Can artificial magnetic fields alter the functional role of the blue mussel, Mytilus edulis?

Along European coasts, the rapid expansion of marine renewable energy devices and their buried power cables, raises major societal concerns regarding the potential effects of their magnetic field emissions (MFs) on marine species and ecosystem functioning. MFs occur at a local spatial scale, which makes sessile species the primary target of chronic and high-intensity exposures. Some of them, as ecosystem engineers, have critical functions in coastal habitats whose behavioral alteration may drive profound consequences at the ecosystem level. In this context, the present experimental study explored the effects of short exposure to direct current MFs, on the feeding behavior of a widespread ecosystem engineer, the blue mussel (Mytilus edulis). A repeated measure design was carried out with adult mussels successively exposed to control treatment (ambient magnetic field of 47 μT) and artificial MF treatment (direct current of 300 μT produced by Helmholtz coils), as measured around power cables. The filtration activity was assessed through valve gap monitoring using an automated image analysis system. The clearance rate was estimated simultaneously by measuring the decrease in algal concentration using flow cytometry. Our findings revealed that mussels placed in MF treatment did not exhibit observable differences in valve activity and filtration rate, thus suggesting that, at such an intensity, artificial MFs do not significantly impair their feeding behavior. However, additional research is required to investigate the sensitivity of other life stages, the effects of mid to long-term exposure to alternative and direct current fields and to test various MF intensities.