Monday August 22, 2022
Geographical —
The underwater world of a pond is a noisy place filled with strange whines, pops and chirps. These are sounds that few people have heard because, until fairly recently, nobody was listening.
Ecoacoustics is an emerging field that combines acoustics and ecology. It can be used to assess and monitor the biodiversity of an ecosystem by studying its soundscape. To date, most ecoacoustic research has focused on marine and terrestrial ecosystems, but Jack Greenhalgh, a freshwater ecology researcher at the University of Bristol, specialises in recording the surprisingly vibrant soundscapes of ponds.
Alongside the stridulations of aquatic insects, his recordings are packed with the low-frequency thrums made by fish, which produce the sounds by pulsating a drumming muscle that sits above their swim bladder, and the fizz of gas bubbles rising up from aquatic plants as they photosynthesise under the midday sun.
One particular type of creature interests Greenhalgh most of all. ‘I’ve been trying to record the sounds of crayfish so that I can try to attribute the sounds that I might be hearing in the soundscape to individual species – specifically the white-clawed crayfish and the signal crayfish,’ he says. The signal crayfish is an invasive US species that was introduced to the UK during the 1970s to be farmed for food. Since then, its numbers have exploded.