Key to global warming: a load of pooh

Plankton pooh could be the answer to understanding just how much carbon dioxide our oceans can actually store, according to scientists in the southern hemisphere.

The key lies in whether the microscopic zooplankton pooh floats or sinks, according to Dr Karin Beaumont, who conducted the research as a collaboration between the University of Tasmania and the Australian Antarctic Division.

“We need to understand where and how carbon dioxide is stored in the oceans. Heavy pooh that sticks together and sinks to the ocean floor is good as it locks up CO2 for thousands of years,” said Dr Beaumont. “But other pooh that breaks up and floats near the surface is not good as this CO2 can be re-released into the atmosphere, adding to the greenhouse effect.”

Approximately 25% of carbon dioxide taken up by the oceans is currently stored in the deep sea, largely due to this phenomenon, according to Dr Beaumont:

“Knowing which plankton contribute to this carbon export will help us understand how changes in their abundance will influence the greenhouse effect. As algae grow in the ocean they take up CO2. Zooplankton then graze on the algae, and hopefully lock up this greenhouse gas in the deep ocean.”

The study shows that, while larger zooplankton pooh transports carbon to the deep sea, microzooplankton does not. The microzooplankton represent around 10 times the biomass of larger zooplankton and process most of the atmospherically derived CO2.

“This finding is important for understanding how much carbon the oceans can take up from the atmosphere,” Dr Beaumont stated.

An internet guide to plankton pooh is being co-authored by Dr Beaumont and associate professor of the University of Massachusetts, Boston, Juanita Urban Rich, who said that the guide would allow researchers to identify which pooh reaches the deep sea and which pooh can keep atmospherically derived carbon in the oceans.

By Jane Kettle

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