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Which algae can make the Red Sea appear reddish brown?
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Red Sea
Map showing the Red Sea and the countries surrounding it. The Red Sea is one of the most heavily traveled waterways in the world. It is about 1,200 miles (1,930 km) long, and its maximum width is about 190 miles (305 km).
The Red Sea is occasionally populated by extensive blooms of the algae Trichodesmium erythraeum. When these organisms die off, they turn the water a reddish-brown color, which is believed to be the origin of the sea's name. This species is a free-floating marine blue-green alga that contains a red pigment in addition to phycocyanin.123