engleski

Do benthic diatom communities reflect abiotic typology? a case study of Croatian rivers and streams

Benthic diatoms are, as good environmental indicators, widely used in Europe and worldwide to access ecological status of running waters. Also, one of key goals of Water Framework Directive is to classify rivers and streams using biological quality parameters and type specific reference conditions. For description of water types system B that allows usage of additional abiotic descriptors (as flow, granulometric properties of waterbed, tuffa forming conditions and permanence of flow) was used in Croatia and in total, 24 types were described. For biological analyses 92 rivers and streams with total of 157 sampling points were chosen. Along with samples of natural benthic diatom communities, samples of water for chemical analyses ware also taken. TWINSPAN analysis was used to define biotypes from species composition and abundance of benthic diatom species. Altogether 11 groups and subgroups of biotypes were indentified. Nonmetric Multidimensional Scaling with grouping according to both typologies was used for their comparison. Although biotypes show similar grouping of samples as abiotic types, especially if we ignore subdivisions of abiotic groups according to elevation, there are three biotype groups consisting of only a few sampling points that could, according to abiotic types, fall into other larger groups. Canonical Correspondence Analysis was used to investigate the relationship between sampling points and nutrient concentrations to reveal if chemical and physical factors were the cause of such separation.

Benthic diatoms; typology; rivers; streams

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