German officials have banned locals from entering a lake in northern Germany while they determine if reports of swimmers urinating in the lake have caused the lakes fish to die.
Eichbaum Lake is currently being studied by researchers who believe that a large amount of human urine is responsible for an algae bloom that killed off an estimated 500 fish.
"Swimmers who urinate in the lake are introducing a lot of phosphate" that can lead 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," he said.
Swimmers are currently banned from the lake due to the high levels of algae, but the city's Urban Development and Environment Authority (BSU) is trying to re-open the lake to swimmers by the time the summer season starts.
In order to identify exactly what is causing the fish to die off, the BSU is requesting the help of a local university to test the urinating hypothesis.
Local media reports have stated that it was not just the "urinators" that were responsible, but the combination of natural causes and a frozen lake.
In the winter time the lake freezes over and is used by many for ice skating. The ice skating may actually disrupt the fish while they are hibernating, leading to their deaths.
"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."
She added that their bodies are only now being found.
Urine, however, is being considered a real threat to the health of the lakes ecosystem. The blog i09 explained that phosphates found in human urine work in a similar fashion as fertilizer which can lead to explosive algae growth.
When levels of algae increase the plants absorb all of the oxygen in the water, which then leads to the fish suffocating.