The macroinvertebrate fauna and hydrogeology of springs in central Sweden

The macroinvertebrate fauna of 23 springs in central Sweden was sampled. A total of 79 taxa was recorded, including three crenobiont, nine crenophilic , 33 lotic, 11 lentic and 21 ubiquitous taxa. Only eight were non-insect ta xa. Geological and hydrogeological maps were used to categorize each spring , resulting in eight glaciofluvial, 11 moraine and four limestone springs. Faunal composition and environmental factors showed an overall similarity a mong spring types, except for geographic position, the almost exclusive occ urrence of crenobionts in glaciofluvial springs, and factors associated wit h high concentrations of calcium carbonate in limestone springs. Canonical correspondence analysis showed that the crenobiont caddisflies Parachiona p icicornis (Pictet), Crunoecia irrorata Curtis were associated with high dis charge and high summer temperature. Lotic taxa, including the stonefly nymp h Isoperla grammatica (Poda), the caddis larvae Halesus sp. and the mayfly nymph Baetis bundyae Lehmkuhl, were associated with high discharge and low summer temperature, while many lentic and ubiquitous taxa, e.g. dytiscids, were characteristic of small springs. It is suggested that the dominance of insect taxa, and the restricted occurrence of crenophilic and crenobiont t axa, are consequences of the glacial history and/or the hydrogeological set ting of springs. Also, the possible influence of 'diffusive rarity' of C. i rrorata and P. picicornis, is discussed.