Bright green algal bloom is so vast it can be seen from聽space
A field of green algae stretching hundreds of kilometres across the ocean surface near Antarctica is so bright that it is clearly visible from space, even through thin layers of cloud.
Scientists from the Australian Antarctic Division who have been monitoring the massive bloom for the past fortnight say it is the biggest occurrence of its kind in living memory.
Jan Lieser, a marine glaciologist who monitors the sea ice conditions in the East Antarctic using satellite data for the Antarctic Climate & Ecosystems Cooperative Research Centre in Hobart, Australia, estimated that the bloom covered an area about 200 kilometres east to west, by 100 kilometres north to south.
Dr. Lieser has captured several images of the algae using NASA鈥檚 Modis instrument on the Terra satellite, at least 650 kilometres above the Earth. He said the giant green field, thought to be phaeocystis algae, was providing 鈥渁 feast鈥� for krill and other zoo plankton, and also bigger marine life that was drawn to the area to feed on the krill.
鈥淲e know that algal blooms are a natural occurrence down south 鈥� it鈥檚 just a part of the Southern Ocean. But I鈥檝e never seen one on this scale before. It鈥檚 been going on for about 15 days now, so it鈥檚 maybe about 鈪� or 戮 of the way through the cycle.鈥�
It was unclear what had precipitated the bloom, he said, but it was thought that a combination of nutrients and sunlight was the main cause.
鈥淚ron is the limiting nutrient in that part of the world, so as soon as you have iron and as soon as you have sunlight and all the other conditions are right, then these algal blooms will quite happily grow and reproduce,鈥� Dr. Lieser said.
鈥淲here the iron is coming from we鈥檙e not quite sure. One idea is that it鈥檚 been taken off the continent by strong offshore winds that take snow and sediment load in the snow into the ocean surface, and the snow melts there and releases the nutrient load.鈥�
Another idea was that sediment was being brought up from the ocean floor and releasing nutrients on the surface. The third option was that decaying 鈥渇ast ice鈥� 鈥� or sea ice which has frozen along coasts 鈥� had broken off and was feeding the bloom.
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