Hot loud ocean: temperature drives acoustic output by a dominant biological sound-producer

The acoustic environment, or soundscape, is fundamental to marine ecosystems, providing rich sensory information to inhabitants, enabling many ecological processes, and reflecting the biodiversity and health of habitats. Increasing anthropogenic noise can affect taxa and habitats, yet little is known about how ambient soundscapes are altered by environmental changes. Snapping shrimp among loudest marine organisms, creating a pervasive broadband crackling in temperate and tropical coastal seas. Using field data and lab experiments, we show that water temperature can profoundly affect snapping shrimp sound production. Measured rates of snapping activity in multi-year monitoring field recordings from the Caribbean and temperate Atlantic (areas of lower and greater temperature fluctuations) found that snap production rates and associated broadband sound pressure levels were closely positively correlated to water temperature. Snap rates changed by 15-60% per ºC, accompanied by changes in sound level between 1-2 dB per ºC. Lab experiments using snapping shrimp widespread in coastal habitats of the Western Atlantic and Gulf of Mexico (Alpheus heterochaelis and A. angulosus) showed this relationship was due to a direct effect of temperature on snap rates. Snap activity was measured for shrimp held at different temperatures (across 10-30 ºC range) under different social environments (individuals, pairs, and mesocosm-groups). Temperature had a significant effect on snap rates for shrimp under all social contexts tested. For individual and shrimp groups, snap production more than doubled between mid-range (20ºC) and high (30ºC) temperature treatments. The data underscore the value of long-term acoustic monitoring and paired experiments. They suggest greater acoustic activity for a dominant marine soundscape component and louder seas as ocean temperatures increase, an effect that could have ecological implications for a wide range of organisms that utilize sound in the sea.