Additional file 4.

Comparison between the frequency of light flicker in downward irradiance and two realistic estimates of Fmax. Fmax was estimated as either 10% (A,B) or 20% (C,D) of CFF. (A,C) The distribution of Fmax values across frequency corresponded well to the power spectrum of flicker across depths. Note, however, that estimation of Fmax as 20% of CFF resulted in Fmax values that often exceeded the sampling frequency limit of light flicker. Depicted power spectrum (shaded gray) represents the envelope of flicker power across the 1 m and 10 m depth range. (B,D) Comparison between the cumulative power of the flicker and Fmax for dim and bright stimuli (closed circles). Conventions for the indices of the distribution of power of flicker across frequencies (fP50, fP90, and fP99), plot specifications, and species included in the analysis are the same as in Figure 3A,B. For estimation of Fmax as 10% of CFF, the median Fmax equaled 1.2 and 2.3 Hz, for dim and bright stimuli, respectively (open circle; red error bars represent the 25th and 75th percentiles). The median Fmax for dim and bright stimuli matched the frequency below which approximately 50% of the cumulative power of flicker was found at 1 m depth. For estimation of Fmax as 20% of CFF, the median Fmax equaled 2.4 and 4.6 Hz, for dim and bright stimuli, respectively. The median Fmax for dim and bright stimuli matched the frequency below which between 50% and 90% of the cumulative power of flicker was found at 1 m depth. For both Fmax estimates, the median Fmax for dim and bright stimuli matched the frequency below which 99% of the cumulative power at 10 m depth was found.

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