Species assemblages of the rocky intertidal at Helgoland (German Bight, North Sea), semi-exposed shore

Environmental variables
Semi-exposed (erosion rates of gypsum blocks reaches 0.14 g/h; de Kluijver, 1991). Mostly relative natural red sandstone; gently sloping substratra; average tidal range: ca. 2.5 m; geomorphological structure: channels (mean height: ca. -1.00 m refer to the height Normal Null (NN) of the German height reference system; width: ca. 3-5 m) and ridges (mean height to NN: ca. -0.60 m; width: ca. 5-15 m) alternating alongshore. The species assemblages showed three distinct vertical zones (high-, mid-, low-shore). […]