Noise exposure is considered a threat to human health, causing not only annoyance or hearing impairment but also hypertension and diabetes. Like humans, many animals do hear and can be affected by noise. Although there is sufficient scientific evidence that noise exposure can threaten biodiversity, this environmental risk has only recently gained attention among resource managers and policy makers.
Because sound travels faster and over longer distances in water than in air, underwater sounds emitted by boat engines, sonars, pile drivers, seismic testing or windfarms can be particularly problematic for marine organisms. Most of our knowledge concerning the impact of underwater noise pollution (UNP) for wildlife is restricted to sea mammals and fish, and typically includes communication signal modifications and decreases in site occupancy at noisy locations. However, responses to noise pollution can be less obvious, especially considering that less motile animals such as most invertebrates cannot flee away from the disturbance and can be exposed to UNP over long periods of time. As more attention and resources are invested in understanding the full ecological and economic impacts of UNP, it has become necessary to explore the many possible risks associated with noise exposure.
In particular, stress responses triggered by human-induced environmental changes are expected to cause disease by intensifying the effects of parasites. In accord to this, UNP is predicted to alter the health of marine invertebrates in three ways:(1) stressed hosts are typically in poor condition and may be more susceptible to infections; (2) stress may increase the impact of parasitism on hosts; (3) the combined effects of stress and parasitism may affect species interactions, e.g. by increasing predation on infected/weakened hosts. Given that parasites are also exposed to the disturbance, UNP could influence parasite traits as well, including infectivity and survival.
This project aimed to assess the effects of UNP on parasitism and predatory interactions of key marine invertebrates: the blue mussel Mytilus edulis and the shore crab Carcinus maenas. By the use of multidisciplinary experimental approaches, the project’s objectives were (1) to identify behavioural and physiological stress responses of molluscs and crustaceans exposed to UNP, (2) to investigate for the first time connections between UNP and parasitic disease, and (3) to conduct a pioneer work on the influence of UNP on parasite-mediated species interactions.
Originally designed for 2 years, the project was significantly shortened to 1.5 month due to unforeseen circumstances. Although this meant that the full set of proposed actions could not be realised, several experiments were still carried out in line with theobjectives. These experimentsaimed at assessing the influence of acute underwater noise pollution on host-parasite interactions by the use of the mussel parasite Himasthla elongata which uses periwinkles as first and musselsas second intermediate host and birds as definitive host. Experimental soundtracks of boat noise or natural/ambient noise were played to infected periwinkles to investigate the effects of noise pollution on the production of free-living infective stages released from the periwinkle hosts. Mussel gaping behaviour infection success of parasites was also studied in a similar setup in presence of absence of infected periwinkles exposed to experimental soundtracks of boat noise or natural/ambient noise.
