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Testing the suitability of leeches (Hirudinea, Clitellata) for biological assessment of lowland streams

Koperski P.

Polish Journal of Ecology

2005

Vol. 53, nr 1

65-80

Certain features of leeches make them potentially very useful in the biological assessment of freshwaters as bio-indicators of water pollution, especially in moderately polluted lowland watercourses. The main aim of the study was to test their usefulness as indicators of the level of habitat degradation. The composition of leech samples and the main abiotic parameters in water samples, which had been taken simultaneously in six lowland streams of north-eastern Poland and the relations between them were investigated. Multivariate methods of data analysis wereused to test if particular leech species or the taxonomic composition of assemblages thereof could be useful in predicting the assessed quality of the environment. The greatest difficulty with analysis of the results is to separate the effect of the stream (site specifics) from the effect of environmental quality, expressed as Cumulative Index of Environmental Quality (CIEQ). An important result of this study is the highly consistent prediction of the level of water pollution to be attained on the basis of leech taxonomic composition using Discriminant Function Analysis. Some common leech species were found to be good, positive or negative indicators of pollution level. The classifications of Glossiphonia complanata and Erpobdella octoculata as negative bio-indicators corroborates the conclusions of numerous previous studies, in contrast with the indicative value of Helobdella stagnalis, shown previously to be rather a negative indicator. It would seem to be necessary, for biomonitoring purposes, to identify detailly the leeches of such ecologically different families as Glossiphonidae and Erpobdellidae.