Circadian rhythms of Arctic zooplankton from polar twilight to polar night – patterns, processes, and ecosystem implications (CircA)
In recent years, research carried out in the Svalbard archipelago challenged the long-lasting paradigm of dormant ecosystems during the polar night at high latitudes due to low food availability and lack of light. Based on data collected with acoustic instruments moored in the water column over one year, these new studies provide evidence of both active and synchronizeddiel vertical migration (DVM) of zooplankton in the midst of Arctic winter. However, the mystery of which species that carry out this winter DVM remains to be solved.
Zooplankton DVM is the most widespread and synchronized movement of biomass on the planet and, thus, should be one of the main factors to consider in order to understand marine food-web interactions and ecosystem structure. Zooplankton perform vertical migrations to balance the need to feed close to the surface, where food is generally most abundant, against the accompanying risk of being eaten where surface typically higher light levels create better conditions for visual predators. Hence, the migrating species remain at depth during daylight hours and move en masse to the surface under cover of darkness. Classically, the cue for this DVM behaviour is widely accepted to be changes in light intensity.
Although the polar night is perceived by the human eye as having continuous and total darkness, the latest data indicate that Arctic zooplankton respond to variations in very low light levels. Accordingly, unanticipated patterns of zooplankton DVM have been discovered and we now need to establish the basic biological foundation behind the behaviours and their wider ecological impacts.
By combining acoustic and optical data, with video plankton recorder and net sampling, we aim to describe the observed DVM patterns and the potential effects on the Arctic marine ecosystem, particularly in the biogeochemical cycling of chemical elements like carbon and nitrogen. The CircA project is a collaboration between UNIS, UiT, Akvaplan-niva and SAMS.
The specific objectives of the CircA project are:
To characterize which species are carrying out DVM during the polar night.
To determine why these organisms migrate (proximate and ultimate explanations).
To investigate theimportance of DVM during the polar twilight/night for Arctic marine ecosystems.
To develop a new set of tools to set these questions into a Pan-Arctic perspective.