May 24 2011

EM Effects – Benthic Organisms

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     Since the cables necessary for transporting electricity from offshore energy generating devices must be laid upon the ocean floor, there is speculation that the electromagnetic fields given off by the underwater cables may disrupt the navigation and behaviors of benthic organisms.

Freshwater Crabs

     In order to assess the effects that electromagnetic fields may have upon these organisms, scientists have conducted many simulation studies.  One such study was on the freshwater crab B. cunicularis.  They found that when exposed to low frequency electromagnetic fields, many of the crab’s behaviors and bodily processes were altered.  For experimental purposes, the crabs were exposed to the LF-EMF for 150 minutes.  During this time they were greatly attracted to the electric current supply, which resulted in a maximum aggression of 100% between 60 and 90 minutes of elapsed exposure time.

Rosario 2010

     After this time period the crabs segregated and began to act like the normal control crabs again.  The exposed crabs also showed a higher feeding rate and lower response to the natural fighting behavior that they use to establish physical superiority.  Scientists expect that the initial response the crabs showed after being exposed to the LF-EMF are due to alterations in their metabolism or in areas of neural circuitry.

Rosario 2010

     The exposed crabs also had much higher amounts of fecal matter than the control crabs.  This can be attributed to increased stress levels due to the imposed electromagnetic fields, which in turn leads to a higher release of digestive enzymes and a higher digestive rate (Rosario 2010).

Rosario 2010


Magnetic Orientation and Navigation in Spiny Lobsters and Mollusks


     It has been found that Caribbean spiny lobsters use magnetic topography to derive their geographic position in order to move in the appropriate direction along a migration path.  These crustaceans live on hard bottoms and coral reefs and use electromagnetic fields to travel significant distances on their nightly foraging trips.  Through tagging, scientists have found that even when they are displaced several kilometers from the capture site, they are always able to return home again.  This navigation is thought to be caused by the use of six specific neurons in their brain that respond to changes in magnetic fields.

     Another species that uses magnetic fields for orientation and navigation is the mollusk Tritoria diomedia.   These organisms use magnetic fields to guide themselves between shallow and deeper areas.  They are able to do this because of the bilaterally symmetric pairs of neurons that respond with altered electric activity to changes in magnetic fields.  Specifically, the Pd5 and Pd6 neurons help to align the organism with particular magnetic directions and to crawl along partial headings.  The Pd7 neuron is suspected to suppress behavior incompatible with orientation or locomotion (S.D. Cain 2005).

Significance of Research

     It is crucial to study all of the negative effects that electromagnetic fields given off by energy generating cables may have on these three organisms because if  only one species is damaged or killed, this will affect the entire food web.  Crabs play a huge role in the seafood industry industry, which alone employs a multitude of people in coastal areas, shipping businesses and restaurants.  Spiny lobsters are also consumed by people and mollusks serve as lower trophic level prey for higher trophic level species.  All of these organisms contribute  to our food sources and ecosystem services.

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