Are Urinating Swimmers Killing Fish?

German officials have banned swimmers from Eichbaum Lake while studying the link between fish death and public urination.

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There’s an old joke about the silent ‘p’ in swimming pools (think about it), but it turns out that urinating in a lake may be far from funny. German researches have come to believe that a significant amount of human urine may be responsible for an algae bloom that poisoned over 500 fish at Eichbaum Lake in northern Germany.

“Swimmers who urinate in the lake are introducing a lot of phosphate” that can contribute to algae blooms, a spokesman for the Hamburger Angling Association told Bild newspaper. “We’re calculating half a liter of urine per swimmer per day.” The Angling Association has been in a long-standing feud with the lake’s swimmers, according to The Local, so that number may be suspiciously high. Bathers are currently banned from the lake due to the high levels of algae, but the city’s Urban Development and Environment Authority (BSU) is working to re-open the lake for swimmers before the summer season starts.

To help resolve the whodunit, the BSU is calling in the local university to test the pee-death theory. According to The Local, the BSU believes that the fish deaths were caused by a combination of natural causes and something far less taboo than public urination: ice skating.  “The ice-skaters make a noise that wakes the fish out of hibernation,” BSU spokeswoman Kerstin Graupner told the Local. “Then they can’t breathe and freeze. That’s a very common phenomenon.” Their bodies are only now being found.

For those questioning whether or not human urine could be responsible for fish death, the answer is yes.  According to i09, the phosphates in human urine act like a fertilizer that can promote algae growth. Algae blooms deplete the oxygen available to fish, causing them to suffocate. Additionally, the scientists in Hamburg believe the algae that has bloomed in the lake is particularly aggressive, releasing a toxin that changes the lakes natural ammonium to the far more deadly ammonia, which restricts the fish’s breathing.

Eichbaum Lake is not the first natural wonder to receive a pee ban. Ecologists warn visitors not to pee when they visit Australia’s Great Barrier Reef for fear that algae blooms will kill the coral.

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