N° 7 2021 
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„hysical and Physiological Effects 
Relative Distance from the Sound Source Location 
Figure 2. Potential effects of noise at different distances from a sound source (based on Richardson et al., (1995) and adapted from Hawkins & 
Popper (2016)) where TTS = Temporary Threshold Shift and PTS = Permanent Threshold Shift. For further explanation see Chapter 3 
in this Future Science Brief, we follow the risk-based approach 
(Figure 1) and the ’zone of noise influence’ model (Figure 2). In 
Chapter 2, we outline the advances in knowledge of anthropogenic 
underwater sound in the Ocean (sources, distribution, propagation 
and trends) corresponding to risk identification (step 1 of the 
risk-based approach) and exposure assessment (step 2). In 
Chapter 3 we then review the advances in knowledge of the 
effects of noise on marine organisms, following the definitions 
in Figure 2, including examples of state-of-the-art projects 
and «corresponding to dose-response assessment (step 3). 
This is followed in Chapter 4 by a summary of what is being done 
to address the issue of underwater noise, particularly in a European 
context, providing examples of successful initiatives. This Chapter 
corresponds to risk management (step 4). Chapter 5 reflects on the 
current key knowledge gaps, barriers and actions needed for the 
proportionate management of underwater noise. Concluding this 
Future Science Brief is a list of the key priority actions/projects that 
could be conducted to address the identified knowledge gaps and 
barriers (Chapter 6). 
Flora and fauna (includina brown alaae, different species of seabream} off the coast of the Cabo de Gata-Niiar Natural Park, Spain.