Research Bart Van de Vijver

Research team

• Ecosphere

Expertise

Diatoms, unicellular autrotrophic algae, are on of the most abundant and diverse algal groups in the worlds. As primary producers, they are at the base of all food chains and as such of prime importance in the functioning of the aquatic ecosystems. Each of the (estimated 50.000) species has its own preferences for a broad variety of environmental parameters such as pH, conductivity, nutrients, heavy metals and organic pollutants. Changes in their (physico-chemical) environment automatically lead to changes in the composition of the diatom communities in rivers, lakes and soils. Since a few years, the European Union obliges its member states to guarantee the good quality of its waterbodies, both standing and running. This so-called European Water Framework Directive requires the constant monitoring of the water quality of lakes and rivers in the entire European Union. One of the principal indicators of changes in water quality are freshwater diatoms. The past 20 years, several systems have been developed to use and transform records of the diatom communities as bio-indicator. The use of diatoms has several advantages: (1) they react very fast to changes in their environment, (2) they are always very abundantly present in waterbodies, (3) their sampling and sample preparation is rather simple and low-cost and (4) the diatom analysis can be very easily be transformed into water quality indices. One of the major disadvantages however is the expertise that is necessary to analyse the diatom community. Not only are there a large number of species (approx. 1500 in Belgium alone), their identification requires the use of a performing light microscope and sometimes even a scanning electron microscope, and a constant training to get familiar with the latest taxonomic updates as new species are constantly described and ecologically better characterized. The proposed research expertise includes professional sampling on site, preparation of the diatom samples and analysis and counting of the diatom slides using a light microscope. Once the diatom counts are available, the software package OMNIDIA allows a fast calculation of the diatom indices. All analyses and techniques are conform the European guidelines EN13946 (diatom preparation) and EN 14407 (diatom counting).