Enchytraeids in imported soil and organic deposits in Pyramiden, an abandoned mining town on Spitsbergen in the High Arctic

Abstract

In Arctic soils, potworms (Clitellata: Enchytraeidae) are a particularly important decomposer group. There are relatively many faunistic records from the Svalbard archipelago, in particular its main island Spitsbergen, but few ecological studies on enchytraeids. With climate change and increasing tourism, the introduction and subsequent spreading of exotic species might pose a threat to native biotic communities. In Pyramiden, a Russian (formerly Soviet) coal mining settlement on Spitsbergen abandoned in 1998, Chernozem soil from southern Russia or Ukraine had been imported in 1983 to create lawns. Today the long central lawn presents an environmental gradient: on one end rather shallow humus-rich soil is fertilized by a sea bird colony on an adjacent building, the central part has a rich organic horizon topping humus-rich mineral soil, whereas on the other end humus-rich soil is covered by deposited mineral soil. In August 2018, we sampled this gradient to study the enchytraeid assemblage. Additional samples were also taken within frames with a vigorous grass turf in front of residential houses and in a vegetated heap of decomposing organic material (mostly woodchips). The objectives were to see (1) if and how the differences between habitats would be reflected by changes of the enchytraeid assemblages and (2) if there were any potentially introduced species. Almost 3700 specimens were identified and 9 species were recorded, which is high for habitats of the High Arctic. One species, Enchytraeus buchholzi s.l., had been recorded before in the archipelago only once, also in imported soil. This small-bodied euryoecious r-strategist is abundant in agricultural and other disturbed soils. Molecular barcoding and comparison with sequences from Central Europe showed close resemblance to several specimens, which makes an introduction with the transferred Chernozem highly probable. Most enchytraeids were concentrated in the upper 3 cm of soil (even if mineral), only in the organic deposits vertical distribution was rather even down to 12 cm depth. Numbers in the organic deposits were exceedingly high (ca 417,000 individuals/m2) and E. buchholzi s.l. represented ca 90 % of all specimens. Ordination (NMDS) showed all habitats to host rather distinct assemblages. Spearman's rank correlation showed significant positive correlation of species richness with conductivity and total nitrogen and of abundance with phosphorous and potassium contents in aqueous solution.