METAZOAN MICROFAUNA IN AN OMBROTROPHIC MIRE AT ABISKO, NORTHERN SWEDEM

The metazoan microfauna (nematodes, rotifers and tardigrades) in an om brotrophic mire at Stordalen, Abisko, in northern Sweden was investiga ted by monthly samplings in the summer season from June to September 1 996. The population density of the three animal groups was rather high , especially in the surface moss layer. Over the sampling period the m ean number of all groups together was 11 x 10(6) ind.m(-2) with a biom ass of 1.6 g fw m(-2). The nematodes dominated the microfauna with mea n abundance, 9.4 x 10(6) ind.m(-2). The composition of the nematode fa una was typical for polar tundra soils. Thirty-four nematode taxa and five taxa of tardigrades were identified. In the surface moss layer, t he proportions of nematodes classified as facultative fungal feeders a nd as bacterial feeders were similar. On the contrary bacterial feeder s dominated over facultative fungal feeders in the underlaying peat. T here was a high proportion of nematode females with uterine eggs in th e beginning of the summer season and the numbers of several population s increased in later season samples. The relative contribution by this fauna to energy and nutrient fluxes appear somewhat higher than in lo w latitude ecosystems.