichia coli and sewage microorganisms at Rothera Research Station, Adelaide Island, Antarctic Peninsula. Cell viability decreased with increased exposure time and with exposure to shorter wavelengths of solar radiation. Cell survival also declined with decreasing cloud cover, solar zenith angle and ozone column depth. However, particulates in sewage increased the persistence of viable bacteria. Ultraviolet radiation doses over Rothera Point were highest during the austral summer. During this time, solar radiation may act to partially reduce the number of viable sewage-derived microorganisms in the surface seawater around Antarctic outfalls. Nevertheless, this effect is not reliable and every effort should be made to fully treat sewage before release into the Antarctic marine environment.

Quantitative characterization of shallow marine benthic assemblages at Ryder Bay, Adelaide Island, Antarctica

Non-destructive photographic techniques are valuable for surveying benthic epifauna in sensitive areas. Inherent in these techniques, however, are selectivity biases related to the scale at which surveys are conducted. Such biases have not been addressed for surveys of marine benthos. The present study surveyed epifaunal assemblages at two depths (8 m and 20 m) and three locations close to Rothera Point, Adelaide Island, Antarctica. Two scales of photographic sampling were employed in order to encompass a broad range of taxon sizes and distributions, and their parallel use allowed qualitative and quantitative comparisons to be made between results from each scale. An additional physical sampling element was incorporated to assess sessile cryptic assemblages. A total of 79 faunal taxa from 10 phyla, together with 6 algal taxa, were recorded in the survey. Echinoderms were the most speciose group at both photographic scales, whereas cryptic assemblages were dominated by bryozoans. There were clear resolution-related differences between scales but all three methods revealed pronounced differences in assemblages by depth and location. Assemblages at both depths were notable for consistently high densities (~100 individuals m−2) of the regular echinoid Sterechinus neumayeri, and at 8 m for high densities (~100 individuals m−2) of the limpet Nacella concinna. The results emphasise the general requirement for sampling methodologies to be matched to the size spectra of the organisms under study and, more specifically, highlight the need for studies to assess the relative importance of biotic and physical factors in structuring the Antarctic benthos.

Sequential reduction of UV-B radiation in the field alters the pigmentation of an Antarctic leafy liverwort

UV-B radiation (280–315 nm), incident on the leafy liverwort Cephaloziella varians growing at Rothera Point on the Western Antarctic Peninsula, was manipulated in late austral spring 1998 by screens consisting of a novel combination of Plexiglas panes and polyester sheets. The screens transmitted approximately 79, 68, 48, 41 and 31% of daily UV-B radiation dose. Plants from under and outside the screens were sampled seven times over 35 days. Correlative analyses indicated that concentrations of an anthocyanin-like pigment located in leaf tips were positively associated with UV-B transmission at the last two samplings, that concentrations of total chlorophylls were negatively associated with UV-B transmission at the final sampling, and that those of UV-B screening pigments were positively correlated with transmission at three intermediate samplings. Plants exposed to low UV-B transmission levels were visibly greener than those exposed to high transmission levels after approximately 23 days. The closest relationships between the treatment and concentrations of UV-B screening pigments were associated with increased ambient biologically weighted UV-B dose received by plants in the 5.5 h before each sampling, which coincided with the passage of the ozone hole over Rothera Point. As C. varians emerged from melting snow and ice, concentrations of the anthocyanin-like pigment and chlorophyll respectively increased and decreased faster in plants exposed to high transmission levels of UV-B, relative to those exposed to low UV-B transmission levels.

Growth in the limpet Nacella concinna from contrasting sites in Antarctica

Annual shell growth was determined by mark and recapture in the limpet Nacella concinna (Strebel 1908) at two contrasting sites in Antarctica. At Signy Island, 60°S, growth was moderately fast, comparable with some limpets in more temperate areas. The fluorescent calcium marker calcein was used to validate the results from the mark/recapture study, and fine-scale growth increments showed that shell growth was seasonal. Further south at Rothera Point, 67°S, mean annual growth over a 3-year period was significantly slower than at Signy, and in 1 year was the slowest yet reported for a limpet. Comparison with an earlier mark/recapture study at Arthur Harbour, Palmer Station (64°S) revealed a cline of decreasing growth performance with increasing latitude along the Antarctic Peninsula. It is not clear whether the slower annual growth rate at higher latitude was caused by physiological constraints, a reduced length of growing season, or a combination of both. Limpets show a global cline in growth performance, which decreases towards higher latitudes.

Influence of seasonal environmental variables on the distribution of presumptive fecal Coliforms around an Antarctic research station.

Factors affecting fecal microorganism survival and distribution in the Antarctic marine environment include solar radiation, water salinity, temperature, sea ice conditions, and fecal input by humans and local wildlife populations. This study assessed the influence of these factors on the distribution of presumptive fecal coliforms around Rothera Point, Adelaide Island, Antarctic Peninsula during the austral summer and winter of February 1999 to September 1999. Each factor had a different degree of influence depending on the time of year. In summer (February), although the station population was high, presumptive fecal coliform concentrations were low, probably due to the biologically damaging effects of solar radiation. However, summer algal blooms reduced penetration of solar radiation into the water column. By early winter (April), fecal coliform concentrations were high, due to increased fecal input by migrant wildlife, while solar radiation doses were low. By late winter (September), fecal coliform concentrations were high near the station sewage outfall, as sea ice formation limited solar radiation penetration into the sea and prevented wind-driven water circulation near the outfall. During this study, environmental factors masked the effect of station population numbers on sewage plume size. If sewage production increases throughout the Antarctic, environmental factors may become less significant and effective sewage waste management will become increasingly important. These findings highlight the need for year-round monitoring of fecal coliform distribution in Antarctic waters near research stations to produce realistic evaluations of sewage pollution persistence and dispersal.

Filamentous ascomycetes inhabiting the rhizoid environment of the liverwort Cephaloziella varians in Antarctica are assessed by direct PCR and cloning

We molecularly assesed the ascomycetous fungal communities inhabiting the rhizoid environment of Cephaloziella varians, collected at Rothera Point on the western Antarctic Peninsula. The RFLP-phenotyped and cloned PCR products of a partial small subunit of the ribosomal RNA gene were sequenced and analyzed with neighbor joining (NJ) and maximum parsimony (MP). Both analyses identified four bootstrap-supported groups: (i) a sister group to Onygenales, (ii) a well-supported clade with Phialocephala fortinii, (iii) a large group of clones nested within Chaetothyriales, and (iv) a group nested within Eurotiales with a likely affinity to the genus Aspergillus. An additional marginally supported clade, including helotialean Hymenoscyphus fructigenus, was detected in the NJ analysis. Placement of one clone (possibly helotialean) was not supported by either analysis. We included Hymenoscyphus ericae (Helotiales) in our analyses to test for its presence in clone libraries. None of our clones showed strongly supported affinity to H. ericae. The culture-independent technique proved useful for assessing the composition of rhizoid fungal communities, although it remains unknown whether any of these fungi colonize C. varians tissues. Direct-community assays of this kind might be best combined with traditional isolation techniques to get a more holistic view of fungi occupying plant tissues.

Filamentous Ascomycetes Inhabiting the Rhizoid Environment of the Liverwort Cephaloziella varians in Antarctica Are Assessed by Direct PCR and Cloning

We molecularly assesed the ascomycetous fungal communities inhabiting the rhizoid environment of Cephaloziella varians, collected at Rothera Point on the western Antarctic Peninsula. The RFLP-phenotyped and cloned PCR products of a partial small subunit of the ribosomal RNA gene were sequenced and analyzed with neighbor joining (NJ) and maximum parsimony (MP). Both analyses identified four bootstrap-supported groups: (i) a sister group to Onygenales, (ii) a well-supported clade with Phialocephala fortinii, (iii) a large group of clones nested within Chaetothyriales, and (iv) a group nested within Eurotiales with a likely affinity to the genus Aspergillus. An additional marginally supported clade, including helotialean Hymenoscyphus fructigenus, was detected in the NJ analysis. Placement of one clone (possibly helotialean) was not supported by either analysis. We included Hymenoscyphus ericae (Helotiales) in our analyses to test for its presence in clone libraries. None of our clones showed strongly supported affinity to H. ericae. The culture-independent technique proved useful for assessing the composition of rhizoid fungal communities, although it remains unknown whether any of these fungi colonize C. varians tissues. Direct-community assays of this kind might be best combined with traditional isolation techniques to get a more holistic view of fungi occupying plant tissues.

UV-B radiation arising from stratospheric ozone depletion influences the pigmentation of the Antarctic moss Andreaea regularis.

Changes to the radiative environment arising from stratospheric ozone (O(3)) depletion and subsequent associations between these changes and the pigmentation of the moss Andreaea regularis were measured in late austral spring and early summer 1998 at Rothera Point on the western Antarctic Peninsula (67 degrees S, 68 degrees W). A strong relationship between O(3) column depth and the ratio of UV-B to PAR irradiance ( F(uv-b)/ F(par)) was recorded at ground level ( r(2)=92%, P<0.001). Weaker, but significant, associations between O(3) column depth and ground level unweighted and biologically effective UV-B radiation (UV-B(be)) were also found. Regression analyses indicated that F(uv-b)/ F(par) was the best predictor for concentrations of UV-B screening pigments and total carotenoids extracted from plant tissues. Concentrations of these pigments were loosely ( r(2)= ca. 30%) but significantly ( P<0.01) positively associated with F(uv-b)/ F(par). Concentrations of UV-B screening pigments were also positively associated with irradiances and daily doses of unweighted UV-B and UV-B(be) radiation. The concentrations of chlorophylls a and b were apparently unaffected by O(3) depletion. The data derived from this study suggest that changes to the radiative environment associated with stratospheric O(3) depletion influence the pigmentation of A. regularis. As a corollary, flavonoids are shown to be present in tissues of A. regularis.

Response of two Antarctic bryophytes to stratospheric ozone depletion

AbstractWe report a study which measured changes to the radiative environment arising from stratospheric O3 depletion at Rothera Point on the western Antarctic Peninsula (67°S, 68°W) and subsequent associations between these changes and the pigmentation and maximum quantum yield of photochemistry (Fv/Fm) of two Antarctic bryophytes, the liverwort Cephaloziella varians and the moss Sanionia uncinata. We found a strong relationship between O3 column depth and the ratio of UV‐B to PAR irradiance (FUV‐B/FPAR) recorded at ground level. Weaker, but significant, associations were also found between O3 column depth and noon irradiances and daily doses of unweighted and biologically effective UV‐B radiation received at ground level. Regression analyses indicated that FUV‐B/FPAR and daily dose of unweighted UV‐B were best predictors for concentrations of total carotenoids and UV‐B screening pigments extracted from bryophyte tissues. Concentrations of these pigments were loosely but significantly positively associated with O3‐dependent irradiance parameters. HPLC analyses of carotenoids also suggested that both species increased the synthesis of neoxanthin during periods of O3 depletion. Violaxanthin, lutein, zeaxanthin and b,bββ‐carotene concentrations were also apparently influenced by O3 reduction, but not consistently across both bryophyte species. Concentrations of chlorophylls a and b were apparently unaffected by O3 depletion.No direct associations between Fv/Fm and O3‐dependent irradiance parameters were found. However stepwise multiple regression analyses suggested that the production of UV‐B screening pigments conferred protection from elevated FUV‐B/FPAR on Fv/Fm in both species and that carotenoids conferred protection on Fv/Fm in Sanionia. Our data suggest that changes to the radiative environment associated with stratospheric O3 depletion influence the pigmentation of two Antarctic bryophytes, but that Fv/Fm is unaffected, at least in part because of rapid synthesis of protective pigments.

Radiocarbon dates from abandoned penguin colonies in the Antarctic Peninsula region

Sixty-three radiocarbon dates on organic remains from 21 abandoned colonies of chinstrap (Pygoscelis antarctica) and Adélie (P. adeliae) penguins on 12 islands in the Antarctic Peninsula region are evaluated for determining the occupation history of penguins in this region. This record also provides a means for assessing sea-level change, glacial advances and retreats, and population responses by penguins to these events. All conventional dates were corrected for the marine-carbon reservoir effect by applying a ΔR = 700±50 BP and marine calibration curves. The 63 calibrated dates give 2σ ranges (95% confidence intervals) from modern to 5990 yr BP. These dates indicate progressively older occupations from north to south along the Antarctic Peninsula. No sites older than approximately 540 BP occur in the northern peninsula, either because they have not yet been found or older sites have been destroyed by solifluction and glacial scouring. Three dates from one locality near Rothera Point, Adelaide Island, also were calibrated with a ΔR = 750 ± 50 and 800 ± 50 BP. No difference was found between calibrated dates using these two other ΔR values, indicating that local corrections for variation in upwelling intensity may not be necessary.

The seasonal energetics of the Antarctic bivalve Laternula elliptica (King and Broderip) at Rothera Point, Adelaide Island

Seasonal changes in feeding activity, metabolic rate and major tissue energy concentrations of the infaunal bivalve Laternula elliptica were monitored over a 12°month period in relation to phytoplankton standing stock. Chlorophyll a concentration displayed the prolonged winter minima and intense annual summer peak characteristic of polar environments. Divers made regular observations on the feeding activity of L. elliptica throughout the year, and siphons were completely withdrawn below the sediment surface at the start of the study in early September 1998. Siphons reappeared as chlorophyll concentrations rose at the end of September and these concentrations continued until late May 1999 when siphons were again withdrawn. There were, therefore, around 4 months in the austral winter when L. elliptica did not feed. Oxygen consumption rates were highly seasonal, varying from 4.3 µmol h–1 late in the winter (August 1999) to 12.9 µmol h–1 in summer (March 1999) for a 50°mm shell height individual, indicating a summer increase in oxygen consumption over winter levels of H×3.0. Nitrogen was excreted as 90% ammonium and 10% urea, and excretion rates were also highly seasonal. The O:N ratio did not vary significantly with size in winter (September, August), but declined with shell length in summer (November, January and March), indicating that larger bivalves used a higher proportion of protein to fuel metabolism than younger animals when feeding in summer. O:N ratios in August 1999 ranged from 3 to 16, indicating a predominantly protein-based metabolism. ANCOVA showed that regressions of dry tissue masses of major non-reproductive body components (musculature, ctenidia and digestive tissue) against shell height did not change between late winter and late summer. ANCOVA also showed that the regression slope for gonad mass against shell height was greater in late summer than late winter (slope F=7.37, P=0.009), and gonad mass was greater in all animals by late summer. Although tissue masses remained constant, energy content of non-reproductive tissues (especially musculature) declined from summer to winter. Muscle tissue also showed the greatest reduction in protein content, which was consistent with O:N estimates of primarily protein-based metabolism, especially in winter. Reduction in whole body energy content (5.84 kJ) agreed closely with total power utilisation during winter estimated from oxygen consumption (5.78 kJ). The data also showed that in contrast to temperate bivalve species, L. elliptica survives the prolonged polar winter with little reduction in body mass.

Seasonality of feeding and nutritional status during the austral winter in the Antarctic sea urchin Sterechinus neumayeri

The seasonal pattern of food intake and tissue energy status was measured over a 2 year period for two populations of the common Antarctic echinoid Sterechinus neumayeri living on contrasting substrata at Rothera Point, Adelaide Island, Antarctica. Food intake was estimated from faecal egestion, and both tissue mass and energy content assessed. Food availability was intensely seasonal, in that water column chlorophyll content and sediment pigment content varied markedly throughout the year. In response, both urchin populations showed an extremely seasonal cycle of faecal egestion, indicating a strong seasonality of feeding activity. Urchins from North Cove living on soft sediment fed at a considerably higher rate, and had a significantly larger Aristotle's lantern, than those in South Cove, 1 km away, living on hard substrata and taking a more cosmopolitan diet. Faecal egestion in both populations was zero for a 7 month period in the austral winter of 1997, and again for a 4 month period in 1998. During the austral summer of 1997/1998, 84% of the total annual energy intake took place in the period January to March. Significant decrease in gut tissue mass provided energy for maintenance in early winter, although progressive reduction of both gonad energy content (but without a detectable change in gonad mass) and body wall organic mass provided energy during the late winter period. The mass of reproductive tissue showed large differences between the two sites, but there was no marked decrease associated with spawning. Tissue proximate composition was assessed stoichiometrically from elemental composition and also checked by direct assay; gonad tissue was richer in lipid than gut tissue, though both were dominated by protein and contained only small amounts of carbohydrate. These data suggest that the very strong seasonality of food intake does not pose a significant energetic challenge for this species.

The relative influence of temperature and food on the metabolism of a marine invertebrate.

Many benthic marine invertebrates exhibit a seasonal cycle in activities such as feeding, growth and reproduction. In temperate regions, this seasonality is typically correlated with coincident cycles in photoperiod, temperature and food availability and it can be difficult to determine which of these environmental factors is the key driver. Polar regions are characterised by greatly reduced seasonal variation in temperature, and an enhanced seasonality of food availability; they therefore form a natural laboratory for distinguishing the ecological effects of food from those of temperature. Here, we report a study of the common shallow water urchin Sterechinus neumayeri from Rothera Point, Antarctica. This species exhibits a marked seasonal variation in metabolic rate and feeding activity (which ceases completely in winter). In this study the metabolic rate of urchins collected in late winter and held in the laboratory without food was compared with that of wild urchins undertaking the transition to summer feeding and growth. Starved urchins showed a small rise in metabolic rate in summer which could be explained entirely by the small increase in temperature (Q(10)=2.5). At the same time, the wild population showed a much larger increase in metabolic rate related largely to the costs of feeding and growth. Rates of nitrogen excretion were also much larger in wild urchins, and the O:N atomic ratio indicated that starved urchins were depending to a greater extent on lipid and carbohydrate. Gut mass and test organic content showed no change in starved urchins, indicating that metabolic substrate was being provided by the gonad. The data suggest that in wild S. neumayeri only 15-20% of the summer increase in metabolism is caused directly by the temperature rise whereas 80-85% is caused by increased physiological activity associated with feeding, growth and spawning.

Do life patterns differ between two Scotia Arc localities? A preliminary investigation of three erect Antarctic bryozoan species

Erect bryozoans are extremely abundant and diverse in polar waters and individual species may span a wide range in latitude and bathymetry. A number of aspects of lifestyle, including polypide recycling, embryo production, distribution, growth form and epibiosis were compared in three species of erect byozoans. These were collected from two locations; Signy Island (60°S) and Rothera Point, Adelaide Island (68°S) and a variety of depths. All three species were in similar stages of polypide cycling within and between the two sites. In the species Isosecuriflustra rubefacta and Nematoflustra flagellata the rate of brown body production (polypide generations) was slower at Signy Island than at Rothera Point. There was little difference between localities (within species) in the pattern of embryo production and no change in embryo size with depth. Embryos of I. rubefacta, however, were significantly larger at Rothera Point than at Signy Island. The proportion of the community occupied by each species changed with depth, but all three species occurred in shallower water at Rothera Point than at Signy Island. Fouling by epibionts decreased with increasing depth and from Signy Island to Rothera Point, both in terms of per cent cover and number of colonizing taxa. Possible trends with depth and latitude are compared with other studies involving bryozoans. The literature on Antarctic benthic taxa, in general, is also considered to determine whether trends within the Bryozoa are reflected in other groups.

The Ecology of an Assemblage Dominant: The Encrusting Bryozoan Fenestrulina rugula

The cheilostome bryozoan Fenestrulina rugula is a major component of the encrusting fauna of physically disturbed shallow water habitats in Antarctica. On rocks collected from Rothera Point, Adelaide Island, F. rugula was the dominant occupier of space (88% of all bryozoans, 76% of all fauna), though spirorbid polychaetes showed more colonisation events per unit area. Growth rate was relatively rapid in comparison with other polar bryozoans, but slower than temperate or tropical species. In fully reproductive colonies almost 80% of zooids carried ovicells. Colonies whose growth brought them into contact with other encrusting fauna (usually another colony of F. rugula) produced smaller zooids and initiated ovicell production earlier than unrestrained colonies. Analysis of overgrowth interactions showed that F. rugula was a relatively poor competitor compared with other encrusting bryozoans, and most within-species interactions were indeterminate. Population mortality was relatively high, averaging 89% per annum, although not as high as in some other species from ephemeral habitats. F. rugula is thus a typical early coloniser in being relatively fast-growing, quick to mature, short-lived and a relatively poor competitor. The population dynamics and ecology of this assemblage dominant appear to have been influenced primarily by the ephemeral nature of its habitat.

The terrestrial arthropod fauna and its habitats in northern Marguerite Bay and Alexander Island, maritime Antarctic

Field surveys of free-living terrestrial microarthropods were made during the 1994–95 summer at four sites in northern Marguerite Bay (Anchorage Island, Lagoon Island, Léonie Island, Rothera Point; c. 68°S, 68°W) and three on southern Alexander Island (Two Step Cliffs, Fossil Bluff, Ablation Valley; c. 71–72°S, 68°W). Detailed site descriptions are presented, as little previous information exists. Twenty species (four Collembola, 16 Acari) were recorded from the Marguerite Bay sites, with a maximum of 17 species at one site. A further four species (one Collembola, two Acari, one Diptera) have been recorded from the same area by other authors. Species diversity at these sites, in particular Léonie Island, is as great as at any known site elsewhere in the maritime Antarctic, although the total area of terrestrial habitat available is small. Individual species and total population densities are also similar to, if not greater than, published studies from the South Shetland and South Orkney Islands. None of the species is new to the maritime Antarctic, although the distributions of several are extended southwards. Only nine species (maximum seven at one site) were found on Alexander Island, concurrent with decreases in population densities to levels similar to those found in many continental Antarctic studies. This still represents a high species diversity for such a high latitude site. The richness of two sites, Ablation Valley and Mars Oasis (Two Step Cliffs), is unlikely to be repeated elsewhere on Alexander Island. The Alexander Island fauna is clearly related to that of the maritime Antarctic, as all except one species occur at more northerly sites elsewhere on the Antarctic Peninsula, and none in the continental Antarctic. One species, Friesia topo (Collembola), is known only from Alexander Island.

Short-offset seismic refraction results near Rothera Station, Antarctic Peninsula

Details are presented of seismic velocities at a site near Rothera Point, Adelaide Island, Antarctic Peninsula. The snow/firn velocity structure was obtained using a 24-channel Bison 9000 seismograph, recording the outputs of geophones of 40 Hz natural frequency attached to 150 mm snow spikes. The refraction velocity of the underlying bedrock was measured using a 48-channel DFS V recorder and 10 Hz geophones. The records were obtained during trials of equipment and techniques which took place in the 1988–89 and 1990–91 seasons. The data will be of interest to other investigators studying firn structure around Antarctica or considering crustal seismology in the Antarctic Peninsula region.

British Antarctic Survey, 1975–76

Six British Antarctic Survey stations were operational during the year. A new station, at Rothera Point, Adelaide Island, is being built to replace Adelaide station. Its development is providing a unique opportunity to study changes in the microbial, invertebrate, plant and birdpopulations as a result of human activities, including the inevitable atmospheric pollution and the localized influence of tracked vehicles. Several small sites have been set up to study these changes. Among the senior Survey staff to visit the bases this season were Dr R. M. Laws (Director), and Mr W. R. Piggott (Head of Atmospheric Sciences). Other visitors included Dr B.B. Roberts, Dr L. Ferraz, a Brazilian observer, and Mr D. Smith, a British artist.