Energy generated by the world’s oceans and rivers offers the potential to make substantial contributions to the domestic and global renewable energy supply. However, the marine and hydrokinetic (MHK) energy industry faces challenges related to siting, permitting, construction, and operation of pilot and commercial-scale facilities. One of the challenges is to understand the potential effects to marine organisms from electromagnetic fields, which are produced as a by-product of transmitting power from offshore to onshore locations through underwater transmission cables.
This report documents the progress of the third year of research (fiscal year 2012) to investigate environmental issues associated with marine and hydrokinetic energy (MHK) generation. This work was conducted by Pacific Northwest National Laboratory (PNNL) for the U.S. Department of Energy’s (DOE’s) Office of Energy Efficiency and Renewable Energy (EERE) Wind and Water Technologies Office. The report addresses the effects of electromagnetic fields (EMFs) on selected marine species where significant knowledge gaps exist. The species studied this fiscal year included one fish and two crustacean species: the Atlantic halibut (Hippoglossus hippoglossus), Dungeness crab (Metacarcinus magister), and American lobster (Homarus americanus).
These species were chosen based on their conservation and management status, and ecological and economic importance in the United States. A behavioral approach was used as a means of providing a sensitive yet rapid screening level assessment. Experimental trials were conducted in a controlled laboratory setting where EMF exposures and responses were actively monitored and quantified. A maximum EMF strength between 1.0 - 1.2 mT direct current (DC) was used for all tests to provide consistency and comparability among species. The EMF intensity was selected as an upper bound of an anthropogenic source that might be encountered based on reviewed literature. Behavioral observations were recorded in a test tank where the maximum EMF strength occurred at the tank center, decreasing to approximately 0.2 mT at each end and compared to identically configured control tanks with uniform background EMF intensities (~0.05 mT). Experimental trials were conducted for 24 hours (lobster), 72 and 96 hours (crab), and 72 hours (halibut). Attributes examined included the location (i.e., where time was spent with respect to the EMF source) and changes in activity levels (e.g., swimming, walking, resting, buried, sheltered, and burrowed). The overall approach was designed to provide preliminary information regarding key marine organisms responses to anthropogenic sources of EMF that will inform the siting and permitting process for MHK energy projects.
Based on the initial laboratory screening studies, the weight of evidence to date for the three tested species showed relatively few behavioral responses that would indicate explicit avoidance or attraction to an approximate 1.1 mT DC EMF intensity. However, for each species there were statistically significant differences related to the use of space and/or activity level within the experimental tanks. Further study is needed to clarify whether these results are related to the directional flow of water current in the tanks, a response to a change in EMF vector orientation relative to background, or some other tank effect. There was a large amount of variability observed between individuals, trials, and seasons; hence the results need to be considered from this perspective. As benthic species, test animals spent a majority of their time in an inactive state, independent of treatment; halibut were motionless 88% of the time; crab were buried/resting 80-91% of time; and lobster were sheltered or burrowed 76% of time. Given these largely inactive baselines, subtle changes in behavior were difficult to detect.
Recommendations for future research include: testing of other life stages (e.g. juveniles) that are likely to have different sensitivities and responses to EMFs; inclusion of other species of regulatory concern in future testing that may be sensitive to EMF (e.g. green sturgeon, elasmobranchs); implementation of tests using a variety of EMF configurations, including an AC source for comparison to the DC EMF results; and implementation of an experimental design in the laboratory to specifically address test animals responses to changes in EMF vector orientation. Finally, larger scale studies using activated cables in the field are needed in order to realistically assess EMF effects on navigation and migration patterns of priority species, including distribution of populations.