If the water is cloudy, has oil-like streaks or is flaky, humans and dogs should not bathe. Blue-green algae are bacteria that are also known as cyanobacteria and occur, for example, in the Baltic Sea or in inland lakes. They can pose a serious danger to your four-legged friend if he swims in water contaminated by blue-green algae or drinks from it. Cyanobacteria multiply especially at summer temperatures and appear as so-called "water blooms". Blue-green algae form toxic substances (toxins), which can be very harmful to your dog.
After oral ingestion, the bacteria migrate via the bile duct system to the liver. There, the poison (which is called "toxin") unfolds its effect: Already after one hour, the destruction of the first liver cells begins. Later, depending on the dose, there may also be coagulation disorders, kidney damage with bleeding, neurological symptoms and finally even death from liver failure.
Blue-green algae poisoning is an emergency. Please do not wait long, but take your dog to the nearest veterinary office immediately.
Like bacteria, blue-green algae have simply constructed cells without a real cell nucleus. In science, they are referred to as cyanobacteria. Some species contain blue phycocyanin in addition to green photosynthetic pigments. They are therefore blue-green in color. The term blue-green algae applies to all cyanobacteria, including species that do not have phycocyanin and may be yellow, green, brown or even red in color. Some species
can form metabolites that are toxic to humans and animals. Caution should therefore be exercised in the case of mass occurrences of blue-green algae. A separate leaflet deals with the red-colored burgundy alga, which also belongs to the blue-green algae and dominates the plant plankton in Lake Zurich. Since it requires very little light and lives at a depth of 10 to 15 meters during the summer, its lifestyle differs fundamentally from that of the other blue-green algae species.
Calm, warm water, sufficient nutrients and sunlight promote the growth of algae. Nutrient-rich lakes and ponds are characterized by highly dynamic biological processes. After a period of changeable weather followed by a period of good weather, algae growth can be strong within a few days. In late summer and autumn, blue-green algae species then often dominate the plant plankton. When the water becomes very turbid due to the high biomass and the algae "frame up" on the surface, this is called an algal bloom. Dying algae are usually accompanied by a noticeable foam formation. If an algal bloom is dominated by species that can produce toxins, chemical analysis must be used to determine the toxin content. Not all algal blooms are toxic; moreover, conditions can vary widely in location and time, making assessment difficult.
Development in the last decades - and in the future?
In the 1970s and 1980s, swimming in our lakes was regularly spoiled by unsightly algal growths. Thanks to the implemented water protection measures, the nutrient concentrations and thus also the biomass of the algae have decreased massively since then. Despite improved water quality, however, strong algae growth can still occur in the Greifensee and in some small lakes in summer and autumn at short notice. Rising water temperatures as a result of climate change extend the phase in autumn when algae still find favorable growth conditions. In recent years, bathing operations could be extended several times by a few weeks. Stable weather conditions with bathing water temperatures until the beginning of October are not
only appreciated by the bathers, but also allow the blue-green algae to grow more. It is therefore possible that blue-green algae blooms will increase towards the end of the bathing season in the coming years.
Source text and image: Department of Health, Department of Construction Canton Zurich & Firstvet.com