Benthic macroinvertebrate fauna is a biological quality element required for classification of the biological status of waterbodies. Rivers, lakes, and transitional waters are outlined as separate categories for which different quality criteria must be applied (WATER FRAMEWORK DIRECTIVE 2000). Actually, hydro-morphological differences between lotic and lentic sites (as well as between permanent and temporary sites) are not always distinct. Streams may begin from lakes, or run through lakes. Between bogs, but also before entering lakes, lotic waters include lentic sections. On the other hand, large lakes may possess wave-zones with a fauna resembling that of rivers rather than that of lakes.Studies of lake macrozoobenthos have traditionally focused on the profundal or the sublittoral. However, to directly compare the macroinvertebrates of lakes, streams, and transitional waters, only shallow-water areas appear to be appropriate because only they occur in each category. The littoral as an area alternative to the profundal was recently recommended for classification of lakes (SOLIMINI et al. 2006). Similarly, stream margins serve as appropriate corresponding area, if water in the middle of channel is too deep (LINKE & NORRIS 2003).Comparison of the shallow-water macroinvertebrate assemblages of different waterbody types is still seldom performed. In the Netherlands, 42 cenotypes, based on macroinvertebrates, were separated from among a wide range of waterbodies (VERooNscHOr & NIJBOER 2000). In Sweden, habitat-scale and ecosystem characteristics explained best among-site variance both for streams and for lakes. No clear-cut functional differences were found between stream riffle communities and stony lake littoral communities (JOHNSON et al. 2004).We tested how well the macroinvertebrate assemblages of different (mostly permanent and unpolluted) habitats in shallow-water areas matched a priori established habitat types in Estonia, involving a wider range of biotopes than merely stony bottom. The study was intended to facilitate biological classification of waterbodies as required by the Directive.
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