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Follow that phytoplankton: modelling the Antarctic

The journey to the seafloor can indicate where there might be life. Creatures such as sea squirts are ‘suspension feeders’, and with sacs that look like blown glass, they catch phytoplankton as it passes The journey to the seafloor can indicate where there might be life. Creatures such as sea squirts are ‘suspension feeders’, and with sacs that look like blown glass, they catch phytoplankton as it passes Jonny Stark
10 Feb
2018
The biodiversity of the Antarctic seafloor has been modelled for the first time

Relatively little is known about life on the Antarctic seafloor. A combination of deep water, ice and inaccessibility means that the type and abundance of creatures living there have been almost impossible to guess – until now.

By crossing the movements of ocean currents with satellite images of phytoplankton, Jan Jansen, a PhD student at Institute for Marine and Antarctic Studies, has been able to create breakthrough predictions of life beneath the cold surface.

Why phytoplankton? ‘For most animals on the seafloor, food originating at the ocean surface is their only source,’ says Jansen. Light cannot reach depths below 200 metres, and no light means no photosynthesis, which in turn means no plants. Therefore, the whereabouts of life-giving phytoplankton can largely dictate the biodiversity on the seafloor. Luckily, it can be seen in swarms on the ocean surface from satellites.

‘That’s where it gets tricky,’ says Jansen, ‘because phytoplankton rarely lands directly on the bottom of where it began on the surface. It is shifted around by open water currents first, and then by currents close to the seafloor before it settles.’

Satellite data needed to be collated with maps of the ocean currents. This was then compared to the amount of phytoplankton collected in seafloor core samples. Curiously, Jansen found that the phytoplankton moved around most when in deep currents near the seafloor. ‘The strength and speed of these deep currents was by far the most important factor determining where the phytoplankton settled.’

The ability to predict biodiversity is especially useful for a region that is difficult for scientists to access. While the study was confined to eastern Antarctica, scientists hope the method could be used to generate maps of biodiversity all around the continent. 

This was published in the February 2018 edition of Geographical magazine.

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