Use of diatom motility features as endpoints of metolachlor toxicity

Modifications de la mobilité des diatomées en réponse à une contamination au métolachlore

N. Coquillé , G. Jan , A. Moreira , Soizic Morin

Many recent ecotoxicological studies suggest a relationship between freshwater contamination andincreasing abundances of motile diatoms (potentially able to move). The capacity to escape would presentadvantages to species in polluted environments. However, actual motility as a response to toxicants hadnot been described and required experimental validation. We designed a specific experiment to assess how a field-isolated diatom (Gomphonema gracile)distributes energy to in situ resistance (increased population growth or photosynthesis) and escape(behavioral changes), when exposed to increasing concentrations of the herbicide metolachlor. We report here the dose-time dependent responses of G. gracile populations. They coped with low con-tamination by resisting in situ, with early hormetic responses highlighted by stimulation of chlorophyll-afluorescence. At a higher dose, harmful impacts were observed on growth after a few days, but an earlierbehavioral response suggested that higher motility (percentage of motile individuals and mean distancecrossed) could be involved in escape.Our findings bring new arguments to support the implementation of real measurements instead ofmotility traits in toxicity assessment. Specifically, motion descriptors have been used as early-warningindicators of contamination in our study. Further works should address the reliability of these endpointsin more complex conditions (interspecific variability, behavior in the field).

Mots clés: DIATOMEE; PESTICIDE; PHYSIOLOGIE; COMPORTEMENT ANIMAL; TOXICITE; CONTAMINATION CHIMIQUE

Domaines: Sciences de l'environnement

N. Coquillé, G. Jan, A. Moreira, Soizic Morin. Use of diatom motility features as endpoints of metolachlor toxicity. Aquatic Toxicology, 2015, 158, pp.202-210. ⟨10.1016/j.aquatox.2014.11.021⟩. ⟨hal-01098297⟩