What is this dark stain reaching along Brazil's Atlantic coast to São Paulo? It showed up in a recent satellite photo, stretching nearly 800 kilometres across the ocean.
The snapshot was taken on 19 January by Aqua, a NASA spacecraft designed to track the Earth's water cycle. Local biologists say the black bloom is made up of hosts of a microscopic animal called Myrionecta rubra. Seen close up, the bloom is deep red, but the play of light on the ocean means it looks black from orbit.
Such blooms sometimes represent a serious threat to marine life, and they have even spurred the development of ultrasound weapons to kill them off.
Is this Myrionecta bloom as ominous as it looks? The animal lives a couple of metres under the water's surface, and it's a thief. It survives by preying on algae, gobbling up their chloroplasts so it can do its own photosynthesis. However, it poses little threat to other animals.
Pockets of water closer to the Brazilian coast appear bright green – probably algae or sediment – while white clouds streak over land and sea.
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