Name: John King
Address: University of Rhode Island, 75 Lower College Rd, Kingston, RI 02881-1966
Phone: +1 401-874-6182
Our understanding of how marine organisms interact with either natural magnetic or electric fields is poor, but our knowledge relating to anthropogenic sources (e.g. subsea cables) is worse. The basis of the project is to conduct field studies that are specifically aimed at quantify the EMF associated with the HVDC cable and determine whether there is any significant response by electromagnetically (EM) sensitive animals to the EMFs emitted. Field work includes direct measurements of the DC magnetic and electric fields, exposure of selected species to EMF from the Cross Island HVDC cable in Long Island Sound, and modelling of the HVDC field and verification.
Department of the Interior, Bureau of Ocean Energy Management
Long Island Sound, Atlantic Ocean
- Synthesize of existing information that updates BOEM report 2011-09;
- Design and execute a field survey plan that will detect statistically significant, very small effects of EMF from HVDC cables on marine species of concern and our approach to conducting the planned work; and
- Develop a model to predict EMF, compare the model predictions with field measurements and evaluate whether the model can be extrapolated to higher capacity cables that are likely to be installed in the future.
- The EMF associated with HVDC cables was specifically measured in situ by the sensitive SEMLA device, which highlighted the presence of unexpected AC components in the EMF emissions for both the CSC and Neptune Cable. DC and AC magnetic fields extended out to 5 and 10 m from either side of the cables respectively, whereas the AC electric fields extended out to 100 m from either side of the cable. On the other hand, the AC fields of the HVAC sea2shore cable were generally ten-fold lower than model predictions.
- The COMSOL model provided good estimates of the magnitude and shape of DC fields from HVDC cables, and is scalable to higher capacity cables.
- The novel acoustic telemetry approach worked well to track movements of marine animals with much higher accuracy (<5 cm for beacon tag) and frequency (<3 second interval) of recorded positions than previous studies which were limited to an accuracy of <1m and frequency of <3 minutes.
- The field-deployed animal enclosures and acoustic telemetry method developed and fully tested in this study successfully allowed the collection of in situ, high frequency three-dimensional positional data on individual animals at both an experimental treatment enclosure on the power cable and an enclosure at a control site for reference.
- Homarus americanus (the American lobster) exhibited a statistically significant but subtle change in behavioral activity when exposed to the EMF of the HVDC cable, which operated at a constant power of 330 MW (1175 Amps). At the treatment enclosure (B), lobsters were on average closer to the seabed and exhibited a higher proportion of changes in the direction of travel (termed large turns), when second in the sequence, compared to the control enclosure (A). They also made more use of the central space of the treatment enclosure (B) compared to the control (A).
- Leucoraja erinacea (the Little skate) exhibited a strong behavioral response to the EMF from the CSC. The cable was powered for 62.4% of the study and most frequently transmitted electrical current at 16 Amps (at 0 MW, 37.5% of time), 345 Amps (100 MW, 28.6%) and 1175 Amps (330 MW, 15.2%). In comparison to the control enclosure (A), the skates at the treatment enclosure (B) traveled further but at a slower speed, closer to the seabed and with an increased proportion of large turns which suggested an increase in exploratory activity and/or area restricted foraging behavior. The increased distance traveled and increased proportion of large turns was associated with the zone of high EMF (>52.5 µT, i.e. above the Earth’s magnetic field) where they were more frequently recorded and spent more time.
- For both species, the behavioral changes have biological relevance in terms of how the animals will move around and be distributed in a cable EMF zone. The EMF associated with the CSC did not constitute a barrier to movements across the cable for either lobsters or skates.