Surveys to set environmental baselines for proposed Davis aerodrome

Scientists have successfully completed an ambitious field season in the Vestfold Hills, undertaking detailed ecological surveys as part of a project to investigate the feasibility of a year-round runway near Davis research station (see Australian Antarctic Magazine 37: 2–5, 2019).

The field season focused on gathering data for environmental baselines to inform the proposed aerodrome’s environmental assessment, with a focus on lake ecology, the sea floor (benthic) environment, vegetation surveys, and seal and seabird surveys.

The surveys focused on areas that could be impacted by construction of the proposed runway and associated infrastructure, or that were under potential flight paths, but also included the broader Vestfold Hills.

Principal Research Scientist with the Australian Antarctic Division, Dr Aleks Terauds, oversaw the ecological surveys and said they represent the most intensive and extensive surveys ever conducted in the region.

“It was an ambitious program that not only required a dedicated and experienced team but also a significant amount of operational support. Fortunately we had both,” he said.

Ecotoxicologist Dr Catherine King spent four months sampling more than 50 lakes across the Vestfold Hills, with colleague Dr Kathryn Brown.

She said the region is biologically unique because of its freshwater and hyper-saline (very salty) lakes, which support diverse microbial life and microscopic invertebrates.

“There are more than 300 lakes and tarns of varying salinity and size, from small ponds to lakes stretching over several kilometres,” Dr King said.

“The region has one of the largest concentrations of ‘meromictic’ (stratified or layered) lakes in the world, with around 35 permanently stratified water bodies.”

Within these water bodies salinity can range from four to 235 parts per thousand, with temperatures between −14 and 24°C, and depths between one and 110 metres. Surface levels range from 30 metres below sea level to 29 metres above.

While most of the soil and lake bottom samples were collected from the lakes’ edge, Dr King and Dr Brown used an inflatable dinghy, transported to site in a helicopter sling, to access nine priority lakes.

The pair collected samples in the centre of each priority lake using a set sampling regime.

“We used a hand-held instrument to measure salinity, conductivity, temperature, pH, dissolved oxygen and other physico-chemical parameters continuously through the water profile, from the bottom of each lake to its surface,” Dr King said.

“A sampling bottle was then lowered through the water profile and snapped shut at particular depths.

“This technique allowed us to sample the different layers, which is especially important in the stratified lakes, where different layers have different characteristics and biological communities.

“We also took sediment grabs from the bottom of lakes to sample the benthic communities, and vertical and horizontal tows to collect phytoplankton and zooplankton for identification and genomics testing.”

Dr King said detailed analysis, now underway, will show whether the lakes are biologically unique and likely to be impacted by the construction of an aerodrome.

For Dr Dana Bergstrom and Associate Professor Patti Virtue, the summer was spent primarily on foot – albeit with a helicopter for their daily commute to and from the Vestfold Hills, where they headed each day to conduct vegetation surveys and collect samples.

The pair walked more than 500 kilometres over the summer, and used a purpose built mobile app to record detailed vegetation and environmental data at over 300 sites – documenting the species present and recording elevation, slope, water availability and other environmental features.

Most Vestfold Hills vegetation communities are ‘sub-lithic’ and ‘endo lithic’ – living beneath rocks or within rock cracks, respectively, especially in areas subjected to salt-laden winds.

Dr Bergstrom said the vegetation patterns seen in their surveys are consistent with previous vegetation studies in the 1970s and 80s.

“The patterns documented in those earlier surveys remain today, but we’ve been able to add to the story,” she said.

The area surrounding Davis station is also home to both penguin and petrel breeding colonies and Dr Louise Emmerson and Dr Colin Southwell had a busy six weeks installing remotely operating cameras, conducting population counts, observing penguin traverse routes across the sea ice, and deploying satellite trackers.

“We want to understand more about the foraging routes of the large population of Adélie penguins in the Vestfold Islands, which has breeding colonies some three kilometres from the site of the proposed runway, and close to the planned flight path,” Dr Emmerson said.

“We deployed 12 trackers on penguins at a breeding site north of the runway, to see the direction they crossed the sea ice to get to the open water for foraging. Our observations of the birds also showed that they don’t always take the shortest route to their foraging grounds. We were reminded that energy efficiency is thrown out the window when it comes to penguins!”

The pair also counted cape petrels in the region.

“We were able to finalise our design of a monitoring strategy and will use our count and data from remote monitoring cameras to assess whether the cape petrel population has changed since the early 1970s,” Dr Southwell said.

“If the aerodrome is approved to proceed, we can use this data to assess whether they experience any impacts from the construction and operation of the runway.”

Another long-term monitoring program at Davis station is the annual seal count, conducted periodically since the 1960s.

Led by environmental scientist Andrew Irvine, expeditioners at Davis counted the Weddell seals, elephant seals and leopard seals.

The team undertook weekly surveys from the arrival of the seals in October, conducting counts on foot, from a helicopter, and using quad bikes and hägglunds to access sites across the sea ice. Small boats were used to access historically popular sites for seal populations when sea ice travel was no longer possible.

Mr Irvine and Assoc. Prof. Virtue also conducted site surveys for nests of snow petrels and the tiny Wilson storm petrels. These nests are under carefully selected boulders that allow for quick entry and exits, to avoid predatory skuas.

While most survey teams were busy above the sea ice, a purpose-built remotely operated vehicle was exploring beneath it.

Dr Jonny Stark and Dr Glenn Johnstone drilled 40 centimetre holes in the sea ice to deploy a mini submarine, revealing never-before-seen habitats surrounding Davis station (see next story).

Since the conclusion of the field season in March 2020, data processing, laboratory work and analysis has commenced. The data will be included in the aerodrome’s Comprehensive Environmental Evaluation, which will be released for public comment in Australia, and internationally through the Antarctic Treaty system.

Science will continue to support the Davis Aerodrome Project through the environmental assessment process and the establishment of environmental monitoring work that will provide important baselines from which to measure change.

The Antarctic Division’s environmental manager, Andy Sharman, said the Division’s efforts to build a comprehensive environmental baseline within the proposed operational area, heralds an improved approach to understanding and managing human impacts in Antarctica.

“What we have done at Davis will inform future environmental monitoring and management for the whole of the Australian Antarctic Program,” Mr Sharman said.

Eliza Grey
Davis Aerodrome project