Ecological Developments of the Recent Decades Generating Social Conflicts in the Life of the Lake Balaton – Brown Discoloration of Water

Abstract

Ecological Developments of the Recent Decades Generating Social Conflicts in the Life of the Lake Balaton – Brown Discoloration of Water The largest quantities of brown coloured dissolved organic substances get into Lake Balaton in the Keszthely-basin through the River Zala and on the south shore from Nagyberek (peat bog) through pumping. Tourists avoid the beaches with brown water despite the fact that it does not pose any danger. Even though the humic substances causing the brown colour are not harmful for bathers, these compounds, however, do influence ecological processes. Humic substances are natural substances which are the decomposition products of dead plants. Their water-soluble fractions are fulvic acids and humic acids, while their third fraction (humin) is not water soluble. Humic substances play multiple ecological roles in surface waters: they serve as a carbon source for bacteria; change the underwater light climate through the increased attenuation of the short-wavelength ultraviolet (UV) radiation of the Sun; their photodegradation produces toxic free radicals containing oxygen (which is transformed to hydrogen peroxide); and they change the behaviour of other substances through their complex-forming property. A significant increase in the chromophoric dissolved organic matter load of the Lake can be anticipated because of the planned extension of the currently flooding area (16 km2) by the lower Kis-Balaton reservoir up to 52 km2.