Fig 4. Spatial patterns in pH across kelp bed/ barren ground interfaces.

(A) pH within shallow kelp beds and on sea urchin barrens in intermediate and deep reefs at St. Helens Island during Aug 2014, data are means of n = 6 replicate bottle samples (note that barrens are not currently found on shallow reefs at this site and at this depth generally in eastern Tasmania); (B) pH within kelp beds, barrens edge and barrens interior at St. Helens Island and Sloop Rock (St. Helens, north eastern Tasmania) during Oct 2013, data are means of n = 6 replicate bottle samples. Different letters indicate significantly different pH between habitats (see S2 Table for analyses of variance in S1 File).