Introduction

Abstract

The current understanding of marine Arctic ecosystems is deeply rooted in the classical view of a bottom-up controlled system with strong physical forcing and seasonality in primary production regimes. Consequently, the Arctic Polar Night has commonly been disregarded as a time of year when biological activities are reduced to a minimum due to a reduced food supply. Recently, based upon a multidisciplinary ecosystem-scale study from the Polar Night on Svalbard, an entirely different view has been presented. Instead of an ecosystem that has entered a resting state, we have documented a system in which activity levels and biological interactions across most trophic levels remain high. In some habitats, biological diversity and presence of juvenile stages were elevated in winter months (November–February) compared to the more productive and sunlit periods (March–October). The main ambition of this book is to present how key environmental variables, such as the light regime (intensity, colour and day length) are important cues for marine ecosystem dynamics, biodiversity, production and eco-physiology across different organism groups during the Polar Night. Ultimately, these results suggest a different perspective regarding ecosystem function that will be of importance for future environmental management and decision making, especially at a time when Arctic regions are experiencing accelerated environmental change due to human activity.