## 3 Results and Discussion
### Nutritional Analysis
multipartita_ had lower amounts of ash, with 28.42 \(\pm\) 0.06 g/100 g dw and 26.56 \(\pm\) 0.02 g/100 g dw, respectively. Additionally, for _S. muticum_ from San Marcos, a significantly different ash content was found (30.17 \(\pm\) 0.30 g/100 g dw) when compared to the sample from Buarcos (28.42 \(\pm\) 0.06 g/100 g dw). According to the studies by [PERSON] et al. [44] and [PERSON] et al. [45], the ash content of wild species of _Ulva_ sp. ranged from 14 to 31 per cent in dry weight (dw), with the maximum value close to our result. As for _S. muticum_, [PERSON] et al. [37] presented a lower value than ours (22.94%). Furthermore, the higher ash content in the San Marcos species indicates lower organic matter (OM) content compared to the Buarcos sample. The lack of data on _G. multipartita_ from the Portuguese coast in previous studies precludes any comparison. However, studies with other species of the same genus, such as _Gracilaria gracilis_ collected from Buarcos beach, have reported ash contents ranging from 18.96% [46] to 24.8% [37]. Thus, _G. multipartita_ seems to contain greater ash content than _G. gracilis_. The ash content of seaweeds varies between locations due to differences in environmental factors, such as salinity, temperature, nutrient availability, and the presence of minerals, such as heavy metals in the water, making seaweeds' biomass less suitable for further biorefinery development [47]. The crude fat (CF) content is always very low, revealing a range between 0.11 g/100 g dw for _Ulva_ sp. and 0.19 \(\pm\) 0.01 g/100 g dw for _S. muticum_ from Buarcos, with the latter showing minimal differences compared to the San Marcos sample (0.19 \(\pm\) 0.05 g/100 g dw). Meanwhile, the fat content for _G. multipartita_ was 0.14 \(\pm\) 0.00 g/100 g dw. The CF content in macroalgae is naturally minimal. Several studies stated higher fat content, namely, those by [PERSON] et al. [48], [PERSON] et al. [49], and [PERSON] et al. [50], who reported a range between 0.23 and 2.0 g/100 g. Despite these variations, the low-fat content in seaweeds is well-documented, and fluctuations are likely due to environmental conditions. The crude fibre content of the three species exhibits a range of values, with the lowest observed at 5.83 + 0.02 g/100 g, followed by 6.17 \(\pm\) 0.35 g/100 g dw, 6.24 \(\pm\) 1.34 g/100 g dw, and 10.88 \(\pm\) 0.20 g/100 g dw for the _Ulva_ sp., _G. multipartita_, and _S. muticum_ species from San Marcos and Buarcos, respectively, with the latter's values being significantly higher than those of the other three samples. The CFi values presented by [PERSON] [51] (52.20%) and [PERSON] et al. [52] (14-18% in dry weight) for red seaweeds and 22-32% dw for brown seaweeds are much higher than the concentrations found in this study. A similar pattern was observed for _Ulva_ sp., with the crude fibre value indicated by [PERSON] et al. [52] (21%) and [PERSON] et al. [53] (41.16%) being higher than that of the present study. These discrepancies may be due to potential inaccuracies or methodological errors in the procedure used to quantify crude fibre [54]. The crude protein content of the samples ranged from 10.13 \(\pm\) 0.07 g/100 g dw in _S. muticum_ (San Marcos) to 18.43 \(\pm\) 0.07 g/100 g dw in _G. multipartita_ (Buarcos), closely followed by _Ulva_ sp., with a protein content of 18.05 \(\pm\) 0.10 g/100 g dw. Despite being harvested in different regions, the two populations of _S. muticum_ exhibit minimal variation between them and have a comparable protein value. The proportion of crude protein present in macroalgae varies considerably depending on the species. Red and green algae typically exhibit high levels of CP, ranging from 3 to 47 per cent [55; 56] and 10 to 30 per cent [2; 57], respectively. In contrast, brown macroalgae generally display a relatively lower proportion of CP, ranging from 5 to 15 per cent [37; 58]. The findings of this study corroborate the claims made by the aforementioned authors, indicating that the green _Ulva_ sp. (18.05 \(\pm\) 0.10 g/100 g) and the red _G.