Gene expression of G. pulex in response to base exposure of multiple stressors
Pesticides are amongst the most important agricultural stressors, inducing stream ecosystem degradation and loss of associated biodiversity. However, assessing the negative effects of pesticides is challenging due to possible interactions with other agricultural stressors such as increased fine sediment load. Further layers of complexity are added when stressors do not affect life-history parameters such as survival or reproduction and hence do not immediately translate in structural alterations of biological communities. In this study, gene expression data was used to quantify the multiple stressor effects of the insecticide chlorantraniliprole and fine sediment exposure on stream macroinvertebrates (here: the amphipod Gammarus pulex). Stressors were applied in a full-factorial design using a mesocosm field experimental setup. The macroinvertebrates were exposed to a pesticide puls for 4 days in three different concentrations, followed by base exposure (i.e. reduced concentration by a factor of 10) for 17 days. After the 3 weeks of stressor exposure, organisms were sampled from the mesocosms and directly preserved in liquid nitrogen. RNA was extracted from 3 pooled individuals per mesocosm. Seven samples failed during RNA extraction, resulting in 57 RNA-seq libraries.