Land-based noise pollution impairs reef fish behavior: A case study with a Brazilian carnival

Anthropogenic sounds have spread across the biosphere, with threats from individual welfare to ecosystem health. Sounds are important to animals in both terrestrial and aquatic environments and detrimental effects have been shown across a wide range of taxa. Despite the ever-growing transformation of coastal lands by human activities, pollutant effects of sounds that propagate from land into coastal water (across realms) have been largely overlooked. We here show that the Brazilian carnival of Salvador, annually taking place along a coastal boulevard, elevated underwater sound pressure levels by more than 30 dB re 1 μPa². We used remotely operated cameras to measure individual abundance and feeding activity of the Brazilian damsels (Stegastes fuscus) and we measured its flight-initiation distance to a model predator. Brazilian damsels did not abandon their reef territories, but their feeding activity and fleeing distance were significantly reduced under elevated noise levels, compared to the ambient control conditions at the same site and at a spatial control site. Apparently, carnival sounds emitted from land affected underwater behavior in our reef fish species. The behavioral effects may be critically important for individual fitness, and the detrimental impact of land-based noise pollution in coastal waters may also apply to other fish and invertebrate species. Humanity is claiming coastlines at a faster rate than any other habitat, and conservation concerns should extend to nearby coastal ecosystems and the possible impacts of underwater sounds emanating from land.