Listening to the North Sea through a fibre-optic cable
Commissioned by GÉANT Association, researchers from Wageningen Marine Research used Distributed Acoustic Sensing (DAS) technology connected to an existing fibre-optic cable in the North Sea to analyse underwater sound patterns over long distances.
The team detected shipping noise, offshore wind farm activities and a controlled explosion in the North Sea, illustrating the potential of existing telecommunications infrastructure for marine acoustic research.
In collaboration with several international partners, the researchers analysed DAS data from a subsea telecommunications cable running between Zandvoort and Leiston (UK). Acoustic signals along the first 80 kilometres of the cable were recorded during a two-week period.
The results from this study revealed several sources of underwater sound, including busy shipping routes, offshore activities related to wind farms and a controlled explosion previously recorded by KNMI.
SURF, who was a partner in this project, facilitated storage and processing of the large amounts of data (>200 TB) that resulted from this study, and enabled a digital research environment that in future will allow researchers from different fields such as oceanography, seismology, and meteorology to safely analyse the data.
Underwater noise and marine ecosystems
“The shipping signatures were clearly visible in the data, particularly in the low-frequency range known to dominate shipping noise,” says researcher Luca Possenti of Wageningen Marine Research. “We also observed differences between operational wind farms and areas where construction activities are still taking place.”
The study focused on anthropogenic underwater noise: sound generated by human activities. The subject is receiving increasing attention because anthropogenic underwater noise can affect marine ecosystems. Many marine organisms rely on sound for communication, navigation and foraging, and anthropogenic noise is known to have a negative impact on these activities. Long-term and large-scale monitoring of underwater anthropogenic noise may help improve understanding of potential impacts on marine ecosystems.
Complementing existing monitoring methods
Traditional acoustic monitoring is often carried out using hydrophones. According to the researchers, DAS technology is not intended to replace this method, but it may provide a complementary approach for continuous monitoring over large distances. Because the approach makes use of existing telecommunications infrastructure, it may also enable acoustic data to be collected on a larger scale, and over long periods of time.
DAS technology could support broader approaches to monitoring human activity in marine environments and contribute to a better understanding of underwater acoustic pollution.
New research questions
“This study is exploratory, but it demonstrates which new research questions become accessible when existing fibre-optic infrastructure is used for acoustic monitoring,” says Luca Possenti. “In follow-up research, we want to better understand how these techniques can contribute to research into shipping noise, offshore activities and potentially also biological signals in marine environments.”
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