Predator-enhanced diel vertical migration in a planktonic dinoflagellate

Abstract

Diel vertical migration (DVM) is a common and conspicuous behavior amongst planktonic organisms. In the case of dinoflagellates, both light and nutrients have been shown to regulate DVM, although the role of predators (grazers) has been understudied. Here we report the results of an experimental study using a system of 'plankton mini-towers' to examine the DVM behavior of the marine planktonic dinoflagellate Akashiwo sanguinea. A. sanguinea undertook a pronounced reverse DVM (down during the night, up during the day) in both the absence and presence of copepod predators (Acartia spp.). In the presence of copepods, however, the amplitude of the DVM was enhanced, providing the dinoflagellate with greater spatial separation from its 'normally' migrating predator. We briefly discuss the causes (cues) and ecological consequences of predator-enhanced DVM in dinoflagellates.