Manganese toxicity to tropical freshwater species in low hardness water

Manganese (Mn) toxicity is significantly higher in slightly acidic, soft waters—such as those found in Magela Creek, Kakadu National Park—compared to previously studied conditions. Research reveals that three tropical freshwater species (Moinodaphnia macleayi, Amerianna cumingi, and Hydra viridissima) are more sensitive to Mn than nearly all species tested internationally, with chronic inhibition concentrations (IC10) as low as 140 μg/L. The study combined existing data with new findings to derive a 99% protection guideline value of 73 μg/L for Mn in such environments, highlighting the need for stricter regulatory limits due to elevated toxicity under these conditions.

Harford, A. J., Mooney, T. J., Trenfield, M. A., & van Dam, R. A. (2015). Manganese toxicity to tropical freshwater species in low hardness water. Environmental Toxicology and Chemistry, 34(12), 2856–2863. https://doi.org/10.1002/etc.3135