*2.2. Size Structure and Density of the P. clavata Population*

The number of colonies of *P. clavata* in each plot (*n* = 23) was counted, and the densities (col m<sup>−</sup>2) of adults and annual recruits recorded. Colony size (in width) was measured by a ruler reported on one side of each square in a top view image. Considering an average annual growth rate of 3 cm y−<sup>1</sup> in width, all colonies were divided into annual age classes according to their size (i.e., size/age classes [12,40]), and all those <4.5 cm were assigned to the 0–1 age class (recruits) according to Cupido et al. [21]. The colonies assigned to classes 2 to 4 were defined as small/young adults, while colonies belonging to classes >5 were considered large/old adults (Figure 2).

Since time series data and the size/age structure of the population between 1998 and 2010 were available [20,21,32], a comparison was made with the data collected in 2013.
