Environmental and Experimental Botany 74 (2011) 140–150 Contents lists available at ScienceDirect Environmental and Experimental Botany j o ur nal homep age : www.elsevier.com/locate/envexpbot Evaluation of the adverse effects of two commonly used fertilizers, DAP and urea, on motility and orientation of the green flagellate Euglena gracilis Azizullah Azizullah a , Adeel Nasir a , Peter Richter a,∗ , Michael Lebert a , Donat-Peter Häder b a Department of Biology, Friedrich-Alexander University, Staudstr. 5, 91058 Erlangen, Germany b Neue Str. 9, 91096 Möhrendorf, Germany a r t i c l e i n f o Article history: Received 20 July 2010 Received in revised form 13 May 2011 Accepted 15 May 2011 Keywords: DAP Urea ECOTOX Euglena gracilis Motility Gravitaxis a b s t r a c t The effect of two commonly used fertilizers, DAP (diammonium phosphate) and urea was studied on the freshwater flagellate Euglena gracilis using the automatic biotest ECOTOX. NOEC and EC 50 values for various parameters like motility, velocity, cell shape and gravitaxis were calculated. The NOEC and EC 50 values obtained for DAP were much lower than those for urea; i.e. DAP showed a stronger inhibitory effect as compared to urea. The inhibition caused by DAP increased with increasing exposure time over 24 h but urea showed no augmentation with increasing exposure time. Application of DAP resulted in an increased pH and high concentrations of ammonia but urea did neither affect the pH nor affect the ammonia concentration. Recovery experiments in deionized water after urea application showed a reconstitution of motility after 72 h. After an application of 1.35 g L -1 (24 h EC 50 for motility) DAP motility recovered after 72 h but motility did not recover when the concentration was doubled (2.7 g L -1 ). The EC 50 values obtained were compared with the EC 50 /LC 50 values reported for other aquatic organisms and were found to be comparable with the reported values. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Due to the increasing need for food for the fast growing human population, the use of agricultural chemicals has become and will continue to be an integral part of modern agriculture. These chem- icals include fertilizers, insecticides, herbicides, and fungicides (Despommier, 2009). In the last decades, agricultural chemicals use has not only been significantly intensified but there are wide spread mismanagement and injudicious uses (Zia et al., 2008). In developing countries the farmers usually apply excessive quanti- ties of agrochemicals, especially fertilizer, in the erroneous belief that applying more agrochemicals will result in higher productivity of the crop (Dung et al., 2000). Under this scenario, where a sub- stantial amount of these substances reaches the soil and air, has led to contamination and pollution of the natural resources. From the soil, these agrochemicals are continuously leaching and precipitat- ing into the water bodies. At different trophic levels of the aquatic ecosystem significant effects caused by agrochemicals have been recognized (Anonymous, 2003a). The problem of environmental contamination by the excessive use of organic fertilizers cannot be neglected (Palanivelu et al., 2005). Although fertilizers are biodegradable their pollution poten- ∗ Corresponding author. Tel.: +49 9131 8528222; fax: +49 9131 8528215. E-mail address: prichter@biologie.uni-erlangen.de (P. Richter). tial is enhanced due to their very slow rate of degradation (Chouhan and Pandey, 1987). Some chemical fertilizers contain substances like heavy metals, inorganic acids and organic pollutants as by- components, which are toxic to living organisms. The long-term application of such chemical fertilizers can possibly lead to the accumulation of these toxic chemicals in the soil (Li and Wu, 2008). Eventually the substances can leach into rivers and lakes affect- ing aquatic ecological environments. The extensive use of mineral fertilizers in modern agriculture can pollute nearby aquatic bod- ies which may affect fish populations (Palanivelu et al., 2005). The toxicity of the intermediate products of nitrogenous fertilizers to many species of fish has been reported (Palanichamy et al., 1985; Rani et al., 1997). Worldwide increases in the use of nitrogen fertil- izers in recent decades are well documented (Galloway et al., 1995, 2003; Howarth et al., 2000; Smil, 2001), and there are enough evi- dences of harmful effects of these increases on aquatic and forest ecosystems (Howarth et al., 2002; Nosengo, 2003). Urea ((NH 2 ) 2 CO) is the most commonly used nitrogen fertilizer and its consumption is increasing steadily. In the last four decades, there has been a 100-fold increase in the use of urea as a nitrogen fertilizer and feed additive in the world, with a doubling in just the past decade alone (Glibert et al., 2006). Although there is a common assumption that urea fertilizer is retained in soils, there is grow- ing evidence of urea transport to sensitive coastal waters (Glibert et al., 2006). DAP (diammonium phosphate, (NH 4 ) 2 HPO 4 ) a source of phosphate and nitrogen, is considered as the most widely used 0098-8472/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.envexpbot.2011.05.011