Joanna Legeżyńska

Climate change effects on Arctic fjord and coastal macrobenthic diversity—observations and predictions

The pattern of occurrence and recent changes in the distribution of macrobenthic organisms in fjordic and coastal (nearshore) Arctic waters are reviewed and future changes are hypothesized. The biodiversity patterns observed are demonstrated to be contextual, depending on the specific region of the Arctic or habitat type. Two major areas of biotic advection are indicated (the North Atlantic Current along Scandinavia to Svalbard and the Bering Strait area) where larvae and adult animals are transported from the species-rich sub-Arctic areas to species-poor Arctic areas. In those Arctic areas, increased temperature associated with increased advection in recent decades brings more boreal-subarctic species, increasing the local biodiversity when local cold-water species may be suppressed. Two other large coastal areas are little influenced by advected waters; the Siberian shores and the coasts of the Canadian Archipelago. There, local Arctic fauna are exposed to increasing ocean temperature, decreasing salinity and a reduction in ice cover with unpredictable effect for biodiversity. One the one hand, benthic species in Arctic fjords are exposed to increased siltation (from glacial meltwater) and salinity decreases, which together may lead to habitat homogenization and a subsequent decrease in biodiversity. On the other hand, the innermost basins of Arctic fjords are able to maintain pockets of very cold, dense, saline water and thus may act as refugia for cold-water species.

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].

Benthic scavengers collected by baited traps in the high Arctic

Abstract Baited traps were deployed in the coastal areas of Svalbard (0–175 m), Franz Josef Land (15 and 20 m), Northeast Greenland (6 and 20 m) and Ellesmere Island (2–145 m). The samples were dominated by Lysianassidae (Amphipoda). In the most extensively sampled locality (Hornsund, Svalbard), differences between the necrophagic fauna of the outer and inner basins were observed. Clear depth separations of closely related species of the Anonyx and Onisimus genera were found between 0 and 175 m in Hornsund. Anonyx nugax and Onisimus edwardsi were the only species found in all of the examined localities.

When season does not matter: summer and winter trophic ecology of Arctic amphipods

Polar marine ecosystems’ functioning is known to be strongly affected by the seasonality of water column production. However, a response of benthic organisms may range from close coupling to total decoupling from seasonal variability of environmental processes, depending on a feeding strategy. In this study, we used a multi-method approach (gut content, lipid and stable isotope analyses) to examine trophic ecology and major food sources of a large set of Arctic sub-littoral amphipods, and to evaluate whether their feeding strategies undergo seasonal changes. The wide range of δ15N values (5.45-12.43‰) indicates that amphipods form a trophic continuum from primary herbivores to carnivores/scavengers. Three main feeding modes, namely scavenging/predatory, deposit-feeding/predatory and phytodetrivory, were distinguished based on the multivariate analysis of whole fatty acid profiles. Total lipid content was low in all species and included primarily short-term energy reserves of triacylglycerols. In general, amphipods feeding habits appeared to be independent of the seasonal phytodetritial pulses. Low reliance on lipid reserves and lack of major changes in the trophic strategies over time suggest that these crustaceans feed continuously, taking advantage of a variety of food sources that are available year-round in shallow polar waters.

Food resource partitioning among Arctic sublittoral lysianassoid amphipods in summer

Five species of lysianassoid amphipods (Anonyx nugax, Anonyx sarsi, Onisimus caricus, Onisimus edwardsii, Orchomenella minuta) co-occur in the shallow sublittoral of Kongsfjorden (Svalbard, Arctic), share similar functional attributes, and exploit a common food base. All species are known to be necrophagous; however, this study revealed through combination of gut-content analysis with the morphological characteristics of their mandibles and available information on feeding ecology, the complexity of their trophic strategies. Only mature individuals of A. nugax are true scavengers; immature individuals of this species feed on both animal and non-animal food. A. sarsi and O. caricus are scavengers and predators; the former prefers polychaetes, while the latter relies mostly on zooplankton. O. edwardsii is an omnivorous feeder, and the set of its primary food consists of carrion, crustaceans, and algae. O. minuta is a detrivorous–carnivorous species. These results indicate that niche overlap among these closely related species is reduced, not only by spatial segregation, but also by the exploitation of different components of food resources.

Hermit crabs (Pagurus spp.) at their northernmost range: distribution, abundance and shell use in the European Arctic

Hermit crabs are important components of Arctic benthic systems, yet baseline data on their densities and distribution patterns in this rapidly changing region are still scarce. Here we compile results of numerous research expeditions to Svalbard, the Barents Sea and northern Norway that were carried out from 1979 to 2011 by the Institute of Oceanology, Polish Academy of Sciences. The diversity of hermit crabs at the northern edge of their occurrence is very low; in Svalbard waters only one species (Pagurus pubescens) was detected. Another species (P. bernhardus), found in northern mainland Norway, north of the Arctic Circle, is likely to extend its distribution northward as the climate warms. Where the two species co-occur, competition between them probably accounts for the smaller sizes and poorer quality shells used by P. pubescens. The composition of the mollusc shells inhabited by these crabs differs between northern Norway and Svalbard, reflecting local mollusc species pools. Hermit crab densities were significantly higher than previously reported (max. mean 10 ind. m−2), suggesting their increasing level of dominance in benthic communities in the studied areas. The first to report the distribution of hermit crabs among habitats, this study showed that most individuals occurred at shallow depths (5–150 m), away from glacier termini and on hard bedrock rather than on soft substrata.

Kelp forest as a habitat for mobile epifauna: case study of Caprella septentrionalis Kröyer, 1838 (Amphipoda, Caprellidae) in an Arctic glacial fjord

Distribution and abundance of the amphipod Caprella septentrionalis in relation to environmental conditions and habitat preferences were investigated in a kelp forest in Hornsund, Spitsbergen. Three sampling sites differed in hydrodynamics, organic and inorganic suspension concentration, and sedimentation rates. None of these abiotic factors or species of a macroalgal host appeared to have a significant influence on C. septentrionalis abundance and size range. An apparent preference towards the blade parts of the algal thalli was observed. These results support the idea of C. septentrionalis as a generalist Arctic–boreal species that takes advantage of the protective nature of kelp forests.

Range extension of a boreal amphipod Gammarus oceanicus in the warming Arctic

Abstract The recent (2008–2016) occurrence of a boreal intertidal amphipod Gammarus oceanicus along the Spitsbergen coast is compared with corresponding data from 1980 to 1994. We aimed to compare the pace of environmental changes in the area (ice retreat, temperature increase) with distribution change of G. oceanicus. Material for the study was collected from intertidal, at low water level from over 100 locations on Spitsbergen, the main island of Svalbard archipelago (expanding from 76 to 80°N). The west coast of the island has been exposed to a steady increase in sea surface and air temperature (2°C in 20 years), as well as a significant decrease in fast ice duration (from over 5 months to less than 1 per year). A total length of more than 3,600 km of the islands coastline has been recently impacted by warming. Of the two sibling Gammarus species that dwell in the Spitsbergen littoral, G. setosus, the local cold water species remains generally where it was observed about 20–30 years ago. By contrast, boreal G. oceanicus has expanded its distribution range by over 1,300 km along the west and north coasts of Spitsbergen and gained dominating position on the number of sites, where it was previously just an occasional species.