Effects of unionised ammonia on tropical freshwater organisms : Implications on temperate-to-tropic extrapolation and water quality guidelines

Research output: Journal Publications and ReviewsRGC 21 - Publication in refereed journalpeer-review

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Original languageEnglish
Pages (from-to)240-249
Journal / PublicationEnvironmental Pollution
Online published17 Jun 2015
Publication statusPublished - Oct 2015
Externally publishedYes


Unionised ammonia (NH3) is highly toxic to freshwater organisms. Yet, most of the available toxicity data on NH3 were predominantly generated from temperate regions, while toxicity data on NH3 derived from tropical species were limited. To address this issue, we first conducted standard acute toxicity tests on NH3 using ten tropical freshwater species. Subsequently, we constructed a tropical species sensitivity distribution (SSD) using these newly generated toxicity data and available tropical toxicity data of NH3, which was then compared with the corresponding temperate SSD constructed from documented temperate acute toxicity data. Our results showed that tropical species were generally more sensitive to NH3 than their temperate counterparts. Based on the ratio between temperate and tropical hazardous concentration 10% values, we recommend an extrapolation factor of four to be applied when surrogate temperate toxicity data or temperate water quality guidelines of NH3 are used for protecting tropical freshwater ecosystems.

Research Area(s)

  • Acute-to-chronic ratio, Freshwater ecosystems, Safety extrapolation factor, Unionised ammonia, Water quality guidelines