We propose that planktivorous fishes on the windward reef face form a “wall of mouths” that removes most of the zooplankton from the water near the reef face before that water physically impinges upon the reef surface. We tested this hypothesis by simultaneously collecting
zooplankton and planktivorous fish on transects determined by the foraging behavior of the planktivorous fish. We sampled seaward of the foraging extent of caesionid species, seaward of, within, and behind the dense schools of hovering pomacentrids, and behind the breaking waves on the reef
flat. We concurrently measured water movements on the reef face. Typically, over 500 individual planktivorous fishes of over 10 different species visually inspected and stripped zooplankton from each m3 of water that flowed over the reef crest. Approximately 0.5 kg m–1
d–1 wet weight zooplankton, mostly larvaceans and copepods entered diurnally into the reef economy. We argue that diurnal input of allochthonous material may be far more important than nocturnal input because of extensive foraging into the water column by planktivorous fish
during the day and that the importance of zooplankton as a source of nutrition for coral reef ecosystems has been seriously underestimated.
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