Hot bathing lakes heat for humans and fish pose a health risk

The Baggersee is very popular - high temperatures stress people and fish

In the sweaty heat wave, there is nothing better than to cool off in a bathing lake. However, the extreme temperatures often ensure a relatively high water temperature. This not only affects the refreshment for us humans, but also makes the fish hard.

Refreshment in the lake

To stay cool in the current heat, it makes sense to visit the nearest lake. But in some places, the lakes and other inland waters are so warm due to the high temperatures that they hardly bring any refreshment. And even water temperatures, which we find pleasant, can be fatal for fish, because with increasing temperatures, the oxygen content in the water decreases. The Leibniz Institute of Freshwater Ecology and Inland Fisheries (ITUC) has issued a statement in this regard.

Although there is hardly anything more beautiful in the summer than to refresh yourself in the lake, the high water temperatures sometimes cause little for cooling. For fish, the heat has much more dramatic effects. (Image: mmphoto / fotolia.com)

Inland waters for recreation more important than the sea

In nature, man can best recover. Especially the water has a strong attraction for us. This also applies to lakes and rivers.

According to the IGB, a survey conducted in cooperation with the Humboldt University in Berlin (HU) showed that two thirds of Germans spend at least once a year in an inland water body to jog or walk.

About half of them swim or bathe regularly in a lake or river or use the shore for sunbathing.

"And around one third of the population in Germany lives in waters to enjoy the animals and plants," explains study leader Prof. Dr. med. Robert Arlinghaus of the ITUC and the HU a reason for the importance of inland waters for the recovery of man.

According to a recent survey in Lower Saxony by the Technical University of Berlin (TU), inland waterways are even more important for local recreation than the sea.

However, little is known about the recreational significance of smaller digger lakes. This is now changing as a result of the research work in the BAGGERSEE project, which is being carried out by scientists from the IGB, HU, TU and the Anglerverband Niedersachsen.

First results show how widespread the water type is Baggersee. In terms of area, around 70 percent of all lakes in Lower Saxony are excavated waters or dredged lakes. In Lower Saxony alone, there are more than 30,000 artificial lakes.

"Dredger lakes, because of their wide distribution, have great social significance for local recreation", said BAGGERSEE coordinator Prof. Dr. med. Robert Arlinghaus.

Optimize recreational value of dredging lakes

However, there are also losers at the Baggersee at the current record heat:

In waters that are heavily contaminated by agricultural and other nutrient inputs, high levels of algae can occur. These make the stay in the water for people sometimes dangerous bathing fun, since skin reactions threaten.

For fish and other aquatic life, the high levels of algae that cause the oxygen in the water to become depleted can become life-threatening.

The project BAGGERSEE now wants to optimize the biodiversity - and thus also the praised recreational value - of dredging lakes.

For example, the introduction of deadwood and the creation of shallow water zones in the steeply sloping dredger lakes will increase the occurrence of fish, amphibians and dragonflies.

Humans also benefit from the good structural diversity of the waters and from the natural development of the quarry lakes. (Ad)