Energy Flow Between the Pelagic and Benthic Zones: Factors Controlling Particulate Organic Matter Available to an Intertidal Mussel Bed

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Abstract
Fluctuations and vertical gradients of particulate organic matter (POM, as indicated by chlorophyll a and phaeopigments) concentration over an intertidal mussel bed were studied over fortnightly tidal cycles. Chlorophyll a variations were not associated with wave amplitude, tidal energy and sigma-t, and phaeopigment concentration was correlated positively with wave amplitude only. Comparison of total pigment concentration in water pumped simultaneously from within 5 cm and from 50 cm above the mussel bed showed significant depletion of POM nearest to the mussel bed throughout the 1st of the 2 fortnightly tidal cycles studied. During this period, POM depletion was negatively correlated with current speed, but not with mussel filtration rate, nor with wave energy. During the other period, POM depletion was significant in 3 of the 6 semidiurnal tidal cycles studied, and depletion was negatively correlated with wave energy only. Food is often depleted immediately above mussel populations and water movement is critical in determining food availability for suspension feeders.