Search Results

You are looking at 1 - 2 of 2 items for

  • Author: Maria Kahlert x
Clear All Modify Search
Open access

Maria Kahlert and Ivana Savatijević Rašić

Abstract

The aim of the present study was to analyze if small-scale spatial variation of benthic diatom assemblages has consequences for biomonitoring. Benthic diatom samples were collected at one sampling site in a mesotrophic stream in Middle-Sweden from stone and plant (macrophytes and mosses) substrate. Our results showed that spatial variation of both the diatom species composition and the calculated bioindices were similar on both small (distance of centimeter) and medium (distance of decimeters) scales. Spatial variation was also similar on both studied substrates. This implies that it does not matter if a small or a larger area is sampled for biomonitoring as long as no major environmental factors impact certain sites systematically. Diatom assemblages and indices were significantly different between substrates. Spatial variation did not contribute much to this variation, and variation on a slide was unimportant. These results confirm earlier findings that smallscale spatial variation is not a problem when using diatoms to detect anthropogenic impacts to a stream or lake.

Open access

Mirko Dreßler, Geurt Verweij, Sonja Kistenich, Maria Kahlert and Petra Werner

Abstract

The first German intercalibration exercise for benthic diatoms was conducted to improve the application of the implementation of the European Water Framework Directive for running waters and lakes in Germany. The intercalibration exercise revealed several taxonomic problems. Among others, considerable problems occurred with identifying and differentiating species of the following four groups: (I) Amphora indistincta Levkov and A. pediculus (Kützing) Grunow, (II) Cocconeis placentula var. euglypta Ehrenberg and C. placentula var. lineata (Ehrenberg) Van Heurck, (III) Navicula cryptotenella Lange-Bertalot and N. cryptotenelloides Lange-Bertalot and (IV) N. reichardtiana Lange-Bertalot and N. caterva Hohn & Hellermann. The taxonomic problems that emerged occurred due to both insufficient use of given taxonomic details (by limnologists) and ambiguous species descriptions and documentation (by taxonomists). Thus, we recommend to the applied limnologist to use the mandatory identification literature and to document any ambiguous valves during routine counts. Also, it would be desirable to further investigate certain species by taxonomists and, in general, to provide more basic data with species descriptions or in identification manuals. These measures will improve the use of diatoms as bioindicators and consequently benefit both applied limnologists and taxonomists.