Springs-neaps cycles in daily total seabed light: Daylength-induced changes

Analytical tools are developed to calculate the percentage of daily total sea surface irradiance reaching the bed at a site of interest on any given day, and to determine the sense of any springs-neaps cycle thereof for a given season. The conditions required for a 'switch' are explored graphically, resulting in the identification of criteria (and a useful parameter) for predicting their occurrence. Consequences for the growth patterns, depth limits and long-term survival of benthic algae and plants are discussed.