Urban stressors: Interactive effects of noise, light regime and fluoxetine on zebrafish behavior

Chemical, noise and light pollution are pervasive anthropogenic stressors. These stressors have been investigated individually; however, to our knowledge no one has investigated interactions between the three or their impacts on fish. The current study investigated the effects of chronic exposure to a common environmental pollutant, fluoxetine (3 and 300 ng/L), light pollution (artificial light at night), and acute environmental noise (motorboat engine) on the behavioral responses of zebrafish (Danio rerio). The effects of these treatments on zebrafish boldness, anxiety, time to feed, habitat preference in the presence of a visual predation cue (bird), and shoaling behavior in the presence of a conspecific alarm chemical and a visual predation cue were measured. Fluoxetine alone decreased zebrafish boldness, although effects were dose-, sex-, and noise-order-dependent. Zebrafish exposed to artificial light at night showed higher activity levels and were bolder than fish that were raised in an environment with a normal 12 h light-12 h dark photoperiod. Noise exposure often resulted in increased activity. However, we also observed interactions between the three factors. In several experiments, fluoxetine suppressed the effects artificial light at night, suggesting an antagonistic interaction. Fluoxetine also reduced behavioral responses to sudden noise in several experiments. The visual predation cue caused significant reductions in activity, but all three factors affected responses to predation, leading to behaviors that may increase zebrafish vulnerability. The order in which fish were exposed to noise pollution was also important. Fish that were tested with noise first often reacted more strongly than those that were initially tested without noise, suggesting that noise increased the stress of adaption to a new environment. Environmental stressors often co-exist in the real world and the limited number of studies in this area underscores the need for more comprehensive research.