Phenanthrene pollution disrupts behavioural individuality and plasticity in the brine shrimp Artemia franciscana

Chemical contaminants are polluting ecosystems around the world and are a growing threat to wildlife. Among the chemical contaminants of concern, polycyclic aromatic hydrocarbons (PAHs) are some of the most common compounds found in coastal waters. Studies have determined the negative effects of PAHs on wildlife, including the alteration of important behaviours of animals. However, whether the effects of such global pollutants impact the individual-level variation in ecologically relevant behaviours of wildlife remains unknown. This is surprising, since individual variation in behaviour has profound ecological and evolutionary consequences, and is essential for populations to survive in a fast-changing world. To fill this gap, we tested the effects of phenanthrene, one of the most abundant PAHs in aquatic environments worldwide, on ecologically relevant behaviours of wild-caught brine shrimps, Artemia franciscana . We exposed individuals to environmentally realistic concentrations of phenanthrene (16 μg/litre and 400 ng/litre) soon after birth until adulthood and repeatedly assayed their activity (distance moved) and risk taking (time spent at the water surface). To better understand the effects of phenanthrene at the individual level, if any, we partitioned the behavioural variance between and within individuals. Our results show that exposure to phenanthrene eroded differences between individuals (behavioural individuality) in activity and within individuals (behavioural plasticity) in risk taking but did not alter mean behaviours. Our evidence indicates that the consequences of living in polluted environments might be more severe than was previously known, since the effects of phenanthrene span beyond mean behavioural changes and compromise both behavioural individuality and plasticity of exposed animals. • Pollution by polycyclic aromatic hydrocarbons (PAHs) threatens wildlife globally. • It is unknown if PAHs alter behavioural individuality and plasticity in animals. • We tested whether phenanthrene impairs behavioural variation in Artemia. • Lifetime exposure shrank individuality in activity and plasticity in risk taking. • Phenanthrene can have ecological and evolutionary consequences for wildlife.