Natural Sea-Water may be Unreliable for the Culture of Acetabularia

Since it was no longer possible to obtain sea-water collected near the Belgian coast as it was previously, the authors had to purchase the sea-water required for the culture of Acetabularia . Although the reasons why certain physiological parameters were altered did not occur to the authors immediately, it turned out that the algae cultivated in natural sea-water were devoid of circadian rhythm (CR) in photosynthesis. The authors briefly compare in this note the morphology, growth curve, photosynthetic performance and rhythms of algae cultivated in autoclaved natural sea-water with those of algae cultivated in artificial sea-water (Mueller's medium). The natural sea-water was collected at Yerseke, 51.29 N, 4.02 E (Zealand) to provide specialized shops with water to keep live shells.