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Warming Microbes May Shrink Southern Ocean Carbon Sink

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The amount of carbon locked away in the depths of the Southern Ocean could fall by almost 20% by 2100 as warming waters lead to increased microbial activity, according to scientists at the Institute for Marine and Antarctic Studies.

The Southern Ocean absorbs a large proportion of heat and CO2 from anthropogenic emissions, with billions of tonnes of carbon locked away as phytoplankton die and sink to the ocean floor. However, modelling and laboratory-based experiments have predicted that ocean microbes will become more active as the climate changes, interrupting the flow of carbon to the seafloor.

These predictions have now been tested by field research in the Southern Ocean, which showed that sub-Antarctic microbes are particularly sensitive to temperature changes.

“Each year dying phytoplankton transfer up to 10 Gt of carbon to the deep sea,” said Dr Emma Cavan, who was lead author of the paper published in Aquatic Microbial Ecology ( “As they sink through the ocean, some phytoplankton are consumed and decomposed by zooplankton and bacteria, releasing carbon dioxide back into the ocean when they respire, making the carbon available again to be released back to the atmosphere.

“During our study we collected microbes on clumps of sinking phytoplankton from...

The full text of this article can be purchased from Informit.