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Monitoring ocean life through underwater soundscapes

Using hydrophones to “eavesdrop” on a reef off the coast of Goa, India, a team of scientists led by the National Institute of Oceanography (NIO) in Goa has recently recorded the duration and timing of mating and feeding sounds produced by 21 marine species. The recordings revealed that, while some species were early risers, making sounds from 3am onwards, others were more active later in the day, starting to create a ruckus from around 2pm. 

Better understanding underwater soundscapes could shed new light on the behaviors of a variety of marine creatures, as well as on the impact human activities have on ocean life, including the effects of anthropogenic climate change on aquatic ecosystems.

“Acoustic monitoring of underwater environments will enable us to know more about the climate and its related long-term changes in the physical and biological condition of the underwater environment,” said co-author Bishwajit Chakraborty, a former chief scientist at NIO. “For example, as coral reefs are the hub of underwater biodiversity, conducting acoustic studies here is extremely essential to know the state and health of the reef and its inhabitants.”

This study – published in the Journal of the Acoustical Society of America – will contribute to a larger project aiming to create a Global Library of Underwater Biological Sounds (GLUBS). This project represents a major legacy of the decade-long International Quiet Ocean Experiment (IQOE), a scientific program running until 2025 and promoting research, observations, and modelling to improve our understanding of ocean soundscapes and the effects of sound on marine species.

GLUBS will be designed as an open-access online platform aiming to collect global information about underwater soundscapes in order to broaden and standardize scientific and community knowledge of these phenomena. Among its many applications, this platform will help improve scientists’ ability to detect in hard-to-access underwater environment how the distribution and behavior of marine life responds to various pressures, such as climate change, fishing, resource development, plastic pollution, or anthropogenic noise.

“Passive acoustic monitoring (PAM) is an effective technique for sampling aquatic systems that is particularly useful in deep, dark, turbid, and rapidly changing or remote locations,” explained GLUBS leader Miles Parsons.

According to Parsons and his colleagues, GLUBS will not only create and maintain a database of all aquatic species confirmed or anticipated to produce sounds, but also help reveal currently unknown species and contribute to their eventual identification and classification.

“Unidentified sounds can provide valuable information on the richness of the soundscape, the acoustic communities that contribute to it, and behavioral interactions among acoustic groups. However, unknown, cryptic, and rare sounds are rarely target signals for research and monitoring projects and are, therefore, largely unreported,” Parsons said.

In addition, GLUBS will also help delineate essential fish habitats, estimate the biomass of spawning aggregations of commercially or recreationally important soniferous species, help evaluate the degradation and recovery of coral reefs, and identify the possible impact of oil and gas, wind power, and other offshore industries on marine ecosystems.

“We need to listen more in the blue symphony halls. Animal sounds are behavior, and we need to record and understand the sounds, if we want to know the status of ocean life,” concluded Jesse Ausubel, an environmental scientist at the Rockefeller University and one of IQOE’s originators.


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