An unmanned surface vehicle (USV) produced by AutoNaut has played its part in a subsea noise monitoring project off the Belgian coast, intended to raise awareness of the the detrimental effects of underwater radiated noise on sea creatures. The USV, Adhemar, was used by The Flanders Marine Institute (VLIZ) to record noise levels in Ostend-Bredene, the Belgian section of the North Sea, in April and May.
As such, VLIZ took advantage of the COVID-19 lockdown – a period in which there was a "15% decrease in shipping intensity", AutoNaut says – to "build a picture of the marine soundscape in conditions that may never again be possible".
Adhemar measures approximately 5m x 0.5m, draws 1m and weighs 250kg. Noise recordings were captured by two hydrophones trailed on an 8m in-water cable with a depth sensor. These recordings "will be compared with the marine soundscape once normal sea traffic and marine activities recommence", AutoNaut explains, adding: "This will help to determine the impact of man-made noise on natural sea life and the marine environment." The recordings also include sounds made by fish, invertebrates and other sea creatures.
"Under normal circumstances, human interventions, such as noise from shipping and pile driving, can affect the soundscape of the coastal waters and North Sea, impacting on marine animals," says AutoNaut. This can lead to some animals sustaining hearing damage, and can cause disruption to their usual breeding habits. "Sound is carried more than four times further in water than in the air, which is precisely why many marine animals use sound to communicate, determine their position and search for prey," the company says.
The VLIZ mission was supported by the Flemish agency for Maritime Services and Coast (MDK) and the Federal Public Service for Mobility and Transport, and its findings are expected to be released in autumn.