Chronic noise unexpectedly increases fitness of a freshwater zooplankton

Abstract

AbstractAlthough there is an increasing interest in the effects of anthropogenic noise on animals, aquatic studies mainly focus on organisms with hearing systems (marine mammals, fish, great arthropods) while many others of substantial ecological importance are not considered. Here we show that the water fleaDaphnia magna, a widespread zooplankton species serving as food source for higher trophic levels, could be affected by noise pollution in a way that we did not expect. We found that isolated individuals exposed to a continuous broadband sound have a higher survival and fecundity, thus a higher fitness. We also found that they are slower than individuals not exposed to additional noise. It could be that the energy saved from reduced mobility is reallocated to fitness. In natural systems, this reduced velocity should result in a more negative outcome forDaphnia’s fitness due to competition and predation. Our result highlights that, despite the absence of a known hearing system, a small crustacean can be affected by noise. Consequently, anthropogenic noise can not only affect communities through top-down cascading effects, when it changes the behaviour of top-predators like fish, but also via bottom-up effects with alterations in zooplankton.