DON’T MISS
IamExpat Job BoardIamExpat HousingIamExpat Webinars
Newsletters
EXPAT INFO
CAREER
HOUSING
EDUCATION
LIFESTYLE
EXPAT SERVICES
NEWS & ARTICLES
Home
Expat Info
Swiss news & articles
Why did Lake Zug turn red this Christmas?
Never miss a thing!Sign up for our weekly newsletters with important news stories, expat events and special offers.
Keep me updated with exclusive offers from partner companies
By signing up, you agree that we may process your information in accordance with our privacy policy

Why did Lake Zug turn red this Christmas?

Never miss a thing!Sign up for our weekly newsletters with important news stories, expat events and special offers.
Keep me updated with exclusive offers from partner companies
By signing up, you agree that we may process your information in accordance with our privacy policy
or
follow us for regular updates:



Related Stories

April 2025 in Switzerland: 10 major changes expats need to know aboutApril 2025 in Switzerland: 10 major changes expats need to know about
Basel to offer 1.500 francs to anyone who gives up their carBasel to offer 1.500 francs to anyone who gives up their car
100 tons of plastic dumped in Lake Geneva every year, new study finds100 tons of plastic dumped in Lake Geneva every year, new study finds
Number of deer in Canton Zurich reaches 38-year highNumber of deer in Canton Zurich reaches 38-year high
Tallest wooden building in the world to be built in ZurichTallest wooden building in the world to be built in Zurich
Car-free HB: Area around Zurich Main Station to be turned into a parkCar-free HB: Area around Zurich Main Station to be turned into a park
Geneva to dim streetlights to help bat populationGeneva to dim streetlights to help bat population
Flock of sheep to be used as lawnmowers in Winterthur, city confirmsFlock of sheep to be used as lawnmowers in Winterthur, city confirms
For expats of all colours, shapes and sizes

Explore
Expat infoCareerHousingEducationLifestyleExpat servicesNews & articles
About us
IamExpat MediaAdvertisePost a jobContact usSitemap
More IamExpat
IamExpat Job BoardIamExpat HousingWebinarsNewsletters
Privacy
Terms of usePrivacy policyCookiesAvoiding scams

Never miss a thing!Sign up for expat events, news & offers, delivered once a week.
Keep me updated with exclusive offers from partner companies
By signing up, you agree that we may process your information in accordance with our privacy policy


© 2025 IamExpat Media B.V.
© 2025 IamExpat Media B.V.
Dec 27, 2022
Jan de Boer

Editor at IamExpat Media

Jan studied History at the University of York and Broadcast Journalism at the University of Sheffield. Though born in York, Jan has lived most of his life in Zurich and has worked as a journalist, writer and editor since 2016. While he has plunged head-first back into life in Switzerland since returning to the country in 2020, he still enjoys a taste of home at pub quizzes and karaoke nights.Read more

While Swiss lakes are usually known for their cleanliness and beauty, there are occasions when crystal blue water can transform into a sea of red. That was the case for the lake near Zug, which turned a shade of blood red around Christmas. Here’s why the lake has turned red and why the police have issued a warning.

Lake Zug turns burgundy-red during Christmas

During the Christmas period, according to Blick, residents of the Swiss city were shocked to find that Lake Zug (Zugersee) had turned a bloody shade of red. The water around Landsgemeindeplatz and Badi Hünenberg was covered with a thick layer of burgundy-red sludge.

Quickly, locals took to the internet to report the horrific red colour, with many worrying that the pigment was the result of an environmental disaster or industrial accident. In response, authorities said that the red colouring was not man-made or pollution-related, but the result of a natural phenomenon.

Im Zugersee, Bereich Landsgemeindeplatz, ist das Wasser aktuell rötlich verfärbt. Es handelt sich nicht um eine Gewässerverschmutzung, sondern um die Burgunderblutalge. Gemäss den Fachleuten können diese Algen, je nach Konzentration, für Tiere gefährlich sein – daher Vorsicht. pic.twitter.com/iSd7decxE3

— Zuger Polizei (@ZugerPolizei) December 25, 2022

Swiss police warn dog owners about algae in lakes

According to the emergency services, the red in the lake was caused by a bloom of burgundy algae, also known as blood algae. Experts told Blick that the planktothrix that makes up the algal cloud adopts different colours based on the depth of the water and their habitat, which in this case made the bloom a vibrant shade of red.

While the algae poses little harm to humans, police in Canton Zug warned against taking animals like dogs into the water. Much like blue-green algae in Switzerland, drinking water with red algae in it can be dangerous for pets and humans. This was demonstrated at an incident during the summer on Lake Greifensee, Canton Zurich when two dogs died after they drank water with algae in it.

By Jan de Boer