One day last autumn, after a rainy spell in the town of Zamora, Spain, residents noticed something strange in the water fountains: They had turned blood-red.
It looked as if the water had become contaminated by something, like maybe a heap of dead bodies, and it was weirdly reminiscent of Biblical plagues, in which rivers turned to blood, killing off all the fish. Everywhere the rainwater pooled, it quickly turned reddish.
A local of a neighboring village, Joaquín Pérez, decided to collect samples of the water and send them to University of Salamanca for testing, and this is pretty much where the potential horror story stops. According to the results, which have recently been published in the Spanish Royal Society of Natural History Journal, the reddish hue was caused by Haematococcus pluvialis, a type of freshwater algae.
The algae is actually fairly common—it's the same kind that freaked out people in India, Sri Lanka, and Texas in recent years, when they, too, found that their water had seemingly turned to blood overnight. The algae normally looks green, but during periods of stress, it produces a reddish pigment. One mystery does remain: The algae isn't native to the part of Spain where it was found, and the researchers couldn't pinpoint exactly where it came from.
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