Exposure to a common antidepressant alters crayfish behavior and has potential subsequent ecosystem impacts

Pharmaceuticals are ubiquitous in aquatic environments, yet little is known regarding their impacts on ecological processes. Selective serotonin reuptake inhibitors (SSRIs) are frequently prescribed human antidepressants and have been shown to alter crayfish behavior. These behavioral alterations are particularly relevant as crayfish play a central role in freshwater ecosystems and often reach high biomass in anthropogenically influenced environments commonly exposed to pharmaceutical contamination. Using a 14‐d artificial stream experiment, we exposed spinycheek crayfish (Faxonius limosus) to citalopram, a common SSRI, at an environmentally realistic concentration (0.5 µg/L). We used a Y‐shaped flume to quantify the effects of SSRI exposure on crayfish behavior and food/conspecific preference. We also tested the interacting effects of citalopram and crayfish on habitat‐specific and whole‐stream ecosystem functions and biomass. Crayfish exposed to SSRIs exhibited increased boldness (time to emerge from shelters; P