# Risk Assessment of a Coastal Ecosystem from SW Spain
## 3 Results and Discussion
### Multivariate Analysis
\begin{table}
\begin{tabular}{l c c} \hline \hline  & **Components** & \\ \cline{2-3}
**Variables** & **Factor 1** & **Factor 2** \\  & **(48.41\%)** & **(24.93\%)** \\ \hline \multicolumn{3}{l}{_Metals in sediments_} \\ Cr\({}_{\text{sed}}\) & & 0.98 \\ Cu\({}_{\text{sed}}\) & & 0.97 \\ Fe\({}_{\text{sed}}\) & & 0.97 \\ Zn\({}_{\text{sed}}\) & & 0.95 \\ \multicolumn{3}{l}{_Metals mobility_} \\ As\({}_{\text{sw}}\) & 0.48 & \\ Cr\({}_{\text{sw}}\) & \(-\)0.51 & \(-\)0.68 \\ Cu\({}_{\text{sw}}\) & \(-\)0.44 & \\ Fe\({}_{\text{sw}}\) & & \(-\)0.49 \\ Ni\({}_{\text{sw}}\) & 0.63 & 0.72 \\ Zn\({}_{\text{sw}}\) & 0.90 & \\ Cu\({}_{\text{elu}}\) & 0.42 & 0.84 \\ Fe\({}_{\text{elu}}\) & 0.51 & \\ Zn\({}_{\text{elu}}\) & 0.43 & \\ _Protons concentration_ & 0.89 & \\ (H\({}^{\dagger}\)) & & \\ _Bioaccumulation_ & & \\ As\({}_{\text{bio}}\) & 0.61 & 0.48 \\ Cr\({}_{\text{bio}}\) & 0.66 & \\ Cu\({}_{\text{bio}}\) & 0.64 & \\ Fe\({}_{\text{bio}}\) & 0.94 & \\ Ni\({}_{\text{bio}}\) & 0.85 & \\ Zn\({}_{\text{bio}}\) & & 0.89 \\ _Acute toxicity_ & & \\ Amphipod mortality & 0.96 & \\ Mussel mortality & 0.84 & 0.38 \\ NRRT at 24 h & \(-\)0.94 & \\ NRRT at 96 h & \(-\)0.89 & \\ NRRT at 10 d & \(-\)0.84 & \\ _Chronic toxicity_ & & \\ Mussels & & \\ Embryo–larval inhibition & 0.78 & 0.46 \\ Sea urchin & & \\ Embryo–larval inhibition & 0.88 & \\ _Ecological integrity_ & & \\ Total abundance & & \(-\)0.96 \\ Diversity (H\({}^{\dagger}\)) & & \(-\)0.87 \\ Richness (d\({}^{\dagger}\)) & \(-\)0.74 & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The sorted rotated factor of the original variables on the two principal factors. Just loadings \(>\)0.4 are shown. observed in the tabular matrix and pie charts (Table 3 and Figure 4, respectively) that showed a significant difference (\(p<0.05\)) in the mobility of metals starting at pH 6.5 for the RSP sediment and at pH 7.5 for the TRO sediment. Furthermore, acute and chronic toxicity were linked in factor one with the metal's mobility and the increase in the concentrations of H\({}^{+}\) (enrichment of CO\({}_{2}\)). These results were indicated in the tabular matrix and pie charts as significantly differenced starting at pH 7.5 and 7.0 for TRO and RSP sediment, respectively, and corroborate with the results found by [9], which showed significant effects starting at pH 7.0 in no contaminated sediment sample. On the other hand, the multivariate analysis identified which metals were correlated with their concentration increase and the toxicity caused to the organisms (As, Ni, and Zn in seawater and Cu, Fe, and Zn in elutriate sediments). These results corroborate previous studies which showed adverse effects on marine organisms associated with increases in the metal concentrations and the pH reduction [10; 16; 22; 34; 35] reported with the mortality of amphiopod _Hyale youngi_ with seawater acidification due to an increase in Ni and As concentrations. In addition, an increase in the mobility of dissolved Zn promoted mortality in bivalves (adults and juveniles) [22; 25] and amphiopods [16]. Furthermore, it was reported that there was a correlation between the increase in the mobility of Cu, Zn, and As with the mortality of _Hediste diversicolor_ polychate [44]. Furthermore, it has been observed that there is variability in the feeding behaviour of marine amphiopods (\(O\). _tuberculata_) in response to ocean acidification [45]. Regarding the results of bioaccumulation of metals, it was correlated that factor one increases in the concentrations of As, Cr, Cu, Fe, and Ni in the tissues of mussels, increases in the mobility of the metals mentioned above, and increases in the concentrations of H\({}^{+}\) protons. These results were described in Table 3 and Figure 4, presenting significant differences from pH 6.5 for both sediment sampling sites. These findings are similar to [44], a study that showed a correlation between the increase of Al, Fe, Mn, Cu, Zn, and As accumulated in the tissues of \(H\). _diversicolor_ with the pH reduction.