An integrated physicochemical and microbiological assessment in the Vjosa River

Abstract

Once regarded as a pristine freshwater system, the Vjosa River is increasingly subject to anthropogenic pressures that compromise both ecological integrity and public health. This study presents an integrated twelve-month assessment (October 2024-October 2025) combining microbiological indicators Escherichia coli and intestinal enterococci with physicochemical parameters measured in situ using a multi-parameter probe (AP-2000 Aquaread). Thirteen monitoring stations were established along the main channel and principal tributaries, with sampling conducted on a monthly basis. Pronounced spatial and seasonal variability was observed throughout the study period. Water temperature ranged from winter minima below 10°C to summer maxima exceeding 24°C, while dissolved oxygen exhibited an inversely correlated seasonal trend. Electrical conductivity and total dissolved solids (TDS) were elevated at stations influenced by urban inputs and tributary inflows. Microbiological analysis revealed widespread faecal contamination, with mean E. coli concentrations predominantly classified within Class II; however, episodic peaks reaching Class III were recorded at several stations. Following internationally accepted microbiological water quality classifications, Class II denotes moderate faecal contamination, while Class III reflects critical pollution levels associated with elevated sanitary risk for both recreational and agricultural water use, consistent with Apha et al. (2017) and Who (2017) guidelines. Elevated water temperatures, reduced discharge, and moderate declines in dissolved oxygen during summer months coincided with marked increases in faecal indicator bacteria (FIB). Conversely, cooler, high-flow periods were associated with significantly lower microbial loads. Stations characterised by elevated conductivity and TDS consistently demonstrated higher levels of faecal contamination, suggesting a strong link between physicochemical conditions and microbiological water quality. These findings demonstrate that physicochemical and hydrological conditions substantially modulate microbiological pollution dynamics in the Vjosa River. The integration of microbial and physicochemical monitoring provides a more robust and comprehensive framework for assessing river health, and enables the identification of critical temporal windows and spatial hotspots of heightened sanitary risk.