Wildlife

Tiny plankton likely to ride out global warming

Plankton have evolved to survive a wide range of conditions, thanks to their unexpectedly vast ocean travels, a new study suggests.

These microscopic organisms support the marine food web, providing food for whales, fish and crustaceans.

Scientists at the University of Technology Sydney (UTS) in Australia and Imperial College London have been modelling how plankton drift with ocean currents to understand whether they are threatened by ocean warming.

The results of the study, published in the journal Proceedings of the National Academy of Science (PNAS), show for the first time the range of temperatures that plankton travel through. In most locations, they endure temperature extremes that go beyond what is predicted by models of global warming.

They found that ocean surface currents can transport drifting particles up to 3,500 kilometres in 500 days, which is about the equivalent of a person rowing from California to Hawaii. During this journey, plankton are subjected to temperature changes of up to 10°C more than if they stayed in one location.

There has been much recent interest in the future of coral reefs, because of their role in supporting biodiversity. But drifting plankton, that are invisible to the naked eye, are responsible for half the Earth’s oxygen and for global fisheries yields, and are therefore important in providing other essential ecosystem services

Waters in the Southern Indian Ocean, for example, had a seasonal temperature range of 13 to 18°C, whereas the study showed plankton that travelled through those waters had experienced temperatures as low as 5°C and as high as 20°C.

Climate change models suggest that ocean temperatures are only likely to warm up to a few degrees in the next century in the Southern Indian Ocean.