<b>Biotoxicolagical monitoring and renaturalization in prevention of rivers from human impact. Integrated environmental and economic solutions</b>

In recent decades, the world’s river resources have been mismanaged across the globe without taking climate change into account. Most of them is eutrophic, contaminated with chemicals coming from human action including mine waters. A significant cause of anthropogenic salinization of surface waters including rivers, is the operation of mines, steelworks and industrial plants. This resulted in toxicity, salinization, HABs of salt- loving species and death of tons of organisms. Due to salinity, the Odra River suffered Europe’s worst ecological disasters in 2022. Massive fish die are indicative of the problem. When the last link in the trophic chain dies (fish), this proves the occurrence of an ecological disaster. Fish can be protected from death by biotoxicological monitoring of rivers using biotest with planktonic crustacean <i>Daphnia magna</i> Straus (water flea), a bioindicator significantly more sensitive to toxins than fish <b>.</b> Fish conservation is not directly dependent on monitoring. Biomonitoring, using indicators from the fish food chain, provides a basis for warning of disturbing phenomena occurring in the aquatic ecosystem that could lead to fish extinction. This article demonstrates the impact of weather anomalies on ecological disasters in large rivers, the economic impact of river disasters between 2010 and 2024 on all continents (except Antarctica), global ecological disasters in rivers caused by ichthyotoxins since 2000 and the impact of river regulation on their ecological function. Recommendation of the water flea <i>D. magna </i>for continuous river biomonitoring. Following ecological disasters in rivers, research on protecting them from fish extinction is rapidly developing. We point to the need for early biotoxicological monitoring to detect <i>Prymnesium</i><i> parvum</i> Carter blooms. The results of this work indicate the use of <i>D. magna </i>as a bioindicator. Huge economic losses, loss of river ecosystems, fish kills, and depletion of aquatic biodiversity compel radical remedial action. Renaturalization and biomonitoring are important tools in river prevention. Suplement: Results of biotoxicological and physicochemical results of Odra River (including chlorophyll) in 2024.