Australia's Chief Scientist

Mapping plankton pathways in the Southern Ocean

Scientists aboard the Aurora Australis, Australia’s Antarctic Flagship, will be using this summer season in Antarctica to continue a 20-year study that is mapping significant changes in one of the ocean’s tiniest creatures.

One of 80 projects underway this season, the Continuous Plankton Recorder Survey uses a special recorder towed behind a research ship to filter and track tiny plankton and krill.

Over the last twenty years, the project has covered more that 278,000 kilometres and taken more than 30,000 samples to help scientists build a map of the creatures’ distribution in the Southern Ocean.

This ocean plays a huge role in the world’s climate, from absorbing carbon dioxide produced from human activities, to driving deep ocean currents.  The information scientists collect about the conditions in this ocean and how they are changing is vital for monitoring the effects of global climate change.

Project Leader, Dr Graham Hosie, said the research was starting to reveal some interesting trends.

“Since the project began in the early 1990s there have been significant changes in the composition of plankton in our samples,” Dr Hosie said.

“We seem to be catching a lot more smaller plankton compared to krill; notably copepods which, like krill, also graze on phytoplankton. 

“We don’t know what is causing this or if competition for the same food will affect krill. But any change from krill to smaller zooplankton may force animals that are dependent on krill, such as whales and penguins, to change their diet in order to survive.

“We have also observed, at times, sudden very large increases in foraminiferans – a calcareous single-cell zooplankton.  These blooms are short lived, but suppress other zooplankton numbers and again we don’t know if this has a flow-on effect to higher animals.”

While the scientists are still working to discover the exact cause of the differences they are observing in plankton distribution, one thing is for certain – changes in sea-ice and ocean temperature are already starting to have an impact on the complex Antarctic food web.

The team’s hard work over the past 20 years has resulted in the first Zooplankton Atlas, which documents the distribution and abundance of the 50 most common zooplankton species in the Southern Ocean.  The Atlas will serve as a reference for other researchers and monitoring programs.

For a first-hand look at the plankton recording project, watch this video.

Image: This photo was taken by Uwe Kils. It shows an amphipod, a type of plankton. The photo was taken using magnification so users can see the amphipod in detail. In reality, most amphipods are only 1 mm to 140 mm in length. Courtesy of Wikipedia Commons