The Tisza River is the longest tributary of the Danube, draining the eastern part of the Carpathian Basin (Central Europe). Five countries share its catchment with different waste production and management practices. Large amounts of waste, including macroplastics (MaPs), are washed into the river. Some of the litter is trapped by the riparian vegetation forming litter accumulations. The study aimed to map the amount of litter by a citizen science program and remote sensing data and to compare the MaP data to the amount of microplastic fragments in sediments. Volunteers reported 3216 riverine litter accumulations from five countries along the entire length of the Tisza (2016–2022). The results suggest that low flow conditions (e.g., impoundment by dams) support litter and MaP trapping. The volume of large accumulations registered by the citizens showed a good correlation with the area of drifting litter revealed on Sentinel-2 images (2016–2022) using machine learning algorithms. Though the MaPs probably fragmentate during their fluvial transport, no clear connection was found between the volume of litter accumulations and the mean microplastic fragment content of sediments (2019–2022). The “Clean Tisza Map“ reveals the high degree of stranded pollutants along rivers and supports public cleanup activities.

The Tisza River is the longest tributary of the Danube, draining the eastern part of the Carpathian Basin (Central Europe). Five countries share its catchment with different waste production and management practices. Large amounts of waste, including macroplastics (MaPs), are washed into the river. Some of the litter is trapped by the riparian vegetation forming litter accumulations. The study aimed to map the amount of litter by a citizen science program and remote sensing data and to compare the MaP data to the amount of microplastic fragments in sediments. Volunteers reported 3216 riverine litter accumulations from five countries along the entire length of the Tisza (2016–2022). The results suggest that low flow conditions (e.g., impoundment by dams) support litter and MaP trapping. The volume of large accumulations registered by the citizens showed a good correlation with the area of drifting litter revealed on Sentinel-2 images (2015–2021) using machine learning algorithms. Though the MaPs probably fragmentate during their fluvial transport, no clear connection was found between the volume of litter accumulations and the mean microplastic fragment content of sediments (2019–2022). The “Clean Tisza Map“ reveals the high degree of stranded pollutants along rivers and supports public cleanup activities.

The sustainable management of water resources requires experts and also citizens who understand the hydrosphere and its key functions. To educate the public about water-related issues, various water literacy concepts have been developed. However, many of these concepts are too complex for people to understand. In contrast, the ocean literacy framework effectively translates knowledge into behavioral changes and actions. The Danube River, known as the world’s most international river, has a catchment area shared by 19 countries. This river basin has experienced unprecedented landscape alterations, floods, droughts, and pollution events, highlighting the need for a new approach to environmental education. Additionally, globally, more people live near rivers than by the ocean. To empower members of riverside communities with water literacy, we aimed to adapt the ocean literacy principles into river literacy principles. In this study, we introduce a novel concept of river literacy, consisting of seven principles. This framework aims to support sustainable development goals through education and to restore and revive damaged freshwater habitats more effectively. The principles were tested in formal education across five countries. The results indicate that participants in river literacy programs became more motivated to protect rivers, and their understanding of fluvial geography and riverine pollution improved.

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.