## 3 Results and Discussion
cretense_ in the southern zone with respect to the other study areas (Table 7). In the case of _S. cretense_, no metal or trace element was found with the highest concentration in the southern zone, with the specimens from the northern zone containing the highest concentrations of B, Ba, Ca, Cd, Fe, K, Mg, Mn, Mo, Na and Zn and the highest concentrations of Al, Cu, Ni and Pb were found in specimens from the eastern zone (Figures 2 and 3). Although there is a high level of tourism activity in the south of Tenerife [17], the highest population density is found in the northern and eastern parts of the island where the capital and the port are located. The population of the capital and the port produce large quantities of discharge, which are responsible for the high concentrations of Al and Pb. The PERMANOVA analysis of the metal content in the liver of _S. cretense_ and _S. articauda_ in each sampling zone identified statistically significant differences between the two species from the southern zone (Table 8). Table 9 shows the pairwise comparisons between the two species for each metal and trace element in each locality, with significant differences in the southern zone for all the metals except Al and Li. _S. articauda_ had a higher metal concentration than _S. cretense_ in all the metals and trace elements except Ni (Figure 3), and this may be due to the fact that _S. articauda_ is a benthic predator species [28]. Therefore, it feeds on organisms that have accumulated higher concentrations of metals, since many of these settle on the seabed [29]. \begin{table}
\begin{tabular}{c c c} \hline \hline _Seranus articauda_ & **North** & **East** & **South** \\ _Sparisoma cretense_ & 0.86 & 0.009 * & 0.056 \\ \hline \(p\) > 0.05. * Statistical significitive diferences. & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Results of the two-way PERMANOVA analyzing the variation in the content of heavy metals and trace elements in muscle tissue in species according to study zone, considering the level of the factor “Zones”. \begin{table}
\begin{tabular}{c c c c} \hline \hline _Seranus articauda_, & **North** & **East** & **South** \\ _Sparisoma cretense_ & & & \\ \hline \hline Al & 0.81 & 0.255 & 0.194 \\ B & 0.086 & 0.806 & 0.162 \\ Ba & 0.12 & 0.012 * & 0.236 \\ Ca & 0.802 & 0.012 * & 0.009 * \\ Cd & 0.003 * & 0.754 & 0.786 \\ Cr & 0.254 & 0.998 & 0.016 * \\ Cu & 0.991 & 0.049 * & 0.001 * \\ Fe & 0.78 & 0.237 & 0.202 \\ K & 0.656 & 0.038 * & 0.492 \\ Li & 0.342 & 0.181 & 0.299 \\ Mg & 0.303 & 0.098 & 0.499 \\ Mn & 0.034 * & 0.001 * & 0.458 \\ Mo & 0.91 & 0.483 & 0.285 \\ Na & 0.884 & 0.352 & 0.387 \\ Ni & 0.892 & 0.38 & 0.206 \\ Pb & 0.472 & 0.006 * & 0.48 \\ Zn & 0.006 * & 0.001 * & 0.001 * \\ \hline \hline \end{tabular} \(p\) > 0.05. * Statistical significitive diferences.  
\end{table} 
Table 5: Results of pairwise tests examining the significant factor of ‘Zones’ obtained in the two-way PERMANOVA analyzing the variation in the content of heavy metals and trace elements in muscle tissue in species according to study zone, considering the level of the factor “Zones”. However, _S. cretense_ is an omnivorous species that feeds in different habitats, so its diet does not depend exclusively on the seabed [30; 31]. The liver contains a large quantity of essential metals, which, a priori, could lead one to think that this organ is of much interest from the nutritional point of view. However, on the other hand, the concentration of toxic metals in the liver tissue is thirty-five times the concentration in the muscle, and, because of this, the consumption of liver could be potentially dangerous; furthermore, the concentrations of trace metals that could be potentially toxic in large amounts are notably higher in the liver [32; 33; 34; 35]. Figure 2: Boxplot of the two species in each sampling area for Ca, Cu and Pb.