Effects of dinoflagellate bioluminescence on the ingestion rates of herbivorous zooplankton

Ingestion rates of Acartiatonsa (Dana) on highly luminescent cultures of Gonyaulax excavata (Braarud) Balech are reduced by 50–75% relative to cultures with low capacity for luminescence. The effect is particularly noticeable at high cell concentrations. It is suggested that the dense array of flashes surrounding an animal disrupts its swimming and/or feeding patterns. The activity of Acartia clausi at a density of 1 animal/3 ml stimulates 1.1% of the cells' capacity for luminescence each minute. Pseudocalanus minutus stimulates only 0.03% per min, except in rare cases where the animals appear to be much more active. Cirripede and copepod nauplii never stimulate any emission. Favorable conditions for bioluminescence may arise before or during a bloom, and the consequent reduction in grazing may contribute to maintenance of the bloom. Natural concentrations of zooplanktonic organisms cannot exhaust the bioluminescence of healthy Gonyaulax excavata cells.