Nathalie Morata

Unexpected Levels of Biological Activity during the Polar Night Offer New Perspectives on a Warming Arctic

The current understanding of 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 is commonly disregarded as a time of year when biological activities are reduced to a minimum due to a reduced food supply. Here, based upon a multidisciplinary ecosystem-scale study from the polar night at 79°N, we present an entirely different view. Instead of an ecosystem that has entered a resting state, we document a system with high activity levels and biological interactions across most trophic levels. In some habitats, biological diversity and presence of juvenile stages were elevated in winter months compared to the more productive and sunlit periods. Ultimately, our 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 [1].

Do benthic meiofaunal and macrofaunal communities respond to seasonality in pelagial processes in an Arctic fjord (Kongsfjorden, Spitsbergen)?

This study explores whether the marked seasonality in pelagic productivity and phytodetritus fluxes to the sea bottom in an Arctic fjord is reflected in variability of benthic communities in terms of taxonomic composition and standing stocks. Three stations located along the Kongsfjorden (west Spitsbergen) axis were visited in four seasons (May, August, October and January), and meiofauna and macrofauna was sampled. The elusive seasonal variability in benthic attributes contrasted with the clear seasonal effects in organic matter productivity and vertical fluxes (with diatom bloom-related peak in spring). No consistent differences in meiofaunal and macrofaunal density, diversity or composition among the four seasons were detected by PERMANOVA tests. Possible responses to spring food supply in meiofaunal reproduction timing were demonstrated in variability in individual size of Nematoda (decline in October after the maximum in August), Harpacticoida (decline in May and increase till October) and macrobenthic Crustacea (minimum in May). The spatial patterns shaped by the environmental gradients related to glacial inputs, the faunal impoverishment in inner basin and a shift in dominants along the fjord axis, were clearly designated and stable throughout the year. The resilience of Arctic fjordic benthic community to marked seasonality in pelagic phytodetritus fluxes may be related to organic matter reserves in sediments (large enough to sustain the detritus feeders on a year-round basis), inclusion of macroalgal carbon into the diet and common employment of lecithotrophic larva or direct development by polar benthos.