Authorities warn swimmers and dog owners about algae

Accumulations of burgundy blood algae can be seen on the surface of the water in places in Lakes Zug and Aegeri. These algae can form toxins.

According to a press release, employees of the Zug Office of Forests and Game (Amt für Wald und Wild) recovered several dead birds (gulls, crows) from mats of burgundy blood algae (planktothrix rubescens) on 18 February. These had been  washed up on the lakeshore in Zug. Working together with the cantonal veterinary service, this office is now investigating the cause of death of the birds.

Due to the incident with the dead birds, the cantonal authorities draw attention to the rules of conduct when blue-green algae occur:

• Blue-green algae occurrences can be recognised by the conspicuous colour of the water surface (reddish, greenish or yellowish streaky mats).
• Do not swim in places where blue-green algae or other algae are present, i.e. if your own feet are no longer clearly visible in knee-deep water.
• In general, avoid swallowing water when bathing in the lake, and always shower after bathing.
• Do not let dogs play or swim in murky water. If your dog has come into contact with possibly contaminated water, prevent him from licking his paws or fur. Wash his fur with clear water as soon as possible.

Burgundy blood algae, here photographed at Zug's Alpenquai, are clearly red in colour     Photo: Forest and Game Department/PD

There are currently accumulations of burgundy blood algae on the surface of Lake Zug and Lake Aegeri, and these are washed up on the shore by the wind. Burgundy blood algae are clearly red in colour, and belong to the group of blue-green algae that grow like plants with the help of sunlight, says the Office of Forests and Game. The current increase in the occurrence of burgundy algae in the lakes is related to the ongoing good weather.

The cantonal authorities continue to monitor the current occurrence of blue-green algae closely and "inform the population if necessary".