Circadian rhythms of Arctic zooplankton from polar twilight to polar night; patterns, processes, and ecosystem implications (CircA)

Circa is a project that works with diel vertical migration of Arctic zooplankton. Such migrations are known from the world's oceans and lakes, and is a process governed by light; small organisms swimming in the upper water layers to eat under cover of darkness and without risk to himself to be eaten by larger predators. When day light is about to return, they disappear into the depths again where sunlight can not make them visible to predators. Recently we discovered that this process is not only important in the Arctic Ocean, it appears to continue through the dark polar night. Why do organisms to swim up and down in the water when there is no sunlight that can make them more visible to predators? And how controlled this process when there is no available sunlight that organisms can tell when it 's time to either hide in the depths or swim up to the surface? The research we have done through CircA points toward some very exciting results. Firstly , we now have clear evidence that the Arctic zooplankton continue their migrations throughout the polar night. But, opposite to what we used to think, these migrations are driven by a predator-prey interaction and regulated by light - even while it is dark. Our results also demonstrate that during the full moon, the Arctic zooplankton turn into werewolves that are regulated by the moonlight, but only for a short week centred around the full moon. After the full moon period, the zooplankton readjust their daily schedule to match the sun and a 24-hour clock again. And perhaps most important of all - an analyses of data series covering the entre Arctic and more than 50 years of data, show that the same happens all over the Arctic; under sea ice, in open water, on the shelf and in the deep sea. The Arctic zooplankton does not take a Christmas vacation, but continue their migrations throughout the dark polar night, regulated by invisible light!

Diel Vertical Migration of zooplankton is the biggest synchronized movement of biomass on the planet, and it is a common feature of all the worlds oceans. In the Arctic, with its unique light climate, DVM of zooplankton has recently been shown to be a con sistent phenomenon also at times of year when the classical paradigm of winter biology holds that most organisms have entered a state of diapause commensurate with the low availability of food. We propose a project that will aim primarily at determining t he physical and biological factors responsible for the vertical migration patterns of zooplankton in the high Arctic during the polar night and twilight period, and to elucidate ecosystem effects of such migrations. More specifically, we will identify whi ch species are conducting DVM (Part 1) during the winter as well as identifying the environmental cues that induce the behaviour (Part 2). Furthermore, we will examine how the DVM is integral to structuring of pelagic and benthic food webs through both tr ophic interactions (Part 2) and carbon/nutrient cycling (Part 3). This involves the ability of zooplankton to detect and respond to subtle changes in light intensities at times of year when solar radiation is either minimal (polar night) or efficiently st opped from penetrating the water column by the combination of a very low sun angle and a thick ice and snow cover. Finally, we will build up a unique and comprehensive dataset collating ADCP data that exist throughout the Arctic shelf seas to create the f irst pan-Arctic acoustic archive with the capacity to address questions relating to DVM at a global scale (Part 4). The proposed project will be a significant step towards a new understanding of high Arctic marine ecosystems (Part 3 and 4) during the pola r night and twilight period, and will greatly enhance our basic understanding of this unique system.