Change is in the air - not just a mild breeze, more of an impending storm. At XXV SCAR in Concepcion, much of the talk at Working Groups and at the Delegates meeting was of change. But why, how and when?

Swimming activity of the Antarctic scallop at a temperature of c. −1.4°C was analysed using in situ video recordings obtained from a remotely operated vehicle (ROV) in Terra Nova Bay, Ross Sea. Data are presented on swimming trajectories, distance travelled and velocity during a swimming bout, adduction frequency, shell gape angle, and the angular opening and closing velocities of shell. This scallop is an effective swimmer although swimming bouts in response to the ROV were generally short, consisting of 2–5 adduction cycles in the take-off phase followed by 1–4 (exceptionally 14) adductions during level swimming. The maximum velocity during each adduction cycle ranged from 19.4–43.1 cm s−1 and the mean velocity during a swimming bout from 12.0–23.5 cm s−1. Each adduction cycle consists of opening, closing and glide phases of approximately equal duration. Adduction frequency during swimming averaged 1.5 adductions s−1.

Two species of lichens, six cyanobacteria, one diatom, 10 chlorophytes and two mycelial fungi were found at La Gorce Mountains (86°30′S, 147°W) at an altitude of about 1750 m. The lichens Lecidea cancriformis and Carbonea vorticosa occurred at a single site which is the most southerly record of lichens. Thousands of small ponds covered extensive ice-cored moraine. Nine ponds sampled had about 30 cm of ice overlying about 26 cm of water and contained algal mats dominated by Phormidium autumnale and cf. Leptolyngbya fragilis. The very low conductivity waters had high nitrate and low dissolved reactive phosphorus concentrations. Of 124 soil samples, five contained visible algae. In 32 there were only microscopic growths but no algae were detected in 87 samples, possibly because of lack of water for much of summer. A visible mat dominated by Hammatoidea normanni occurred in a rock fissure at the lichen site. At Price Bluff, green patches of Desmococcus cf.olivaceus, up to 20 cm2, were scattered over the moraine. Growths were revealed at the soil–ice interface when overlying soil up to one centimetre thick was removed. It is suggested that although dispersal of algae from local populations may be readily achieved establishment of populations is a rare event outside the pond environment.

Bacterial cultures obtained through selective enrichment of beach sand collected 60 days and one year after treatment of sites in a pilot oil spill trial conducted at Airport Beach, Vestfold Hills, East Antarctica, were examined for the ability to degrade n-alkanes and phenanthrene. The effects of different hydrocarbon mixtures (Special Antarctic Blend [SAB] and BP-Visco), fish oil [orange roughy]) and inoculation of replicate sites with water from Organic Lake (previously shown to contain hydrocarbon-degrading bacteria) on the indigenous microbial population were examined. Of the cultures obtained, those from sites treated with SAB and BP-Visco degraded n-alkanes most consistently and typically to the greatest extent. Two mixed cultures obtained from samples collected at 60 days and two isolates obtained from these cultures extensively degraded phenanthrene. 1-Hydroxy-naphthoic acid formed the major phenanthrene metabolite. Lower levels of salicylic acid, 1-naphthol, 1, 4-naphthaquinone and phenanthrene 9-10 dihydrodiol were detected in extracts of phenanthrene grown cultures. This study shows that under laboratory conditions indigenous Antarctic bacteria can degrade n-alkanes and the more recalcitrant polycyclic aromatic hydrocarbon, phenanthrene. The enrichment of hydrocarbon degrading microorganisms in Antarctic ecosystems exposed to hydrocarbons is relevant for the long term fate hydrocarbon spills in this environment.

On the high Antarctic shelf, 374 different epibiotic relationships of the megafauna were photographically registered and statistically analysed. These comprised 47 different epibiotic and 96 substratum taxa and had obvious differences in abundance and presence in three different benthic assemblages. Six abundant obligatory relationships in which the epibiont occurred almost exclusively on one type of substratum had highly specialized epibionts. For an additional eight relationships, a statistical test revealed that the epibionts preferred specific living and elevated mineral substrata. Most of these relationships are interpreted as commensalism (sensu Odum) in which the suspension feeding epibiont profits from the elevated position. Here it has better access to food compared with life on the sediment. The evolution of a rich and mainly sessile epifauna on parts of the high Antarctic shelves and the successful development of epibiotic behaviour in other species are suggested as a major reason for the high species richness in the benthic fauna. The results provide evidence that the Antarctic megabenthos is more biologically accommodated than physically controlled.

Historical observations of the large-scale flow and frontal structure of the Antarctic Circumpolar Current in the Scotia Sea region were combined with the wind-induced surface Ekman transport to produce a composite flow field. This was used with a Lagrangian model to investigate transport of Antarctic krill. Particle displacements from known krill spawning areas that result from surface Ekman drift, a composite large-scale flow, and the combination of the two were calculated. Surface Ekman drift alone only transports particles a few kilometres over the 150-day krill larval development time. The large-scale composite flow moves particles several hundreds of kilometres over the same time, suggesting this is the primary transport mechanism. An important contribution of the surface Ekman drift on particles released along the continental shelf break west of the Antarctic Peninsula is moving them north-northeast into the high-speed core of the southern Antarctic Circumpolar Current Front, which then transports the particles to South Georgia in about 140–160 days. Similar particle displacement calculations using surface flow fields obtained from the Fine Resolution Antarctic Model do not show overall transport from the Antarctic Peninsula to South Georgia due to the inaccurate position of the southern Antarctic Circumpolar Current Front in the simulated circulation fields. The particle transit times obtained with the composite large-scale flow field are consistent with regional abundances of larval krill developmental stages collected in the Scotia Sea. These results strongly suggest that krill populations west of the Antarctic Peninsula provide the source for the krill populations found around South Georgia.

Gobionotothen gibberifrons <1 year old, of the 1977, 1980, 1981, 1985, 1986, 1990 and 1995 cohorts, were sampled using nets, in various periods during summer (December to February) at South Georgia. Growth in standard length (Ls) was estimated using the exponential model. Among the seven cohorts, average growth rate varied between 0.33–2.1% Lsd−1, and predicted Ls for mid-January varied between 21.6–29.1 mm. Average growth rate was inversely related to mean date of sampling but was not significantly related to mean Ls. Mean sea surface temperatures were available for the 1981–95 cohorts. Average growth rate and predicted Ls for mid-January were both negatively conelated with mean December–January sea temperature, but were not significantly related to mean weekly sea surface temperature during the sampling periods. Greater average growth rate and greater Ls in cooler summers may be partly due to a large-scale pattern of environmental variability, indicated by sea temperature, that governs the timing and magnitude of the production cycle and food availability.

A detailed study was made of the extent of genetic variation within populations of two moss species, Bryum argenteum and Hennediella heimii, from the Garwood Valley in Southern Victoria Land, Antarctica. RAPD (Random Amplified Polymorphic DNA) technology was used to analyse over 30 clumps of each species, collected from adjacent sites in five small meltstream drainage channels. Overall, extensive genetic variation was found, with no two samples being identical in either species. For both species, most clumps showed within-clump variation, although generally the shoots from each clump were most closely related to other shoots from that clump, indicating somatic mutation. Of the B. argenteum isolates, most showed distinct clustering corresponding to the five drainage channels, with some clustering within the top, middle or bottom of the channels, and separation of northern and southern sides of the valley. There was some evidence of across-channel dispersal for B. argenteum. For H. heimii, the situation was quite different; there was very little clustering of clumps according to channel from which they were collected. Rather, the isolates appeared to form one continuous population across the five channels, with partial separation of northern and southern sides of the valley. These results are consistent with the predicted means of dispersal of these species in Antarctica: predominantly by water for B. argenteum, and by wind for H. heimii.

Erosion of bedrock from lower intertidal reefs by waves acting on attached plants of bull-kelp (Durvillaea antarctica) was investigated over one year at Macquarie Island, Southern Ocean. At a site on the more sheltered east coast, such erosion occurred during four separate storms, each casting up 834–1078 large kelp plants km−1 of coast, of which 30–45% were still attached to jagged, freshly quarried bedrock fragments over 2.5 cm long. The largest fragment weighed was 74.6 kg; rounded cobbles and boulders attached to kelp plants and weighing up to 102.2 kg (and probably more than 160 kg) were also cast up on beaches. 19–21% of the standing crop of large kelp plants was removed by storms during the year of observation. Break points for 10 kelp stipes were found to be at least 90–161 kg. Total annual erosion by kelp-plucking is at least 1.56 tonnes of rock km−1 of coast. However, in terms of erosion this computes to only 0.1 mm yr−1, far below the rate of uplift of the island.

Lithium distributions in lake and pond waters of the McMurdo Dry Valleys of southern Victoria Land, Antarctica were studied to elucidate the origin of dissolved salts and the evolutionary history of the lakes and ponds. The EfLi [(Li/Cl)sample/(Li/Cl)seawater] values of the bottom waters in Lakes Bonney and Fryxell were higher than unity (EfLi=4–7), indicating that the salts originated from sea salts (probably relict seawater) and have been subsequently modified by the contribution of meltwaters containing atmospheric fallout and/or rock and soil weathering products. In contrast, extremely high Li concentrations with high EfLi values in the Don Juan Pond water (EfLi = 180) and the bottom waters of Lake Vanda (EfLi = 40) suggest that the salts originated from deep groundwaters influenced mainly by saline water-rock interactions, as supported by the dissolution experiments of granite in NaCl solution. The low Li concentrations of pond waters with high EfLi values in the Labyrinth indicate that the salts are derived from atmospheric fallout. The decrease of the EfLi values with the increase of Cl concentrations can be explained by the repeated cycles of the migration of Li into the ice phase and subsequent ablation of surface ice, as indicated by seawater freezing experiments.

The relationship between colony area and population density of Adélie penguins Pygoscelis adeliae was examined to determine whether colony area, measured from aerial or satellite imagery, could be used to estimate population density, and hence detect changes in populations over time. Using maps drawn from vertical aerial photographs of Adélie penguin colonies in the Mawson region, pair density ranged between 0.1 and 3.1 pairs m−2, with a mean of 0.63 ± 0.3 pairs m−2. Colony area explained 96.4% of the variance in colony populations (range 90.4–99.6%) for 979 colonies at Mawson. Mean densities were not significantly different among the 19 islands in the region, but significant differences in mean pair density were observed among colonies in Mawson, Whitney Point (Casey, East Antarctica) and Cape Crozier (Ross Sea) populations. The relationship between colony area and population may be locality-and/or species-specific, and a robust data set is required to validate the relationship.

Deception Island is a large volcanic centre in Bransfield Strait, a very young marginal basin between the South Shetland Islands and Antarctic Peninsula. It has a historical record of volcanic activity, with the most recent eruption occurring in 1970. The island is a stratovolcano with a large flooded caldera forming a natural harbour known as Port Foster. It has been a focus of human activity since early last century, as a base for whaling and sealing expeditions and the locus of several scientific stations. During that period, many bathymetric surveys were carried out, the earliest in 1829 and the most recent in 1993. This study concentrates on surveys from 1948 onwards. Because Port Foster can be classified as a restless caldera, the bathymetric records were analysed for evidence of volcano-tectonic deformation, particularly caldera resurgence (uplift) which could have significant consequences for hazard and risk assessments of the volcano. The results show that a distinctive pattern of shallowing and uplift is present, correlating well with known and inferred volcanic and volcanotectonic processes on the island. In particular, bathymetric records between 1949 and 1993 show uplift rates as high as 0.3–0.5 m a−1, far exceeding normal sedimentation rates in a caldera this size. Rapid uplift in an arcuate offshore area not affected by the sedimentation of recent eruptions suggests that volcano tectonic resurgence or tectono-magmatic effects of an upward migrating magma chamber present a significant risk to the considerable human activity taking place in the region.

The Mesozoic-Cenozoic volcanic arc of the Antarctic Peninsula is represented on Adelaide Island by a sedimentary and volcanic succession intruded by plutons. 40Ar-39 Ar step-heating age spectra have been obtained from volcanic rocks and hornblende separates from sedimentary clasts of plutonic origin. These spectra show evidence for some argon loss, but, in general, have plateau ages which are consistent with the mapped stratigraphy and with other geochronological controls, suggesting that they approximate to original ages. As a result the following events in the evolution of Adelaide Island can be recognized:

1) mostly marine Mesozoic sedimentation, 2) Early Cretaceous (c. 141 Ma) plutonism (recorded in clasts from conglomerates), 3) Cretaceous volcanism, 4) Late Cretaceous (possibly Tertiary) sedimentation, 5) Early Tertiary volcanism, which was acidic in eastern outcrops and intermediate elsewhere, and 6) Eocene intermediate volcanism and deposition of arc-derived conglomerates. Volcanism was possibly coeval with known Palaeocene-Eocene plutonic activity on Adelaide Island (part of the Antarctic Peninsula Batholith) and with volcanism of similar age in northern Alexander Island and the South Shetland Islands. The volcanism on Adelaide Island and the South Shetland Islands, at least, was associated with a westward migration of the Antarctic Peninsula arc.

Minette dykes intersect the Precambrian crystalline basement of Schirmacher Oasis, East Antarctica. The rocks have intermediate to basic compositions, showing shoshonitic to ultrapotassic character. The samples show enhanced concentrations of compatible elements and high mg# combined with extreme enrichments in LILE (especially Ba) and LREE. Mantle-normalized trace element patterns are characterized by coupled relative depletions of Nb and Ti and strong fractionations between LILE and HFSE. The minettes display fractionated chondrite-normalized REE patterns with high and varying LREE concentrations in contrast to relative low and nearly constant HREE contents. High magma-ascent and cooling rates of lamprophyric magmas argue against a fundamental change of the primary geochemical signatures in minette magmas by interactions with the continental crust during ascent. The major and trace element abundances of the studied minettes point to varying degrees of partial melting of a mantle source, which was enriched in LILE and LREE during or before the melting event. Incompatible element signatures argue for the involvement of subducted pelagic sediments.

The first fossil stylasterid from Antarctic is reported from La Meseta Formation (Telm1: Early Eocene) of Seymour Island (Antarctic Peninsula): Conopora mariae sp. nov. This also is the earliest reliable fossil record of the genus Conopora. Conopora mariae differs from congeners by having much larger cyclosystems (diameter 2.5–4.5 mm). Cyclosystems of that size are exceptional among the Stylasteridae.

Observations of satellite passes monitored at Halley and Terra Nova Bay have been combined to produce for the first time measurements of ionospheric electron content spanning the Antarctic continent. Results are presented from a sequence of four successive passes made during a period of some two hours that illustrate the development of the ionosphere over this wide spatial region. The observations are discussed in terms of the convective behaviour of the ionization, using results from the PACE radar and a standard model of the plasma flow.

This paper examines two strong or gale-force wind events which began suddenly at Platcha, near the Antarctic ice sheet edge in the Vestfold Hills of East Antarctica, and at a later time were recorded at Davis after progressing slowly across the intervening 25 km of relatively low hills.