The surroundings of the small city of Winterswijk in the eastern part of the Netherlands were one century ago famous for the abundance of rare desmids, occurring in many small lakes, situated in species rich heathlands. During the past century this landscape impoverished tremendously. In 1979 I investigated what was still left of the former richness in desmid species. It was disappointing that no more than about 110 species could be found, mostly common species. In 2020 I repeated the inventory, investigating four lakes that were in 1979 rather rich in species. Two of them were acid lakes without any buffering, two were slightly buffered. Two of the lakes had still more or less the same species composition of desmids, one had a strongly increased number of species, due to improved water management. Surprisingly in the fourth lake I found no desmids any more. We could not find any explanation for this absence of species. Most surprisingly, near the slightly buffered lakes some new small lakes were created. These proved to be very rich in species, including some rare species like Cosmarium simplicius and C. galeritum. Totally, 178 species were found.

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Desmidiologische Mededelingen
Nederlandse Sieralgenwerkgroep

B.F. van Tooren. (2021). De sieralgen van Winterswijk. Desmidiologische Mededelingen, 6, 16–21.