Mean percentage cover (±SE) of dominant macroalgal species in May (a) and September (b) at high (n = 6), intermediate (n = 14) and reference (n = 14) levels of CO₂ in Methana.

<p>Round points represent canopy-forming species (<i>S. vulgare</i> dark grey, <i>C. corniculata</i> light grey), rhomboids represent calcifying species (CCA black, <i>J. rubens</i> grey). Different letters and numbers indicate significant differences between groups.