Bruno Rossaro 1 Laura Marziali 2 Paolo Cortesi 1 1 Department of Food, Environmental and Nutritional Sciences, Universita ` degli Studi di Milano, Milano, Italy 2 CNR-IRSA, Istituto di Ricerca sulle Acque, Brugherio Monza-Brianza, Italy Research Article The Effects of Tricyclazole Treatment on Aquatic Invertebrates in a Rice Paddy Field The benthic macro-invertebrate community response to tricyclazole treatments in an experimental rice paddy field was analyzed using univariate and multivariate statistical analysis. The observed community presented low species diversity, domi- nated by the gastropods Gyraulus albus and Physa fontinalis, the oligochaetes Branchyura sowerbyi, and the hirudinea Alboglossiphonia heteroclita. No significant effect was detected following tricyclazole treatments, while a moderate shift in community composition was observed during the sampling period, with gastropods prevailing at the end of the experiment. Multivariate classification tree analysis emphasized the importance of sampling date over tricyclazole treatments. The limited period of submersion of the rice paddy field, the low oxygen content and the high water temperatures are supposed to be the reasons of the low community diversity observed. Keywords: Benthic macro-invertebrates; Ecotoxicology; Food; Freshwater; Fungicide Received: April 11, 2012; revised: August 12, 2012; accepted: September 24, 2012 DOI: 10.1002/clen.201200215 1 Introduction Rice paddy fields as man modified ecosystems derived from natural wetlands [1], characterized by periodic floods and droughts can become the ideal habitat for some aquatic invertebrate species. Despite the significant contribution of macroinvertebrates to eco- system equilibrium and biodiversity [2, 3], they have received less attention than birds and amphibians, which are often the focus of attention because of the presence of endangered species [4]. Rice paddy fields are finalized to rice production, therefore crop management is focused to maximize yield, which often includes direct actions aimed at hindering the development of species harmful to rice growth, with unfavorable side effects on non-target aquatic invertebrates. Man-made actions in rice paddies can be categorized into hydraulic, chemical, and biological. Hydraulic actions are the management of water inflow and outflow; chemical actions are the application of herbicides, insecticides, and fungicides to inhibit the growth of competitors and parasites. The introduction or the removal of species potentially useful or harmful to rice growth can be defined as bio-manipulation. This ecosystem management promotes often unforeseen indirect effects, as the abnormal pro- liferation of unwanted species of interest in medical entomology such as mosquitos, and in general determines an unfavorable modi- fication in species composition. Among chemicals employed in rice paddy fields in Italy, the fungicide tricyclazole is widely used to manage rice blast epidemics, determined by the fungus Magnaporthe oryzae [5–7]. At present the information about the side effects of fungicides on benthic macroinvertebrates in rice fields is scant [8–11] and none have considered the effect on aquatic macroinvertebrates of tricyclazole applied in the field. The application of a fungicide could interfere with aquatic macroinvertebrate metabolism, for example it is possible that it interferes with chitin synthesis [12], altering the biological interactions between different components of the community (competitors, predators). The aim of the present research is to estimate the effect of tricyclazole, applied with a different time schedule and concentration, on the community com- position composed of benthic macroinvertebrates in a rice paddy field. 2 Materials and methods The rice paddy field studied is located at Poiago farm in Carpiano (Milan, Italy). The experimental design consisted of five plots, each of 42 m 2 , inside a field with continuous water supply. Each plot was delimited by soil dykes and had independent inlet water supply and no outlet to avoid cross contamination. Plots were sown in dry soil, with Oryza sativa subsp., japonica cv. Sirio, and the crop was submerged at three leaf-tillering phenological stages. Fungicide treatments were randomly assigned to plots. Tricyclazole was applied as commonly used to manage rice blast epidemics, i.e., two treatments at 300 g ha 1 of the commercial fungicide Beam (tricyclazole 75%) and single treatments at 600 and 1200 g ha 1 of Beam (Tab. 1). Fungicide aqueous solutions were sprayed on the crop at 500 L ha 1 with the motorized backpack sprayer Fox F320 and a hand-held 1.5 m boom, operating at 500 kPa. Benthic macroinvertebrates were sampled with a cylindrical core sampler, 7 cm diameter. Four random replicate samples were col- lected within each plot, plots 1 and 5 were used as controls and were Correspondence: Professor B. Rossaro, Department of Food, Environmental and Nutritional Sciences, Universita ` degli Studi di Milano, via Celoria, 2, I-20133 Milano, Italy E-mail: bruno.rossaro@unimi.it 1 ß 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.clean-journal.com Clean – Soil, Air, Water 2013, 00 (0), 1–7