The study addresses the use of strontium (Sr) isotope ratios (⁸⁷Sr/⁸⁶Sr) as a geochemical tracer to understand hydrological connectivity and human impacts in a geologically diverse Alpine basin covering the areas of Austria and Slovenia. It focuses on the Mura River and its tributaries, where water samples were collected at 45 locations under three different hydrological conditions to capture seasonal and spatial variability. A total of 28 tributaries were sampled to assess their influence on the isotopic composition of the main river. Isotopic analyses were performed using multi-collector inductively coupled plasma mass spectrometry, complemented by geo-information mapping and multivariate statistical methods. These analyses were coupled with measurements of concentrations of 26 elements, allowing the investigation of interactions between terrestrial and aquatic environments and human impacts.

The results show a marked temporal and spatial variability of the ⁸⁷Sr/⁸⁶Sr ratio (from 0.70853 to 0.71322), reflecting both the geological diversity of the area and the different contributions of the tributaries. A preliminary isosurvey of the water system has also been developed to monitor the connectivity of the watercourses and the effects of geological and anthropogenic factors under different flow conditions. Tributaries, such as the Mürz, have a significant influence on the isotopic signal in the main channel and often override local geological features. Using isotopic pattern parsing, the Mürz River contributes approximately 17 % to the isotopic signature of the Mura River downstream of the confluence. Correlations between the ⁸⁷Sr/⁸⁶Sr ratio and metal concentrations further confirm the usefulness of this isotopic ratio as an indicator of the origin of matter and an assessment of human impacts.

By establishing a preliminary strontium isoscape for the area, the study provides new insights into the connectivity of river systems, catchment-scale processes and ecosystem dynamics. The integration of isotopic data contributes to interdisciplinary understanding at the interface of geology, chemistry and ecology and supports the development of isotopic tools for sustainable monitoring and management of aquatic systems, including potential applications in fish ecology and habitat tracking.

Based on Moser, U., Čeplak, B., Wagner, S. et al. Spatio-temporal variations of strontium isotope ratios in the Mur River: a tool to support river management. Aquat Sci 88, 25 (2026). https://doi.org/10.1007/s00027-025-01253-4