## 4 Discussion
polyschides_ harvested in the late summer/early autumn [46] had a lipid content of 3.3% dw, which is also remarkably similar to our results. Conversely, _M. pyrifera_ showed a lipid content (1.28%) close to that reported by [PERSON] et al. (1.57%) [54]. These results show that the lipid content of seaweeds not only depends on the season in which the seaweed was harvested, but also varies according to geographical location, climate and environmental conditions such as light intensity, day length, temperature, salinity and nutrient availability. All of these factors influence the metabolic activities of seaweeds and consequently the production of metabolites. The increase in lipid concentration in the residual pulp biomass is likely a consequence of the prior aqueous extraction process, which may have partially compromised the integrity of the residual pulp cell membranes. In fact, the membrane stability can be affected by processing conditions, such as temperature, pH variations and exposure to organic or polar solvents [72; 73]. When cell membranes are destabilized, subsequent steps in the analysis, particularly those involving mechanical or solvent-based disruption, can lead to enhanced cell lysis and the release of intracellular components, including lipids. Therefore, the elevated lipid content detected in the residual pulp may not reflect a true increase in lipid abundance, but rather a higher extractability due to membrane permeabilization and breakdown during the initial extraction step, making lipids more readily available for quantification compared to the untreated sample. Palmitic acid and the oleic acid were the most abundant fatty acids in the three seaweeds, a finding confirmed by several authors [44; 74; 75; 76]. Besides, the amount of the polyunsaturated fatty acids linoleic acid (ALA), arachidonic acid (ARA), eicosapentaenoic acid (EPA), and docosahexaenoicenoic acid (DHA) was always higher in the residual pulp and _M. pyrifera_ than in the other two species. [PERSON] et al. [77] found rather similar results but measured different values depending on the structure of the _M. pyrifera_ biomass evaluated. The presence of EPA in both the residue and _M. pyrifera_ and DHA in the residual pulp (albeit at low levels) suggests that this seaweed and the byproducts of its transformation can be used as functional ingredients in aquafeed. Both matrices contain nutrients essential for the growth and survival of marine larvae [78; 79]. Alpha-linolenic acid (ALA) and docosahexaenoic acid (DHA) were not detected in the studies by [PERSON] et al. and [PERSON] et al. [74; 76], while [PERSON] et al. [77] found no DHA in their seaweed samples. The n6/n3 ratio is often used to assess the quality of fats in a healthy diet. The ideal ratio for a balanced diet should be close to one, as this value reflects the recommended balance of essential fatty acids [80]. The ratios of omega-6 and omega-3 fatty acids obtained in this study for _L. ochroleuca_ and _S. polyschides_ (1.75 and 3.92, respectively) are higher than those reported by [PERSON] et al. [71], while similar or higher ratios have been reported for _S. polyschides_ in samples collected off the coast of Morocco, in Peniche (Portugal) and in the Gulf of Cadiz (Spain), with ratios of 6.62, 3.31 and 10.9, respectively [45; 74; 76]. Interestingly, the best ratio was obtained by the residual pulp biomass with a ratio of 0.87, which can be explained, again, by the disruption of the cell membrane, allowing some fatty acids to be extracted more easily. Lower temperatures favour an increase in the PUFA content of _Macrocystis pyrifera_, compared to those found in warmer waters (_L. ochroleuca_ and _S. polyschides_) [74; 81]. This increase in PUFA contributes to the greater fluidity of cell membranes in low temperature environments [64]. As previously mentioned, brown seaweeds are used in the food industry for their alginate content [82].