The attached form of the endangered freshwater alga Aegagropila linnaei Kützing (Chlorophyta) is found in the Zuideindigerwiede, The Netherlands

The freshwater green macroalga Aegagropila linnaei used to occur in several locations in The Netherlands in unattached growths forms (including the enigmatic ‘lake balls’) more than 60 years ago. A recent survey of most of the historical collection sites of the species reported the attached growth form for the first time for The Netherlands, but only in miniscule quantities and from one location only. Here we report on the finding of the attached form from the Zuideindigerwiede, one of the two historical collection sites that had not been surveyed previously. Unattached growth forms do not seem to occur anymore in The Netherlands, and the species as a whole must be regarded as rare and endangered.