The principal islands of the Svalbard Archipelago lie in the European Arctic between 74 and 81°N and 10 to 35°E (Fig. 1). The land area comprises 61 200 km² with a maximum elevation of 1700 m (Hisdal 1985) and of which some 60% is under permanent snow and ice. Mean annual air temperature in Barentsburg is −6.1°C but monthly mean air temperatures are above 0°C between June and September, peaking in July at +5.5°C (Norwegian Meteorological Institute 2012; Fig. 2). Mean annual precipitation is 525 mm, most of which falls during the winter as snow. The period of the midnight sun lasts 126 days, from 20 April until 23 August. Conversely, the duration of the polar night is 81 days, from 11 November to 30 January.

A total of 15 10×10×5 cm-thick soil samples were collected from the bottom and sides of a gully formed in the organic soils accumulated down a westerly facing slope under the abandoned cowsheds in Barentsburg in Grønfjord (78° 04.3N, 014° 12.09 E; Fig. 1) on 8 July 2011. The sampling site (Fig. 3, location A) can be readily identified by the comparatively lush green vegetation to the left of the derelict cowsheds. The soils formed layers several metres thick, created from a mixture of discarded greenhouse soil and manure from the animal houses. Some coal dust is also present. The flora here is rich in introduced species (Liška & Soldán 2004), including species, such as Achillea millefolium L. and Anthriscus sylvestris (L.) Hoffm. (Fig. 4).

It has proved difficult to determine with certainty the origin of the soils imported to Barentsburg. Despite the willingness to assist by the mining company in Barentsburg, Trust Arktikugol, records of the origin of the soils after over 30 years were not available. Liška & Soldán (2004) were similarly unable to determine precisely the source of the fodder for the animals as it was at that time considered to be of strategic importance by the then Soviet authorities. There was a network of suppliers of soil for greenhouses in the former USSR. The Murmansk Company, Cvety Zapolyarya, bought the soils from various companies in the Moscow and Leningrad regions, Republic of Udmurtia. It is known that the soils were imported from the central or southern European parts of Russia in the 1980s. After approximately 30 years, it has proved impossible to obtain more precise information as to the precise geographical source of the soils.

The invertebrate fauna of the cowshed soils is presented in Table 1. In total, 46 species were recorded, 11 of which have not been recorded from other locations in Svalbard.

Eight species of Enchytraeidae were identified from the cowshed samples (Table 1).

The Lumbricidae community of the cowshed soils consisted of two species: Dendrodrilus rubidus (Savigny, 1826) sensu Sims & Gerard (1985) and Dendrobaena hortensis (Michaelsen, 1890). In addition, the BLAST search gave a 99% COI match with two unpublished barcodes (GenBank accession numbers: HQ562578.1 and HQ562579.1). According to the collector, they originate from an Eisenia-like species collected from a compost bin in Curitiba, southern Brazil (Samuel W. James, unpubl. data).

The oribatid mite fauna consisted of eight species (Table 1). Five species of gamasid mite were collected. Only one individual spider was collected, a male Erigone arctica (White, 1852). Eighteen species of Collembola were present. The extracted Chironomidae larvae could be positively associated by barcodes to adult females of the genus Smittia, which have been collected in other on-going projects in the Arctic (Stur & Ekrem, unpubl. data). Two species were recognized, both previously known only as females from the Arctic. The larvae of the other species could be associated with females of Smittia sp. 2, presumably an undescribed species from Spitsbergen (Adventdalen) and Greenland. As with the Chironomidae, the extracted sciarid larvae could be associated by barcodes with adult individuals of the genus Lycoriella, subgenus Hemineurina. Despite some variation between the barcodes (approximately 1%), the originating cluster within the larvae is likely to represent one species. However, at present the studied adult individuals cannot be identified to species with certainty. Only one species of beetle was collected, the staphylinid Atheta graminicola (Gravenhorst, 1806).

In the natural soils, the temperature at 1 cm depth varied greatly and rapidly, especially during winter, with temperatures swinging from close to 0° to below -14°C on several occasions (Fig. 5). The cowshed soils tracked the temperature decline of the natural soils during the autumn but showed a slight delay in the rate of cooling and smaller diurnal fluctuations. During September and October, the cowshed soils reached an absolute minimum temperature of -3.3°C, after which temperatures increased and remained close to 0°C until late May (Fig. 5). There was a delay of some two weeks between the spring rise in temperature of the cowshed soils compared to the natural soils. Moreover, the cowshed soils remained cooler than the natural soils throughout the campaign period in the summer of 2012 and diurnal fluctuations were less marked.

There is a gradually increasing knowledge of the soil invertebrate fauna of Svalbard, especially from locations on the west coast (Coulson 2007Coulson 2013). However, there have been no investigations of the invertebrate fauna inhabiting anthropogenic sites in the archipelago such as the cowshed soils in Barentsburg.

The enchytraeid species collected from the Barentsburg soils are all Holarctic or cosmopolitan. Two species, Enchytraeus dichaetus and Cognettia glandulosa, are not known from other locations in Svalbard and are considered to be recent human introductions with the imported soils (Coulson et al. 2013). In total, more than 30 species of enchytraeids have been recorded from all types of soil habitats in Svalbard (Nurminen 1965; Dózsa-Farkas 1999) and abundance can exceed 50 000 individuals per square metre under favourable conditions (Birkemoe 1995). Excluding the two introduced species, six species were identified, similar to species diversity at other locations around Svalbard (Dózsa-Farkas 1999; Birkemoe et al. 2000). There are some indications that enchytraeid diversity is positively related to plant diversity and the development of organic soil. Birkemoe & Dózsa-Farkas (1994) observed the greatest enchytraeid diversity, 10 species, in wet moss with grasses, while only one species was present in samples consisting predominantly of detritus from black-legged kittiwake (Rissa tridactyla) nests or dominated by moss. The community observed in the Barentsburg soils does not show a unique or unusual assemblage of species compared to natural sites in Svalbard. This may be since the anthropogenic habitat was created too recently for colonization by enchytraeids from other locations in Svalbard. However, the soils are likely to be heavily contaminated with coal dust and also have reduced pH values. Such effects may be especially challenging for animals such as Lumbricidae or Enchytraeidae in contact with the soil solution (Frouza et al. 2011).

Both the lumbricids are only known from the Barentsburg soils (Coulson et al. 2013) and Lumbricidae otherwise appear to be largely absent from the natural environment in Svalbard (Coulson 2007Coulson 2012). The Lumbricidae recorded here are globally widespread, including with records from the Southern Hemisphere. While D. rubidus can be considered as resident in large parts of the Holarctic, D. hortensis has only been occasionally found in Scandinavia. Stöp-Bowits (1969) recorded D. hortensis from a “heap of foliage manure” in the University Botanical Garden in Oslo and Julin (1949) considered it (as “Eisenia veneta, var. hortensis”) an accidental guest in Sweden based on isolated records from gardens in the Swedish province of Uppland. Erséus (unpubl. data) recently collected and barcoded specimens of D. hortensis from Västergötland (south-western Sweden) and Gotland (an island in the Baltic Sea). The record from Gotland is a worm with the same COI haplotype as all the barcoded D. hortensis from Svalbard (Erséus, unpubl. data). Nurminen (1965) reported finding one immature lumbricid specimen in samples taken from clayey soils close to the river in Adventdalen (close to Longyearbyen) but the specimen was too badly damaged to be identifiable. Nurminen merely states that the arrangement of the setae prohibit the animal being Dendrobaena octaedra (Sav.) which in Finland can occur above the tree line. D. hortensis is widely distributed but not so often reported, which may be partly due to the fact that it has been erroneously identified as either Dendrobaena veneta or one of the various “compost worms” belonging to Eisenia. There is little doubt, however, that it is an anthropochorous species and that it is likely that it was recently introduced in Svalbard. Similarly, Rundgren (2007) speculated that the lumbricid fauna of Iceland might be in part due to non-native species imported with ballast soils. D. rubidus on the other hand could, in some areas, be a natural component of the sub-Arctic and Arctic terrestrial fauna. For instance, it was recently found at 70°N in Vardø (eastern Finnmark, Norway), and appears to be common throughout northern mainland Norway (Erséus, unpubl. data). It is also abundant in greenhouses in northern settlements of north-east Russia (Yakutia, Magadan oblast and Chukotka). Up to 120 000 egg cocoons of D. rubidus tenuis per square metre of greenhouse soil were recorded by Berman et al. (2010) in these areas. In winter, these greenhouses are not heated and the temperature may decline to below-40°C. Nonetheless, the cocoons in spring are viable, thereby demonstrating significant cold hardiness as seen in other species of earthworms (Holmstrup 2003).

Of the five species of gamasid mite collected, two species are not recorded elsewhere in Svalbard, Paragamasus insertus and Vulgarogamasus remberti (Ávila-Jiménez et al. 2011). The remaining three species Antennoseius oudemansi, Arctoseius haarlovi and Arctoseius multidentatus are widespread in Svalbard and recorded from a variety of habitats (Ávila-Jiménez et al. 2011; Gwiazdowicz & Coulson 2011) including Salix and Dryas tundra, Cassiope heaths and under bird cliffs. A. multidentatus is one of the most widespread gamasid mite species occurring at 10 of the 18 locations throughout Svalbard investigated by Ávila-Jiménez et al. (2011). A. oudemansi and A. haarlovi are likewise almost as prevalent, found at seven and five of the 18 locations, respectively. Excluding the two introduced species of gamasid mite (Coulson et al. 2013), the overall gamasid diversity observed in the cowshed soils is not very much different from other vegetation types in Svalbard (Ávila-Jiménez et al. 2011; Gwiazdowicz & Coulson 2011).

The eight species of observed oribatid observed are all previously known from Svalbard (Coulson & Refseth 2004; Bayartogtokh et al. 2011) with wide distributions throughout the Palaearctic or Holarctic (Bayartogtokh et al. 2011). The species number is very poor and the composition representing species with broad ecological tolerance and often present in diverse habitat types. It is most probable that the oribatid mites sampled have colonized the cowshed soils from the adjacent localities and are populations native to Svalbard. However, it is possible that some populations of Tectocepheus velatus, Oppiella nova, Liochthonius brevis, Liochthonius sellnicki, Oribatula tibialis and Oppiella neerlandica collected here may also have been imported to Svalbard together with the greenhouse soil as they occur in chernozem soils in the European part of Russia, where the soils are thought to have been sourced. The range of Diapterobates notatus is mainly in the Arctic–boreal zone (Melekhina 2011). Identification of the oribatid mites in this study was done by morphological taxonomy. Hence, we cannot conclude if the species identified here, but already present in the invertebrate inventory of Svalbard, have been introduced with the soils or not. However, it is appreciated that there can be marked genetic divergence within species of oribatid mites (Schäffer et al. 2010). Hence, the possibility of the introduction of cryptic species should not be discounted. The composition and structure of the oribatid species found in our material is unusual compared to samples from natural habitats in Svalbard (Solhøy et al. unpubl. data). Of the 761 specimens recovered, the Oppiidae accounted for 57% and the Brachychthoniidae for 42%. The specimens of T. velatus (1), O. tibialis (2) and D. notatus (3) made up only 1% of the community represented by stray individuals. This could indicate that the Oppiidae (O. neerlandica and O. nova) and the Brachychthoniidae (at least L. brevis and L. sellnicki) were introduced by human activity. They are all parthenogenetic and probably establish more easily than sexual species (Norton & Palmer 1991).

The majority of the 18 species of Collembola are widespread outside the Arctic (Fjellberg 1998, 2007) except for Friesea quinquespinosa which is an exclusively Arctic species. The five species only recorded from Barentsburg (Coulson et al. 2013) are typical members of a fauna associated with soils having a high organic content such as compost, garden soil and wrack beds along seashores and stream banks. It is likely that these five species of Collembola are all human imports. The remaining 13 species are common in a variety of habitats throughout Svalbard (Coulson 2007) and do not represent an unusual species assemblage.

In the ornithogenic soils from bird cliffs, predominantly little auk (Alle alle), Zmudczynska et al. (2012) observed seven species of Collembola. Few other studies in Svalbard have targeted the invertebrate communities in such habitats but in a study that included the Florabukta bird cliffs and polar desert-type vegetation in the vicinity of Kinnvika, Nordaustlandet (north-east Svalbard), Coulson et al (2011) recorded 24 species of Collembola. Similarly, Fjellberg (1997) identified 26 species of Collembola from Florabukta and noted the strong relationship between floral diversity and cover with Collembola species diversity. Interestingly, Fjellberg (1997) also observed that while amongst the Nordaustlandet habitats surveyed species diversity was greatest at Florabukta, the number of species per soil sample was not particularly great. Fjellberg also noted that sites with a lower total species diversity often had the greatest densities of individuals. Studies using chronosequences across proglacial margins have also revealed a relationship between vegetation cover/diversity and collembolan biodiversity (Hodkinson et al. 2004). Nonetheless, despite the organic soil and high plant diversity (Liška & Soldán 2004), the soils examined here do not appear to have a distinct collembolan community from other locations in Svalbard, excluding the introduced species. Thirteen species of Collembola in the samples are not untypical for habitats in the archipelago and the species observed are all widely distributed throughout the region (Coulson 2007Coulson 2012)

The chironomid larvae extracted from the Barentsburg soil were associated with two species of the genus Smittia only known as females and of which one probably is new to science. Smittia brevipennis (Boheman 1865) was described from Spitsbergen more than 150 years ago. This species has not been recorded from the European continent but is known from Arctic Siberia (Sæther 2004). It is not unlikely that these species are parthenogenetic (or at least facultative parthenogenetic) as reproduction by parthenogenesis has been documented from Smittia and is known to be more frequent in the Arctic than at lower latitudes (Oliver 1970). Both species of Chironomidae have previously been found in the Arctic. Concerning the Sciaridae, four species belonging to the subgenus Hemineurina have previously been recorded from Spitsbergen (Coulson & Refseth 2004). Hence, the larvae from Barentsburg may well represent a resident species. The staphylinid beetle, A. graminicola, is widespread in Svalbard and particularly so under bird cliffs preying on the often abundant collembolan Megaphorura arctica (Coulson pers. obs). However, it should be recognized that the sampling and extraction techniques are not efficient for these last groups and hence, it is likely that not all species of Diptera, Coleoptera or Araneae were collected.

The composition of the soils, especially the significant organic enhancement from the cowshed manure, and the westerly facing aspect of the site in Grønfjord create an unusual habitat in Svalbard. The open aspect and open water in front of the site enable continual insolation during the summer months. The deep and rich organic soils provide a habitat with excellent water-holding potential throughout the summer. This in particular may explain the persistence of the Lumbricidae observed in these soils. Where snow cover is thin, the soil temperature may track air temperature more closely and decrease to below -20°C (Coulson et al. 1995) but under a snow blanket soil temperatures may not decline much below -5°C. Air temperatures during winter 2011–12 were highly atypical. Monthly mean monthly air temperatures in January and February were -3.4 and -5.5°C, respectively, some 11.9 and 10.7°C above long-term normals (Norwegian Meteorological Institute 2012). Nonetheless, the lack of deep snow cover on natural soils resulted in soil temperatures closely tracking air temperatures, with large variation in temperatures. In stark contrast, the cowshed soils remained at close to 0°C throughout the entire winter. This is in part due to the thick litter layer accumulated from plants such as A. sylvestris but there may also be some thermogenic activity due to the slow decomposition of the large quantities of organic matter in the soils. This extremely ameliorated winter environment may explain in part the persistence of some of the exotic species identified in these soils (Coulson et al. 2013). Although, compared to the natural soil site, the cowshed soils are warmer during the winter, these soils warmed later in the following spring and remained at lower temperatures than the natural soil site. This is likely to be due to the shaded location of the site, the presence of accumulated litter and the tall plants hindering the warming of the soil surface by solar insolation.

In contrast to the natural soils, the anthropogenic soils provide a nutrient-rich, organic soil with excellent water-holding properties and with a cool moist environment during the summer but an extremely ameliorated habitat during the winter. However, soil pollution levels, for example, PCB₇ (polychlorinated biphenyl) and the insecticide dichlorodiphenyltrichloroethane (DDT), in Barentsburg are generally high (Jartun et al. 2009). In the area sampled, PCB₇ levels are up to 0.5 mg/kg (Geological Survey of Norway 2010) and the pollution report publicised by the Russian Federal Service of Hyrometeorology and Environmental Monitoring (FSHEM 2009) found DDT levels of 1.3 µg/g in soils close to the cowsheds. Coal dust is also present. Such dust, and associated heavy metals contaminants such as lead and arsenic (FSHEM 2009), may also have toxic or repellent effects on the invertebrate fauna (Frouza et al. 2011). Hence, the resident Svalbard invertebrate fauna, not generally challenged by high pollutant levels, may have difficulties fully exploiting the new habitat perhaps partly explaining the diversity observed.

In conclusion, the soil invertebrate fauna observed in these anthropogenic soils is a mixture of species widespread throughout Svalbard , including a few probably introduced species (Coulson et al. 2013), and is likely to represent a unique community in the archipelago. However, excluding the introduced species, the invertebrate fauna does not form an especially atypical community. On the contrary, the community shows strong similarities with other habitats in Svalbard, both nutrient poor and enhanced. The soils therefore may well provide a habitat for introduced species, possibly in some cases the only location in Svalbard that is suitable, but, as yet, do not seem to furnish a particularly favourable site when considering overall invertebrate species diversity.