T3 AM Ecological Risk Assessment (Part 2)
Tuesday, 15 November 2005: 8:00 AM - 11:40 AM in Ballroom 3

(BAR-1117-840329) Assessing the impact of a herbicide on the ecological function of a rice paddy.

Barrett, K¹, Jenkins, W¹, Johnson, Ian¹, ¹ Huntingdon Life Sciences, Huntingdon, Cambridgeshire, UK

ABSTRACT- In Europe, over 3.2 million tons of rice is produced annually from a cultivated area of 600,000 hectares. In the hot summer months, the populations of plants and animals that develop in the transient aquatic environment of the rice paddy provide a food source for many species of mammals and birds that inhabit these wetlands. The EC Guidance document Sanco/1090/2000 on the risk assessment of active substance used on rice, places some importance on the protection of the ecological function of these environments. We have assessed the impact of a herbicide on ecological function by determining the biodiversity of zooplankton, nekton and benthic invertebrates in rice paddies in Spain and Italy in plots established for field dissipation and plant residue assessment. Zooplankton communities in control and treated plots both contained rotifers and pollution-sensitive micro-crustaceans (Daphnids, copepod nauplii); Shannon-Weiner diversity indices of each were essentially similar (1.447 and 1.142 respectively). Nekton diversity was highest in plots in recently established rice paddies in Italy and that of the benthos, where Oligochaetes and Pulmonate snails predominated, in plots situated in long established rice paddies in Spain. Although differences in the composition of the Oligochaete population were observed, Shannon-Weiner indices in three sets of control and treated plots (two in Spain, one in Italy) were similar (overall range 1.253 to 2.022). We concluded that the presence of sensitive invertebrates in control and treated plots and the similarity of their diversity indices, indicated that herbicide treatment had little impact on the ecological function of the paddy.

Key words: rice, paddy, herbicide, ecological function