Water systems are significant but vulnerable components of karst areas. Our paper presents the results of a multidisciplinary approach focused on the identification of a whole complex of influences that can affect water quality in a karst area. We delineate results on the example of Jedovnicky brook, representing one of the main watercourses bringing water and, concurrently, pollution from the non-protected area out of karst to the Protected Landscape Area Moravian Karst (Czech Republic). The main aim is to present the development of human impacts on water quality in the period 1931 and 2010. The development of physical-chemical status (monitoring campaigns from 1949 to 2014; mass flows of BOD, NH4-N, NO3-N, and PO4-P) as well as historical land use and demographic changes were assessed. Agricultural activities, population growth and changes in settlements were identified as the main sources of the pollution in the past. Agricultural activities have undergone major positive changes - especially in the way of management and the use of fertilizers. Currently, the strong suburbanization trend (rising population after the year 2000, the expanding built-up areas, increasing amount of municipal wastewaters) is the most important risk factor for the deterioration of Jedovnice brook water quality and, as a result, karst water quality.

We developed, tested, and optimized two laboratory denitrification assays for both managers and scientists to assess the effects of xenobiotics on the denitrification process over 7 days (short batch assay, SBA) and 28 days (long semi-continuous assay, LSA). The assays facilitate (1) measuring the efficiency of nitrate removal under the influence of xenobiotics, (2) determining the removal of the tested xenobiotics via adsorption or biotic decomposition, and (3) testing the influencing parameters for optimizing the denitrification process. The adsorption of the xenobiotics was assessed by inhibiting all biological processes through the addition of HgCl₂. Our tests demonstrate that the ratio of the initial nitrate concentration to the amount of bioavailable organic matter provided is essential to avoid organic carbon or nitrate limitation. While a pH < 7 resulted in decreased denitrification, a pH > 8 led to nitrite accumulation, indicating incomplete denitrification. Over durations of more than a week, weekly replenishments of the nitrate and HgCl₂ and weekly purging with argon gas to reduce the oxygen concentrations are needed. The assays provide information about the accumulation of xenobiotics in the bioreactors that is necessary for the environmentally friendly treatment of the bioreactor fillings and provide insight into the potential of the bioreactors to remove pesticides from polluted water resources.