Name: Normandeau Associates, Inc.
Address: 25 Nashua Rd. Bedford, NH 03110
Anthropogenic electromagnetic fields (EMFs) have been introduced into the marine environment around the world and from a wide variety of sources for well over a century. Despite this, little is known about potential ecological impacts from EMFs. For decades, power transmission cables have been installed across bays and river mouths, and connecting near-shore islands to the mainland, with little consideration of possible effects to marine species from EMFs. At a time of greater environmental awareness, the US now faces the possibility of a new source of EMFs over a much greater extent of the seabed from offshore renewable energy facilities in coastal waters. This literature review synthesizes information on the types of power cables and models the expected EMFs from representative cables. Available information on electro- and magnetosensitivity of marine organisms, including elasmobranchs (sharks and rays) and other fish species, marine mammals, sea turtles, and invertebrates is summarized and used in conjunction with the power cable modeling results to evaluate the level of confidence the existing state of knowledge provides for impact assessment. Gaps in our knowledge of power cable characteristics and the biology needed to understand and predict impacts are summarized and form the basis of recommendations for future research priorities. Potential mitigation opportunities are described with a discussion of their potential secondary impacts as well as suggested methods for monitoring mitigation effectiveness. Finally, because interest in offshore renewable energy has increased throughout US coastal waters, there is a concern that organisms could be exposed to multiple seabed power cables. Cumulative effects of this exposure are discussed.
This study was funded by the Bureau of Ocean Energy Management, Regulation and Enforcement, U.S. Department of the Interior, Washington, D.C., under Contract Number M09PC00014
This document provides a compilation of relevant literature (through 2009) that can be used in the licensing process to assess EMF effects on individual projects within the Bureau of Ocean Energy Management, Regulation, and Enforcement (BOEMRE) planning areas of the contiguous states and Alaska in order to meet two primary study objectives:
- Characterization and quantification of EM fields produced or predicted to be produced by underwater transmission cables associated with offshore renewable energy projects;
- An understanding of which marine species occurring in the study area may be sensitive to either electric or magnetic fields, the physiological basis for those sensitivities, life history and behavioral characteristics that may affect potential for exposure, and potential effects of exposure to EMFs from offshore renewable energy projects.
The focus of this review is the undersea cabling associated with offshore renewable energy. These cables can produce exposures to EMF in three ways: the electric field produced by the voltage applied to the cables, the magnetic field produced by current flow on the cable, and an indirect AC electric field induced by alternating magnetic fields from the cables or movement through a DC field of the earth or cables.
This synthesis of available data and information clearly demonstrates that more work is needed to understand the nature and magnitude of any potential impacts to marine species from undersea power cable EMFs. Nonetheless, EMF modeling results in this report provide a general reference for understanding the magnitude and characteristics of magnetic and induced electric fields from undersea cables. The listing of priority species for US waters provides a focused list of species for which evidence suggests magneto- or electrosensory capabilities. The analyses of potential impacts and compilation of data gaps and research priorities provide direction to guide further efforts to address the question of effects from power cable EMFs on marine species.
- Conclusions that can be drawn from the information gathered in this report include:
- Anticipated EMFs from power cables can be modeled easily as long as specific information is available:
- Cable design
- Burial depth and layout
- Magnetic permeability of the sheathing
- Loading (amperes)
- Modeling of DC cables must take local geomagnetic field into account to accurately predict field strength
- Voltages of interconnection cables are lower than on export cables resulting in lower magnetic fields than from within-array cabling
- Species with electrosensitivity are likely to be able to detect EMFs from both DC and AC cables with high sensitivity to DC cables. Taxa include:
- Some teleost fish
- Some decapod crustaceans
- Species with magnetosensitivity are more likely to be able to detect EMFs from DC cables than from AC cables. Taxa include:
- Sea turtles
- Some marine mammals
- Some decapod crustaceans
- Electrosense is well documented among elasmobranchs so knowledge about the effects of exposure to EMFs on one species can be cautiously applied to another species with similar physiology and behavioral patterns (e.g., preferred position in the water column, prey items, habitat preferences)
- Behavioral responses to electro- or magnetic fields are known for some species but extrapolation to impacts resulting from exposure to undersea power cables is speculative.
- Demersal species (some elasmobranchs, other fish species, or decapod crustaceans) are more likely to be exposed to higher field strengths than pelagic species.
- Despite the fact that the available biological information allows only a preliminary level of impact assessment, modeling indicates that the electromagnetic fields emitted by undersea power cables are limited spatially (both vertically and horizontally). This spatial limitation must be considered in any impact assessment as it reduces the risk that any given organism will be exposed.
Normandeau Associates; Exponent; Tricas, T.; Gill, A. (2011). Effects of EMFs from Undersea Power Cables on Elasmobranchs and other Marine Species. Report by Normandeau Associates Inc. pp 426.