Additional file 2.

Amplitude and temporal frequency of the light flicker in sideward irradiance are wavelength dependent. (A,B) Examples of light flicker time series of sideward irradiance at 1 m depth and light wavelengths of 400 and 600 nm. The amplitude of the light flicker at 600 nm is larger than at 400 nm. (C) The amplitude of light flicker in sideward irradiance decreased with growing water depth, and increased monotonically toward longer light wavelengths. The ratio between the amplitude at the longest and shortest wavelengths did not vary considerably across depths, and ranged between 2.26 and 2.79 (presented next to each spectrum). (D) The frequency distribution of the flicker at a depth of 1 m differed across the light spectrum. The power spectrum of light flicker, normalized to the dominant frequency (1.69 Hz), is presented for different wavelengths at 50 nm intervals. The frequency distribution of flicker at 2, 4, 6, and 10 m depth also differed between wavelengths (not presented). (E) The frequency distribution of light flicker at 500 nm differed across water depths, with the dominant frequency (1 m, 1.69 Hz; 2 m, 1.30 Hz; 4 m, 0.83 Hz; 6 m, 0.78 Hz; 10 m, 0.59 Hz) and the relative power at high frequencies decreasing with growing depth. (F) The wavelength dependence of light flicker became weaker with growing depth.

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Sabbah and Hawryshyn BMC Biology 2013 11:77   doi:10.1186/1741-7007-11-77