Laminaria hyperborea off the island of Helgoland (North Sea, Germany) was sampled along a depth gradient (0.5, 2, 4, 6 m) throughout summer 2014. Discs were cut from three different blade regions (5, 25 and 50 cm above the stipe-blade transition zone). The maximum quantum yield of photosystem II was measured after cutting and after one night of wound healing before oxygen measurements were conducted using pulse-amplitude-modulated fluorometry (PAM 2100, WALZ, Germany).

Additional funding was provided by the Postdoctoral fellowship grant of the Fonds de recherche du Québec - Nature et technologies and the Weston Foundation.