Wednesday, August 26, 2015

Water quality assessment

Caloneis amphisbaena
Diatoms are microscopic algae living in both fresh and salt water.  They are unicellular organisms with silica impregnated cell walls. Living diatoms are among the most abundant forms of plankton and represent an essential part of the food chain in the ocean. Diatoms are responsible for at least 25% of global carbon dioxide fixation. Once dead, their shells accumulate on the seabed and eventually form siliceous sediment deposits.

Given that diatoms are photosynthetic algae, they are restricted to the sunlight zone, i.e. the depth of the water in a lake or ocean that is exposed to sufficient quantities of sunlight to allow for survival. They are highly sensitive to any environmental changes such as light availability, temperature, salinity etc.  In general, diatoms prefer cold, nutrient rich waters. This is what makes them so valuable as indicators for water quality. The specific composition of diatom communities is a very sensitive instrument to measure changes in aquatic environments.

Diatoms have been regularly used as bioindicators to assess water quality of surface waters, especially in developed countries. Many of the widely used diatom indices have been developed as part of studies of European rivers.

Jonas Zimmermann, a German PhD student, developed a reliable DNA Barcoding system for freshwater diatoms which can be used for above mentioned water quality assessments. His protocols and suggestions for extended metadata will likely become part of the methods used to comply with the European Water Framework Directive. He not only provided protocol and tests for optimal marker systems but also discovered four new species in water samples of the nation's capital (Berlin) waterways. His results not only confirmed the utility of the proposed DNA Barcode 18S (V4 region) for protists but he was also able to show that it provided good results for both cultivated samples as well as environmental samples.

For his work he was honored with the Horst-Wiehe Price of the German Botanical Society. This scholarship honors young researchers for exceptional scientific work in the field of botany.

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