Overview - Chemistry
The lakes in East Denmark and North Germany are highly influenced by being situated in calicum-rich glacial moraines. The calcareous soil and its clay release calcium and bicarbonate into lake water. This ensures a high a stable alkalinity in the water ( pH 7-8) despite acidic particulates in precipitation deriving from European industry and traffic.
The growth of both the phytoplankton in lake water and submergent aquatic plants in lake sediment are limited by nitrogen and phosphorous – the same substances used in agriculture for fertilisation to increase yields. Nitrogen and phosphorous are necessary for lakes to have a diverse botany, although oversupply of these nutrients (called eutrophication) results in blooms of phytoplankton. This causes the lake water to become greenish and turbid to the degree that light cannot penetrate to the bottom and the bottom vegetation is shaded to death.
The vast majority of the amount of nitrogen and phosphorous entering lakes derives from human activities in the lake’s drainage basin. The improved sewage treatment in many towns and industries have reduced phosphorus discharges in particular, and improved fertilisation techniques in agriculture have similarly reduced the runoff of nitrogen from the soil. However, the current status is that most lakes in our region remain overloaded with nutrients.
