## 3 Results
### Rhodoliths  
Differences in rhodoliths composition were observed by comparing Non-impacted and Low effort history areas with respect to Medium effort history and High effort areas (Figure 7). In the central part of the Menorca Channel, biomass of _L. valens_ and _S. fritticulosus_ was higher in Non-impacted area (45.0 \(\pm\) 15.2 and 33.2 \(\pm\) 13.2 kg/1000 m\({}^{2}\), respectively) than in Low effort history area (4.1 \(\pm\) 0.8 and 11.7 \(\pm\) 4.32 kg/1000 m\({}^{2}\), respectively). No significant differences in biomass of _Phymatolith calcareum_ were found between Non-impacted and Low effort history areas (4 \(\pm\) 3 and 3 \(\pm\) 1 kg/1000 m\({}^{2}\), respectively). \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Species/Taxa**} & \multicolumn{2}{c}{**Medium Effort History**} & \multirow{2}{*}{**Species/Taxa**} & \multicolumn{2}{c}{**High Effort**} \\ \cline{2-3} \cline{5-5}  & **A** & **\%C** & & **A** & **\%C** \\ \hline _Ophiconis forbesi_ & 307.1 & 16.3 & _Ophiconis forbesi_ & 250.8 & 23.4 \\ _Pagurus prideaux_ & 138.4 & 11.7 & _Anapagurus laevis_ & 88.2 & 10.3 \\ _Anapagurus laevis_ & 106.5 & 6.8 & _Pagurus prideaux_ & 99.4 & 8.7 \\ _Aplidium nordamuni_ & 121.6 & 6.6 & _Pagurus forbesii_ & 48.1 & 6.4 \\ _Spatangus purpureus_ & 114.8 & 5.2 & _Gibbula fanulum_ & 47.1 & 4.4 \\ _Molgula appendiculata_ & 111.1 & 4.3 & _Dardanus arrosor_ & 41.4 & 3.7 \\ _Dardanus arrosor_ & 49.5 & 3.8 & _Turritella turbona_ & 29.9 & 2.7 \\ _Cestogogurus timidus_ & 39.4 & 3.4 & _Echinaster sepositus_ & 26.4 & 2.6 \\ _Pagurus forbesii_ & 37.8 & 3.2 & _Molgula appendiculata_ & 32.7 & 2.5 \\ _Turritella turbona_ & 48.0 & 2.9 & _Paguristes eemita_ & 31.2 & 2.4 \\ _Echinaster sepositus_ & 33.0 & 2.4 & _Cestogogurus timidus_ & 30.2 & 2.1 \\ _Calyptrane chinensis_ & 36.0 & 2.2 & _Ophipisella archaea_ & 55.5 & 2.0 \\ _Inachus dorsetlensis_ & 32.3 & 2.1 & _Ebalia tuberosa_ & 21.9 & 1.9 \\ _Ebalia tuberosa_ & 23.5 & 2.1 & _Buenia affinis_ & 28.3 & 1.7 \\ _Gibbula fanulum_ & 28.8 & 2.0 & _Clausinella fasciata_ & 13.4 & 1.7 \\ _Liocarcinus spp._ & 29.9 & 1.9 & _Calyptraen chinensis_ & 18.1 & 1.7 \\ _Buenia affinis_ & 71.7 & 1.6 & _Aplidium nordamuni_ & 29.3 & 1.6 \\ _Ophiposila archaea_ & 76.0 & 1.5 & _Inachus dorsetlensis_ & 15.9 & 1.3 \\ _Galdathe nitrendelia_ & 22.8 & 1.1 & _Ophirun albida_ & 15.1 & 1.2 \\ _Indchus thoracicus_ & 15.0 & 1.0 & _Parthemopaides musema_ & 16.4 & 1.1 \\ _Suberites domuncula_ & 13.8 & 0.9 & _Buenia massutili_ & 24.9 & 1.1 \\ _Buenia massutili_ & 20.9 & 0.9 & _Serranus hepatus_ & 35.7 & 1.0 \\ _Ascidia mentula_ & 11.1 & 0.9 & _Lanice conchilega_ & 8.9 & 1.0 \\ _Polycarpa mammilaris_ & 14.5 & 0.8 & _Diplecogaster bimaculata bimaculata_ & 9.4 & 0.9 \\ _Mimachlamys varia_ & 20.3 & 0.7 & _Ascidia mentula_ & 7.9 & 0.8 \\ _Serranus hepatus_ & 26.5 & 0.7 & _Laetmonice hystrix_ & 12.5 & 0.7 \\ _Parthemopaoides masseau_ & 10.2 & 0.7 & _Pagurus cuanensis_ & 7.1 & 0.7 \\ _Paguristes eemita_ & 12.4 & 0.7 & _Inachus thoracicus_ & 10.2 & 0.7 \\ _Macropodia rostrata_ & 9.1 & 0.7 & & & \\ _Odondebuenia balearica_ & 10.6 & 0.7 & & & \\ _Eurynome aspera_ & 10.0 & 0.6 & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Results of SIMPER analysis, estimated from standardized abundance data in beam trawl samples in Medium effort history and High effort areas, showing mean abundance (A; individuals/1000 m\({}^{2}\)) and percentage contribution (%C) of each species contributing up to 90% of within-group similarity. Mean values of size and roundness for the rhodolith species selected are shown in Figure 8. Size and roundness of _L. valens_ were higher in Non-impacted area (size: 44.5 \(\pm\) 1 mm; roundness: 0.43 \(\pm\) 0.01) than in Low effort history area (size: 40.8 \(\pm\) 0.9 mm; roundness: 0.37 \(\pm\) 0.01). Size and roundness of _S. frucitulosus_ were also higher in Non-impacted area (size: 35.8 \(\pm\) 0.7 mm; roundness: 0.73 \(\pm\) 0.01) than in Low effort history area (size: 32.4 \(\pm\) 0.7 mm; roundness: 0.67 \(\pm\) 0.01). _P.