(a) Percentage of red (black), brown (gray) and green (white) macroalgal species recorded in Königshafen, Sylt, in different periods during the 19th to the 20th century (n=total no. of species recorded, after Schories et al. 1997). (b) Relative abundance of red, brown and green algae dredged in tidal channels in the north Frisian Wadden Sea in 1932–1940 (filled bars, n=27) compared to 1987–1988 (hatched bars, n=78) after Reise et al. (1989).