Light as a Cue for Life in Arctic and Northern Seas

Light is the primary source of energy for most life on Earth. In this respect, only few other environments are as hostile to life as the Arctic waters during the polar night. Yet, latest studies have revealed not only life, but also light-synchronized biological activity in the marine Arctic even during the darkest period of year. Which species are responsible for this activity is still a mystery. Zooplankton, which is fundamental to the marine Arctic ecosystem, has adapted to react to extremely small light differences present during the polar night. Even though light conditions during the polar night may be extreme, natural fluctuations are quite predictable. Sea-ice reduced by climate change and increasing light pollution are about to alter the light dynamics, and it is unclear how well the Arctic zooplankton can cope with these disturbances. Not all light in the oceans comes from above the surface. There are plenty of marine species producing their own light by bioluminescence during the polar night. Bioluminescent signals are variable and even though the phenomenon itself is well known, a deeper understanding about its species-specific details and ecological significance is still missing. In LightLife, we will study which species are present in the light-driven vertical migration in Svalbard waters in the high Arctic during the polar night using latest genetic techniques and couple zooplankton movement to the exact light levels in the environment. Further, we will investigate the limits of vision in the key zooplankton species in order to draw comparisons between populations from different latitudes and light environments. Bioluminescence characteristics in zooplankton species will be studied in order to gain new insights on the ecological relationships and to develop tools for species recognition. To develop management tools to minimize the impact of increasing light pollution, we need better understanding of how light affects biodiversity in marine ecosystems.

Global warming is causing reduction in both sea-ice thickness and coverage in the Arctic with substantial effects on high latitude ecosystems. In combination with constantly increasing light pollution and climate change-induced alterations in ambient light conditions this puts Arctic and Nordic marine ecosystems under pressure. The visual systems of aquatic animals in high latitude environments, however, are adapted to living in very dim light conditions and almost complete darkness during the polar night. It has been discovered recently that light-guided behaviour occurs throughout the year in the Arctic, even though the light intensities eliciting this behaviour are barely measurable with modern acquisition systems. LightLife brings together experts from different fields of biology to quantify the effects of light to the biological relationships and key functions in Arctic and Nordic ecosystems, focusing on zooplankton species which form the basis of the ecosystems. The project consists of three work packages (WPs). In WP 1, plankton species dynamics and role of light in vertical migration during the Arctic spring bloom will be determined by combining automatically acquired light data from the Arc-Light observatorium in Svalbard with species data gained by echolocation, net sampling and latest technologies around metabarcoding. WP 2 concentrates on the natural functional light regime in key species with emphasis on latitudinal effects. In this WP we determine the intensity scope for visual functions and its acclimation capacity in certain zooplankton species by laboratory experiments and electrophysiology. In WP 3, the contribution of bioluminescence as a light source and its role in the ecological interactions will be studied by state-of-the-art techniques both in the laboratory and in the field. The WP will also lead to a tool for identifying bioluminescent species by their luminous fingerprint.