Applied use of taxonomy: lessons learned from the first German intercalibration exercise for benthic diatoms

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

Quality assurance of diatom counts in Europe: towards harmonized datasets

Investigations on organism ecology, biodiversity and biogeography often use large compiled datasets to extract information on species ecological preferences, which then can be used in environmental assessment. Freshwater benthic diatoms are commonly used in this context. However, it is important that the taxonomic information of the separate diatom datasets is compatible. At present, inconsistencies between diatom datasets, mainly due to differences and uncertainties in diatom identification, may misinform diatom taxon-specific ecological preferences, geographical distribution and water quality assessment. It is our opinion that these inconsistencies in diatom datasets can be reduced with quality assurance (QA), such as identification exercises. However, the results of these exercises must be well documented and well communicated; otherwise, gained knowledge may not spread inter-regionally or internationally. As a first step to reach greater consistency in QA/harmonization studies, this article (1) presents and compares information of existing diatom identification and counting QA from published and grey (non-peer reviewed) European literature to identify advantages and drawbacks of each approach; (2) summarizes taxa that can easily be misidentified according to European identification exercises; and (3) suggests a consistent design of identification exercises for diatom dataset QA

Geochemistry, grain size, VIS reflectance spectroscopy, mass accumulation, diatom and ostracod assemblages derived from lacustrine surface sediment samples from Schweriner See, NE-Germany

Productivity parameter, heavy metals, visible reflectance spectroscopy and diatom assemblages derived from lake surface sediment samples from Schweriner See, NE-Germany, were used to infer depositional processes and their influences. Samples were taken in a grid using an Ekman-Birge grab samples in a distance of 1.3 to 2 km forming an almost equally spaced grid covering the entire northern basin of Schweriner See and from water depths ranging from 0.5 to 51.5 m. Parameter could be divided into three main processes: productivity (e.g. TOC), carbonate precipitation (e.g. TIC) as well as wave- and wind-induced processes (e.g. sand percentage). Surface sediment sampling provided an thorough untderstanding of depositional processes, which proved valuable for core site selection as in Schweriner See sediment reworking in shallow water areas by wave- and wind-induced processes or carbonate precipitation resulting from groundwater inflow may have altered the desired signal