The Biological Bulletin, Vol 194, Issue 2 194-223, Copyright © 1998 by Marine Biological Laboratory

CELL BIOLOGY

Evaluation of the Effects of Extremely Low Frequency Electromagnetic Fields on Movement in the Marine Diatom Amphora coffeaeformis

M. S. Davies, R. Dixey and J. C. Green
Department of Medical Electronics, St. Bartholomew's Hospital, West Smithfield, London, EC1A 7BE, UK

Published work has shown that population motility in the marine diatom Amphora coffeaeformis can be influenced by externally applied electromagnetic fields (EMFs). Here we report attempts to repeat these experiments, which have been proposed as a model for assessing the effects of EMFs on biological systems. Susceptibility to EMFs was tested using five strains of diatoms on agar plates at a very broad range of field conditions, but no effect on population motility was demonstrated. Exposure period to the EMFs, cell density, and position in the cell cycle had no effect on EMF susceptibility, and the direction and distance moved by the diatoms were not affected by EMFs. When tested after at least a month of preincubation at 20 {mu}T, diatoms of strains #2038, IIIB, and IIIF did show an EMF-induced increase in population motility over control cells (up to ~20%) at conditions predicted by the "ion cyclotron resonance" model, but this effect was ephemeral. Later, IIIB showed a similar increase that was abolished when (1) non-pre-incubated cells were used, (2) the EMF-producing coils were not energized, and (3) even harmonics were used. On observing the response of diatoms to EMFs in real time, a significant increase (~2-fold) in diatom speed over control cells was evident at "ion cyclotron resonance" conditions, using strain #2038 (pre-incubated at 20 {mu}T). The effect was abolished at an even harmonic. We conclude that EMFs can modulate diatom motility, but that the system is, as yet, not consistently reproducible.