Bow-tie diagram for underwater noise
Bow-tie diagram aligns with the DAPSIR narratives in the Thematic Assessment - provisional confidence assessment: Medium (Medium Agreement on DAPSIR content + Medium Evidence to support connections) based on approach described in Agreement 2019-02
The bow-tie analysis for underwater noise shows the relationships between the DAPSIR components which need to be considered in a cumulative effects assessment. Human activities have been identified which exert either impulsive and / or continuous underwater noise pressures with the potential to both individually and cumulatively contribute to biodiversity state changes in the thematic assessments for:
- Fish - Input of anthropogenic sound (impulsive, continuous): Anthropogenic noise can result in behavioural impacts, physical and/or physiological impacts, masking and death. The behavioural impacts can be displacement and changes in swimming patterns, which can impact their fitness, survival and reproduction success. Masking due to anthropogenic noise makes it difficult to detect biologically important sound, and this can result in reduced survival for fish species. The physical and/or physiological impacts can be temporal threshold shift (TTS) or permanent threshold shift (PTS). (Hawkins & Popper, 2016)
- Marine Mammals - Input of anthropogenic sound (impulsive, continuous): Anthropogenic noise can have behavioural and physiological impacts on marine mammals. The behavioural impacts can be changes in resting, breathing, and diving patterns, vocalizations, changes between spatial relationships and avoidance behaviour. Masking due to anthropogenic noise may interfere with social interaction and communication. The physiological impacts can be temporal threshold shift (TTS) or permanent threshold shift (PTS). In the worst case, underwater noise can lead to injury or even death.
Input levels, frequency of occurrence, spatial extent and exposure to different human activities all collectively contribute to the extent to which underwater noise pressures are exerted on fish and marine mammals. To undertake a full quantitative analysis of cumulative effects requires consideration of the exposure pathways and ecological impacts. The annual risk maps for harbour porpoise (Figure S.4 in the State section) exposure indices (Figure S.5) and the associated narrative provide an indication of cumulative disturbance trends from reported impulsive sound in the North Sea. Further analyses and evidence of ecological impacts are required in order to progress the assessment of cumulative effects.
Underwater noise can also combine with other pressures to collectively affect marine species and habitats. The assessment of cumulative effects is considered within the biodiversity Fish and Marine Mammal Thematic Assessments.
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