Translation of articles, research, rock crevices, boulders presence of pools, depressions, etc. (McCoy.and Bell, 1991), using the chain link method (Beck, 1998). To thisend, we deployed a heavy iron chain and a tape multiple timesacross each transect where the quadrat sampling was conducted(see above). The chain links (length ¼ 2.5 cm) closely followed thesurface and the tape only touched the highest parts of the rocks.Thus the ratio between the linear distances (tape) vs. the apparentdistance (chain) can be considered as a measure of the structuralcomplexity of the substratum (hereafter Complexity Index; Beck,1998). As the AL sampling consisted of contiguous quadrats (seeabove) we followed the same protocol for the chain-tape sampling.We deployed a 1-m long chain and tape (linear distance) multipletimes along a contiguous path, i.e. the beginning of the chain (andtape) was placed on the end point of the previous chain placement(15e20 times for each transect), on the breakwater and naturaladjacent platforms along the same transects (totalling 30 to 40samples for each habitat) where AL sampling was conducted (seeabove). In this way, we obtained 30 to 40 measures for thecomplexity index for each habitat. At one of the seven study localitiesthis sampling could only be partially completed (Vi~na delMar), given that the strong and persistent wave surge and slope ofthe breakwaters at the sampling time (AugusteDecember 2015)restricted the access to this site. Thus, we only include partial datasets (10 measures of the Complexity Index) for this locality forfurther spatial analyses (see below).Given inherent differences between intertidal breakwaters (e.g.made of granite boulders versus cement tetrapods see Fig. 2), wefirst conducted a pilot study using three different chain link size;2.5 cm, 4 cm, and 6 cm per link.We determined that a chain link of2.5 cmwas sufficient to characterize the spatial distribution of bothgranite boulders and tetrapods at the study sites considered, andconsequently all results reported are based on this link size.
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