Beyond Masses and Blooms: The Indicative Value of Oligochaetes |
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Authors: | Piet F M Verdonschot |
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Institution: | (1) Alterra, Green World Research, P.O. Box 47, 6700 AA Wageningen, The Netherlands |
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Abstract: | The European Water Framework Directive (WFD) defines a framework for assessing water bodies in Europe in the future. The conditions
in the Directive impose a strong demand for “new” assessment systems. The AQEM project developed an assessment system for
European streams using macroinvertebrates. Almost 900 samples were taken in about 400 streams covering 29 stream types distributed
over eight countries. The role of the Oligochaeta within this European database was analysed. Almost half a million specimens
of oligochaetes were collected in 772 samples. Eight families, 41 genera and 69 species were recorded, although identification
emphasised the families Tubificidae and Naididae. Three countries identified oligochaetes to species level, most others restricted
their identifications to easy identifiable taxa. Numbers of specimens, species, genera and families differed strongly between
the countries due to method, although standardised, and taxonomic knowledge. About 50% of all collected oligochaete taxa had
assigned biological and ecological indicator values for metric calculation in the AQEM assessment system. A further refinement
of this indication list as well as increased coverage of oligochaete taxa was advised. Weighted averaging was used to evaluate
the relation between oligochaete distribution and ecological quality class. It was concluded that when higher taxonomic levels
are used in assessment, the quality evaluation results become biased. Furthermore, oligochaetes can tell us much more about
the ecological status of streams than is commonly assumed. Differences in ecological optima among Limnodrilus udekemianus, Ilyodrilus templetoni, Aulodrilus pluriseta, Nais communis, and Spirosperma ferox are shown. |
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Keywords: | Oligochaeta assessment streams weighted averaging ordination ecological quality |
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