## 5 Conclusions  
The results of the biomolecular and functional screening showed that the target seaweed species and their byproducts have high potential for various uses. This approach is in line with the concept of the circular economy, promoting the integral use of natural resources and helping to reduce environmental impact. The analysis revealed that the residual pulp and _S. polyschides_ render a high yield of alignates, which are essential for applications as thickeners and stabilisers in food, including ice creams, yoghurts, and cosmetic products. In addition, the levels of polyunsaturated fatty acids, including eicosapentaenoic acid (EPA, C20:5) and alpha-linolenic acid (ALA, C18:3), suggest applications in food supplements and balanced aquaculture feeds. The lipid profile of the residual pulp also shows a favourable n6/n3 ratio, ideal for formulations that promote human cardiovascular and metabolic health.  
In terms of minerals, _S. polyschides, M. pyrifera_ and the residual pulp have good levels of phosphorus, and both _M. pyrifera_ and residual pulp have high levels of potassium, suggesting their use in agricultural fertilisers and biostimulants. Future studies could evaluate the efficacy of these compounds in agricultural systems and explore the impact of their inclusion in diets for invertebrates and fish in aquaculture systems.  
Antivoidant analysis of the hydroethanolic extracts revealed high levels of polyphenols and a significant capacity to reduce iron ions, reinforcing the extracts' potential as a source of antioxidant compounds for the cosmetic and pharmaceutical industries. These compounds could be used in anti-ageing products, photo protectants and formulations designed to mitigate oxidative stress.  
Conceptualization, T.M., S.L. and C.N.A.; methodology, T.M., C.N.A., S.L., M.V.F.; validation, T.M., C.N.A. and S.L.; formal analysis, H.S.F., T.M., C.N.A. and S.L. investigation, H.S.F., M.H.M. and M.V.F.; writing--original draft preparation, C.N.A., H.S.F. and T.M.; writing--review and editing, T.M., C.N.A. and S.L.; visualization, H.S.F.; supervision, T.M., C.N.A. and S.L.; project administration, T.M., C.N.A. and S.L.; funding acquisition, T.M., C.N.A. and S.L. All authors have read and agreed to the published version of the manuscript.  
This work had the support of national funds through Fundacao para a Ciencia e Tecnologia (FCT), within the scope of the projects UID/04292/MARE-Centro de Ciencias do Mar e do Ambiente and LA/P/0069/2020 (ARNET Associate Laboratory) ([[https://doi.org/10.54499/LA/P/0069/2020](https://doi.org/10.54499/LA/P/0069/2020)]([https://doi.org/10.54499/LA/P/0069/2020](https://doi.org/10.54499/LA/P/0069/2020))), and also the doctoral grant awarded to [PERSON], UI/BD/150957/2021 ([[https://doi.org/10.54499/UI/BD/150957/2021](https://doi.org/10.54499/UI/BD/150957/2021)]([https://doi.org/10.54499/UI/BD/150957/2021](https://doi.org/10.54499/UI/BD/150957/2021))). Sflvia Lourenco is supported by the strategic project LA/P/0069/2020 ([[https://doi.org/10.54499/LA/P/0069/2020](https://doi.org/10.54499/LA/P/0069/2020)]([https://doi.org/10.54499/LA/P/0069/2020](https://doi.org/10.54499/LA/P/0069/2020))) granted to the Associate Laboratory ARNET by FCT.  
Not applicable.  
The raw data supporting the conclusions of this article will be made available by the authors on request.  
The authors would like to thank [PERSON] and his team on the SeaForester Project for harvesting _Laminaria chroleuca_. The authors are truly thankful to the Kelp Forest Foundation for providing the _Macrosystis pyrifera_ biomass and residues. The authors would like also to thank [PERSON] and [PERSON] for their valuable assistance and insightful suggestions concerning, respectively, the elemental and fatty acid profile analyses, carried out in this study.  
The authors declare no conflicts of interest.