Title : Multi-scale responses of freshwater communities to anthropogenic noise with a focus on invasive species
PhD awarded in Nov 28, 2022
Advisor: Vincent Médoc, HDR, PhD.
Key words: anthropogenic noise, freshwater, feeding strategies, invasives species, planktonic communities
There are few natural soundscapes that are free of sounds associated with human activities. These anthropogenic sounds are now recognized as a source of pollution with effects on the anatomy, physiology or, more often, the behavior of exposed organisms, which can lead to a decrease in their selective value. However, while individual responses are well described, the effects on biodiversity and ecosystem functioning are still unknown. Also, ecosystems are unevenly documented and compared to terrestrial and marine environments, noise pollution in freshwater environments is only marginally studied and is not yet subject to any legislation. This thesis is a multi-scale project (temporal, spatial and biological) on the effect of anthropogenic noise on trophic (feeding relationships between individuals in the same ecosystem) and non-trophic relationships in freshwater. The aim was to study the direct effects via behavioral alterations during feeding, and indirectly via top-down forcing exerted by the fish population and noise pollution on the dynamics of planktonic communities. A widespread response was observed during short-term (min) exposure to noise with a distraction effect observed in fish accompanied by a decrease in feeding (sun perch, pseudorasbora parva, roach), except for the round goby, an increasingly common invasive freshwater species where an increase in feeding performance was observed. However, in the long term (weeks) individual responses did not ultimately predict feeding consequences given its recovery (habituation process, tolerance). We also found that interspecific interaction (interaction with conspecifics) had a stronger effect that it modulates and modifies the individual response. At the food web scale, long-term exposure also revealed that lower trophic levels (zooplanktonic communities) were affected by noise with respect to modification of community composition. This thesis is the first study to combine laboratory and large-scale responses to understand the overall community response to stress induced by anthropogenic pollution in freshwater.