Messages in Bottles – Short and Long-Term Tracking of Plastic Bottles in Riverine Systems with a Multidisciplinary Approach

This study is inspired by the Plastic Cup’s unique “bottle mail” collection, an extensive archive of marked bottles gathered over more than a decade of river cleanups. These personal messages, carried by rivers across years and borders, motivated us to rely on public engagement to better understand the dynamics of plastic pollution in freshwater systems. In response to this environmental challenge, our research combines citizen science, advanced tracking technologies, and long-term datasets to study both short- and long-term plastic bottle mobility in rivers of the Danube Basin. The bottle-tagging citizen science programme engages schools, NGOs, and local communities through a catch-and-release methodology. Following the long-standing tradition of the “message-in-a-bottle” approach, plastic bottles collected from the environment are fitted with unique identifiers then reintroduced into the wild. As of the submission of this abstract, 184 bottles have been tagged in 7 Danube countries, with 7 confirmed re-captures. To compensate for the inherent limitations of citizen science, a professional component was added to the methodology through GPS-based tracking. Plastic bottles equipped with GPS transmitters are deployed to monitor riverine transport in near real-time, enabling high-resolution mapping of movement and accumulation patterns over days and weeks. These datasets offer insights into flow-dependent transport, hydrological event impacts, and potential hotspot areas requiring intervention. Integrating citizen-generated and GPS-based data supports a more comprehensive understanding of short- versus long-term transport dynamics. As an ongoing initiative, data collection is not complete yet. Hereby we present partial results with the intention to inspire the scientific community as well as to increase participation in citizen science efforts while contributing to a multidimensional understanding of plastic transport in rivers.