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Abstract

Abstract From the measurement of chemical parameters in 2 small German streams there are no indications of direct hunman influence on the chemistry of the water. In the woodland stream Rohrwiesenbach the concentrations of dissolved organic compounds (COD) increase with increasing discharge (W). Equations of the form log COD = a * log W + b were calculated. The proportion of dissolved organic compounds which come from primary producers of the stream is very low, most substances being of allochthonous origin. In the open grassland stream Breitenbach the allochthonous influence is of less importance. In the Rohrwiesenbach the primary production of "Aufwuchs", measured with the ¹⁴C-method by use of exposed "Aufwuchs" carriers, was 22.2 and 20.1 g C/m²/year. In the Breitenbach the production was only 11.2 g C/m²/year, but the production by macrophytes and by "Aufwuchs" on macrophytes was not measured. The quantity of primary production of the moving body of water was very low in comparison with the "Aufwuchs" production. The input of coarse particulate organic matter was 634 g C/m²/year in the woodland part of the Rohrwiesenbach; in the Breitenbach only 46.8 g C/m²/year were found. The fixation of CO₂ in the dark as a possible measure of bacterial activity was rather high in the moving body of water. Sometimes it exceeded primary production.