[All] Officials worry urinating swimmers may be reason for 500 dead fish

[Neil E Taylor]

Officials worry urinating swimmers may be reason for 500 dead fish


By Isolde Raftery, msnbc.com  May 13, 2012

Peeing while swimming in a lake may not just be taboo - it could also be
lethal, for the fish.

At least that's what a group of anglers contend, blaming swimmers for
<http://www.thelocal.de/sci-tech/20120511-42491.html>  the 500 dead fish
that have turned up in a picturesque German lake near Hamburg, The Local
reported.

"Swimmers who urinate in the lake are introducing a lot of phosphate,"
Manfred Siedler, a spokesman for an angler's group, told Bild newspaper.
"We're calculating half a liter of urine per swimmer per day."

Skeptics questioned whether the outcry was an attempt by fishermen to oust
bathers - with whom they have long feuded, according to The Local - but are
saying this could be possible.

IO9.com, a <http://io9.com/5909846/can-peeing-in-a-lake-really-kill-fish>
Gawker science blog posed the question, "Can anything as natural as peeing
in a lake kill the fish?"

The answer, apparently, is yes.

The urine itself doesn't harm the fish but sets off a series of
environmental events that ultimately suffocate the fish.  First, the urine
acts as a fertilizer for the blue-green algae in the water. Once they have
consumed all the fertilizer, the algae continue sucking up available oxygen
in the water, IO9.com explained. When the algae die and start to decompose,
they further use up oxygen. That's when fish start to die.

Bild reported that authorities have poured more than half a million dollars
of an anti-phosphate agent called Bentophos into the lake, to no avail.
(Bentophos has been tested
<http://www.phoslock.pl/pliki/presentation_poznan_en.pdf>  in artificial
lakes that were shut down due to massive bacterial blooms.)

For now, the lake is closed to swimmers because of the high levels of algae
(which can cause swimmer's itch), but the city's environmental authority is
fighting the closure, The Local reported.

Kerstin Graupner, a spokeswoman for the environmental authority, told The
Local that she blamed natural causes and ice-skaters.  "The ice-skaters make
a noise that wakes the fish out of hibernation," Graupner said. "Then they
can't breathe and freeze. That's a very common phenomenon."

Graupner's agency called on a university in Hamburg to test the anglers'
theory. According to The Local, it appears the anglers may have a point -
the scientists found anabaena algae blooms, which produce a toxin that
ultimately restricts fish breathing.  

The German lake isn't the only place where officials worry about swimmers;
signs
<http://www.hottnez.com/to-pee-or-not-to-pee-10-places-you-should-never-pee/
>  at the Great Barrier Reef ask swimmers not to urinate in the water. Doing
so apparently kills the corals, which grow in low nutrient waters.


Can peeing in a lake really kill fish?


 <http://img.gawkerassets.com/img/17mfxs2po0pf0jpg/original.jpg> There's
been a story kicking around in the news recently about a fight in Hamburg,
Germany, where recreational swimmers have supposedly killed fish by peeing
in Eichbaum Lake, making fishermen really (get ready) pissed off. Reading
this set off my potential-Internet-baloney alarm bells: short
<http://www.foxnews.com/world/2012/05/12/swimmers-urine-to-blame-for-500-fis
h-deaths-german-fishermen-say/>  articles, coming from a foreign country,
based off one English-language
<http://www.thelocal.de/sci-tech/20120511-42491.html>  report, with a
spokesman from the Hamburger Angling Association as the main source. Is
there anything to this? Can anything as natural as peeing in a lake kill the
fish?

In a word, yes. Whether pee was the murder weapon in this particular
whodunnit depends on some factors that aren't clear from these scant
reports, like how many people are swimming there and the chemistry of the
lake. But urine certainly can kill fish, though it's not actually the urine
that does it.

Urine includes plenty of nitrogen, potassium, and phosphorus, nutrients that
are helpful for plant growth. In fact, those are the three main ingredients
in both industrial fertilizer and natural fertilizers like manure. (The
nitrogren in urine isn't N2, the gas that makes up most of the
atmosphere-it's N3-, the "fixed" nitrogen that plants need.) If you let your
pee sit around for a long while (I don't recommend doing this, for obvious
reasons), it will precipitate out an
<http://www.sswm.info/category/implementation-tools/reuse-and-recharge/hardw
are/reuse-urine-and-faeces-agriculture/fertili>  odorless fertilizer called
struvite.

So if you add a lot of urine to a lake, you're essentially dumping in a
bunch of fertilizer, which cases a bloom of algae. After they've used up the
fertilizer, the algae continue using oxygen, and when they die, their
decomposition consumes still more, drastically lowering the levels of oxygen
in the lake, which is what generally kills fish. The same kind of fish
die-off happen when agricultural
<http://en.wikipedia.org/wiki/Eutrophication#Sources_of_high_nutrient_runoff
>  run-off reaches rivers and lakes-the run-off includes lots of fertilizer,
which is basically urine, after all. And Eichbaum's fish may be facing an
unusual additional danger: Hamburg University scientists have reportedly
found a particular type of algae in the lake that actually releases a toxin.

Ultimately, it seems plausible that some seemingly harmless urine is
actually harming the lake's fish. It wouldn't be the first time a large body
of water faced the same risk: ecologists warn
<http://www.hottnez.com/to-pee-or-not-to-pee-10-places-you-should-never-pee/
>  visitors not to pee when they visit the beautiful Great Barrier Reef
(pictured above) for fear that algae blooms will kill the coral.

 

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