Microcystin-WR is primarily known for its role as a potent hepatotoxin produced by certain strains of cyanobacteria, especially Microcystis aeruginosa. Its main significance lies in environmental and public health monitoring due to its frequent presence in freshwater systems during harmful algal blooms. It is used as a biomarker to assess water quality and to evaluate the risk of cyanotoxin contamination in drinking water sources, recreational waters, and aquatic ecosystems. Due to its high toxicity and stability, Microcystin-WR is also employed in scientific research to study liver cell damage, oxidative stress mechanisms, and the inhibition of protein phosphatases 1 and 2A. It serves as a molecular tool to probe cellular signaling pathways involving phosphorylation. Additionally, it is used in the development and testing of detection methods such as ELISA, PCR, and mass spectrometry for monitoring toxin levels in environmental and biological samples. Because of its toxicity, it has no commercial or industrial applications and is strictly handled under controlled laboratory conditions.