Cassandre Aimon (MSc Thesis 2015)
Behavioural and physiological impacts of anthropogenic noise vibrations of two marine invertebrates, Mytilus edulis and Carcinus maenas
|Supervisors: Rick Bruintjes, Maurizio Urbina (University of Exeter)
|Organisms can be affected by acoustic noise, which increased drastically in the past few decades. Induced physiological and behavioural changes have been demonstrated on a variety of species, however, the focus has been on vertebrates species; little attempt has been done to study its impact on invertebrates. Additionally invertebrates are recognized to sense vibrational component of sounds. In this study we focus on the impact of anthropogenic vibration on two invertebrate species. We conducted a series of experiment to study the impact of simulated anthropogenic vibration on two invertebrates species, the blue mussels Mytilus edulis and the shore crab, Carcinus maenas. The results show clear responses to the vibration stimulus, showing physiological and behavioural changes. In this study, close respirometry was used to evaluate metabolic rate of the two invertebrates species. The feeding rate was also investigated for M. edulis. And series of behaviours were considered in the investigations of anthropogenic vibration impact in this two species. Both species showed immediate reaction to the beginning of the stimulus, with the closing of the shell of M. edulis and increase in antennae beats rate of C. maenas within the first minute during the stimulus. Anthropogenic vibration was likely to induce different responses in the two species investigated. M. edulis, tended to demonstrate a quick recovery in the opening of its shell, reopening in the first five minutes during the exposure, while crabs showed in average higher antennae beats than in ambient vibration for the whole experiment. Distraction of crabs or reduction in attention to vibrations by mussels could lead to additional risk of predation. In addition, M. edulis showed a reduction in activity, by also decreasing its feeding rate, but no change in metabolic rate was found. This could lead to fitness problem for the population on long term exposure. A sex-specific response was found in C.maenas, demonstrating that females increased their metabolic rate and males increase the duration of their activity while they are exposed to anthropogenic vibration. Our findings suggest that anthropogenic vibration of low-frequency are perceived by invertebrates and induce physiological and behavioural changes in these two ecologically important species which could lead to deleterious effect at the population level if responses last on a long term. Further studies are needed to investigate the effect of the vibration component of anthropogenic noise which continue to increase, with studies on the field especially in order to be able to manage impacts of this pollutant.