During the PhD course “Fate of the Arctic spring bloom” organized by Torkel Gissel Nielsen in 2012, we went out to sample the zooplankton community day and night with a Video Plankton Recorder. Our aim was to study diel vertical migration behaviour. Two years later, our results are published in the journal "Marine Biology".
Diel vertical migration is a prominent adaptation for avoiding visual predation during daylight hours and still being able to feed on surface phytoplankton blooms during night. DVM is a common behavior adopted by zooplankton species. Here, we report on a DVM study using a Video Plankton Recorder (VPR), a tool that allows mapping of vertical zooplankton distributions with a far greater spatial resolution than conventional zooplankton nets.
The study took place over a full day–night cycle in Disko Bay, Greenland, during the peak of the phytoplankton spring bloom. The sampling revealed a large abundance of copepods performing DVM (up during night and down during day). Migration behavior was expressed differently among the abundant groups with either a strong DVM (euphausiids), an absence of DVM (i.e., permanently deep; ostracods) or a marked DVM, driven by strong surface avoidance during the day and more variable depth preferences at night (Calanus spp.).
The precise individual depth position provided by the VPR allowed us to conclude that the escape from surface waters during daytime reduces feeding opportunities but also lowers the risk of predation (by reducing the light exposure) and thereby is likely to influence both state (hunger, weight and stage) and survival. The results suggest that the copepods select day and night time habitats with similar light levels (~10⁻⁹ μmol photon s⁻¹ m⁻²). Furthermore, Calanus spp. displayed state-dependent behavior, with DVM most apparent for smaller individuals, and a deeper residence depth for the larger individuals.
Link to the paper: http://link.springer.com/article/10.1007%2Fs00227-014-2475-x