Combined chemical (fluoranthene) and drought effects on lumbricus rubellus demonstrate the applicability of the independent action model for multiple stressor assessment

Sara M. Long, Fredrik Reichenberg, Lindsay J. Lister, Peter K. Hankard, Joanna Townsend, Philipp Mayer, Julian Wright, Martin Holmstrup, Claus Svendsen, David J. Spurgeon

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

The combined effect of a chemical (fluoranthene) and a nonchemical stress (reduced soil moisture content) to the widely distributed earthworm Lumbricus rubellus were investigated in a laboratory study. Neither fluoranthene (up to 500 mu g/g) nor low soil moisture (15% below optimal) had a significant effect on the survival of the exposed worms, but a significant effect on reproduction (cocoon production rate) was found for both stressors (p < 0.001 in both cases). The response of cocoon production to each stressor could be well described by a logistic model; this suggested that the joint effects may be applicable to description using the independent action (IA) model that is widely used in pharmacology and chemical mixture risk assessment [1]. Fitting of the IA model provided a good description of the combined stressor data (accounting for 53.7% of total variation) and was the most parsimonious model describing joint effect (i.e., the description of the data was not improved by addition of further parameters accounting for synergism or antagonism). Thus, the independent action of the two responses was further supported by measurement of internal fluoranthene exposure. The chemical activity of fluoranthene in worm tissue was correlated only with soil fluoranthene concentration and not with soil moisture content. Taken together these results suggest that the IA model can help interpret the joint effects of chemical and nonchemical stressors. Such analyses should, however, be done with caution since the literature data set suggests that there may be cases where interactions between stressors result in joint effects that differ significantly from IA predictions.
Original languageEnglish
JournalEnvironmental Toxicology and Chemistry
Volume28
Issue number3
Pages (from-to)629-636
ISSN0730-7268
DOIs
Publication statusPublished - 2009
Externally publishedYes

Keywords

  • Drought
  • Polycyclic aromatic hydrocarbons
  • Multiple stressors
  • Independent action
  • Chemical activity

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