Many marine animals have evolved sensory abilities to use electric and magnetic cues in essential aspects of life history, such as to detect prey, predators and mates as well as to orientate and migrate. Potential disruption of vital cues by human activities must be understood in order to mitigate potential negative influences. Cable deployments in coastal waters are increasing worldwide, in capacity and number, owing to growing demands for electrical power and telecommunications. Increasingly, the local electromagnetic environment used by electro-and magneto-sensitive species will be altered. We quantified biologically relevant behavioural responses of the presumed, magneto-receptive American lobster and the electro-sensitive Little skate to electromagnetic field (EMF) emissions of a subsea high voltage direct current (HVDC) transmission cable for domestic electricity supply. We demonstrate a striking increase in exploratory/foraging behaviour in skates in response to EMF and a more subtle exploratory response in lobsters. In addition, by directly measuring both the magnetic and electric field components of the EMF emitted by HVDC cables we found that there were DC and unexpectedly AC components. Modelling, restricted to the DC component, showed good agreement with measured results. Our cross-disciplinary study highlights the need to integrate an understanding of the natural and anthropogenic EMF environment together with the responses of sensitive animals when planning future cable deployments and predicting their environmental effects. Electromagnetic fields (EMFs) pervade the whole of the earth's environment and have been present throughout evolution of life on earth. The most dominant natural EMFs in the marine environment are the Earth's geomagnetic field (25-65 µT) and motionally induced electric fields, resulting from conductive seawater moving through the geomagnetic field 1. Organisms themselves also emit important but weak bioelectric fields resulting from cellular processes and muscular movements 2. Electromagnetic (EM) senses in marine animals have evolved multiple times across many taxa with a variety of, and sometimes multiple, sensory systems including magnetite-based, photo-chemical mechanisms, lateral lines and ampullae of Lorenzini 3,4. Magneto-sensitive animals respond to small changes in the inclination, intensity and/or direction of a magnetic field 4. They employ either a magnetic compass and/or magnetic map enabling homing and/or migration over short and long distances 5. Electro-sensitive species are able to detect weak electric fields used to detect prey and predators, to communicate, find mates and/or locally orientate 6. Electro-sensitive species are also able to respond to magnetic fields using electro-sensory apparatus and some species may have both electro and magneto-sensory apparatus 7. While we are still trying to understand the mechanisms involved in EM-sensing 4,7 , the functional roles are clearly of fundamental ecological importance. Interference with animal's sensory abiliti...

With the large scale developments of offshore windpower the number of underwater electric cables is increasing with various technologies applied. A wind farm is associated with different types of cables used for intraturbine, array-to-transformer, and transformer-to-shore transmissions. As the electric currents in submarine cables induce electromagnetic fields there is a concern of how they may influence fishes. Studies have shown that there are fish species that are magneto-sensitive using geomagnetic field information for the purpose of orientation. This implies that if the geomagnetic field is locally altered it could influence spatial patterns in fish. There are also physiological aspects to consider, especially for species that are less inclined to move as the exposure could be persistent in a particular area. Even though studies have shown that magnetic fields could affect fish, there is at present limited evidence that fish are influenced by the electromagnetic fields that underwater cables from windmills generate. Studies on European eel in the Baltic Sea have indicated some minor effects. In this article we give an overview on the type of submarine cables that are used for electric transmissions in the sea. We also describe the character of the magnetic fields they induce. The effects of magnetic fields on fish are reviewed and how this may relate to the cables used for offshore wind power is discussed.

In the marine environment there are natural magnetic and electric fields associated with both physical and biological sources, and there are anthropogenic electromagnetic fields (EMFs) that permeate it. Many marine animals can detect electric and magnetic fields and utilize them in such important life processes as movement, orientation and foraging. Here, these EMFs are explored and discussed in terms of how they arise, their properties (particularly those that are measurable) and the animals that have the ability to detect them. Then the evidence base for whether anthropogenic EMFs can affect sensitive receptor animals is explored. As marine renewable energy developments (MREDs) expand rapidly worldwide, with multiple devices and networks of subsea cables that emit EMFs into the marine environment, it is necessary to focus on their interaction with marine animals. The MRED industry has to take EMFs into account, so the industry perspective is also covered. Finally, suggestions are made on how research on EMFs associated with MREDs (and other sources) and its interaction with marine animals should advance in future. Overview and TerminologyHumans are generally unaware that they live within an electromagnetic world. The concept that we are surrounded by charged particles may seem ethereal but is more real than generally acknowledged. We are familiar with an occasional lightning storm, but we are also bombarded continually with electromagnetic emissions from the sun and encompassed by the Earth's own geomagnetic field (and other sources, such as granite geology). At a local level, humans are immersed among anthropogenic electromagnetic emissions that emanate from the plethora of electrical appliances and technologies that have been developed to become part of everyday life.Animals with which humankind shares the environment are also exposed to electromagnetic fields (EMFs) both natural and anthropogenic in origin. Several animals are known to be able to detect EMFs (or more specifically the component electric and/or magnetic field) and to use them for activities that are vitally important in terms of resource gain and movement around their environment. This is particularly true of marine animals, many of which undertake large-scale movements that apparently follow the orientation of the Earth's geomagnetic field (Kirschvink 1997). Moreover, some animals possess specialist electroreceptive organs that can detect weak bioelectric fields emitted by their prey and conspecifics.Although knowledge of how marine animals use magnetic and electric fields is increasing, there is still scant understanding of how animals interact with anthropogenic sources of EMF. The purpose here, therefore, is to provide an overview of what is currently known about EMFs in the marine environment and to evaluate how electromagnetically sensitive receptor animals interact with the EMFs associated with marine renewable energy developments (MREDs). The latter are being developed to transform renewable sources of energy into electricity ...

During last decades, anthropogenic underwater sound and its chronic impact on marine species have been recognised as an environmental protection challenge. At the same time, studies on the spatial and temporal variability of ambient sound, and how it is affected by biotic, abiotic and anthropogenic factors are lacking. This paper presents analysis of a large-scale and long-term underwater sound monitoring in the Baltic Sea. Throughout the year 2014, sound was monitored in 36 Baltic Sea locations. Selected locations covered different natural conditions and ship traffic intensities. The 63 Hz, 125 Hz and 2 kHz one-third octave band sound pressure levels were calculated and analysed. The levels varied significantly from one monitoring location to another. The annual median sound pressure level of the quietest and the loudest location differed almost 50 dB in the 63 Hz one-third octave band. Largest difference in the monthly medians was 15 dB in 63 Hz one-third octave band. The same monitoring locations annual estimated probability density functions for two yearly periods show strong similarity. The data variability grows as the averaging time period is reduced. Maritime traffic elevates the ambient sound levels in many areas of the Baltic Sea during extensive time periods.

The effect of sound pressure on the hearing of fish has been extensively investigated in laboratory studies as well as in field trials in contrast to particle motion where few studies have been carried out. To improve this dearth of knowledge, an instrument for measuring particle motion was developed and used in a field trial. The particle motion is measured using a neutrally buoyant sphere, which co-oscillates with the fluid motion. The unit was deployed in close vicinity to a wind turbine foundation at Utgrunden wind farm in the Baltic Sea. Measurements of particle motion were undertaken at different distances from the turbine as well as at varying wind speeds. Levels of particle motion were compared to audiograms for cod (Gadus morhua L.) and plaice (Pleuronectes platessa L.).