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Evaluation of river model biofilm for assessing pesticide effects: a case study with atrazine

“…For the ecological risk assessment of pesticides on river biofilms, it is necessary to consider the variability of natural river biofilms because several factors, such as the microbial composition and developmental stage of natural river biofilms and their different sensitivity to pesticides, and environmental conditions of river water, are expected to affect toxicity. In the above studies of Guasch et al, [13][14][15][16] the largest difference in the EC 50 values of atrazine for natural river biofilms was about 20 times. Based on the data, the safety factor for ecological risk assessment might be tentatively set at 20 considering the variability among natural river biofilms, but more data from other pesticides and river biofilms are necessary to obtain a more reasonable value.…”

“…Additional experiments with a wider range of concentration are necessary to obtain more reliable results and other endpoints such as the no observed effect concentration (NOEC). Guasch et al [13][14][15][16] examined the toxicity of atrazine on the photosynthetic activity of river biofilm which formed on a glass slide set in European rivers. The EC 50 values obtained in these studies ranged with almost even distribution from 41 to 716 ppb (nϭ67) depending on the river, season, stage of biofilm development, and light intensity during exposure.…”

“…There have been reports on the pesticide effects on a river biofilm formed on stones or artificial substances set in a river or in a laboratory experimental system [7][8][9] ; however, it would be difficult to evaluate the effects of pesticides on natural biofilms due to the poor reproducibility of biofilm settlement in which biological parameters such as biomass, activity and community structure vary among season and sites, 10,11) and are affected by environmental conditions. 12) Additionally, it has been reported that environmental conditions influence the effects of pesticides on river biofilm [13][14][15][16][17] ; therefore, a test system with high reproducibility and reliable endpoints should be established to determine the toxicity of pesticides on natural river biofilms. In our previous study, 18) we constructed a model biofilm consisting of known microorganisms (two diatom and three bacterial strains) on the inside surface of a glass test tube continuously rotated under a light-dark regime under controlled conditions to assess the pesticide effects on biofilm formation.…”

Impact of diuron and S-metolachlor on the freshwater diatom Gomphonema gracile: Complementarity between fatty acid profiles and different kinds of ecotoxicological impact-endpoints

“…(w/w) of terbuthylazine (TBA) and 30.2% (w/w) of S-metolachlor; 2) the applied concentration was 10 µg.L -1 , a much lower concentration compared to other studies enabling the defense mechanisms to be efficient. For example, Robert et al (2007) studied the impact of metolachlor but the concentrations applied were 5.7; 7.09 and 8.5 mg.L -1 ; 3) the high concentrations of nutrients provided by the Dauta medium may have stimulated diatoms metabolism and masked, at least partially, pesticide toxicity (Guasch et al 1998, Guasch et al 2004); 4) the species G. gracile is less sensitive than those used in the previous studies. Wood et al (2016) showed that the mode of action of herbicide did not change the most sensitive benthic diatom response used in their study, except for G. gracile.…”