Freshwater ecosystems, encompassing lakes, rivers, streams, and wetlands, are vital aquatic habitats supporting a remarkable 41% of the world's known fish species. These diverse systems are broadly categorized as lentic (slow-moving waters), lotic (faster-moving waters), and wetlands, with monitoring methods evolving from addressing early human health threats like cholera to assessing chemical and biological indicators. Despite their ecological importance, freshwater biodiversity faces extensive threats such as overexploitation, widespread water pollution, habitat degradation, and flow modification by dams.
Climate change, marked by increasing water temperatures by about 1 °C and declining ice cover, along with invasive species, further exacerbates these issues. The World Wide Fund for Nature reported an alarming 83% decline in freshwater vertebrate populations between 1970 and 2014, outpacing losses in marine and terrestrial systems. The cumulative effects of these pressures, compounded by emerging contaminants and microplastic pollution, pose a critical and ongoing challenge to the health and survival of these essential ecosystems.