Soundscape Ecology

The acoustic signature of an environment is called soundscapes. According to Krause (1987), the soundscape is the result of three major sources of sound: i) geophonies (sounds produced by natural agents like wind, rain, water flow, or volcanoes); ii) biophonies (sounds represented by organismic calls, alarms and songs produced by specific organs, such as the syrinx in birds, vocal folds in terrestrial mammals, and stridulating organs in insects); iii) anthropophonies (the result of human-made sounds generated from cars, trains, vessels, airplanes, and various other industrial and domestic devices).

The sounds of nature can have an important role in the evaluation of the quality of a place. A high-fidelity (Hi-Fi) sonic environment is characterised by the ability of a listener to easily distinguish various sounds from one another (a quiet location without covering noises), while a low-fidelity (Lo-Fi) sonic environment has a level of noise that impedes the capacity for listeners to distinguish between various sounds comprising the soundscape (Truax, 1999). Moreover, a degraded landscape usually has a very poor soundscape, while an intact landscape often presents a richer soundscape (Farina et al., 2014).Because sounds travel faster in water than in air, sounds may be used more by marine animals than terrestrial species (Simpson et al., 2005). 

Objective 1: The first aim of the project is to describe temporal and spatial acoustic features of different marine habitats inside and outside Marine Protected Areas, highlighting the contribution of the main source of noise (biotic, abiotic and anthropogenic).

Reason: In the marine environment, a soundscape provides a set of acoustic cues that can influence many aspects of the behaviour of marine organisms, including mating, feeding activity, predator or prey detection, orientation, territory defence, both in invertebrates, fish and marine mammals. Despite nearshore waters are the areas that are subject to the highest human activities and related noise, there are relatively few studies that characterise the coastal acoustic environment. It was demonstrated that fish and invertebrate larvae use acoustic cues during settlement, thus understanding how habitat soundscapes vary over small spatial scales and through different habitat could help explain the distribution of marine organisms. 

Objective 2: Does boat noise elicit a behavioural response in fish?

Loud and/or continuous sounds (e.g., shipping and boat traffic) can have a dramatic effect on the nearby fish. Increased noise might result in the masking of biologically relevant signals (e.g. communication calls), considerably reducing the range over which individuals are able to exchange information. Furthermore, noise can cause avoidance from favourable habitats, stress and physiological changes; destruction of the auditory sensory cells and temporary or permanent loss of hearing capability. Finally, exposition to high sound levels could affect animal behaviour in various ways by: i) causing a reduction of activity and locomotion; ii) acting as a distracting stimulus; iii) masking crucial acoustic cues; iv) influencing settlement, foraging, social interactions and anti-predator behaviour. In our study area we have the great opportunity to study - in the wild - the behaviour of one of the few Mediterranean fish able to produce sound, the brown meagre (Sciaena umbra). Since 2014 we have been conducting a collection of behavioural data, using fixed underwater cameras, and noise levels, by means of Passive Acoustic Monitoring devices (PAMs) in the Marine Protected Area Capo Caccia - Isola Piana (North-Sardinia, Italy).

Reason: One of the main sources of underwater noise in coastal area is recreational boat traffic, which has undergone a considerable increase over the past years. Recreational boats generally produce noise in the frequencies below 1000 Hz; this frequency range falls within the hearing of many fish species. Not considering the last few years, the impact of boat noise on fish behaviour has been neglected in the past, with only a few exceptions, likely because of the difficulty to link human activities to specific changes in animal behaviour. The majority of studies in this topic have been carried out under controlled laboratory conditions, which allow more detailed and accurate data collection than field-based studies. However, care must be taken when extrapolating findings to real-world situations, because captive conditions may represent a highly simplified and artificial environment. To our knowledge, this represents one among the few studies for the determination of the behavioral response of fish to boat noise, conducted in a wild context where the animals were free of any movement constraint. 

Click here to read: La Manna et al. (2016). Behavioural response of brown meagre (Sciaena umbra) to boat noise. Marine Pollution Bulletin (2016) 

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