DIN EN 13946:2014-07

Diatoms are an important component of aquatic ecosystems and constitute a water quality monitoring tool where the primary objective is either a measure of ecological status based on diatoms as one compartment of the ecosystem or the impact of specific components of water quality (for example eutrophication, acidification). The requirement for the monitoring of such processes is inherent in the Water Framework Directive (2000/60/EC) and Urban Waste Water Treatment Directive (91/271/EEC) in addition to other EU Directives and international agreements. This European Standard covers aspects of sampling and preparation relevant to assessment of water quality and ecological status using benthic diatoms. These sampling instructions will result in samples suitable for quantifying relative numbers of benthic diatom taxa present. If it is necessary to quantify absolute numbers of taxa, or fresh weight per unit area, modifications to the method are required, which are not within the scope of this European Standard. The use of diatoms as indicators of river and lake quality is widely accepted both in Europe and beyond. The methodology is based on the fact that all diatom species have tolerance limits and optima with respect to their preference for environmental conditions such as nutrients, organic pollution, pH value, etcetera. Polluted waters will tend to support an increased abundance of those species whose optima correspond with the levels of the pollutant in question. Conversely, certain species are intolerant of elevated levels of one or more pollutants, whilst others may occur in a wide range of water qualities. This document specifies a method for the sampling and laboratory preparation of benthic diatoms for ecological status and water quality assessments. Data produced by this method are suitable for production of water quality indices based on the relative abundance of taxa. Benthic diatoms from submerged hard surfaces or submerged macrophytes in rivers, streams or littoral zones of lakes are sampled in order to produce representative collections of the diatom assemblage indicative of water quality. Samples are cleaned using strong oxidizing agents in order to prepare diatoms for identification and enumeration. All numerical values given in this European Standard are approximate. Compared with DIN EN 13946:2003-09, the title has been changed to reflect the expansion of the scope to include water body type "lakes". The preliminary work has been carried out by Working Group CEN/TC 230 (WG 2) ("Biological methods") under the chairmanship of BSI (secretariat: United Kingdom). Regarding the German collaboration NA 119-01-03-05-06 AK "Biologisch-ökologische Gewässeruntersuchung" ("Biological-ecological water examination") of NA 119-01-03 AA "Wasseruntersuchung" ("Water examination") at the Water Practice Standards Committee (NAW) was involved in the revision. The national revision of this project was funded by the Länderfinanzierungsprogramm "Wasser, Boden und Abfall" (federal funding programme "Water, soil and waste").