OES-Environmental distributes metadata forms (questionnaires) to solicit information from researchers around the world who are exploring the environmental effects of marine renewable energy. This page provides a description and contact information related to the research. Content is updated on an annual basis.

Renewable Energy in situ Power Cable Observation

Study Status: 
Completed
Princple Investigator Contact Information: 

Name: Milton S. Love        

Email: love@lifesci.ucsb.edu

Project Description: 

The research was divided into two parts: Task 1 took place in inshore waters (10–14 m) and Task 2 in offshore waters (76–213 m). Here following, we will divide the descriptions and significant results of our research into those two categories.

 

Task 1

Between 1 February 2012 and 26 February 2014 using scuba, we surveyed the fishes, invertebrates, and marine plants living on two energized submarine power cables, adjacent pipe, and natural habitat. Along cable, pipe, and over sandy bottom, we installed six permanent 30 m-long transects; three at a shallow depth (10–11 m) and three in slightly deeper waters (13–14 m depth). The end of the shallow transects and beginning of the deep ones were separated by about 120 m. The beginning and ending of each transect at each site was marked by sand anchors as was each 5 m segment along each transect. Transects were 2 m wide, centered on the pipe or cable or an imaginary line between sand anchors that delineated the sandy control transect. During the surveys, we measured the electromagnetic fields (EMF) emitted by the cable, pipe, and natural habitat. Fishes and plant surveys were conducted from the beginning to end of the study — from 1 February 2012 to 26 February 2014. Invertebrate surveys were conducted beginning on 22 June 2012 and continued until the end of the study. We conducted a total of 38 days of fish surveys, 30 days of invertebrate studies, and 38 days of plant studies during the three years.

 

Task 2

We conducted surveys of energized and unenergized cables and of the nearby sea floor during 2012 (6–9 October), 2013 (3–5 October) and 2014 (23–25 October) at depths between 76 and 213 m using a manned submersible. During 2012, only the east side of each cable was surveyed, while in 2013 and 2014 we surveyed both sides of the cables at similar depths. All natural habitat surveys were conducted between 100 and about 500 m from the nearest cable. In 2012, we measured the EMF levels at three distances from energized Cable A. These measurements were taken at four locations along the cable (at bottom depths of 108 m, 112 m, 135 m, and 158 m). In 2013 and 2014, we measured EMF on all energized and unenergized cables on the cable at one location each, and on the sea floor

 

Funding Source: 

BOEM Cooperative Agreement No. M11AC00008

Location of Research: 

California, USA

Project Aims: 

Specific objectives of this study were to determine:

  1. The differences among fish and invertebrate communities associated with energized and unenergized cable habitat and those communities in soft seafloor habitats lacking cables.
  2. Whether electrosensitive species that are regionally important such as sharks and rays respond (via either attraction or repulsion) to the EMF’s of an in situ power transmission cable.
  3. The strength, spatial extent, and variability of EMF’s along both energized and unenergized cables.
  4. The potential effectiveness of the commonly proposed mitigation of cable burial.
Project Progress: 

Completed

Key Findings: 

Task 1

  1. The differences among fish and invertebrate communities associated with energized and unenergized cable habitat and those communities in soft seafloor habitats lacking cables.

    We did not find any biologically significant differences among fish and invertebrate communities between energized cables, pipe, and natural habitat. In particular, only three species of fish showed statistically significant, but slight, differences in densities between the cables and pipe. Plant communities did differ among habitats and within habitats between depths. These differences were almost certainly structure and depth, rather than EMF, related.

  2. Whether electro-sensitive species that are regionally important, such as sharks and rays, respond (via either attraction or repulsion) to the EMFs of an in situ power transmission cable.

    We observed only one elasmobranch individual, a swell shark, during the course of this study. Thus, it would appear that the EMFs generated by these energized cables are either unimportant to these organisms or that at least other environmental factors take precedence.

  3. The strength, spatial extent, and variability of EMFs along both energized and unenergized cables.

    The strength of the EMF along the energized cable was relatively stable over time and along its length. The EMF produced by the energized cables diminishes to background levels about one meter away from the cable. Similarly, both the pipe and natural habitat sites had extremely small or undetectable EMFs.

  4. The potential effectiveness of the commonly proposed mitigation of cable burial.

    Given the rapidity with which the EMF produced by the energized cables diminishes and the lack of response to that EMF by the shallower fish and invertebrates, cable burial would not appear necessary strictly for biological reasons. In this and similar cases, cable burial, at sufficient depth, would be an adequate tool to prevent EMF emissions from being present at the seafloor.

 

Task 2

  1. The differences among fish and invertebrate communities associated with energized and unenergized cable habitat and those communities in soft seafloor habitats lacking cables.

    We did not observe any significant differences in the fish communities living around energized and unenergized cables and natural habitats. A very slight, and likely biologically insignificant, difference in mean sizes was observed as fishes at unenergized cables were marginally larger than those around energized ones. Overall species diversity and the densities of the most important fish species (define as comprising at least 1% of all fishes observed) were higher at the cables than at the natural habitats. This is likely reflective of the more complex habitats afforded by the cables than the primarily soft substrata natural habitats.

     

    Similar to the fish communities, the invertebrate assemblages living around energized and unenergized cables and natural habitats were similar to one another and variability between these communities was primarily driven by sea floor depth. Among the three habitat types, there were some statistically significant differences in densities for all nine of the most abundant species. These differences included: 1) two species, sand star and black crinoid, whose densities differed between energized and unenergized cables, 2) three species, thin sea pen, red octopus, and white sea urchin which differed between cable sides, 3) seven species, white-plumed anemone, spot prawn, thin sea pen, California sea cucumber, red octopus, unidentified Urticina anemone, and black crinoid that exhibited bottom depth differences, and 4) two species, thin sea pen and sand star, whose densities varied among years. Sand star densities were greater at unenergized cables, 4/1/m3 v 2.7 m3, and black crinoid densities were greater at energized cables, 1.7/m3 v 0.3/m3

  2. Whether electro-sensitive species that are regionally important, such as sharks and rays, respond (via either attraction or repulsion) to the EMFs of an in situ power transmission cable.

    We observed very few individuals of electro-sensitive species on the energized or unenergized cables or on the natural habitats. Only five ratfish (three at the energized cables and two on the unenergized ones) and one California skate (at the unenergized cable) were noted. Thus, we found no compelling evidence that the EMF produced by the energized power cables in this study were either attracting or repelling these fishes.

  3. The strength, spatial extent, and variability of EMFs along both energized and unenergized cables.

    The EMFs produced by the energized cables were similar both over the three years of the study and along the cables. EMF strength dissipated relatively quickly with distance from the cable and approached background levels at about one meter from the cable. The EMF at unenergized cables was similar to that found at the natural habitats.

  4. The potential effectiveness of the commonly proposed mitigation of cable burial.

    Given the rapidity with which the EMF produced by the energized cables diminishes and the lack of response to that EMF by the fishes and invertebrates in this study, cable burial would not appear necessary strictly for biological reasons. In this and similar cases, cable burial, at sufficient depth, would be an adequate tool to prevent EMF emissions from being present at the seafloor.

.

 

Related Publications: 

Love, M.; Nishimoto, M.; Clark, S.; Bull, A. (2016). Renewable Energy in situ Power Cable Observation. Report by University of California Santa Barbara. pp 106.

Find Tethys on InstagramFind Tethys on FacebookFind Tethys on Twitter
 
CAPTCHA
This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.