Zug, 11.06.2019

Green slime on parts of lake expected to disappear shortly


Last week a number of shoreline areas of Lake Zug were adversely affected by an unpleasant green slime. Fortunately, the problem is not expected to persist.

It is just unfortunate that the green slime, naturally occurring harmless algae, appeared just at a time when temperatures rose above 28°C for the first time, conditions which lure one into the lake for a cool dip.


As Peter Keller of the Cantonal Office of the Environment explained, the algae begin to grow in the spring as the weather gradually gets warmer but this year it only got warmer towards the end of May, hence this recent spurt.


It is particularly evident in certain bays, as can be seen in the photograph showing the Choller area, the wind blowing it to more stagnant areas where it remains.


While the algae will not disappear completely, the problem is likely to become less evident shortly, making bathing in the lake more pleasurable again.


Then lake grass begins to grow and continues to do so until the autumn. While some bathers are not keen on this as their legs can get entangled in it, it does provide fish with an area where they can hide. Keller thought the fact that one can feel plants in the lake enhanced the experience of swimming in natural surroundings, something one cannot experience at a pool, for example.


Of note too, is that, according to the Cantonal Office of Consumer Protection, which tests the water for germs at the start of every bathing season, the quality of the water in Lake Zug, and of that in Lake Aegeri, is of grade A quality, a reassurance to all who bathe in them.