Anthropogenic sound is increasingly considered a major environmental issue, but its effects are relatively unstudied. Organisms may be directly affected by anthropogenic sound in many ways, including interference with their ability to detect mates, predators, or food, and disturbances that directly affect one organism may in turn have indirect effects on others. Thus, to fully appreciate the net effect of anthropogenic sound it may be important to consider both direct and indirect effects. We report here on a series of experiments to test the hypothesis that anthropogenic sound can generate cascading indirect effects within a community. Specifically, we tested they hypothesis that “rock and roll ain’t noise pollution”, a hypothesis first posited by the band AC/DC. Experiments were conducted with a system of lady beetles, soybean aphids, and soybean plants in plant growth chambers. We used several types of music, as well as a mix of urban sounds (e.g., sirens, vehicles, construction equipment), to evaluate their effect on predation rates in 18-hr feeding trials. Next, we conducted a 14 day experiment to evaluate how sound pollution directly and indirectly affects plant biomass, by altering top-down control of herbivores.
Results/Conclusions
Although lady beetles were effective predators on aphids in control (no sound) treatments, rock music and urban sounds reduced predation rates by as much as 35%. Other types of music, including folk and country, had no effect on predation rates. Similarly, lady beetles in control treatments were effective at controlling aphid population growth rates and had a positive effect on plant biomass after 14 days. In contrast, constant exposure to rock music reduced predation rates and allowed aphid density to increase >10 fold, reducing plant biomass by ~25%. While we found no evidence of a direct effect of sound pollution on plant biomass, our results show that anthropogenic sound can indirectly reduce plant biomass. Although it remains unclear what characteristics of sound inhibited predation rates, our results reject the AC/DC hypothesis and demonstrate that altered interspecific interactions can transmit the indirect effects of anthropogenic sound through a community.