Benthic diatoms as indicators of herbicide toxicity in rivers – A new SPEcies At Risk (SPEARherbicides) index

Rebecca J. Wood, Simon M. Mitrovic, Richard P. Lim, Michael St J. Warne, Jason Dunlop, Ben J. Kefford

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)


Benthic diatom communities are used widely as indicators of river health due to their rapid response to changes in water quality. The ability for diatom-based indices to detect eutrophication has been well documented; however, an index designed specifically to detect herbicide impacts is yet to be established. This is required as herbicide contamination of rivers is common in agricultural regions and poses a potential threat to aquatic ecosystems. This study developed a new biomonitoring index (SPEARherbicides) using benthic diatom communities to detect the toxic impacts of herbicides in rivers, and tested it across 14 rivers in the Great Barrier Reef catchment area, Australia. The new index uses diatom species traits to classify diatoms as either sensitive or tolerant to herbicides and calculates the fraction of sensitive taxa within a sample. The SPEARherbicides index showed a decline in herbicide sensitive diatoms with increasing herbicide toxicity of the sites. The impacts of herbicide toxicity on the diatom community were only apparent after the wet season when aqueous herbicide concentrations typically peak and diatoms were able to recover during the dry season when herbicide concentrations were lower. SPEARherbicides values had a negative relationship with the percentage of grazing and cropping in catchments but had a positive relationship with the percentage of conservation in catchments. SPEARherbicides also had a negative relationship with co-occurring potential stressors such as nutrients and total suspended solids.

Original languageEnglish
Pages (from-to)203-213
Number of pages11
JournalEcological Indicators
Early online date21 Dec 2018
Publication statusPublished - 1 Apr 2019


  • Biomonitoring
  • Diatoms
  • Field effects
  • Herbicide tolerance
  • Traits

ASJC Scopus subject areas

  • Decision Sciences(all)
  • Ecology, Evolution, Behavior and Systematics
  • Ecology

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