Indicating the trophic state of running waters by submersed macrophytes and epilithic diatoms. Exemplary implementation of a new classification of taxa into trophic classes

Abstract

The macrophyte vegetation, the epilithic diatoms and the physico-chemical characteristics of the stream Lauterbach, a small calcareous stream in Bavaria (Germany) were studied. The stream Lauterbach was divided into 20 mapping sections. In each section the quantity of macrophyte species was estimated according to a five degree scale. A sample of epilithic diatoms was taken and the physico-chemical characteristics were measured in each section. The distribution of 'trophic points' was calculated according to a new classification of species in trophic classes developed in Bavaria. The comparison of the results of the macrophytes and the diatoms showed various differences, but according to both systematic groups the stream Lauterbach can be classified as oligotrophic. The chemical and physical parameters support this classification. The physico-chemical differences between the 20 mapping sections were too small to give a clear picture of differences in the trophic situation on a smaller scale. Regardless of the overall characterisation of the stream Lauterbach as clearly oligotrophic the macrophytes showed three typical declines in the proportion of 'oligotrophic plus oligomesotrophic points'. Two of these declines are clearly associated with the observation of massive growth of green algae in those areas. They are possibly caused by the influence of a golf court and an inflow into the stream Lauterbach. The third one can be linked to a noticeable amount of waste in the stream.