An anthropogenic cacophony: Sound travels faster and farther in water than in air. Over evolutionary time, many marine organisms have come to rely on sound production, transmission, and reception for key aspects of their lives. These important behaviors are threatened by an increasing cacophony in the marine environment as human-produced sounds have become louder and more prevalent. Duarte et al. review the importance of biologically produced sounds and the ways in which anthropogenically produced sounds are affecting the marine soundscape. Science , this issue p. eaba4658

There is increasing concern that ocean acidification, caused by the uptake of additional CO ₂ at the ocean surface, could affect the functioning of marine ecosystems; however, the mechanisms by which population declines will occur have not been identified, especially for noncalcifying species such as fishes. Here, we use a combination of laboratory and field-based experiments to show that levels of dissolved CO ₂ predicted to occur in the ocean this century alter the behavior of larval fish and dramatically decrease their survival during recruitment to adult populations. Altered behavior of larvae was detected at 700 ppm CO ₂ , with many individuals becoming attracted to the smell of predators. At 850 ppm CO ₂ , the ability to sense predators was completely impaired. Larvae exposed to elevated CO ₂ were more active and exhibited riskier behavior in natural coral-reef habitat. As a result, they had 5–9 times higher mortality from predation than current-day controls, with mortality increasing with CO ₂ concentration. Our results show that additional CO ₂ absorbed into the ocean will reduce recruitment success and have far-reaching consequences for the sustainability of fish populations.

Noise-generating human activities affect hearing, communication and movement in terrestrial and aquatic animals, but direct evidence for impacts on survival is rare. We examined effects of motorboat noise on post-settlement survival and physiology of a prey fish species and its performance when exposed to predators. Both playback of motorboat noise and direct disturbance by motorboats elevated metabolic rate in Ambon damselfish (Pomacentrus amboinensis), which when stressed by motorboat noise responded less often and less rapidly to simulated predatory strikes. Prey were captured more readily by their natural predator (dusky dottyback, Pseudochromis fuscus) during exposure to motorboat noise compared with ambient conditions, and more than twice as many prey were consumed by the predator in field experiments when motorboats were passing. Our study suggests that a common source of noise in the marine environment has the potential to impact fish demography, highlighting the need to include anthropogenic noise in management plans.