Palmaria decipiens (Reinsch) R.W.Ricker is a ecologically important red seaweed restricted to high latitudes of the southern hemisphere. Here, we contribute to the bioinformatics and evolutionary systematics of the Palmariales by performing high throughput sequencing analysis on a specimen of P. decipiens from the western Antarctic Peninsula. The P. decipiens mitogenome is 26,645 base pairs (bp) in length and contains 49 genes (GenBank accession MN967053) and the plastid genome is 193,007 bp and contains 245 genes (GenBank accession MN967052). The mitogenome and plastid genome of P. decipiens are similar to P. palmata from Japan in pairwise genetic distances (93.71% and 98.14%, respectively), and P. palmata from the Maine, USA (87.45% and 94.57%, respectively). The genomes of P. decipiens showed high gene synteny with P. palmata, however several tRNA differences are documented. Organellar genome content and phylogenetic analyses of P. decipiens supports its placement in the genus Palmaria.

The sub-Antarctic Magellan Ecoregion is a unique biogeographic area located in the southern end of South America with notable marine flora and high endemism. Brown macroalgae, particularlyMacrocystis pyrifera, dominate the coastlines and are considered critical ecosystem engineers, providing shelter, food, and reproduction sites for various species. Additionally, they are essential components used in the food industry and biomedicine due to their lipids, amino acids, and fiber content. In this study, we determined the fatty acid content in different thallus structures (holdfast, stipes and fronds) ofMacrocystis pyriferacollected inRinconada Bulnes(53°35ʼ47.76” S; 70°56ʼ08.52” W) in the spring of 2021. The stipes had a highest total lipid content (3.73%) than the fronds (2.74%). The fatty acid profile showed higher values of monounsaturated fatty acids in the stipe (Ʃ 43.0%) and holdfast (Ʃ 41.7%), while fronds displayed higher values of polyunsaturated fatty acids (Ʃ 32.4%). This study provides insights into the nutritional and biomedical potential ofM. pyriferaand highlights the importance of understanding the distribution of fatty acids in different thallus structures.