Davis Station Research Articles

High‐ and Middle‐Latitude Neutral Mesospheric Density Response to Geomagnetic Storms

AbstractWe report the first observations of a high‐ and middle‐latitude neutral mesospheric density response to geomagnetic storms. Interhemisphere mesospheric densities are estimated using data from meteor radars at Davis Station (68.6°S, 77.9°E), Svalbard (78.3°N, 16°E) and Tromsø (69.6°N, 19.2°E), which are located under the auroral zone; the Mohe (53.5°N, 122.3°E), and Beijing (40.3°N, 116.2°E) meteor radars, located in northern midlatitudes, and the Microwave Limb Sounder (MLS) on the Aura satellite. Both case studies and a superposed epoch analysis indicate that geomagnetic storms can significantly influence mesospheric density, causing a greater than ~10% decrease in the auroral zones and a ~5% decrease at higher midlatitudes. With such large changes, it is reasonable to suspect that geomagnetic storms influence the dynamics of the high and middle latitudes mesosphere.

Ocean acidification impacts primary and bacterial production in Antarctic coastal waters during austral summer

Polar waters may be highly impacted by ocean acidification (OA) due to increased solubility of CO2 at colder water temperatures. Three experiments examining the influence of OA on primary and bacterial production were conducted during austral summer at Davis Station, East Antarctica (68°35′ S, 77°58′ E). For each experiment, six minicosm tanks (650L) were filled with 200μm filtered coastal seawater containing natural communities of Antarctic marine microbes. Assemblages were incubated for 10 to 12days at CO2 concentrations ranging from pre-industrial to post-2300. Primary and bacterial production rates were determined using NaH14CO3 and 14C-leucine, respectively. Net community production (NCP) was also determined using dissolved oxygen. In all experiments, maximum photosynthetic rates (Pmax, mgCmgchl a−1h−1) decreased with elevated CO2, clearly reducing rates of total gross primary production (mgCL−1h−1). Rates of cell-specific bacterial productivity (μgCcell−1h−1) also decreased under elevated CO2, yet total bacterial production (μgCL−1h−1) and cell abundances increased with CO2 over Days 0–4. Initial increases in bacterial production and abundance were associated with fewer heterotrophic nanoflagellates and therefore less grazing pressure. The main changes in primary and bacterial productivity generally occurred at CO2 concentrations >2× present day (>780ppm), with the same responses occurring regardless of seasonally changing environmental conditions and microbial assemblages. However, NCP varied both within and among experiments, largely due to changing nitrate+nitrite (NOx) availability. At NOx concentrations <1.5μM photosynthesis to respiration ratios showed that populations switched from net autotrophy to heterotrophy and CO2 responses were suppressed. Overall, OA may reduce production in Antarctic coastal waters, thereby reducing food availability to higher trophic levels and reducing draw-down of atmospheric CO2, thus forming a positive feedback to climate change. NOX limitation may suppress this OA response but cause a similar decline.

A Climatological Study of Short‐Period Gravity Waves and Ripples at Davis Station, Antarctica (68°S, 78°E), During the (Austral Winter February–October) Period 1999–2013

AbstractA scanning radiometer deployed at Davis Station, Antarctica (68°S, 78°E), has been recording infrared (1.10–1.65 μm) images of a small region (24 km × 24 km) of the zenith night sky once per minute each austral winter night since February 1999. These images have been processed to extract information on the passage of gravity waves (GWs) (horizontal wavelength, λh &gt; 15 km) and ripples (λh ≤ 15 km) over the observing station. Phase speeds, periods, horizontal wavelengths, and predominant propagation directions have been deduced. Observed speeds were found to be highly correlated with horizontal wavelengths as has been reported in previous studies. Reverse ray tracing of the detected GWs only enabled us to identify four distinct groups. On average, only 15% of waves detected can be traced back to the troposphere, and a large proportion (~45%) were not successfully reverse traced substantially below the airglow layer. Two smaller groups were found to reach a termination condition for reverse ray tracing at altitudes near 50 km and 75 km. Of those that reached the termination altitude in the troposphere (10 km), most of the end points fell within a radius of 300 km of the station, with a very pronounced concentration of wave initiation to the northwest of the observing point. The predominant direction of propagation was southward, and they were observed throughout the year. Recent reports suggest the interaction of planetary waves with the background wind field as a potential source for these waves.

Detection and eradication of a non-native Collembola incursion in a hydroponics facility in East Antarctica

A non-native incursion of the collembolan, Xenylla sp. was found within the hydroponics facility at Davis Station, East Antarctica in May 2014. A rapid response was implemented to eradicate the incursion, including localised insecticide use, incineration of plants and growing media, sterilisation of the facility and three cycles of freezing/thawing of both internal rooms and external sub floor areas. Two consecutive years of summer monitoring programs have not detected any Collembola in station buildings or in the surrounding environment, suggesting the eradication was successful. This case highlights the importance of a multiple barrier approach to non-native species risks, and how activation of the last barrier—regular surveillance—resulted in early detection. The use of an online, real-time incident reporting system facilitated efficient communication between scientific experts, operational managers and expeditioners on site, resulting in a rapid and effective response following detection and potentially the first successful eradication of a non-native microarthropod in Antarctica. Monitoring will continue to confirm eradication.

Water quality risk management strategies for remote operations

Abstract The delivery of treatment and supply solutions for the management of water infrastructure for small and remote communities presents unique challenges. The identification of water quality hazards, the management of risks and conducting plant performance validation and verification activities can all be problematic. The ‘Demonstration of Robust Water Recycling’ (Robust Recycling) Project was funded by the Australian Water Recycling Centre of Excellence (AWRCoE) and the Australian Antarctic Division (AAD) as a means of developing strategies for the provision of small scale water treatment schemes from non-traditional water sources. Using the example of the AAD's Davis Station, this project featured an alternative approach to the establishment of a risk management framework for water recycling. This approach may be applicable to both drinking and recycled water schemes in other small and remote communities.

Small Scale Direct Potable Reuse (DPR) Project for a Remote Area

An Advanced Water Treatment Plant (AWTP) for potable water recycling in Davis Station Antarctica was trialed using secondary effluent at Selfs Point in Hobart, Tasmania, for nine months. The trials demonstrated the reliability of performance of a seven barrier treatment process consisting of ozonation, ceramic microfiltration (MF), biologically activated carbon, reverse osmosis, ultra-violet disinfection, calcite contactor and chlorination. The seven treatment barriers were required to meet the high log removal values (LRV) required for pathogens in small systems during disease outbreak, and on-line verification of process performance was required for operation with infrequent operator attention. On-line verification of pathogen LRVs, a low turbidity filtrate of approximately 0.1 NTU (Nephelometric Turbidity Unit), no long-term fouling and no requirement for clean-in-place (CIP) was achieved with the ceramic MF. A pressure decay test was also reliably implemented on the reverse osmosis system to achieve a 2 LRV for protozoa, and this barrier required only 2–3 CIP treatments each year. The ozonation process achieved 2 LRV for bacteria and virus with no requirement for an ozone residual, provided the ozone dose was &gt;11.7 mg/L. Extensive screening using multi-residue gas chromatography–mass spectrometry (GC–MS) and liquid chromatography–mass spectrometry (LC–MS) database methods that can screen for more than 1200 chemicals found that few chemicals pass through the barriers to the final product and rejected (discharge) water streams. The AWTP plant required 1.93 kWh/m3 when operated in the mode required for Davis Station and was predicted to require 1.27 kWh/m3 if scaled up to 10 ML/day. The AWTP will be shipped to Davis Station for further trials before possible implementation for water recycling. The process may have application in other small remote communities.

The environmental impact of sewage and wastewater outfalls in Antarctica: An example from Davis station, East Antarctica

We present a comprehensive scientific assessment of the environmental impacts of an Antarctic wastewater ocean outfall, at Davis station in East Antarctica. We assessed the effectiveness of current wastewater treatment and disposal requirements under the Protocol on Environmental Protection to the Antarctic Treaty. Macerated wastewater has been discharged from an outfall at Davis since the failure of the secondary treatment plant in 2005. Water, sediment and wildlife were tested for presence of human enteric bacteria and antibiotic resistance mechanisms. Epibiotic and sediment macrofaunal communities were tested for differences between sites near the outfall and controls. Local fish were examined for evidence of histopathological abnormalities. Sediments, fish and gastropods were tested for uptake of sewage as measured by stable isotopes of N and C. Escherichia coli carrying antibiotic resistance determinants were found in water, sediments and wildlife (the filter feeding bivalve Laternula eliptica). Fish (Trematomus bernacchii) within close proximity to the outfall had significantly more severe and greater occurrences of histopathological abnormalities than at controls, consistent with exposure to sewage. There was significant enrichment of 15N in T. bernacchii and the predatory gastropod Neobuccinum eatoni around the outfall, providing evidence of uptake of sewage. There were significant differences between epibiotic and sediment macrofaunal communities at control and outfall sites (<1.5 km), when sites were separated into groups of similar habitat types. Benthic community composition was also strongly related to habitat and environmental drivers such as sea ice. The combined evidence indicated that the discharge of wastewater from the Davis outfall is causing environmental impacts. These findings suggest that conditions in Antarctic coastal locations, such as Davis, are unlikely to be conducive to initial dilution and rapid dispersal of wastewater as required under the Protocol on Environmental Protection to the Antarctic Treaty. Current minimum requirements for wastewater treatment and disposal in Antarctica are insufficient to ameliorate these risks and are likely to lead to accumulation of contaminants and introduction of non-native microbes and associated genetic elements. This new understanding suggests that modernised approaches to the treatment and disposal of wastewater are required in Antarctica. The most effective solution is advanced levels of wastewater treatment, which are now possible, feasible and a high priority for installation. As a direct outcome of the study, a new advanced treatment system is being installed at Davis, effectively avoiding environmental risks.

A new integrated potable reuse process for a small remote community in Antarctica

To meet water reuse and discharge requirements in Davis Station, Antarctica, an advanced water treatment plant (AWTP) had been designed and tested for nine months. The key design factors for operating in small communities in remote areas included low maintenance requirement (low chemical inventory, minimal onsite labour), high LRVs for pathogens, robust operation, and high automation. Based on these requirements, the seven-barrier AWTP included ozonation, ceramic microfiltration, biological activated carbon, reverse osmosis, ultraviolet radiation, calcite filtration and chlorination. The nine month test demonstrated that the plant was able to provide minimum LRVs of 12.5 for virus and bacteria, and 10 for protozoa. The overall estimated chemical consumption was lower than equivalent continuous operations elsewhere due to a reduced number of Clean in Place (CIP) cycles as compared to industry. This was achieved by optimised integration of the barriers. Furthermore, there was no functional failure of major barriers and the automated online pressure decay test (PDT) validations for MF and RO were successful. Although some minor improvements, such as a reduced frequency of RO pre-filter cartridge replacement, are still needed, the new integrated plant has fulfilled the requirements of high pathogen LRVs, remote online control and validation, and relatively low chemical consumption.

Increasing CO2 changes community composition of pico- and nano-sized protists and prokaryotes at a coastal Antarctic site

Ocean acidification is a globally recognised phenomenon, but little is known of its impacts on Antarctic marine microbes. Here we report on the community response of pico- and nanophytoplankton, heterotrophic nanoflagellates (HNF) and prokaryotes ( Archaea and Bacteria ) to elevated CO 2 during 3 minicosm experiments over the 2008/2009 summer at Davis Station, Antarctica. Coastal seawater was incubated in 650 l minicosms ( n = 6) for ≤ 12 d at CO 2 concentrations ranging from preindustrial levels to those predicted for 2100 and beyond. The abundance of pico- and nano-sized protists and prokaryotes were determined by flow cytometry, using chlorophyll autofluorescence to discriminate the phytoplankton, SYBR-Green to stain the prokaryotes and LysoTracker Green stain to discriminate the HNF. While the effects on nanophytoplankton abundance were inconclusive, our results show that increasing CO 2 can alter the composition of the microbial community in Antarctic coastal waters. Our 3 experiments consistently showed lower concentrations of HNF and higher abundances of picophytoplankton and prokaryotes in treatments exposed to elevated CO 2 . While the mechanism remains to be confirmed, our study suggests that CO 2 may reduce the mortality of picoplankton by HNF grazing. Our results indicate that changes in the composition of Antarctic microbial communities may occur within the concentration range of 750 to 1118 ppm CO 2 , potentially impacting the Antarctic food web through reduced food availability.

Benthic myodocopid Ostracoda (Philomedidae) from the Southern Ocean.

This study is based on the material of myodocopid ostracodes of the family Philomedidae collected by the Russian Antarctic Polar Expeditions (1963-2007) and the Germany Expeditions on R/V "Polarstern" (1990-2002) from the continental shelf and upper slope near the Mawson and Davis stations, the Weddell Seas, the region of the South Shetland Islands near the Russian Polar station "Molodezhnaya" and adjacent waters. Eight philomedid species belonging to two genera were identified in these collections. Scleroconcha tuberculata sp. nov. is described and figured as a new species. Additional descriptions and figures for the species S. gallardoi Kornicker, 1971, Philomedes assimilis Brady, 1907, P. charcoti Daday, 1908, P. heptatrix Kornicker, 1975, P. rotunda Skogsberg, 1920, P. orbicularis Brady, 1907 and P. tetrathrix Kornicker, 1975 are given. Keys for all species of the mentioned genera known from the Southern Ocean are presented. A list of sampling stations and species collected is provided in the Appendix 1.

Enhanced CO2 concentrations change the structure of Antarctic marine microbial communities

The impacts of anthropogenic enhancement of the partial pressure of carbon dioxide (pCO2) on marine organisms remain unclear, especially in Antarctic waters, which are predicted to be amongst the earliest and most severely affected by the consequent changes in ocean chemistry. Marine microbes are the base of the Antarctic food chain, and the nature of their response to elevated pCO2 is important as they are key determinants of the biogeochemical cycles that affect global climate. We studied the response of a natural community of Antarctic marine microbes from near-shore waters off Davis Station, Antarctica, to pCO2 ranging from the concentration in the water column at the time the experiment began (ambient, 84 μatm) to that predicted by the year 2300 (2423 μatm) using 6 gas-tight, environmentally controlled tanks (minicosms; 650 l) to which CO2-saturated seawater was added. The microbial community showed little difference between 84 and 643 μatm CO2 (0.2 to 1.7 times present), indicating that they can tolerate the large seasonal range in pCO2 in Antarctic coastal waters. Concentrations ≥1281 μatm reduced the accumulation rate of chlorophyll and particulate carbon, changed the microbial community, and enhanced the relative abundance of small phytoplankton. If our results are indicative of the future responses of Antarctic marine microbes, elevated CO2 could profoundly affect the structure and function of the Antarctic food web by reducing the availability of food for higher trophic levels and decreasing the efficiency of the biological pump.

Profile: Dennis BormannThe man who introduced Antarctica's Davis Station to 3-D printing

Profile: Dennis BormannThe man who introduced Antarctica's Davis Station to 3-D printing

Dispersal and dilution of wastewater from an ocean outfall at Davis Station, Antarctica, and resulting environmental contamination

The Antarctic Treaty permits the discharge of wastewater into Antarctic marine waters providing that conditions exist for initial dilution and rapid dispersal. We investigated the dilution and dispersal of macerated wastewater around Australia's Davis Station in East Antarctica and examined sediments for evidence of contaminants. Methods used to examine hydrodynamic conditions included current meters, dye release experiments and measurement of sewage-associated microbial markers and surfactants in the water column. We measured marine sediments for metals, nutrients, PBDEs, hydrocarbons and faecal sterols. We propose that if there is adequate dilution and dispersal there would be no significant difference in contaminant concentrations in sediments around the outfall compared to distant control sites. Currents were strongly correlated with prevailing wind conditions. Modelling indicated that diffusivity of wastewater had the greatest effect on dilution factors and that neither discharge rates nor local currents had as much effect. During summer conditions of open water, wastewater is likely to be constrained in a narrow plume close to the coast. Concentrations of sewage bacteria were high around the outfall and detected up to 1.5 km away, along with dye. There were significant differences in sediment concentrations of metals, PBDEs, hydrocarbons, nutrients and faecal sterols between sites within 2 km of the outfall and control sites. We conclude that dilution and dispersal conditions at the Davis outfall are insufficient to prevent the accumulation of contaminants in local sediments and that microbial hazards posed by wastewater are an environmental risk to local wildlife.

Population structure and long-term decline in three species of heart urchins Abatus spp. near-shore in the Vestfold Hills region, East Antarctica

Patterns of fine-scale spatial population structure in Antarctic benthic species are poorly understood. There is a high proportion of brooding species in the Antarctic benthos, and a brooding life history strategy is expected to restrict their dispersal abilities and therefore foster population structure. Additionally, genetic structuring of populations can preserve signals of historic processes (such as Pleistocene glaciations) on species distributions and abundances. We developed a set of seven microsatellite markers to examine population genetic variation and infer the demographic history of three sympatric Antarctic sea urchin species from the order Spatangoida (Abatus ingens, A. shackletoni and A. philippii), all with brooding life history strategies. Samples were collected at five sites separated by up to 5 km, in the near-shore area surrounding Davis Station in the Vestfold Hills area of the Australian Antarctic Territory. We found evidence of a long-term population decline in all three species, and the estimated timing of the decline precedes anthropogenic activities and is compatible with long-term climate variability. Two genetic clusters in A. ingens and A. shackletoni suggest secondary contact after population differentiation in glacial refugia. Life history is not a good predictor of fine-scale population structure in these species, with gene flow possible at distances of 5 km. Finally, no evidence was found for a potential impact of pollution from Davis Station on genetic variation. The reduced effective population size observed for these Antarctic benthic species highlights their fragility and the need for conservation concern.

A method for estimating the height of a mesospheric density level using meteor radar

AbstractA new technique for determining the height of a constant density surface at altitudes of 78–85 km is presented. The first results are derived from a decade of observations by a meteor radar located at Davis Station in Antarctica and are compared with observations from the Microwave Limb Sounder instrument aboard the Aura satellite. The density of the neutral atmosphere in the mesosphere/lower thermosphere region around 70–110 km is an essential parameter for interpreting airglow‐derived atmospheric temperatures, planning atmospheric entry maneuvers of returning spacecraft, and understanding the response of climate to different stimuli. This region is not well characterized, however, due to inaccessibility combined with a lack of consistent strong atmospheric radar scattering mechanisms. Recent advances in the analysis of detection records from high‐performance meteor radars provide new opportunities to obtain atmospheric density estimates at high time resolutions in the MLT region using the durations and heights of faint radar echoes from meteor trails. Previous studies have indicated that the expected increase in underdense meteor radar echo decay times with decreasing altitude is reversed in the lower part of the meteor ablation region due to the neutralization of meteor plasma. The height at which the gradient of meteor echo decay times reverses is found to occur at a fixed atmospheric density. Thus, the gradient reversal height of meteor radar diffusion coefficient profiles can be used to infer the height of a constant density level, enabling the observation of mesospheric density variations using meteor radar.

Application of a quantitative histological health index for Antarctic rock cod (Trematomus bernacchii) from Davis Station, East Antarctica

A quantitative Histological Health Index (HHI) was applied to Antarctic rock cod (Trematomus bernacchii) using gill, liver, spleen, kidney and gonad to assess the impact of wastewater effluent from Davis Station, East Antarctica. A total of 120 fish were collected from 6 sites in the Prydz Bay region of East Antarctica at varying distances from the wastewater outfall. The HHI revealed a greater severity of alteration in fish at the wastewater outfall, which decreased stepwise with distance. Gill and liver displayed the greatest severity of alteration in fish occurring in close proximity to the wastewater outfall, showing severe and pronounced alteration respectively. Findings of the HHI add to a growing weight of evidence indicating that the current level of wastewater treatment at Davis Station is insufficient to prevent impact to the surrounding environment. The HHI for T. bernacchii developed in this study is recommended as a useful risk assessment tool for assessing in situ, sub-lethal impacts from station-derived contamination in coastal regions throughout Antarctica.

Lidar observations of gravity wave activity in the middle atmosphere over Davis (69°S, 78°E), Antarctica

AbstractA 16 month series of lidar measurements in the stratosphere and mesosphere‐lower thermosphere (MLT) region over Davis Station (69°S, 78°E) in Antarctica is used to study gravity waves. The unprecedentedly large number of observations totaling 2310 h allows us to investigate seasonal variations in gravity wave activity in great detail. In the stratosphere the gravity wave potential energy density (GWPED) is shown to have a large seasonal variation with a double peak in winter and minimum in summer. We find conservative wave propagation to occur between 29 and 41 km altitude in winter as well as in summer, whereas smaller energy growth rates were observed in spring and autumn. These results are consistent with selective critical‐level filtering of gravity waves in the lower stratosphere. In the MLT region the GWPED is found to have a semiannual oscillation with maxima in winter and summer. The structure of the winter peak is identical to that in the stratosphere, suggesting that the gravity wave flux reaching the MLT region is controlled by the wind field near the tropopause level.

Summer time Fe depletion in the Antarctic mesopause region

We report common volume measurements of Fe densities, temperatures and ice particle occurrence in the mesopause region at Davis Station, Antarctica (69°S) in the years 2011–2012. Our observations show a strong correlation of the Fe-layer summer time depletion with temperature, but no clear causal relation with the onset or occurrence of ice particles measured as noctilucent clouds (NLC) or polar mesosphere summer echoes (PMSE). The combination of these measurements indicates that the strong summer depletion can be explained by gas-phase chemistry alone and does not require heterogeneous removal of Fe and its compounds on ice particles.

Physical, chemical, biological and ecotoxicological properties of wastewater discharged from Davis Station, Antarctica

The properties and toxicity of untreated wastewater at Davis Station, East Antarctica, were investigated to inform decisions regarding the appropriate level of treatment for local discharge purposes and more generally, to better understand the risk associated with dispersal and impact of wastewaters in Antarctica. Suspended solids, nutrients (nitrogen, phosphorus), biological oxygen demand (BOD), metals, organic contaminants, surfactants and microbiological load were measured at various locations throughout the wastewater discharge system. Wastewater quality and properties varied greatly between buildings on station, each of which has separate holding tanks. Nutrients, BOD and settleable solid levels were higher than standard municipal wastewaters. Microbiological loads were typical of untreated wastewater. Contaminants detected in the wastewater included metals and persistent organic compounds, mainly polybrominated diphenyl ethers (PBDEs). The toxicity of wastewater was also investigated in laboratory bioassays using two local Antarctic marine invertebrates, the amphipod Paramoera walkeri and the microgastropod Skenella paludionoides. Animals were exposed to a range of wastewater concentrations from 3% to 68% (test 1) or 63% (test 2) over 21days with survival monitored daily. Significant mortality occurred in all concentrations of wastewater after 14 to 21days, and at higher concentrations (50–68% wastewater) mortality occurred after only one day. Results indicate that the local receiving marine environment at Davis Station is at risk from existing wastewater discharges, and that advanced treatment is required both to remove contaminants shown to cause toxicity to biota, as well as to reduce the environmental risks associated with non-native micro-organisms in wastewater.

Solar radiation and relative humidity based, empirical method, to estimate hourly reference evapotranspiration

A new empirical method which estimates hourly reference evapotranspiration is proposed, that utilizes two meteorological variables, namely incoming solar radiation and relative humidity. It also utilizes a term that combines both variables. The inverse of the natural logarithm of relative humidity and the vapor pressure deficit of the atmosphere were investigated and were found to correlate quite well. The equation was calibrated in a semi arid environment, using data from Davis station (year 2000), of the CIMIS network. The estimations of both, the empirical method and the ASCE PM method, were compared. Validation of the method was performed with hourly data from the same station for 8 years, using various statistical indices. The hourly empirical equation was investigated for the whole period, for each year separately and for the summer period. It was found that it performed satisfactorily in all cases. Yearly RMSE ranged from 0.036 to 0.045mm/h with an average for the whole period 0.042mm/h. For the summer period RMSE ranged from 0.040mm/h to 0.055mm/h with an average for all the values of the summer period 0.047mm/h. It was also validated with data from the grass reference meteorological station in the experimental field of the Agricultural University of Athens in Copais, Greece and was found to perform satisfactorily with RMSE equal to 0.043mm/h. The deviations of the new empirical method from the ASCE PM method were investigated for various ranges of wind speed and vapor pressure deficit data values. It was found that the empirical method estimates were acceptable for practically all cases when 0.073mm/h was considered as the threshold RMSE value. The proposed hourly empirical equation is recommended for use in semi arid climates.