ИСТИНА

Here, we discuss diel vertical migration (DVM) of zooplankton at three locations: Young Sound fjord in Northeast Greenland, northeast of Churchill in Hudson and the Southeastern Beaufort Sea in the Canadian Arctic. At all three locations, we deployed ice-tethered or bottom-anchored moorings equipped with Acoustic Doppler Current Profilers (ADCP), and conductivity and temperature (CT) sensors. At three locations the backscatter intensity and vertical velocity time series from the mooring ADCPs revealed a typical pattern for zooplankton DVM, even under sea-ice during winter. Using existing models for solar and lunar illuminance, and the transmission of this light through the sea ice and snow covers, we estimated under ice illuminance and compared it with the known light sensitivity of Arctic zooplankton. From the acquired data we observed the interaction of vertical migration with lunar light, tides, water and sea ice dynamics. In all three locations, we observed DVM modification or completely disruption during either highly energetic current, upwelling, downwelling or spring tide events. In Young Sound, our modelled analysis suggests that the zooplankton in question have an outstanding sensitivity to low illuminance levels of lunar light attenuated by sea ice and snow cover. Unlike other Arctic and sub-Arctic locations DVM in Hudson Bay is controlled by solar illumination throughout the whole year, not by moonlight. The disruption of DVM in Hudson Bay are also of the lunar origin, but they should be attributed to the tidal dynamics rather than the moonlight, because disruptions occurred during the full moon and new moon phases. The presented data constitutes a first-ever observed presence of DVM in Hudson Bay during winter as well as its interaction with the tidal dynamics.