Seasonal effects on microbial transformation rates of an herbicide in a freshwater stream: Application of laboratory data to a field site

David L. Lewis, Leonard F. Freeman, Maribeth E Watwood

Research output: Contribution to journalArticle

7 Scopus citations


Seasonal effects on microbial transformation rates of an herbicide, 2,4-dichlorophenoxyacetic acid butoxyethyl ester (2,4-DBE), in a freshwater stream were investigated using low concentrations (less than 100 μg L-1) of the herbicide mixed with an inert dye, rhodamine WT, to correct for dilution. Although water temperatures decreased from 22 ± 0.5 to 8.0 ± 0.5 °C and water velocities decreased from 0.09 ± 0.01 to 0.03 ± 0.003 m s-1, microbial transformation rates, as indicated by pseudo-first-order transformation rate coefficients, increased as much as threefold in the cold months over those in the spring and summer. The increased winter transformation rates were associated with leaf-litter accumulation, which provided additional colonized surface area in the stream. Therefore, the increased colonized surface area more than compensated for the effects of temperature and water velocity (under conditions of mass-transport limitation) that otherwise would have reduced microbial transformation rates in the winter months.

Original languageEnglish (US)
Pages (from-to)791-796
Number of pages6
JournalEnvironmental Toxicology and Chemistry
Issue number9
StatePublished - 1986
Externally publishedYes



  • Biodegradation
  • Herbicides
  • Microbial transformation
  • Seasonal effects
  • Temperature effects

ASJC Scopus subject areas

  • Toxicology
  • Health, Toxicology and Mutagenesis
  • Environmental Chemistry
  • Environmental Science(all)

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