Kongsfjorden is a glacial fjord in the Arctic (Svalbard) that is influenced by both Atlantic and Arctic water masses and harbours a mixture of boreal and Arctic flora and fauna. Inputs from large tidal glaciers create steep environmental gradients in sedimentation and salinity along the length of this fjord. The glacial inputs cause reduced biomass and diversity in the benthic community in the inner fjord. Zooplankton suffers direct mortality from the glacial outflow and primary production is reduced because of limited light levels in the turbid, mixed inner waters. The magnitude of the glacial effects diminishes towards the outer fjord. Kongsfjorden is an important feeding ground for marine mammals and seabirds. Even though the fjord contains some boreal fauna, the prey consumed by upper trophic levels is mainly Arctic organisms. Marine mammals constitute the largest top‐predator biomass, but seabirds have the largest energy intake and also export nutrients and energy out of the marine environment. Kongsfjorden has received a lot of research attention in the recent past. The current interest in the fjord is primarily based on the fact that Kongsfjorden is particularly suitable as a site for exploring the impacts of possible climate changes, with Atlantic water influx and melting of tidal glaciers both being linked to climate variability. The pelagic ecosystem is likely to be most sensitive to the Atlantic versus Arctic influence, whereas the benthic ecosystem is more affected by long‐term changes in hydrography as well as changes in glacial runoff and sedimentation. Kongsfjorden will be an important Arctic monitoring site over the coming decades and a review of the current knowledge, and a gap analysis, are therefore warranted. Important knowledge gaps include a lack of quantitative data on production, abundance of key prey species, and the role of advection on the biological communities in the fjord.

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We present observations of temperature, salinity and phytoplankton from late winter of 1999 obtained along a meridional transect running from 52 to 72°N through the northern North Atlantic and Norwegian Sea. The field work was conducted with the intention to find evidence for a postulated relationship between convection and primary production in the open ocean in winter. In the investigated area, convection ventilates water masses in a deep mixed layer which may cover several hundreds of meters, depending on atmospheric forcing and stratification. Inspired by the results of a coupled phytoplankton convection model, we postulated that sinking phytoplankton from the seasonal thermocline in autumn is dispersed within the mixed layer by vertical orbital motions and turbulence induced by convection. Orbital motions allow intermittent visits of plankton to the euphotic layer from much deeper depths. Hence, convection distributes the chance of plankton receiving light over the entire mixed layer. This supports production and allows compensation of losses due to sinking. We hypothesised that a winter stock of living phytoplankton in the open ocean would always coincide with the deep mixed layer formed by convection, irrespective of its depth. Indeed, along the entire meridional transect, living phytoplankton was found within the layer, whereas only marginal amounts or virtually no phytoplankton existed beneath it. The layer extent varied between 300 and 800 m. In the northern North Atlantic, average concentrations of chlorophyll a (as a measure of phytoplankton biomass) in the mixed layer were about 0.3 mg m -3, and 0.6 mg m -3 in the Norwegian Sea. We concluded that this winter stock forms the inoculum for a spring production in the open ocean. KEY WORDS: Primary production · Winter · Convection · Vertical orbital motionsResale or republication not permitted without written consent of the publisher

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