Figure 22. Plots of light irradiance (% of surface irradiance) to different depths
(m), measured using a light sensor probe at six time intervals (noted in the figure
legend) at King Harry Pontoon, in the Fal Estuary.
Although there was variation between depths at the six time intervals, Figure 22
shows that light irradiance decreased with depth across the time series. The greatest
surface irradiance of 67.3% occurred at 0840 UTC, but the surface irradiance did
not follow a specific pattern, with varying cloud cover over the six time intervals
affecting the results. However, the irradiance had decreased to between 0.13% and
2.60% of the surface irradiance at 5m, at each time interval, confirming that light
attenuates exponentially with depth.
