Vijf soorten kiezelalgen nieuw voor de Nederlandse oppervlaktewateren

Diatoms are a major group of unicellular micro-algae with a silica-based cell wall. They comprise an abundant and highly diverse group of algae which are found in and around all water types. Their lifestyles are various and include planktonic species that live suspended in the water column, while other species grow on substrates such as plants, macroalgae, and rocks. The substrate bound species are categorized in different life forms. For example, epipsammic diatoms are directly adhered to sand grains or other sediment particles and are immobile in contrast to epipelic diatoms, which are more or less motile. This paper concentrates on epiphytic life forms, diatoms that are attached to other plants and algae, including larger diatoms (Barber 1994). Diatoms are very suitable indicators for measuring the ecological status of surface water, because they: (1) react promptly to changes in the environment, (2) there is a good understanding of their ecological background, and (3) they are relatively easy to identify to species level. Currently, most diatom research is applied to estimate the water quality of streaming waters, but this could be easily extended to other water types. As diatom frustules preserve well in the soil for long periods of time, they can also be of use in archeological or paleo-ecological research. The presence of certain species can provide information about the environment or landscape of hundreds of years ago. Hitherto ca. 2000 diatom species are known from the Netherlands, but every year new diatom species are found in Dutch water bodies. Most of these new species are already known to occur in neighbouring countries, but occasionally an unknown species is discovered. Based on this information, it is estimated that in total approximately 3000 diatom species occur in the Netherlands. This article presents five diatom species which are new to the Netherlands. These species were found in diatom slides made from samples that were taken from different water types, which were sampled at a few locations throughout the Netherlands. These species are: Achnanthes minuscula Hustedt 1945, found in nutrient-rich gently streaming water, Lyrella sulcifera (Hustedt) Witkowski 1994 en Pinnularia quadratarea (A. Schmidt) Cleve 1895, both found in a deep and clear brackish water lake, P. latarea Krammer 2000, found in a nutrient-rich shallow lake, and Stauroneis pseudagrestis Lange-Bertalot & Werum 2004, found in a nutrient-rich stream on sandy ground. Kiezelalgen (diatomeeën) zijn een groep eencellige algen met een met kiezel verstevigde celwand. Kiezelalgen komen in veel watertypen voor. Van de meeste kiezelalgsoorten is veel bekend over het milieu waarin ze leven en ze reageren bovendien snel op veranderingen in hun omgeving. Daarom worden kiezelalgen gebruikt voor de ecologische beoordeling van, veelal stromende, wateren. De kiezelschaaltjes blijven ook lang in de bodem bewaard en worden in de archeologie en paleo-ecologie gebruikt voor landschapsreconstructies en klimaatveranderingen. Er zijn in Nederland ruim 2000 soorten en variëteiten van kiezelalgen bekend en nog altijd worden jaarlijks soorten waargenomen die niet eerder in de Nederlandse wateren zijn aangetroffen. In dit artikel worden vijf soorten kiezelalgen beschreven die nog niet eerder in de Nederlandse oppervlaktewateren zijn gerapporteerd. De soorten zijn: Achnanthes minuscula Hustedt 1945, gevonden in een voedselrijke beek, Lyrella sulcifera (Hustedt) Witkowski 1994 en Pinnularia quadratarea (A. Schmidt) Cleve 1895, beiden gevonden in een diepe en heldere brakwaterplas, Pinnularia latarea Krammer 2000, gevonden in een voedselrijke ondiepe plas, en Stauroneis pseudagrestis Lange-Bertalot & Werum 2004, gevonden in een voedselrijke beek op zandgrond.