The sandhopper Talitrus saltator is common on sandy beaches at different latitudes. Therefore, behavioural variations allowing them to cope with a wide range of environmental variation are expected. To test the hypothesis that behavioural adaptations to natural environments are characterised by different salinities, we compared two behaviours (substrate choice and escape from immersion) of two T. saltator populations from a Mediterranean (high salinity) and a Baltic Sea (low salinity) sandy beach. T. saltator preferred to burrow in the high salinity substrate, irrespective of its beach of origin. Regarding orientation to escape from immersion, Baltic sandhoppers always oriented landwards, whereas Mediterranean sandhoppers showed a significant orientation landwards only when immersed in high salinity sea water. These behavioural traits matched the different environments, and this adaptation capability can be used as a model to analyse the response of a keystone species to environmental changes.

Although, pelagic Ostracoda are locally abundant component of the mesozooplankton in the waters around Svalbard, the group remains poorly characterised both taxonomically and ecologically. Herein, the spatial and vertical variations in abundances and species composition of the pelagic Ostracoda assemblages are examined and related to the water masses. The study is based on a series of zooplankton samples collected with a multinet plankton sampler (MPS; HydroBios, Kiel), consisting of five nets fitted with a 180-lm mesh net. Samples were collected from deep stations (i.e., with bottom depths [300 m) around Svalbard and included localities influenced by the West Spitsbergen Current and the East Spitsbergen Current and to the north of Svalbard, between years 2001 and 2006. Throughout all the samples studied Discoconchoecia elegans was the numerically dominant species. The other species found were Boroecia maxima, Boroecia borealis, Obtusoecia obtusata, and a rare novel Boroecia species. Analyses of the pelagic Ostracoda assemblages showed that their variability was predominantly influenced by four factors: water temperature, geographical position, bottom depth and season. The highest densities of D. elegans were correlated with salinities [35 PSU whereas B. maxima distribution was dependent on latitude. Highest concentrations of B. borealis were determined by longitude. Abundances of O. obtusata were positively correlated with warmer water temperatures. Thus this work suggests that halocyprids have the potential to be good indicators of environmental changes associated with shifts in climate at high latitudes in the North Atlantic.