Aquatic Toxicology 98 (2010) 328–335 Contents lists available at ScienceDirect Aquatic Toxicology journal homepage: www.elsevier.com/locate/aquatox Behavioural changes in three species of freshwater macroinvertebrates exposed to the pyrethroid lambda-cyhalothrin: Laboratory and stream microcosm studies Ulrik Nørum a,∗ , Nikolai Friberg b , Maria R. Jensen a , Jakob M. Pedersen a , Poul Bjerregaard a a Institute of Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark b Department of Freshwater Ecology, National Environmental Research Institute, Aarhus University, Vejlsøvej 25, DK-8600 Silkeborg, Denmark article info Article history: Received 28 February 2010 Accepted 3 March 2010 Keywords: Video tracking Locomotory behaviour Drift Stream macroinvertebrates Pyrethroids Lambda-cyhalothrin abstract Pesticides are transported from crop fields to adjacent streams via surface run-off, drains, groundwater, wind drift and atmospheric deposition and give rise to transient pulse contamination. Although the concentrations observed, typically <10 gL -1 , cannot be expected to be acutely lethal, effects in streams at the population and ecosystem level have been reported. One of the most conspicuous phenomena associated with these transient pesticide pulses is drift, where large numbers of freshwater invertebrates are carried along by the current and disappear from the contaminated stretch of the stream. The aim of the present study was to evaluate the feasibility of linking laboratory studies of the sublethal effects of pulse exposure to the pyrethroid lambda-cyhalothrin on the locomotory behaviour of stream invertebrates with effects on drift behaviour under more environmentally realistic conditions in stream microcosms. In the laboratory as well as in the microcosms, the order of sensitivities of the three species tested was (with Leuctra nigra being the most sensitive): L. nigra > Gammarus pulex > Heptagenia sulphurea. The LOECs determined for L. nigra (1 ng L -1 ), G. pulex (10 ng L -1 ) and H. sulphurea (100 ng L -1 ) are all within expected environmental concentrations. For the species of invertebrates investigated, it was possible to extrapolate directly from pyrethroid-induced behavioural changes observed in the laboratory to drift under more realistic conditions in stream microcosms. Consequently, the fast and cost-effective video tracking methodology may be applied for screening for potential effects of a wider range of pesticides and other stressors on the locomotory behaviour of freshwater invertebrates. The results indicate that such behavioural changes may be predictive of effects at the ecosystem level. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Recently, Schulz (2004) has reviewed existing knowledge of the exposure to and effects of insecticides in natural surface waters due to contamination from agricultural nonpoint-sources. The major routes of transport of insecticides, and other pesticides, from crop fields to adjacent streams are via surface run-off, drains, ground- water, wind drift and atmospheric deposition. Often the pesticide contamination occurs as transient pulses with elevated concentra- tions, especially when a field spraying is followed by significant amounts of precipitation or when pesticides are released as a result of illegal handling, e.g. direct overspraying or discharges from farm- yards where pesticides are handled and spraying equipment is cleaned. ∗ Corresponding author. Present address: Department of Freshwater Ecology, National Environmental Research Institute, Aarhus University, Vejlsøvej 25, DK- 8600 Silkeborg, Denmark. Tel.: +45 8920 1400; fax: +45 8920 1414. E-mail address: uln@dmu.dk (U. Nørum). Although the effects of the pesticides in freshwater ecosystems remain to be fully elucidated, the concentrations observed, typ- ically <10 gL -1 , cannot be expected to be acutely lethal. Still, effects in streams at the population and ecosystem level following transient pulses of insecticides, especially pyrethroids, originat- ing from the spraying of crop fields, have been reported (Schulz, 2004; Schulz and Liess, 1999a). The pyrethroids are the most important group of insecticides used in Denmark, and according to the annual pesticide statistics from the Danish Environmental Protection Agency 89% of the insecticide treated crop area was sprayed with pyrethroids in 2008 (Danish EPA, 2009). The toxicity of the pyrethroids is caused by their agonistic effect on voltage- dependent sodium channels in the nervous system (Narahashi, 1996; Vijverberg and Vandenbercken, 1990). One of the most conspicuous phenomena observed during, and for some time following, these transient pesticide pulses is drift, where large numbers of freshwater invertebrates are carried along by the current and disappear from the contaminated stretch of the stream. Drift may conveniently be divided into two categories: behavioural drift and catastrophic drift (Waters, 1965). Behavioural 0166-445X/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.aquatox.2010.03.004