## 3 Results and Discussion
### Nutritional Analysis
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{4}{c}{**Taxon**} \\ \cline{2-5}
**Mineral Composition** & **Ulva sp.** & _G. multipartita_ & _S. muticum_ & _S. muticum_ \\  & **(Buarcos)** & **(Buarcos)** & **(Buarcos)** & **(San Marcos)** \\ \hline Macronutrients (mg/g dw) & & & & \\ Potassium (K) & 7.05 \(\pm\) 0.53 \({}^{\rm c}\) & 36.94 \(\pm\) 1.02 \({}^{\rm b}\) & 15.04 \(\pm\) 0.42 \({}^{\rm c}\) & 86.19 \(\pm\) 9.06 \({}^{\rm a}\) \\ Sodium (Na) & 73.80 \(\pm\) 0.45 \({}^{\rm a}\) & 64.07 \(\pm\) 5.96 \({}^{\rm a}\) & 73.52 \(\pm\) 6.93 \({}^{\rm a}\) & 29.36 \(\pm\) 3.82 \({}^{\rm b}\) \\ Calcium (Ca) & 8.99 \(\pm\) 0.56 \({}^{\rm b}\) & 17.55 \(\pm\) 0.95 \({}^{\rm a}\) & 21.22 \(\pm\) 1.48 \({}^{\rm a}\) & 11.05 \(\pm\) 1.33 \({}^{\rm b}\) \\ Magnesium (Mg) & 15.47 \(\pm\) 0.96 \({}^{\rm ab}\) & 7.89 \(\pm\) 0.21 \({}^{\rm c}\) & 13.6 \(\pm\) 0.41 \({}^{\rm b}\) & 17.21 \(\pm\) 0.86 \({}^{\rm a}\) \\ Phosphorus (P) & 1.13 \(\pm\) 0.00 \({}^{\rm c}\) & 2.17 \(\pm\) 0.07 \({}^{\rm a}\) & 1.07 \(\pm\) 0.02 \({}^{\rm c}\) & 1.57 \(\pm\) 0.09 \({}^{\rm b}\) \\ \hline Trace elements (\(\mu\)g/g dw) & & & & \\ Iron (Fe) & 221.21 \(\pm\) 6.86 \({}^{\rm b}\) & 238.61 \(\pm\) 9.00 \({}^{\rm b}\) & 279.52 \(\pm\) 5.65 \({}^{\rm a}\) & 116.30 \(\pm\) 6.68 \({}^{\rm c}\) \\ Zinc (Zn) & 8.37 \(\pm\) 0.81 \({}^{\rm bc}\) & 9.63 \(\pm\) 0.43 \({}^{\rm b}\) & 28.90 \(\pm\) 1.10 \({}^{\rm a}\) & 5.60 \(\pm\) 0.34 \({}^{\rm c}\) \\ Manganese (Mn) & 1.04 \(\pm\) 0.16 \({}^{\rm c}\) & 8.68 \(\pm\) 0.96 \({}^{\rm b}\) & 71.06 \(\pm\) 1.08 \({}^{\rm a}\) & 3.69 \(\pm\) 0.14 \({}^{\rm c}\) \\ Copper (Cu) & 20.76 \(\pm\) 1.39 \({}^{\rm ab}\) & 22.28 \(\pm\) 0.78 \({}^{\rm a}\) & 20.20 \(\pm\) 0.17 \({}^{\rm ab}\) & 17.86 \(\pm\) 0.19 \({}^{\rm b}\) \\ \hline Na+/K+ ratio & 10.50 & 1.74 & 4.90 & 0.34 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Mineral composition (mg/g dw) of samples of three species of seaweed, _Ulva_ sp., _Gracilaria multipartita_, and _Sargassum muticum_, from Buarcos beach and _S. muticum_ from San Marcos beach. The results were expressed as mean values \(\pm\) standard deviation. Different letters (\({}^{\rm a,b,c,d}\)) represent statistical differences between the samples. the other taxa and lower than the concentration of Na. The results also show that Na was the highest in _Ulva_ sp. (73.80 \(\pm\) 0.45 mg/g dw), followed by _S. muticum_ (73.52 \(\pm\) 6.93 mg/g dw) and _G. multipartita_ (64.07 \(\pm\) 5.96 mg/g dw). _S. muticum_ from San Marcos was the species with the lowest Na content (29.36 \(\pm\) 3.82 mg/g dw). Seaweeds therefore have a very diverse Na:K ratio, with the lowest Na:K ratio value being obtained in _S. muticum_ (4.9 mg/g dw) and _Ulva_ sp. (10.5 mg/g dw). The World Health Organisation (WHO) recommends a Na intake of less than 2000 mg per day and a K intake of more than 3510 mg per day, i.e., a Na:K ratio of \(\leq\)1.0, which is considered optimal for maintaining cardiovascular health [61]. The best result was thus obtained for _S. muticum_ from San Marcos, which presents a value of less than 1, as recommended by the WHO [61]. The ratio between the elements Na and K provides a means of counterbalancing the effects of modern Western diets, which are characterised by high intake of Na and low intake of K, concerning hypertension and associated cardiovascular diseases [62]. The Na concentration was significantly higher than that reported by several authors cited by [PERSON] et al. [63], and it was only comparable to that of the brown seaweed _Undaria pinnatifida_. In the literature, concentrations of Na ranged from 11 to 24 mg/g in _Ulva_ spp. and from 10 to 16 mg/g in _Gracilaria_ spp., while in _Sargassum_ spp., 27 mg/g was found [64]. The two _S. muticum_ harvesting sites differed significantly, with the San Marcos sample being closer to the values reported by [PERSON] et al. [64], who also registered a large variation between sites. Conversely, the K concentration in Buarcos was lower than those reported in the literature [63; 64].