Respiratory metabolism of Alaskozetes antarcticus

Measurements of oxygen consumption in all post-embryonic life stages of U.K. cultured Alaskozetes antarcticus (Acari: Cryptostigmata) showed that log₁₀ respiration rate was linearly related to log₁₀ live weight, while log_e metabolic rate was linearly related to the reciprocal of the absolute temperature over the range 273–283°K, although the magnitude of response to temperature shown by different life stages was found to vary. Differences were apparent between cultured animals and previous measurements made on field animals, especially in respect of the relationship between respiration rate and live weight. The data were found to support the hypothesis of cold adaptation by means of metabolic rate elevation and a possible mechanism in discussed.     

The structure and stability of the bacterioplankton community in Antarctic freshwater lakes, subject to extremely rapid environmental change

In this study, variation in the bacterioplankton community structure of three Antarctic lakes of different nutrient status, was determined in relation to physical and chemical gradients at depth and at time intervals, across the seasonal transition from winter ice-cover to the summer ice-free period. The three lakes studied were: Moss Lake (low nutrient, with typical nutrient concentrations of 80 microg l(-1) nitrate and 10 microg l(-1) dissolved reactive phosphate), Sombre Lake (low nutrient, but becoming progressively enriched, with typical nutrient concentrations of 185 microg l(-1) nitrate and 7 microg l(-1) dissolved reactive phosphate) and Heywood Lake (enriched, with typical nutrient concentrations of 1180 microg l(-1) nitrate and 124 microg l(-1) dissolved reactive phosphate). Bacterioplankton community structure was determined using a combination of PCR amplification of 16S rRNA gene fragments and denaturing gradient gel electrophoresis (DGGE). Results indicated marked changes in this bacterioplankton community structure, which were particularly associated with the transition period. However, significant changes also occurred during the period of holomixis. Comparison of the results from lakes of different nutrient status suggest that increased levels of nutrient input, and in the timing and duration of ice cover will lead to marked changes in the structure and stability of the bacterioplankton community at existing levels of environmental change.     

Dispersal, habitat differences, and comparative phylogeography of Southeast Asian seahorses (Syngnathidae: Hippocampus)

Four distinct phylogeographical patterns across Southeast Asia were observed for four species of seahorse (genus Hippocampus) with differing ecologies. For all species, genetic differentiation (based on cytochrome b sequence comparisons) was significantly associated with sample site (Phi(ST) = 0.190-0.810, P < 0.0001) and with geographical distance (Mantel's r = 0.37-0.59, P < 0.019). Geographic locations of genetic breaks were inconsistent across species in 7/10 comparisons, although some similarities across species were also observed. The two shallow-water species (Hippocampus barbouri and Hippocampus kuda) have colonized the Sunda Shelf to a lesser degree than the two deeper-water species (Hippocampus spinosissimus and Hippocampus trimaculatus). In all species the presence of geographically restricted haplotypes in the Philippines could indicate past population fragmentation and/or long-distance colonization. A nested clade analysis (NCA) revealed that long-distance colonization and/or fragmentation were likely the dominant forces that structure populations of the two shallow-water species, whereas range expansion and restricted dispersal with isolation by distance were proportionally more important in the history of the two deeper-water species. H. trimaculatus has the most widespread haplotypes [average clade distance (D(c)) of nonsingleton haplotypes = 1169 km], indicating potentially high dispersal capabilities, whereas H. barbouri has the least widespread haplotypes (average D(c) = 67 km) indicating potentially lower dispersal capabilities. Pleistocene separation of marine basins and postglacial flooding of the Sunda Shelf are extrinsic factors likely to have contributed to the phylogeographical structure observed, whereas differences among the species appear to reflect their individual ecologies.     

Cold-active DnaK of an Antarctic psychrotroph Shewanella sp. Ac10 supporting the growth of dnaK-null mutant of Escherichia coli at cold temperatures

Shewanella sp. Ac10 is a psychrotrophic bacterium isolated from the Antarctica that actively grows at such low temperatures as 0°C. Immunoblot analyses showed that a heat-shock protein DnaK is inducibly formed by the bacterium at 24°C, which is much lower than the temperatures causing heat shock in mesophiles such as Escherichia coli. We found that the Shewanella DnaK (SheDnaK) shows much higher ATPase activity at low temperatures than the DnaK of E. coli (EcoDnaK): a characteristic of a cold-active enzyme. The recombinant SheDnaK gene supported neither the growth of a dnaK-null mutant of E. coli at 43°C nor phage propagation at an even lower temperature, 30°C. However, the recombinant SheDnaK gene enabled the E. coli mutant to grow at 15°C. This is the first report of a DnaK supporting the growth of a dnaK-null mutant at low temperatures.     

Molecular evolution of haemoglobins of polar fishes

The Arctic and the Antarctic differ by age and isolation of the respective marine faunas. Antarctic fish are highly stenothermal, in response to stable water temperatures, whereas the Arctic ones are exposed to seasonal and latitudinal temperature variations. The knowledge of the mechanisms of phenotypic response to cold exposure in species of both polar habitats offers fundamental insights into the nature of environmental adaptation. In the process of cold adaptation, the evolutionary trend of Antarctic fish has led to unique specialisations, including modification of haematological characteristics, e.g. decreased amounts and multiplicity of haemoglobins.Unlike Antarctic Notothenioidei, Arctic teleosts have high haemoglobin multiplicity. Although the presence of functionally and structurally distinct haemoglobins is a plesiomorphic condition for many perciform-like fishes, it seems that the oxygen-transport system of teleost fish in the Arctic region has been adjusted to temperature differences and fluctuations of Arctic waters, much larger than in the Antarctic. The amino-acid sequences used to gain insight into the evolution history of α and β globins of polar fish have clearly shown that Antarctic and Arctic globins have different phylogenies, leading to the hypothesis that the selective pressure of environment stability allows the phylogenetic signal to be maintained in the Antarctic sequences, whereas environmental variability would tend to disrupt this signal in Arctic sequences.     

Calcareous nannofossil biostratigraphy of the Paleocene sediments of the Odessa Gas Field (NW Black Sea)

Calcareous nannofossils from Paleocene sediments of two boreholes (Odeska-6 and 20) from the north-western shelf of the Black Sea are examined. Five nannofossil Zones are identified according to the standard zonations of Martini (1971) and Quillévéré et al. (2002): the Chiasmolithus danicus Zone (NP3), the upper part of Ellipsolithus Macellus Zone (NP4b), the Fasciculithus tympaniformis Zone (NP5), the Heliolithus kleinpelli Zone (NP6) and the Heliolithus riedelii Zone (NP8). This biostratigraphical work allows us to correlate the Bilokamian and Kachian regional stages of the Stratigraphic Scheme of Southern Ukraine (Zernetskiy et al., 1993) to the standard nannofossil zonations and, therefore, to the International Chronostratigraphic scheme. The presence of an unconformity between the Bilokamian and Kachian regional stages in the borehole section of Odeska-6 is suggested by Linear Sedimentary Rates estimated for the two boreholes. This unconformity corresponds to the upper part of the Chiasmolithus danicus nannofossil Zone (NP3) and the lower part of Ellipsolithus Macellus (NP4a), and is estimated to last nearly 1.94 Ma.     

Bioremediation of hydrocarbon-contaminated polar soils

Bioremediation is increasingly viewed as an appropriate remediation technology for hydrocarbon-contaminated polar soils. As for all soils, the successful application of bioremediation depends on appropriate biodegradative microbes and environmental conditions in situ. Laboratory studies have confirmed that hydrocarbon-degrading bacteria typically assigned to the genera Rhodococcus, Sphingomonas or Pseudomonas are present in contaminated polar soils. However, as indicated by the persistence of spilled hydrocarbons, environmental conditions in situ are suboptimal for biodegradation in polar soils. Therefore, it is likely that ex situ bioremediation will be the method of choice for ameliorating and controlling the factors limiting microbial activity, i.e. low and fluctuating soil temperatures, low levels of nutrients, and possible alkalinity and low moisture. Care must be taken when adding nutrients to the coarse-textured, low-moisture soils prevalent in continental Antarctica and the high Arctic because excess levels can inhibit hydrocarbon biodegradation by decreasing soil water potentials. Bioremediation experiments conducted on site in the Arctic indicate that land farming and biopiles may be useful approaches for bioremediation of polar soils.     

Biogeographical distribution and ecological ranges of benthic cyanobacteria in East Antarctic lakes

For the first time, the cyanobacterial diversity from microbial mats in lakes of Eastern Antarctica was investigated using microscopic and molecular approaches. The present study assessed the biogeographical distribution of cyanobacteria in Antarctica. Five samples were taken from four lakes spanning a range of different ecological environments in Larsemann Hills, Vestfold Hills and Rauer Islands to evaluate the influence of lake characteristics on the cyanobacterial diversity. Seventeen morphospecies and 28 16S rRNA gene-based operational taxonomic units belonging to the Oscillatoriales, Nostocales and Chroococcales were identified. The internal transcribed spacer was evaluated to complement the 16S rRNA gene data and showed similar but more clear-cut tendencies. The molecular approach suggested that potential Antarctic endemic species, including a previously undiscovered diversity, are more abundant than has been estimated by morphological methods. Moreover, operational taxonomic units, also found outside Antarctica, were more widespread over the continent than potential endemics. The cyanobacterial diversity of the most saline lakes was found to differ from the others, and correlations between the sampling depth and the cyanobacterial communities can also be drawn. Comparison with database sequences illustrated the ubiquity of several cyanobacterial operational taxonomic units and their remarkable range of tolerance to harsh environmental conditions.     

Levels of Hexachlorocyclohexanes and Dichloro-Dipheny-Trichloroethanes in Penguin Droppings Collected from Ardley Island,Maritime Antarctic

This article reports the concentrations of hexachlorocyclohexanes (HCHs) and dichloro-diphenyl-trichloroethanes (DDTs) in fresh Gentoo penguin (Pygoscelis Papua) droppings deposited on the Ardley Island (62°13′S, 58°56′W), West Antarctica, and those in the island's two lake cores. In the fresh penguin droppings, metabolites were the predominant constituents of the DDT group, most likely due to the ban on DDT use in agriculture and the higher stability of the metabolites in the environment. In contrast, γ-HCH comprised 66% of the total HCHs, apparently due to the continuous use of Lindane in the Southern Hemisphere. The concentrations of HCHs and DDTs in the fresh droppings are many times higher than those in penguin plume, the latter currently being used as biomaterial for monitoring coastal contaminations in Antarctica. Results of this study indicate that penguin droppings have a good potential for use as another biomonitoring material in detecting the organochlorine pesticides and other contaminants in the maritime Antarctic. Because penguin droppings can be well preserved in lake sediments, they also provide a good and continuous historical record of these contaminants. The slight increase of DDTs since the 1990s, as observed in the aged penguin droppings in the sediment cores, suggests there have been new inputs of DDT into the Antarctic coastal ecosystem, probably from the illegal use of DDT in the Southern Hemisphere.     

The reproductive behaviour of Pogonophryne scotti confirms widespread egg-guarding parental care among Antarctic notothenioids

In this paper, the first documentation of egg-guarding behaviour in an artedidraconid species, Pogonophryne scotti, through in situ photographic imagery obtained during video transects is provided. The male specimen was observed closely guarding a well-defined multi-layered egg mass deposited on the sea floor at 240 m on the southern South Orkney Islands shelf in the northern Weddell Sea. Egg-guarding parental care is present in species that are distributed among all of the major lineages of Antarctic notothenioids; however, lack of information on egg-deposition behaviours in Bovichtidae and Pseudaphritis prevents assessment of whether parental care originated prior to the origin of the Antarctic notothenioid radiation.