EMF Effects from Marine Hydrokinetic Devices

Regardless of what type of technology is employed, marine hydrokinetic devices (MHK) all share one commonality; they all transport their power back to the shore grid via subsea cables.  Current passing through these high voltage cables generates an electromagnetic field (EMF) in the seawater environment that has the potential to be detected by marine organisms.  A large number of marine species are either electro- or magneto-receptive and at least one group, the elasmobranch fishes (sharks, skates, rays) likely respond to both stimuli.  Various industries, including power, telecommunications, military, and petroleum, have reported detrimental interactions between marine species and subsea cables.  Typically these interactions involve the cables being bitten by sharks resulting in costly repair or replacement.  The projected growth of the MHK industry will result in large numbers of devices being installed, often in large arrays of dozens of units.  These installations are typically in relatively shallow, near shore environments where they have the greatest potential to be damaged by marine organisms, thus providing a significant economic concern.  In addition, it is unclear how anthropogenic EMF may impact the behavior and movements of commercially important, as well as threatened, or endangered species.  For example, whereas a migrating organism might be able to compensate for a localized magnetic anomaly from a single cable, an array of subsea cables might significantly interfere with navigation.  Therefore, a necessary first step is to quantify what EMF stimuli are being introduced into the marine environment by MHK devices.  In conjunction, it is critical to understand how EMF is perceived by various marine organisms to ascertain whether the fields produced by MHK devices pose a threat to sensitive species and potentially endanger the devices themselves.  These concerns will be addressed, along with recommendations for specific studies and potential mitigation techniques.