Increasing from year to year number of tourists visiting the Great Mazury Lakes in the summer significantly affects the water quality deterioration in reservoirs. Incorrect usage of the reservoirs may even lead to the lakes dying.
These are the conclusions of research conducted in July and August by a team of researchers from the University of Warsaw, who assessed the quality of water and the risk of eutrophication of lakes in the southern part of the Great Mazury Lakes. Their water supplies the largest lake in Poland, Śniardwy, called the Mazury Sea.
The study was conducted in collaboration with the Local Fishermen Group "Mazury Sea". Experts tested the water of lakes Niegocin, Boczne, Jagodne, Szymoneckie, Szymona, Tałtowisko , Ryńskie, Talty, Mikołajskie, Bełdany and Śniardwy.
Lead researcher Prof. Ryszard Chróst from the Department of Microbial Ecology, Institute of Botany, University of Warsaw, told PAP that the largest impact on water quality of lakes, which is associated with the ongoing process of eutrophication, has the use and management of the Great Mazury Lakes basin, and the tourist traffic.
Eutrophication is a process of water fertilization, which may lead to overgrowth and the slow decay of the reservoir.
According to scientists, the main factor contributing to the deterioration of water quality in water bodies is the centralized water and sewage system. The second reason is insufficient treatment of wastewater in municipal wastewater treatment plants built by the lakes.
Wastewater containing nitrogen and phosphorus compounds are discharged into deep water of lakes, where during the spring and autumn circulation they mix with the entire basin waters.
Prof. Chróst suggested that this can be prevent by additional treatment of wastewater. This can be done in hydrobotanical systems that use natural substrate and plant filters.
The researchers have shown that the increasing tourist traffic on the water also contributes to the deterioration of water quality. The problem are cabin motor boats and sailing boats, from which tourists dispose of wastewater directly into the water. Rules governing the registration and authorization of large cabin sailing boats do not impose on their owners and users an obligation to install sanitary systems. There is also no obligation to dispose of wastewater from boats in the eco-marinas.
Prof. Chróst emphasised that at the end of the tourist season in August , in most lakes the surface water layer, where the content of oxygen dissolved in the water allowed for the existence of fish, significantly decreased. "This means that the volume of lake water with a fish habitat potential has decreased significantly, limiting their occurrence and feeding conditions" - he stressed.
The Great Mazury Lakes are located in the centre of the Mazury Lake District. The lakes cover the area surface of 482 km sq.
PAP - Science and Scholarship in Poland
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