|K081: Antarctic Aquatic Ecosystems|
What we do: Our goal is to understand how aquatic ecosystems (small streams and ponds to large lakes) are structured by the highly unusual physical conditions under which they develop. To do this we are developing climate-driven models that describe the physical and chemical processes within aquatic ecosystems. In these systems, transitions from liquid to ice are accompanied by changes to water chemistry as salts are selectively precipitated out as temperatures decrease and, even more so than in the temperate world, physics and chemistry are tightly linked.
We are also determining the structure, diversity and dynamics of the biological communities within these systems. Most communities are dominated by perennial cyanobacteria-dominated microbial mats, which have the ability to survive the long, frozen winter and begin photosynthetic growth almost immediately they are re-hydrated by summer melting of ice.
Key questions are: how important are the durations and intensities of the frozen/unfrozen period on ecosystem structure and function, and how are the key ecosystem processes (photosynthesis, respiration, anaerobic metabolism, nutrient transformations). Work is carried out at sites in the McMurdo Dry Valleys, Cape Hallett and the McMurdo Ice Shelf.
Why we do it: Some people find it strange to find New Zealand scientists studying aquatic ecosystems on the world's coldest and driest landmass. However, while air temperature is below zero for much of the time in the areas we work, sunshine can have a magical effect during summer, transforming ice and snow into life-supporting liquid water. Albeit for a few weeks in many cases, aquatic ecosystems ranging from small streams and ponds to large lakes spring into action, algae and cyanobacteria grow and provide the fuel for a microbially-dominated ecosystem. These aquatic systems are very much the foci of life in the Antarctic desert.
Some things we've found out so far: In the 2004/05 season we focused on one of the unique lake systems of the McMurdo Dry Valleys. Here we dived through a hole made through 5m of ice that floats on the surface of the lake and deployed advanced instrumentation to examine the rates of photosynthesis of benthic cyanobacterial mats. We obtained the first in situ measures of photosynthesis, and showed how these communities are so well adjusted to the small amount of blue-green light that penetrates the ice cover of the lake that they can carry out net photosynthesis at light intensities lower than just about any other biological system on earth. This research contributes to the Latitudinal Gradient Project (LGP) and is an International Polar Year project.
Biological and chemical characteristics in water samples from ponds and Lake Wilson in the Darwin Glacier area