A decade of underwater noise research in support of the European Marine Strategy Framework Directive

Numerical investigation of shipping noise in the Red Sea

Underwater noise pollution is a significant environmental issue that can have detrimental effects on marine ecosystems. One of the main sources of underwater noise pollution is ship traffic, which has been shown to negatively impact marine animals by masking communication signals and altering their behaviors. This study represents the first comprehensive analysis of underwater ship noise in the Red Sea, wherein noise maps of ships sailing through the main shipping lane in the Red Sea were simulated by integrating both anthropogenic and environmental variables. These maps offer valuable insights for policymakers, enabling them to make informed decisions and implement targeted mitigation efforts.

First basin scale spatial-temporal characterization of underwater sound in the Mediterranean Sea

Anthropogenic underwater noise is an emergent pollutant. Despite several worldwide monitoring programs, only few data are available for the Mediterranean Sea, one of the global biodiversity hotspots. The results of the first continuous acoustic programme run at a transnational basin scale in the Mediterranean Sea are here presented. Recordings were done from March 2020 to June 2021, including the COVID-19 lockdown, at nine stations in the Northern Adriatic Sea. Spatial-temporal variations of the underwater sound are described, having one third octave band sound pressure levels (SPLs) from 10 Hz to 20 kHz as metrics. Higher and more variable SPLs, mainly related to vessel traffic, were found close to harbours, whereas Natura 2000 stations experienced lower SPLs. Lower values were recorded during the lockdown in five stations. Median yearly SPLs ranged between 64 and 95 as well as 70 and 100 dB re 1 µPa for 63 and 125 Hz bands, respectively. These values are comparable with those previously found in busy shallow EU basins but higher levels are expected during a business-as-usual period. This is a baseline assessment for a highly impacted and environmental valuable area, that needs to be managed in a new sustainable blue growth strategy.

Sound and sturgeon: Bioacoustics and anthropogenic sounda)

Sturgeons are basal bony fishes, most species of which are considered threatened and/or endangered. Like all fishes, sturgeons use hearing to learn about their environment and perhaps communicate with conspecifics, as in mating. Thus, anything that impacts the ability of sturgeon to hear biologically important sounds could impact fitness and survival of individuals and populations. There is growing concern that the sounds produced by human activities (anthropogenic sound), such as from shipping, commercial barge navigation on rivers, offshore windfarms, and oil and gas exploration, could impact hearing by aquatic organisms. Thus, it is critical to understand how sturgeon hear, what they hear, and how they use sound. Such data are needed to set regulatory criteria for anthropogenic sound to protect these animals. However, very little is known about sturgeon behavioral responses to sound and their use of sound. To help understand the issues related to sturgeon and anthropogenic sound, this review first examines what is known about sturgeon bioacoustics. It then considers the potential effects of anthropogenic sound on sturgeon and, finally identifies areas of research that could substantially improve knowledge of sturgeon bioacoustics and effects of anthropogenic sound. Filling these gaps will help regulators establish appropriate protection for sturgeon.

Small reductions in cargo vessel speed substantially reduce noise impacts to marine mammals

Global reductions in the underwater radiated noise levels from cargo vessels are needed to reduce increasing cumulative impacts to marine wildlife. We use a vessel exposure simulation model to examine how reducing vessel source levels through slowdowns and technological modifications can lessen impacts on marine mammals. We show that the area exposed to ship noise reduces markedly with moderate source-level reductions that can be readily achieved with small reductions in speed. Moreover, slowdowns reduce all impacts to marine mammals despite the longer time that a slower vessel takes to pass an animal. We conclude that cumulative noise impacts from the global fleet can be reduced immediately by slowdowns. This solution requires no modification to ships and is scalable from local speed reductions in sensitive areas to ocean basins. Speed reductions can be supplemented by routing vessels away from critical habitats and by technological modifications to reduce vessel noise.

Addressing underwater noise: Joint efforts and progress on its global governance

Underwater noise generated by human activities has become a major reason of concern over the past decades as human exploitation of world seas became more intense. A key to reduce human-generated acoustic pressure on aquatic ecosystems depends on an approach based on international cooperation. Over the past years, scientists worldwide worked together to assess trends in underwater noise levels in order to develop mitigation measures that would allow the effective protection of endangered species without reducing the possibilities for a sustainable use of seas. This review focused on international programmes dedicated to underwater noise monitoring, mapping and to programs dedicated to mitigate noise and its effects on marine fauna. All together this review shows the existence of a growing, general, international consensus on the fact that anthropogenic underwater noise should be significantly reduced by setting appropriate mitigation measures and effective regulatory actions.