Diatom Scales

(Image from: link ) In the year 2000 the Water Framework Directive or WFD (European Commission 2000) was created to homogenize freshwater quality care throughout Europe. One of the main objectives was the expansion of water protection to all water bodies. Another aim was to get to a specific water quality in a given time and to regulate a basin-based water management. Europe homogenized pollution limits, prices, citizen involvement and a simplification of legislation. To obtain an ecological water status standard, it was no longer to be obtained only chemically. It also used bioindicators. The goal of this international effort was to improve water quality of European rivers. A deadline of a “good”-status in 2015 was placed, always using the “one out, all out” approach. If one indicator had less than “good” quality, the site is regarded as less than good. To establish it, firstly, undisturbed or “reference” sites were selected and described. Intercalibration exercises...

Diatoms do not only have a use in water quality management, but other economical uses as well. These organisms are sought for their nutritional value. Silicon is an important micronutrient and diatoms have been steadily marketed for this reason. Other products are derived from diatomaceous earth (Fig. 1). This marine sediment is used as pest repellent or within filters, and has even been used in toothpaste. It also produces improved solar energy cell efficiency, which is readily publicized (Thomas 2014). More uses are known, including as a stabiliser for TNT, fertilizer and pesticide. Other economic effects of diatoms are less positive. They are early and active participants in the process of biofouling (Wahl 1989).   ​ ​ S M L   Fig. 1 Diatomaceous earth (By Doc. RNDr. Josef Reischig, CSc. (Author's archive) [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons)] Finally, as already remarked, the ecological effect is important. Di...

 Fig. 1 Example of diatoms from the freshwaterbenthos at the Ebro river. a) Achnanthidium pyrenaicum ,  b) Cymbella excisa , c) Navicula cryptocephala , d) Diatoma tenuis, e) Navicula cryptotenella , f) Aulacoseira granulata , g) Achnanthidium minutissimum , h) Nitzschia inconspicua , i) Cocconeis lineata , j) Cyclotella cf. ocellata , k) Denticula tenuis , l) Gomphonema olivaceum , m) Gomphonema stoermeri , n) Amphora pediculus , o) Encyonema minusculum, p) Reimeria sinuata , q) Encyonopsis minuta , r) Nitzschia supralitorea . Image taken with a Zeiss AxioImager Z.2 with Metafer 4 automatic slide scanner system. Diatoms are unicellular algae in a glass case (or frustule). They pertain to the Heterokontophyta phylum , only due to an extinct ancestor, although sperm from centric diatoms can have a flagellum. Diatoms occur in every kind of water and can even survive on relatively dry substrate. They have been divided classically into two groups: pennate (bilat...