Results of the principal component analysis (PCA) of environmental and biotic variables in the salinity gradient.

<p>The ordination plot summarizes the variation of the environmental and biotic variables across the 119 samples (indicated by site number) included in the fourth-corner analysis of the salinity gradient. Salinity = surface water salinity at each sampling site, Temperature = surface water temperature at each sampling site, DIN = dissolved inorganic nitrogen, DIP = dissolved inorganic phosphorus, DSi = dissolved inorganic silicate, N:P = molar DIN:DIP ratio, EXP = exposure to waves cf. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0109993#pone.0109993.s005" target="_blank">Table S5</a>, BEACH = beach type cf. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0109993#pone.0109993.s005" target="_blank">Table S5</a>, SAND = ash weight of sand grains on the stones, ADW = total ash-free dry weight on the stones, ADW% = % ash-free dry weight (a measure of the relative amount of macroalgae on the stones), Richness = number of diatom taxa in 1000 valves.