Microbial and chemical quality assessment of the small rivers entering the South Baltic. Part I: Case study on the watercourses in the Baltic Sea catchment area

The area of the Coastal Landscape Park (CLP) due to its location is extremely attractive touristic area. In the summer season, a significant increase in population density is observed, which influences surface water quality. Large numbers of tourists generate an increased amount of municipal wastewater, being treated in local treatment plants and discharged into rivers and streams. The paper presents preliminary research from summer 2016 on three watercourses ending in the Baltic Sea: Piasnica, Karwianka and Czarna Wda rivers. It is a part of a long-term project conducted in CLP to assess surface waters quality. The scope of research included measurements of in situ parameters (temperature, conductivity, pH, dissolved oxygen). Chemical Oxygen Demand was determined using a spectrophotometer. Ion chromatography was used to determine ions concentrations (including biogenic compounds). Sanitary state of watercourses was assessed based on fecal coliforms abundance, which number was determined by the cultivation method. The determination of microbiological parameters such as: prokaryotic cell abundance expressed as total cells number (TCN), prokaryotic cell biovolume expressed as average cell volume (ACV), the prokaryotic biomass (PB) and prokaryotic cell morphotype diversity was determined using epifluorescence microscopy method. Results showed that water quality of Piasnica and Czarna Wda rivers were affected by discharged treated wastewater. In the case of Karwianka River, the main pollution source could be surface runoff from fields and unregulated sewage management in this area. The conducted research confirmed the urgent need for better protection of this area to conserve both its ecosystem and value for tourism.