Imazethapyr and imazapic, bispyribac-sodium and penoxsulam: Zooplankton and dissipation in subtropical rice paddy water Geovane B. Reimche a, ⁎, Sérgio L.O. Machado a , Maria Angélica Oliveira b , Renato Zanella c , Valderi Luiz Dressler c , Erico M.M. Flores c , Fábio F. Gonçalves d , Filipe F. Donato c , Matheus A.G. Nunes c a Department of Plant Protection, Federal University of Santa Maria (UFSM), 97105-900 Santa Maria, RS, Brazil b Department of Biology, Federal University of Santa Maria, Santa Maria, RS, Brazil c Department of Chemistry, Federal University of Santa Maria, Santa Maria, RS, Brazil d School of Chemistry and Food, Federal Foundation University of Rio Grande (FURG), 95500-000 Santo Antônio da Patrulha, RS, Brazil HIGHLIGHTS • Selective herbicides in paddy rice fields, do not affect water quality. • Zooplankton communities show good response with herbicide dissipation. • The use of commercial herbicide mixture has strong effects on freshwater Rotifers. abstract article info Article history: Received 21 October 2014 Received in revised form 14 January 2015 Accepted 18 January 2015 Available online xxxx Editor: Daniel A. Wunderlin Keywords: Aquatic ecosystem Freshwater Water quality Herbicides Crustacean Rotifers Herbicides are very effective at eliminating weed and are largely used in rice paddy around the world, playing a fundamental role in maximizing yield. Therefore, considering the flooded environment of rice paddies, it is nec- essary to understand the side effects on non-target species. Field experiment studies were carried out during two rice growing seasons in order to address how the commonly-used herbicides imazethapyr and imazapic, bispyribac-sodium and penoxsulam, used at recommended dosage, affect water quality and the non-target zoo- plankton community using outdoor rice field microcosm set-up. The shortest (4.9 days) and longest (12.2 days) herbicide half-life mean, estimated of the dissipation rate (k) is shown for imazethapyr and bispyribac-sodium, respectively. Some water quality parameters (pH, conductivity, hardness, BOD 5 , boron, potassium, magnesium, phosphorus and chlorides) achieved slightly higher values at the herbicide treatment. Zooplankton community usually quickly recovered from the tested herbicide impact. Generally, herbicides led to an increase of cladocera, copepods and nauplius population, while rotifer population decreased, with recovery at the end of the experi- ment (88 days after herbicide treatment). © 2015 Elsevier B.V. All rights reserved. 1. Introduction The current widespread use of a range of herbicides in agriculture as a means of controlling weed has been contributing to a growing concern with the contaminations of surface and groundwater bodies. Likewise, the use of herbicides must be considered as a potential risk for aquatic life as well as for the quality of drinking water. Once releases into the environment, the behavior of the herbicide has great influence on its soil activity and weed control. Herbicides can be lost by volatilization, photolysis, microbial degradation, chemical degradation, or plant uptake (Goetz et al., 1990). The dissipation rates, persistence and environmental fate of the herbicide are subject to in- trinsic herbicide physicochemical properties such as vapor pressure, water solubility, octanol–water (K ow ) and organic carbon (K oc ) partition coefficients. Furthermore, dissipation is affetcted by many abiotic fac- tors such as water temperature, pH, organic contents like dissolved or- ganic matter (Goetz et al., 1990), inorganic contents like the presence of reduced sulfur species (Zeng et al., 2011, 2012) and even human ac- tivities as agricultural practices (Damalas and Eleftherohorinos, 2011). However, risk assessment of chemicals is still based on the effects on individuals and data are often generated only through single species toxicity tests (EU, 1997). Therefore, it is difficult to extrapolate the ef- fects resulting from single species laboratory studies to the effects on natural ecosystems (Wendt-Rasch et al., 2003). Nevertheless, most lab- oratory experiments (and some mesocosm experiments) are ‘renewed’ experiments that keep up a constant pesticide concentration. We thus Science of the Total Environment 514 (2015) 68–76 ⁎ Corresponding author at: Department of Plant Protection, Federal University of Santa Maria, 97105-900 Santa Maria, RS, Brazil. E-mail address: geovane_reimche@yahoo.com.br (G.B. Reimche). http://dx.doi.org/10.1016/j.scitotenv.2015.01.055 0048-9697/© 2015 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv