Abstract
The dinoflagellate Pyrocystis lunula emits light in response to water motion. The statistical features of the bioluminescence, emitted by P. lunula, owing to shear stress in oscillatory boundary layer flows over ripped bed were studied in this paper with the aim to develop a new imaging technique for measuring fluid strain rate and shear using plankton that emit light in response to mechanical stimulation. The flash intensity has been found to correlate with fluid strain rate estimated from fluid velocity over ripples. Thus the instantaneous planar distribution of the fluid shear can be estimated from video images of the bioluminescence in a fluid region by using the empirical relation determined in this study.
Highlights
In shallow water, turbulence produced in the wave boundary layer disturbs and carries sediments for forming wavy rippled seabed which intensifies fluid shear in the lee of the ripple crest to induce vortices and turbulence
The ensemble averages of the normalized flash intensities at each phase shows the flash intensities distribute in the corresponding high strain regions, indicating that the dinoflagellate flashes as a response of the fluid shear stress that is proportional to the strain
The time series of the flash intensity and the measured absolute shear averaged over one ripple are compared in figure 7
Summary
Turbulence produced in the wave boundary layer disturbs and carries sediments for forming wavy rippled seabed which intensifies fluid shear in the lee of the ripple crest to induce vortices and turbulence. Blaser et al (2002) studied the flash responses of the bioluminescent dinoflagellate Pyrocystis fusiformis in laminar shearing pipe flow. Stokes et al (2004) applied the bioluminescence imaging technique to ocean breaking waves, where strong turbulence and shears are organized and developed during wave propagation, suggesting a possible application in which a statistical calibration of the cell-flash could be used to measure the actual wave field.
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