Combination of two indication systems in pre-alpine lakes - diatom index and macrophyte index

Since the climax of eutrophication in the early 1980s mainly greater lakes have been investigated and monitored in terms of their nutrient charge. In the future there will still be a need to develop guidelines for monitoring the trophic status of smaller lakes. Four small lakes were investigated by the author in the years 1996 and 1997. In order to define the nutrient char ge of those lakes more precisely, special emphasis has been put upon the tw o criteria diatoms and macrophytes. Eventually an evaluation of the lakes' catchment areas will also be an important component of these studies. Benth ic diatoms are the main part of periphyton. As unicellular fast reproducing organisms they are excellent indicators for trophic situations in lakes. T he diatom index denotes the trophic status of the littoral zone during the last few weeks before sampling. The macrophytes, however, reflect the nutri ent charge over a longer period, i.e. several years. The macrophyte index i s based on the fact that some species are most prevalent at certain nutrien t loads. The effort to combine these two indication systems carries a high resolution of spatial nutrient changes as well as in temporally changes. (C ) 2000 Elsevier Science B.V. All rights reserved.