Thursday 1 April 2010, 11:30 AM (AAD Theatrette)

Science in the Spotlight - 15 min showcase presentation from three science programs

Andrew Davidson

Environmental Protection & Change

Effects of ocean acidification on microbes in Antarctic coastal waters

Ocean acidification is a newly recognised threat to marine ecosystems. Though its effects are likely to be felt first in Antarctic waters, little is known of its impact on Antarctic marine life, especially on marine microbes that comprise most of the living matter and are the base of the food web in the Southern Ocean. We report results from 3 experiments conducted during the 2008/09 summer at Davis Station using mesocosms. Near-shore sea water was incubated in six, 650 l tanks with CO2 added to simulate conditions from pre-industrial to beyond 2100. The structure and function of microbial communities in each tank were then measured over 10 to 12 d. We found that at CO2 concentrations up to approximately 2x present, protistan biomass was high and the community was dominated by large species of phytoplankton and protozoa (protists). At higher concentrations the biomass declined and the community became dominated by small protists and bacteria. The change in community was caused by high CO2 directly inhibiting phytoplankton production and indirectly reducing the mortality of small cells by inhibiting protozoan grazers. Marine microbes currently experience seasonal changes in pCO2 from approximately 420 ppm beneath the sea ice in spring to around 100 ppm during the height of the phytoplankton bloom. Our study indicates that above these tolerances, CO2 may reduce the biomass and size of protists, thereby reducing food availability to higher trophic levels, increasing respiration of carbon substrates in near-surface waters and exacerbating accumulation of CO2 in the atmosphere.

Steve Nicol

Southern Ocean Ecosystems

Elysium: Shackleton's Antarctic Visual Epic

On the 10th of February the RV Professor Molchanov left Ushuaia on a 3 week voyage to the Antarctic loaded with 57 of the world's best nature photographers, artists and a couple of scientists. The aim of the expedition was "to document the above and below scenes, flora and fauna that Shackleton and his team would have seen and missed after losing the Endurance - from the Weddell Sea to Elephant Island and the heroic sail to South Georgia" but in the comparative luxury of an ice-strengthened expedition vessel. The end products " will serve as a gift for future generations with an imaging epic that guarantees to inspire, invigorate and challenge for preservation of planet earth" . These productions will include simultaneous exhibitions at the Maritime Museums in Sydney and Greenwich later in the year, a book and at least one film documentary that will emerge in a couple of years, assuming everyone's luggage arrives back from Argentina. I'll provide an overview of the activities of the voyage and try and impart some of the flavour of sharing a small ship with some very talented people and some very large egos.

Simon Alexander

Ice Ocean Atmosphere & Climate

The stratosphere: Quantifying wave energy, nacreous cloud and trace gas distribution

The presence of the springtime ozone hole above Antarctica is a graphic illustration of how chemistry, dynamics and radiation conspire to induce major changes in the stratosphere (10 – 50km altitude). Despite the far-reaching consequences of the ozone hole, we are still learning about important processes which transfer energy and trace gases into and out of the winter-time stratosphere. Using recent results from winter operation of the Davis lidar, complemented by other ground-based and satellite-based observations, I will discuss how observations of temperature and nacreous clouds are enabling us to examine and quantify key stratospheric parameters in the Antarctic region for the first time, and how knowledge of these variables is necessary in the context of understanding the broader global atmosphere.