Aquatic Toxicology 167 (2015) 20–30 Contents lists available at ScienceDirect Aquatic Toxicology j o ur na l ho me pag e: www.elsevier.com/locate/aquatox Choice of experimental venue matters in ecotoxicology studies: Comparison of a laboratory-based and an outdoor mesocosm experiment Zsanett Mikó a,∗ , János Ujszegi a , Zoltán Gál a , Zoltán Imrei b , Attila Hettyey a a Lendület Evolutionary Ecology Research Group, Plant Protection Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Herman Ottó út 15, Budapest 1022, Hungary b Applied Chemical Ecology Department, Plant Protection Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Herman Ottó út 15, Budapest 1022, Hungary a r t i c l e i n f o Article history: Received 30 January 2015 Received in revised form 16 June 2015 Accepted 24 July 2015 Available online 29 July 2015 Keywords: Experimental venue Herbicide Life-history trait Multiple stressors Predator Rana dalmatina tadpole a b s t r a c t The heavy application of pesticides and its potential effects on natural communities has attracted increasing attention to inadvertent impacts of these chemicals. Toxicologists conventionally use laboratory-based tests to assess lethal concentrations of pesticides. However, these tests often do not take into account indirect, interactive and long-term effects, and tend to ignore different rates of disinte- gration in the laboratory and under natural conditions. Our aim was to investigate the importance of the experimental venue for ecotoxicology tests. We reared tadpoles of the agile frog (Rana dalmatina) in the laboratory and in outdoor mesocosms and exposed them to three initial concentrations of a glyphosate- based herbicide (0, 2 and 6.5 mg a.e./l glyphosate), and to the presence or absence of caged predators (dragonfly larvae). The type of experimental venue had a large effect on the outcome: The herbicide was less lethal to tadpoles reared in outdoor mesocosms than in the laboratory. Further, while the herbicide had a negative effect on development time and on body mass in the laboratory, tadpoles exposed to the herbicide in mesocosms were larger at metamorphosis and developed faster in comparison to those reared in the absence of the herbicide. The effect of the herbicide on morphological traits of tadpoles also differed between the two venues. Finally, in the presence of the herbicide, tadpoles tended to be more active and to stay closer to the bottom of laboratory containers, while tadpole behaviour shifted in the opposite direction in outdoor mesocosms. Our results demonstrate major discrepancies between results of a classic laboratory-based ecotoxicity test and outcomes of an experiment performed in out- door mesocosms. Consequently, the use of standard laboratory tests may have to be reconsidered and their benefits carefully weighed against the difficulties of performing experiments under more natural conditions. Tests validating experimentally estimated impacts of herbicides under natural conditions and studies identifying key factors determining the applicability of experimental results are urgently needed. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Biodiversity is declining worldwide at an accelerating rate, so that identifying the complex causes of species extinctions has become one of the greatest challenges in ecology (May, 2010; Pereira et al., 2010). The major causes of these declines are habi- tat loss and fragmentation, but further causes have been put forward recently, including climate change, increasing UV-B radi- ation, invasive or spreading predators, competitors and parasites, ∗ Corresponding author. Fax: +36 13918653. E-mail address: miko.zsanett@agrar.mta.hu (Z. Mikó). emerging diseases and the heavy use of pesticides (e.g., Blaustein and Kiesecker, 2002; Clausen and York, 2008; Clavero et al., 2009; Dirzo and Raven, 2003; Hayes et al., 2010; Hof et al., 2011). The application of pesticides is an effective way of improving productivity in agriculture and the advantages of pesticide use are well documented (Jones et al., 2010). However, pesticides can affect physiology and decrease reproductive success, disrupt endocrine functions and have immunotoxic effects not only in pests, but also in non-target organisms as well (Albers, 2003; Colborn et al., 1996; O’shea and Tanabe, 2003; Ratcliffe, 1967). Hence, pesticides and their residues can negatively impact persistence of species and, ultimately, biodiversity (Sotherton and Holland, 2003). What adds to the problem is that many users do not have sufficient http://dx.doi.org/10.1016/j.aquatox.2015.07.014 0166-445X/© 2015 Elsevier B.V. All rights reserved.