Detect coastal disturbances and climate change effects in coralligenous community through sentinel stations

background water temperatures in the sampling zones. These series reflected no anomalous increases or decreases in temperature and only exhibited oscillations that were attributable to seasonality. The covers of both species were clearly greater in the vertical orientation than in the horizontal orientation. An increase and a decrease were observed in the covers of A. calycu- laris and P. clavata, respectively, but there were no significant differences. This decrease in the coverage of P. clavata throughout the period studied coincides with that observed in other studies [47]. Environmental factors such as climate change may be affecting certain species more slowly these trends may be analyzed when they have a longer period. RM-ANOVA of the cover of each species in each of the two orientations (Table 1) indicated significant differences (p<0.05) in the covers of Mesophyllum sp. and Salmacina incrustans in the shady (vertical) location over the time period. Regarding the sunny (horizontal) location, the covers of Mesophyllum sp. and Crambe sp. exhibited significant differences (p<0.05). No significant differences (p>0.05) were detected in the covers of the remaining species. The RM-PERMANOVA analysis indicated significant differences in the coralligenous assemblages (p<0.05) for the orientation factor (i.e., vertical vs. horizontal) but not for the time factor. The interaction of these two factors was also not significant (Table 2). The nMDS analysis (Fig 9) revealed a clear differentiation of the values between the vertical and horizontal orientations (Stress: 0.14).

Discussion Sampling procedure and analysis of the submarine images Previous studies have indicated that fixed monitoring stations constitute one of the most robust methods for detecting changes in benthic communities over time [69,102–105]. An area of at least 1 m2 is sufficient for integrating various colonies and individuals of diverse fauna in a single sample, and such diversity is a typical characteristic of benthic rocky bottom communities [69,106]. However, the definitive sampling grid size must be defined by the final Fig 6. Graphic representation of the evolution of the cover of the main species observed at the monitoring stations. H: horizontal; V: vertical. https://doi.org/10.1371/journal.pone.0231641.g006 PLOS ONE Detect coastal disturbances in coralligenous PLOS ONE | https://doi.org/10.1371/journal.pone.0231641 May 5, 2020 9 / 23