Meiofauna of springs in Finland in relation to environmental factors

The meiofauna was studied from springs in Finland which was completely ice-covered during the last glacial epoch. Of the 31 springs that were examined, 15 were in areas considered to be in a natural state and 16 had catchment areas subject to anthropogenic disturbance from one of four sources: agriculture, inhabitation, gravel extraction or winter road de-icing with NaCl. The taxa recorded were a mixture of those already described from epigeic waters or groundwaters and some which may be regarded as characteristic of springs. Statistical analysis revealed differences in the meiofaunal taxa in relation to the water quality or catchment area variables. Of the major meiofaunal groups the nematodes favoured springs influenced by agriculture, oligochaetes were most tolerant of road de-icing, cladocerans and copepods preferred springs in a natural state, ostracods could withstand the influence of road de-icing and gravel extraction, whilst dipteran larvae could withstand the influence of agriculture. Oligochaetes comprised 13.4% of meiofaunal numbers. The most abundant species was Aeolosoma quaternarium, which was most numerous in springs in a natural state, while Dero digitata preferred eutrophic conditions. Harpacticoids comprised 14.1% of individuals and clearly preferred a natural state, Bryocamptus echinatus and Moraria brevipes being the most abundant species. Ostracods, of which the most abundant species was Potamocypris pallida, were the most numerous animal group, constituting 21% of the meiofaunal population, and their numbers were greatest in springs influenced by road de-icing or gravel extraction. Dipteran larvae, of which the majority were chironomids, comprised 14.9% of individuals. The ostracods Potamocypris pallida and three species of Candona and the harpacticoid Bryocamptus cuspidatus are new records for Finland.