Figure 5.

Correlation between the sulfated fucan content of isolated cell walls of brown algae and their position in the intertidal zone. (A). Fucose content (% w/w) vs. duration of emersion (% of time). (B) Sulfate substituent content (% w/w) vs. duration of emersion. The maximal duration of emersion in a daily tidal cycle was calculated for Roscoff (Brittany, France), based on species belt zonation in the intertidal (taken as the medium height relative to the lowest astronomical tide), using the spring tide mid-water mark for Pelvetia canaliculata, Fucus ceranoides, F. spiralis, F. vesiculosus, and Ascophyllum nodosum and the neap tide mid-water mark for F. serratus, Bifurcaria bifurcate, and Laminaria digitata. See Supplementary Table S2 for the corresponding data values.