Effects of the neonicotinoid insecticide imidacloprid on fish and its implications in ecological risk assessment.

MENONE MIRTA LUJÁN; ITURBURU FERNANDO GASTÓN; AMÉ MARIA VALERIA

Buenos Aires

Conferencia; Colloquium of the Alexander von Humboldt Foundation; 2018

Alexander von Humboldt Foundation

Human activities are able to modify the aquatic environment through removal of biomass and habitats and via the addition of contaminants. In intensively cultivated regions, streams are severely affected by the input of agrochemicals such as pesticides (for example insecticides, herbicides or fungicides) and nutrients. The neonicotinoid insecticide imidacloprid (IMI) is nowadays one of the most sold pesticides worldwide. From 2013, IMI and other two neonicotinoids began to be re- evaluated by the European Union because its toxicity on non- target organisms, mainly pollinators. Moreover, IMI is a hydrophilic compound which could reach by different processes water bodies nearby its application place. Consequently, IMI has been found in lakes and rivers, and its effects on fishes living in these ecosystems are scarcely known. Hence, the objective of this work was to evaluate sublethal toxic effects of IMI on the native freshwater fish Australoheros facetus, studying a) IMI uptake and distribution, b) oxidative stress and c) DNA damage biomarkers. Short- term bioassays were performed (24 and 48 h), with IMI concentrations ranging environmentally relevant concentrations (1, 10 and 100 ug/L) and higher ones (1000 and 2500 ug/L). Imidacloprid bioaccumulation was measured in liver, brain, gills, muscle, gut and blood of A. facetus. Oxidative stress enzymes as well as protein and lipid oxidation products were evaluated in liver, gills and brain of fishes. DNA fragmentation and bases oxidation were evaluated in fish erythrocytes. Imidacloprid was detected in all the tissues tested, and through the calculation of bioconcentration factors it was possible to establish that IMI did not bioaccumulate in liver, gills, gut, muscle, brain or blood. The activity of the enzyme superoxide dismutase decreased in liver, gills and brain after 48 h of exposure to IMI, concomitantly with an increase of the oxidant H2O2 in liver, indicating the oxidative stress process. Nevertheless, oxidative damage did not take place since neither protein nor lipid peroxidation were detected in these tissues. On the other hand, DNA bases oxidation was detected in fish erythrocytes, being possible to establish that an exposure of 1 ug/L of IMI during 48 h triggered this effect on A. facetus. DNA fragmentation occurred with 100 and 1000 ug/L IMI, according with comet assay and micronucleus test. Results obtained draw attention to the need of more studies on the negative environmental effects of neonicotinoids on non- target organisms. Given their ubiquity in aquatic ecosystems, a deeper understanding of neonicotinoid insecticides sublethal effects on fish will allow us to develop a more accurate ecological risk assessment for these compounds.