Exploring the effect of electromagnetic fields on dinoflagellate bioluminescence

Bioluminescence is a common feature in coastal waters where luminescent plankton can be abundant, and is commonly stimulated by fluid agitation. In the context of Navy nighttime operations, swimmers or underwater vehicles are vulnerable to detection due to their stimulation of bioluminescence. The objective of this study is to investigate the effectiveness of electromagnetic fields in reducing flow-stimulated bioluminescence. Dinoflagellates, plankton ubiquitous in coastal waters, are the most common sources of shallow-water bioluminescence. Dinoflagellate bioluminescence is triggered by a mechanical stimulus that initiates a complex series of events involving a Ca²⁺ signaling pathway and action potential that leads to acidification of the cell, activating the luminescent chemistry. Certain electric and magnetic field strengths and frequencies may inhibit or suppress bioluminescence by affecting intracellular Ca²⁺ concentrations or reducing enzyme levels critical to light production. In this study, the effect of electromagnetic fields on the bioluminescence of the dinoflagellate Pyrocystis lunula was tested using a broad survey of discrete and broadband electromagnetic fields, within the frequency range of 0 to 20 kHz. Magnetic field strengths were set at 2.45 milli-Tesla (mT) for alternating current (AC) fields and 25 mT for direct current (DC) fields. Electrical field strengths were dependent on frequency response of the test circuit, established by a 1.1 kV voltage drop across electrode blocks for AC fields and a 1.2 kV voltage drop for DC fields. The initial phase of experiments investigated the effect of electromagnetic fields on background (spontaneous) emission. All test treatments were compared with simultaneous control samples of cell-free media to determine the contribution of electromagnetic noise. A low frequency electrical field test band, (60 Hz-5 kHz), tended to stimulate photon emissions, and this effect may be inversely proportional to frequency from 60 Hz to 20 kHz. Only the 15-20 kHz electrical field test band resulted in a significant difference in emission levels, due to suppression of bioluminescence. Magnetic field test band results suggest a non-linear response versus frequency during field exposure, but experiments did not- produce significantly different spontaneous emission levels during or after exposure.