Virtual Posters

Ongoing climate change likely has pronounced effects on the Arctic environment and its endemic organisms. The intrusion of Atlantic water masses to the area has increased in later years, along with an increment of boreal species, such as Calanus finmarchicus. Little auk (Alle alle) is a central place forager, feeding on plankton (especially Calanus spp.), and thus relying upon energetic and abundant prey within a reachable area from its nesting site in order to raise its chick. Bimodal feeding strategy has been described for little auk; food collected during short trips is used for chick allocation and long trips are realized in order to replenish the adult’s own body reserves. It has been hypothesized that the length of foraging trips is directly related to prey availability within the foraging range. During years of poor food conditions, little auks should spend longer time searching for prey, and less time when availability and quality of prey improve. Little auk is mainly consuming Calanus spp., and thus its dependence upon these lipid-rich organisms is apparent. Relatively large and energy-rich Calanus glacialis and C. hyperboreus are indicatives of Arctic water masses, and preferred by Little auk, compared to the smaller, Atlantic C. finmarchicus with lower energy content. With this kind of diet specialization, the Little auk is regarded as a sensitive indicator of the changing Arctic marine environment. We have put forward a hypothesis concerning the relation between prey availability and trip duration, which we wish to test for different climatic conditions, i.e. under dominance of Atlantic (warm scenario) and Arctic (cold scenario) water masses. Furthermore, we will determine how changes in trip duration affect the breeding success of Little auk. Intensive fieldwork campaigns have been carried out in Isfjorden, Svalbard, during five consecutive years (2006-2010). Samples of gular pouches, zooplankton, water masses (CTD data), and 48-h observations have been collected. Preliminary results indicate higher chick survival when shorter time is spent on the long foraging trips, although this may be compromised by less body reserves.